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Arginta Group originates from the Lithuanian capital private limited company Arginta with the lifetime dating back to 1991. Promising ideas during over 20 years have grown into a big market leader and a very profitable company. The territory of the company has expanded as well: until 2007 Arginta occupied 1 500 m2 premises, whereas in 2012 Arginta Group already had 12 600 m2 industrial-administration premises, used by the companies of the Group and leased to the companies from the outside. Manufacturing activities have expanded from metal processing to equipment design and production. One of the fundamental reasons of successful activities is the attempt to continually develop. The Group focuses on quality production and top-level services within equipment design and production, water management, as well as renewable energy. We had an opportunity to enlighten our colleagues engineers and salesmen about the possibilities of a micromolding technology and how advanced plastic molding is in Lithuania. Many questions and long discussion of like-minded people helps to better understand our strengths and limitations which can be all exchanged under close collaboration of the cluster.

Laser & Engineering technologies cluster LITEK was established in 2010 but cooperation between science and SMEs continues for more than 20 years already. It all started when manufacturers of laser systems in cooperation with scientific institutions began to develop unique products in the field of photonics. Companies of LITEK together with scientific institutions understood that combining different areas of knowledge, close cooperation, interdisciplinary (in photonics and engineering fields) sharing ideas and convenient business environment are one of the main reasons for more efficient business operations and growing results. That’s how companies and scientific institutions got together in a cluster – LITEK. Being a part of the cluster allows its members not to compete with each other but by combining resources and knowledge direct all the energy for the competition in international markets and easier enter new ones. We had an opportunity to spread the word about plastic micro injection molding for the Laser & Engineering technologies cluster (LITEK) member companies. Our CEO Dominykas Turčinskas presented our capabilities and explained the main differences of micro injection molding and traditional molding.

Creating microfluidic chips is a difficult and precise process. Manufacturers have several options available for creating small channels, holes, and V-grooves. While some use chip making techniques like embossing, photolithography, or micro 3D printing for these purposes, micro milling microfluidic chips is still the preferred option for prototyping, though not for serial production. However, micro milling is useful for much more than making chips. Manufacturers can also use it for making the tools used in the injection molding process. However, the main use of micro milling is that it allows the rapid creation of chips for prototyping. This article explains what micro milling is and the issues manufacturers must consider when using this technique. What Is Micro Milling? Micro milling is a subtractive manufacturing process that leverages cutting tools to remove material from a part. Manufacturers create a 3D model of the intended part, such as a chip, using computer-aided design (CAD) software. With the design in place, the micro milling process uses rotating cutting tools to remove material until the part matches the design. With micro milling, manufacturers can narrow features down to micron-level making it a flexible process ideal for creating micro components that have complex shapes. The process’s speed and adaptability make it ideal for rapid prototyping of microfluidic chips. The Benefits of Micro Milling Microfluidic Chips There are several advantages to micro milling microfluidic chips: · The process requires no complex tooling, which saves enormous amounts of time for manufacturers. As a result, micro milling is the ideal option for rapid chip prototyping, allowing manufacturers to test their designs before beginning a full production run. · Having the ability to cut various types of materials using micro milling make it a viable option for quickly testing various materials for microfluidic devices. · Micro milling allows for the fabrication of multi-height features, which is difficult to achieve with photo-lithography. The Limitations of Micro Milling Though micro milling has many applications, there are some limitations manufacturers must consider before using the process. Aspect Ratio Endmills and drills are rarely good options when the manufacturer needs to create small features that have high aspect ratios. For example, 200µm diameter endmills typically achieve a top aspect ratio of 3:1, which may be not enough for the part. Furthermore, increasing the diameter of an endmill leads to higher aspect ratios being required due to the tool becoming more rigid. As such, manufacturers may find it more difficult to fabricate high-aspect ratio features, such as narrow and deep trenches, with micro milling. Run-Out Run out is a discrepancy of the cutting path and tool diameter at a certain spot along the outer edge of the cut. When tool rotates it is crucial that each flute would hit at the exact same point along the cutting path. In the research paper “A Study of Surface Roughness in the Micro-End-Milling Process,” researchers from UC Berkely examined the effects of run-out on the micro milling process. They discovered that run-out plays a significant role in the surface quality achieved when micro milling parts. Using 6061 aluminum, they found that the dominant cutting marks on the material had a period of twice the chip load. This means that one cutting edge makes a deeper cut than the other, leading to an uneven cut. Still, the study concluded that micro milling can produce a high surface quality if the manufacturer accounts for run out. Surface Roughness and Resolution Surface roughness is the measurement of the smoothness of a surface’s profile. It’s typically calculated by measuring microscopic variations from the peak and valley of the surface. In milling, surface roughness influences how a part interacts with its surrounding environment. Visible machining lines, which micro milling may produce, can affect how a microfluidic chip interacts with the parts that surround and support it. Burr Formation Burrs come into play in both polymer and metal manufacturing. The term refers to the formation of rough ridges or edges on a piece. The presence of burrs reduces part safety, creates additional stress during part operation, and makes the part more susceptible to corrosion. Unfortunately, micro milling is one of several machining processes that create burrs. As such, manufacturers must use a micro-deburring technique when micro milling microfluidic chips. Examples of this include the following: · Hand deburring involves special technicians removing burrs while examining the part under a high-resolution microscope. · Waterjet deburring uses highly focused and pressurized water streams to remove burrs. · Thermal deburring burns off the burrs using an explosive gas mixture to create thermal energy. · Electromechanical deburring combines a salt solution with electricity to dissolve burrs without affecting the surrounding material. Internal Radius In micro milling, any machinery a manufacturer uses has limitations in terms of it’s the angles, curves, and contours it can achieve. These machines typically have a corner radius, which is a term that refers to the internal radius of the corners of the machined part. Due to rotational nature of the milling the tools are round and thus they have some radius which is unavoidable. This means that while milling internal pockets the corners will be with radiuses which will be equal half the diameter of the tool. However, this is not valid for outer corners. Alternatives to Micro Milling Micro milling isn’t the only option available to manufacturers when creating microfluidic chips. Laser Machining/Ablation Laser machining uses laser pulses to create structures and cut holes. It works in a similarly subtractive way to micro milling. However, in this case, the process involves using laser light to vaporize unwanted material. This creates a clean process and allows for greater flexibility in designs. On the other hand, the process is relatively slow and thus very expensive. On average 1 cubic centimeter can be ablated in one full day for the metal material. Photolithography Photolithography involves coating the material with a photoresist layer before exposing it to a precise pattern of intense ultraviolet light. This process allows for the creation of extremely small features. However, it’s only suitable when used with flat substrates. Plus, the process is far more expensive than micro milling and even laser ablation. Selective Laser Etching This technique allows the manufacturing of complex features by laser affected and later etched out material, which often makes it useful when creating biomedical devices. Selective laser etching also offers a short time-to-market and offers few constraints when designing part geometry. Consider Micro Milling for Microfluidic Chips Micro milling microfluidic chips is an effective technique because micro milling offers short lead times and excellent flexibility. This combination allows for the rapid creation of complex geometries, making it ideal for prototyping and production processes that require fast turnarounds.

This week we had guests of Directors of the Alliance of Lithuanian Clusters. On the meeting agenda was Lithuanian clusters future and perspectives where CoMI had an opportunity to present its strategy and collaboration opportunities across the country. We had an honour to show our premises for the guests and introduce them to micro molding technology too. Our CEO explained the differences between micro injection molding and traditional injection molding. The guests had a chance to check on how micromolding machines and micro-milling works as well as to touch and feel still hot molded samples.

The need for tiny, even micron-scale parts has increased over the past few years, and thus the relevance of micro technologies is increasing due to the drive toward miniaturization. Because of microinjection molding capacity for mass production and relatively cheap production costs, it may be considered one of the fundamental technologies for mass micro manufacturing (replication). Micro injection molding involves shaping micron-level geometries to a plastic product with the help of molds which have cavities and cores. The process starts with moving of material, which is in the form of pallets, from a hopper into a plasticizing unit where it melts and liquefies. The molten polymer is then injected, under pressure, into a mold cavity and core, where it is held under pressure for a certain amount of time to account for material contraction. When the melt cools down inside the mold's shape, the component is ejected, and the process is repeated. When technology is adapted, this cyclic operation enables mass replication of micro parts. Micro-injection molding is not a traditional molding Even though, microinjection moulding seems to be no different from traditional injection molding in its nature, the challenges lurk in the details. When molded components or their features gets small variety of challenges arises: demoldability (ejection), high aspect ratios (HAR), melt flow penetrability, capillary effects, advanced venting solutions, extreme mold and injection temperatures, hesitation effects, mold manufacturing (micro-machining) problems (tool breaking, positioning, inspection), material selection, optical quality checking and packaging/handling of micro parts. Micro-injection molding hesitation effects and penetrability problems Image Source: https://www.researchgate.net/publication/339661059_Flow_and_solidification_of_semi-crystalline_polymer_during_micro-injection_molding The huge surface to volume ratio of many micro parts results in quick cooling times of the injected material inside the tools. It is crucial to take this into account when designing the mold. Despite the fact that polymers often exhibit a "self-isolating" effect and have low heat conductivity, the injected materials quickly cool down on the cavity and core walls, making it impossible to completely penetrate into the micro-cavities. Micro components have thin walls and large surfaces compared to their volume, which causes the melt's temperature to quickly equalize to the mold’s, thus it is always good to minimise this factor early in the design phase. Micro mould advanced venting solutions In order to avoid faults in the molded part caused by compressed air inside the cavity, the proper venting has to be assured. It is another main factor in determining the quality of the micro component that is molded. A special built mechanism to evacuate the air from the microcavities is needed if the micro geometries are too small to be vented normally through the parting line of the molds or traditional venting channels. Another good solution to this problem is vacuum the cavity before the injection. However, this technology still requires adaptation and research for a reliable use. Changing micro machined inserts not the molds Another common application in the micro injection molding is the use of inserts. For example, to mold microfluidic channels electroplated nickel inserts can be used. They can be placed and replaced inside the mold to expand the micromachining capabilities when tooling. The key benefit of employing a mold with interchangeable inserts is the opportunity to test various micro-part geometries without changing the fundamental structure of the mould. In a process where the finalized mould design is developed through a number of iterative steps in which parts are injected and the mould design is revised, the usage of moulds with inserts lowers the overall cost of process setup. However, this benefit comes with a certain cost – different mold and insert materials have different deformations at varying temperatures which may cause misalignments or even tool damage. Micro-injection molding material selection The experimental results have been impacted by the use of various polymeric materials in the production of micro parts. The use of materials with high shear thinning rheology is recommended because it enables mold filling with the least amount of injection pressure. Determining the best material for each application without testing it under various conditions is difficult due to the interplay between the type of polymer used and the moulded component. Viscosity in micro-cavities The efficiency of molding is influenced by the chosen plastic's characteristics, such as viscosity, specific heat coefficient, and thermal expansion. In recent studies, measurements of melt viscosity in small-dimension geometries were made utilizing high-fluidity amorphous ABS and PS resins, high-low density PE resins, and high crystallinity POM resin. It is feasible to determine the viscosity values from the recorded pressure drop received from pressure sensors and melt volumetric flow rate. When compared to information provided from a conventional capillary rheometer, it was discovered that ABS, PS and POM viscosity increases as micro-channel size reduces. Wall-slip effect When melt flows through micro-channels, wall-slip effect occurs. Wall-slip effect results in a higher viscosity reduction as micro-feature size decreases. Also, when melt temperature rises, the wall-slip effect becomes more pronounced. The ratio of slip velocity to mean melt velocity and the percentage reduction in viscosity within the micro cavities rise with decreasing micro-channel size. It seems that the wall-slip effect plays a dominant role in viscosity reduction. Micromolding parameters for high quality micro-parts Throughout the years of experience, it has been found that the following are the primary injection molding variables influencing the part quality during the cycle time of molding: Injection pressure Cooling time Mould temperature Holding time Holding pressure Melt temperature Injection speed There might be a variety of good combinations of those parameters to deliver required quality of the part, however, there is no single formula which would lead to the general solution. In most cases the play with these variables lead to empirical parameters combination settings which are individual for every project. This burden sits on micro moulder’s shoulders and only his proficiency determines the right settings. Micro moulding in the scope of micro-manufacturing For the production of polymeric micro-components, the micro injection molding technology is gaining significant relevance nowadays. This process has the potential to play a key role in sustaining the demand for micro components in biomedical, optical, and electronics fields. By discovering new materials, process controls, simulation techniques, and methods for quality checking, field of micro injection molding is advancing quickly and appears to be able to surpass most of the current technological constraints.

Texturing (also referred to as engraving or graining) is the procedure through which you add a pattern to the mold’s surface. Doing so will replicate the desired pattern on the plastic part you’re molding. A product’s texture drastically impacts its functional and esthetic characteristics. That’s why it’s crucial to plan it before the molding process. You need a deep understanding of the texturing process and how different patterns are added to parts. In this article, you’ll learn about the texturing process and how to select the right texture for your mold. Let’s start with the basics. What Is Surface Texture and Why Is It Important? Surface texture can be described using three different parameters: Waviness – imperfections on the surface caused by repeated cyclical vibrations of the texturing machine. Lay – describes the general direction of a surface’s pattern. Roughness – average vertical deviations due to the surface and cutting or sanding tool’s interactions. There are many reasons to texture a product, and they’re categorized into esthetic and functional purposes. You can greatly improve a product’s visual appeal with the right texture. Deeper matte textures can add depth to the product or create contrast on a glossy finish. Depending on the target design, a texture can serve various esthetic purposes. As for functionality, the texture improves a product’s grip, which is crucial for ease of use and safety. In addition, texture supports later design changes like adding paint or labels since it helps with adhesion. Types of Plastic Surface Textures SPI (Society of the Plastics Industry – rebranded to PLASTICS) There are many different surface texture types you can get through several processes, which you’ll learn about later in this article. The first categorization you should know about is the SPI (Society of the Plastics Industry – rebranded to PLASTICS) standard. It separates surface finishes and textures into four categories: Grade A (High Gloss) – Finished with 1,200-6,000 grit diamond buff Grade B (Semi-Gloss) – Polished with 320-600 grit sandpaper Grade C (Matte) – Polished with 320-600 grit stone powder Grade D (Textured) – Sandblasted with aluminum oxide or glass beads Each grade encompasses three levels that describe allowable deviation from the perfect texture within the category. That gives 12 distinct types to choose from: A1-A3 – Glossy and smooth, often used on products like mirrors and visors. B1-B3 – Good for removing mold tool marks, mostly used for less visually-important parts. C1-C3 – The most popular types due to their cost effectiveness, used in a variety of parts and products. D1-D3 – Coarse matte textures, often used in products that require a firmer grip or for similar functional reasons. The grade you’ll go with significantly impacts the end product’s cost due to the time and materials necessary to create the texture. For instance, Grade A textures are made through diamond buffing, which is far more expensive than sandpaper polishing used for Grade B textures. VDI (Verein Deutscher Ingenieure) Another important categorization is VDI (Verein Deutscher Ingenieure). It’s a mold texture standard used by many tool producers. Other than the above texturing methods, VDI textures rely on EDM (Electrical Discharge Machining). These textures have VDI values starting at 12 and increasing in 3-point increments up to VDI 45. They can vary greatly in surface roughness. VDI 12 has a roughness of 0.4µm, while VDI 45 is 18µm. Due to this range, VDI textures can be used in a variety of parts and products with different esthetic and functional requirements. Mold-Tech Finally, we have the Mold-Tech texturing specifications. Mold-Tech also classifies textures into four categories – A, B, C, and D. These textures are created either through laser alteration or chemical etching of the cavity. Within each grade, there are lots of different textures, denoted by five-digit codes reflecting the texture’s serial numbers and roughness. Grade A finishes are the most common because they offer a wide spectrum of textures. MT-11010, for instance, has a sand-like texture found in many plastic products. On the other hand, MT-11555 offers a wood panel design often used for cosmetic purposes. Whether you need diamonds, checkerboards, concrete, or any other pattern, Mold-Tech options will give you the exact texture you need. There are hundreds of them, so finding the right one shouldn’t be an issue. As you can see, many processes can yield all kinds of surfaces. Let’s explain them in more detail. How the Texturing Process Works SPI textures rely on traditional engraving methods. For instance, you’ll go through two steps to get Grade D textures. First, stone powder is used to smoothen the surface. Then, the machine uses glass beads or aluminum oxide to blast it. Dry blasting doesn’t involve linear or circular motions like those involved in Grades A-C, so you’ll get a chaotic non-directional texture. As mentioned, EDM is a process used for VDI textures. An electrical discharge is created between the part and the machine’s electrode or wire. It causes a spark that removes material from the part, creating the desired texture. Lastly, chemical etching or milling is a subtractive texturing process. It’s a more complex method that involves several steps: Photoresist film is applied to the material. Glass or mylar masks are applied, containing the negative image of the desired texture High-intensity UV light shines through the masks and crosslinks the film wherever the light isn’t blocked. The non-crosslinked film is chemically removed, revealing bare metal. An etchant is sprayed, dissolving the bare metal and leaving the desired texture. Because of all the steps involved, texturing can sometimes be quite expensive. Let’s see how to choose the right texture to save money. How to Choose the Right Texture? It’s crucial to decide on the texture during the embodiment design stage. This is because the product’s texture will determine the material selection, as well as the draft angle. If you’re unsure which texture to go with, here are some factors to consider. Molding Material Different plastic types can give vastly different textures, even if other parameters stay the same. The same goes for additives and fillers. They can change the material’s properties, significantly influencing the finish. You can use the specifications mentioned here as guidelines for the type of material you should go with. It’s possible to use tables outlining what textures are the most suitable for each material. There are strict rules to follow here, which eliminates most guesswork and testing. Mold Tool Material The most common mold tool materials are steel and aluminum, although other metals can also be used. You need to know what material you’ll use, as it will impact the product’s texture. For instance, aluminum produces rougher textures than steel. So, if you need deeper textures, it might be a more suitable option. Tooling Cost There aren’t many shapes that you can texture or polish automatically. This only goes for the simplest ones, while more complex parts or products often get quite labor-intensive. Costs of this labor can add up over time, causing you to overspend. That’s why you should be mindful of tooling costs when deciding on the product’s texture. Think about its target functionality and look to determine the most cost-effective solution. Injection Velocity and Temperature The speed at which you inject the material can significantly impact its texture, as can the temperature. Generally speaking, to get a more textured surface, you should inject the material more slowly. In addition, higher temperatures usually lead to smoother textures, so this is another parameter you should keep in mind. Choose the Right Texture As you can see, a lot of thought goes into selecting the best texture for your product. Now that you know the details of the texturing process and different types, think about the best option for your needs. Remember to design the product with its texture in mind from the get-go. Doing so can avoid the need for costly modifications later in the manufacturing process.

Before you start the mold injection process, you need to consider potential modifications. Due to the subtractive nature of mold production, you can’t add material back to the mold; you can only carve it out. If you don’t get the design right, you might have to replace the molding tool altogether. Other than the above scenario, there are times when you might have to change the molding tool. Doing so can be costly and time-consuming, so you should do everything possible to avoid it. This article will give you some tips for planning with mold modification in mind. But first, let’s discuss the situations where changes are even possible. Modify or Rebuild the Mold? A solid set of molds involves a significant investment. Luckily, it’s usually more than worth it, especially if you produce high volumes of plastic parts or products. Your per-unit costs will stay low as long as your products don’t require changes. As your business grows, you might have to change your production. Perhaps you’ll have to resize your product, add or remove features, or change the material. You can make some changes without having to replace your mold. These include: Expanding part geometry – You can make incremental metal reductions in your molds. This way, you can slightly increase the product’s size or change its geometry. Wall thickness can be increased and through-hole diameter can be decreased. Adding features – If you use well-built inserts that fit into your mold’s cavity and core, you should be able to add small features to it – like holes, slots. However, you should discuss such changes with your engineering team first. Adding or extending ribs, bosses, gussets – If the wall or other geometry is not sufficiently strong it is possible to add ribs, bosses and gussets by machining some portions of the mold. Making Snap fit tighter – when the fit of two mating parts is not sufficiently tight it is always possible to make the fit stronger but not vice versa, thus it is good to start with looser fits. Adding back the material to the mold (doing the impossible) – at some cases it is still possible to increase the diameter of the hole just by substituting pins that shape the hole. Also, at some extreme cases it is possible to solder, weld back some mold material so that it could be again machined and fixed. Changing surface finish – What is also good about injection molding that mold texture and surface roughness can be changed. For example, if sand blasted surface finish appeared too soft it is possible to make EDM machined texture. The only thing is that the overall dimension of the part can slightly increase. Basically, whenever you need to make small changes to your product that involve adding to it, you should be able to modify the mold accordingly. On the other hand, here are some common changes that involve a replacement: Reducing a part’s size – While you can remove some metal from the mold, you can’t add it in. That’s why shrinking a product requires a new mold. In some cases, you might be able to change the core, though this often doesn’t do the trick. Changing the parting line – Any parting line changes will impact the mold’s gates and vents. Because of this, parting line modifications call for new molds. Changing the materials (if tolerances are strict) – Molds are generally built with specific resin shrinking in mind. If you change the resin type, it will likely have different shrinking properties, so you’ll need a new core and cavity set to accommodate this. Other than product changes, you might need to replace the molds due to wear and tear. Metal-on-metal contact is bound to amortize your molds after a few years, and no modification will help. Tips for Mold Modification If your circumstances allow for mold modification, here are some tips for ensuring it goes smoothly. 1. Prepare in Advance You should plan for all changes to your product or molds in the design phase. The design should be “steel-safe,” meaning that it allows for the metal to be removed from the mold to account for any changes. In addition, you should plan all product features and parameters ahead. If you don’t have your mind set on them, make sure there’s room for changes that won’t involve new molds. For instance, if you are unsure about wall thickness, start with thinner product walls. You can always increase thickness by machining the mold, but not vice versa. The same goes for holes and pins; you can only reduce the diameter of the hole. Make sure your design team knows how to account for potential mold modifications, and you’ll save yourself many headaches down the line. 2. Be Wary of Geometry Changes Will your product or part need undercuts? If so, this is another thing you need to consider before production starts. While adding side-action cams to the mold is possible, it’s an extensive change that won’t always make financial sense. Eliminating undercuts is generally considered an excellent way to reduce production costs. But if this isn’t possible, plan such complex features in advance. 3. Consider the Minimum Cutting Depth As mentioned, you can remove some metal from the mold to increase the product’s size or slightly change its geometry. However, you should keep in mind that you can only remove the metal in fixed increments. To remove metal from the mold, you’ll have to mill it, so you need to factor in the minimum cutting depths. For example, you may be able to carve out 0.250 mm of metal, but removing less than that might not be possible. So, if you plan to expand your product, ensure the expansion matches the cutting depth. 4. Choose Your Resin Wisely How much will the plastic you use shrink during the molding process? Will your product need different materials with varying shrink rates? Will your material have glass fiber additive (which is abrasive for molds)? These are some of the most critical questions you need to answer before you start the molding process. Depending on the extent of the shrink rate change, it may be difficult to impossible to modify the mold so that it accounts for the variations. You can find many resources online that offer detailed shrink rates for each resin. Use them as guidelines for building a mold that will fit your materials. When testing different resins, it’s always best to design for those higher shrink rates. You can machine down prototypes that shrink less and configure the final mold appropriately. Aluminum mold will not work well with abrasive GF filler; thus steel molds have to be used. However, for low-volume production and several cycles aluminum could help, and thus manufacturing volume must be also taken into account prior tooling process. Be Proactive They say that a good plan is half the job done. When it comes to injection molding, it’s much more than that. The initial stages are often the most complicated but worth your time and effort. This is especially true if you consider that many mold modifications aren’t a result of planned changes, but design errors. To avoid costly mistakes and ensure that production goes according to plan, take your time to scrutinize every detail of your product’s design. Only then can you build a mold that will let you reap the cost benefits of mass production. Mold changes are likely to happen anyway due to amortization, but there’s no reason to expose yourself to additional costs due to design mishaps. Think a few steps ahead, and you’ll save a significant amount of money in the long run.

Even though injection molding is a cost-effective mass production method, it does involve expenses that can add up over time. At some point, you might realize that your per-unit cost is higher than you’re comfortable with. This can happen for several reasons, most notably the time necessary for tooling production. The more complex the part, the longer it takes to produce, driving up the costs. Materials also play a big role as some are easier to mold than others. Fortunately, there are many things you can do to lower injection molding costs. Let’s look at some of the most effective methods. 1.Think a Few Steps Ahead (subtractive nature of the mold machining) Once a part goes into production, tool modifications aren’t possible – you can’t add material back to the mold. This is why you need to plan the process in advance. Let’s say the wall is too thick due to an error at the design stage. You can’t make the wall thinner, so you’d need an entirely new mold. To prevent this, you could start with a thinner wall, as you can always make it thicker if necessary. 2. Analyze the Plastic Part's Structure Before you start the production process, you should closely analyze the part’s structure to identify the areas that impact its quality and function the most. For instance, you may notice areas where a gusset is better than a solid area. Don’t hesitate to make design modifications before production, as they can save you money in the long run. 3. Choose Materials Wisely While you should always strive toward high product quality, ask yourself if you can achieve the same standard with more cost-effective materials. You might not need a high-end plastic resin to ensure quality and durability. Lower-end options paired with the right additives might meet all the requirements without the same outlay. 4. Reconsider Your Molds Investing in steel molds might not always be a good idea. Even though their performance is unquestionable, you might be overspending if you can produce the part with different molds. See if aluminum molds can give you the results you’re looking for. In some cases, you can also go with 3D printed options if not contrary to the product specifications. Finally, if the part isn’t larger than 20cc in volume, you can go with micro molds. 5. Eliminate Unnecessary Features From a budget perspective, a good product isn’t the one jam-packed with features, but the one that ensures quality and functionality without unnecessary extras. Certain features involve processes like bead blasting or EDM, which can come at a high cost. For that reason, think about your product’s features and how many of them you really need. 6. Decrease Cycle Time Cooling the plastic to achieve a solid state takes up around 85% of the injection molding cycle time. Naturally, reducing the cooling time is the best opportunity to drive down the whole cycle length. Check if you can reduce the melt temperature without disrupting the process. Any decrease, no matter how small it may seem, can save you a lot of resources with time. 7. Don’t Use Automatic Sliders If you’re producing high quantities of complex parts, automatic sliders make perfect sense. But they’re only worth the investment in high-volume production. With low-volume production, it might be better to opt for manual work. Doing so will help you avoid overspending on a process you don’t necessarily need. 8. Optimize the Product’s Design As mentioned, cost reduction should start at the design phase. Rather than putting the product into production as soon as the design is complete, review it to see if you can make any changes that will simplify the molding process and avoid unnecessary costs. For instance, just by eliminating undercuts, you can remove the need for complex tooling and drastically reduce molding time and cost. You should also be mindful of finishes. While they undoubtedly add to the product’s look and function, you shouldn’t pay too much for cosmetic features. 9. Conduct a DFM analysis Building on the above, it’s always a good idea to conduct a Design for Manufacturability (DFM) analysis. Aside from design concerns, the analysis gives you a close look at your entire system to see if improvements can be made. Cost reduction is among the main goals of a DFM analysis, so you can rest assured that the assessment will provide detailed input on everything you can do to drive the costs down. 10. Review Part Tolerances Tight tolerances aren’t always necessary. They’re only justifiable if the return on the investment is large enough to cover the costs involved. For instance, Lego® building blocks have extremely tight tolerances (10 micrometers), but this is necessary to ensure consistency and is more than justified by the revenue. Not all products call for this, so specify the tolerances that are actually necessary for the product’s function. This way, you’ll reduce molding and production costs, along with residual maintenance costs. 11. Automate Your Processes Your mold injection process should be consistent and efficient. In many cases, manual labor can’t ensure this. Of course, some steps of the process must be manual, but you should look for opportunities to automate as many of them as possible. You might be able to automate part picking, stacking, and palletizing. You can even automate sorting and set up tolerance alarms. Depending on your exact process, there should be at least some steps you can automate, so don’t hesitate to do so. Even the seemingly insignificant changes can add up to substantially decrease costs. Improve Your Bottom Line Hopefully, the tips provided here have given you an idea of how you can lower your injection molding costs. Granted, not all of them are universally applicable to every project, but there’s bound to be something that can improve your efficiency and save you more money. Striking a balance between cost reduction and quality is anything but simple. It requires many considerations and meticulous planning. Start thinking about your budget from the design stage, and you’ll remove unnecessary costs. Modify your process as you go, and you’ll reach a standard that maximizes your profits without sacrificing the product’s functionality.

How a product looks and feels can make a world of difference to its value. That’s why choosing the right surface finish for injection molded parts is crucial. However, a surface finish goes beyond aesthetics, as it can significantly impact a product’s usability. In this article, you’ll learn about the different surface finish types and how to choose the right one. But first, we need to make an important distinction. Tool Surface Finish vs. Texture While often used interchangeably, surface finish and surface texture aren’t the same. Finish refers to the general condition of the surface. Texture, on the other hand, is a quantitative characteristic of a material that encompasses three major determinants – lay, waviness, and roughness. Think of texture as a sub-category of surface finish. In other words, surface finish includes the texture, along with other characteristics like coating (painting or anodizing). In practical terms, this means that you’ll use different processes for finishing and texturing. Now that we’ve explained the terminology, let’s move on to the importance of a product’s surface finish. Why You Should Use Different Finishes As previously noted, surface finish impacts many of the product’s core characteristics. In retail, for example, the surface finish can make or break a product’s perceived value due to aesthetics. Plus, it can conceal some of the product’s imperfections like sink or line marks. The surface finish also determines the product’s functionality to a certain degree. Many products require a user to have a firm grip on them for proper use, such as fitness equipment. In this case the finish should be slip resistant. Getting the finish wrong can be a costly mistake. To help you avoid that, let’s dive into various finish types. Explaining Different Types of Finishes Mold manufacturers and designers must plan a product ahead to ensure that the surface finish suits its specifics and materials. To make this easier, the Society of the Plastics Industry (SPI) defined finish standards so everyone involved in the process can follow them. The standards encompass 12 different surface finish grades categorized into four groups (A, B, C, and D). These categories describe the roughness of the finish and range from glossy and smooth to dull and rough finishes. It’s important to understand this classification as it provides guidelines on what surface finish to use with each material. For example, when working with ABS, it’s best to choose a finish ranging from B-3 to D-2. For acrylic, however, it’s best to use A-1 to A-3. SPI is also important for determining the finish treatment method. For instance, C-1 to C-3 finishes are polished with fine stone powder. D-1 to D-3 use the same method, except they’re dry-blasted afterward. SPI isn’t the only standard out there. You should also consider VDI (Verein Deutscher Ingenieure). It’s an international standard for matte surface texturing. VDI finishes are commonly treated using EDM (Electrical Discharge Machining), although traditional techniques like sandpaper or stone texturing are also applicable. Finally, Mold-Tech (MT) specifications classify finishes according to texture depth and serial number. You can form MT finishes by chemical etching and laser-altering the mold cavity. With many options to choose from, how do you know what finish you should use? Let’s look at how to select the right one. What to Consider When Choosing a Finish? There are a few factors that you should take into account when deciding on the surface finish. Here are some of the most impactful. 1. Injection Speed and Temperature Generally, faster injection always provides a smoother and glossier surface, regardless of other parameters. Combine this with higher mold temperatures, and you’ll get a glossy SPI finish. Lower temperatures and injection speed may meet other requirements, but they won’t give such a smooth finish. By increasing the injection speed, you can also reduce the visibility of weld lines due to minimized fiber orientation. 2. Mold Choice The mold you go with plays a critical role in the surface finish. You can make the mold out of various metals, although aluminum and steel are the most widely used. Even between these two materials, you can get very different finishes. If you don’t need a highly smooth or glossy finish, an aluminum tool should do the trick. However, if a product calls for low roughness, it’s best to use a hardened steel tool. 3. Materials There’s a wide range of materials used in injection molding. Each has specific properties that impact the finish regardless of the molding process and its parameters. For example, certain plastics are easier to smooth than others, and you need to know these characteristics to get the desired finish efficiently. This is where it pays to remember the SPI specifications. To make things simpler, here’s a short compatibility list according to the SPI grade: · Grade A – Acrylic, PC · Grade B – Nylon, PP, Polystyrene, ABS, HDPE · Grade C – Nylon, PP, Polystyrene, ABS, HDPE · Grade D – Nylon, PP, Polystyrene, ABS, HDPE, TPU It’s also crucial to remember the additive compounds that you’ll mix with the resin, as they can greatly change their properties. For example, carbon black reduces surface roughness, while fiberglass lowers gloss. 4. Functionality Surface finish doesn’t just impact the end product’s functionality from the user’s perspective. It can also influence other manufacturing stages. Let’s say the product will be painted. In this case, you shouldn’t go with a smooth finish as doing so will make it harder for the paint to adhere properly. The same goes for adding labels – it takes some roughness to ensure it sticks. Therefore, always keep the end product in mind when choosing the finish. Know Your Finishes As you can see, choosing a finish is an important decision that involves quite a bit of critical thinking. If you haven’t already, it pays to familiarize yourself with the types and specifications mentioned here, as understanding them is crucial to choosing the right finish. It’s best to decide on the finish early in the manufacturing process. As mentioned, surface finish impacts many other choices you’ll make in the later stages. Take some time to think about the finished product’s design and functionality, consider the molding process, and choose the finish that perfectly complements all of these factors.

In injection molding, wall thickness is one of the most crucial design elements. Selecting the appropriate injection molding wall thickness ensures the manufacturer optimizes the part’s appearance and moldability. It also improves the mold’s performance, leading to lower manufacturing costs. Most manufacturers use the prototyping stage to test different wall thicknesses and their impacts on the resulting part. Nevertheless, there are some best practices most manufacturers follow to ensure they select the appropriate injection molding wall thickness. This article examines those best practices, the issue of wall uniformity, and explains why uniformity is so important when designing a mold. The Importance of Uniformity in Injection Molding Wall Thickness Uniformity ensures that every wall used for a part is of the same thickness. The most important benefit is that uniform wall thickness ensures consistency when making multiple parts. Manufacturers don’t have to worry about changing flow or cooling rates when the melt moves from thick to thin walls or vice versa. Instead, they get consistent flow and cooling. Maintaining uniform thickness also improves the part’s stress distribution, minimizes shrinkage, and generally allows manufacturers to save money when creating their molds. What Can Happen if Injection Molding Wall Thickness Isn’t Uniform? If a manufacturer doesn’t maintain uniform wall thickness, they must account for variations in thickness in their design and the way they inject melt into the mold. Failure to do that can lead to an array of issues: · Warping may occur if the part experiences uneven shrinkage as a result of varying wall thickness. This usually presents as twists and bends in the part. · Sink marks tend to form on the thickest sections of uneven walls. These small crates occur due to the melt not being able to fully cool inside the mold. · Uneven wall thicknesses can cause varying flow rates, leading to the creation of flow lines. · If the melt is intended to flow from a thin section into a thick one, short shots may cause issues. A short shot happens when the melt cools prematurely in the thin section of the mold, which prevents the melt from flowing into the thicker section. · Uneven wall thicknesses create cooling challenges. The melt in the thicker areas of the part takes longer to cool than that in the thinner areas. The aforementioned short shot issues can occur because of this. However, inconsistent cooling times can create other visual defects and may lengthen the manufacturing process. The Best Practices for Selecting the Appropriate Wall Thickness It isn’t always possible to maintain uniform injection molding wall thickness for a part. But even in those cases, manufacturers have several best practices to follow that can account for variances and help them achieve as much uniformity as possible. Understand the Melt Material’s Wall Thickness Guidelines The material used for the melt plays a huge role in determining a part’s ideal wall thickness. Every material is different, with some having lower tolerances for thickness than others. The following is a useful at-a-glance guide for some of the most common melt materials: · ABS: 1.143 mm – 3.556 mm · Acetal: 0.762 mm – 3.048 mm · Acrylic: 0.635 mm – 12.7 mm · Liquid Crystal Polymer: 0.762 mm – 3.048 mm · Long-Fiber Reinforced Plastics: 1.905 mm – 27.94 mm · Nylon: 0.762 mm – 2.921 mm · Polycarbonate: 1.016 mm – 3.81 mm · Polyester: 0.635 mm – 3.175 mm · Polyethylene: 0.762 mm – 5.08 mm · Polyphenylene Sulfide: 0.508 mm – 4.572 mm · Polypropylene: 0.889 mm – 3.81 mm · Polystyrene: 0.889 mm – 3.81 mm · Polyurethane: 2.032 mm – 19.05 mm Staying within these recommendations ensures the manufacturer avoids cooling and flow rate issues. If Wall Thickness Varies, Make It Gradual Uniformity isn’t always possible, especially if some areas of a part are thicker than others. In these cases, manufacturers must manage the transition from thick to thin or vice-versa carefully. Changes in wall thickness should be gradual because sudden changes can cause cooling issues. The example of shifting straight from a thin wall to a thick wall applies, as this sudden change can lead to the previously mentioned short shots. Follow the Wall Uniformity Best Practices There are several general best practices that manufacturers use to achieve uniform wall thickness: · Regardless of variances, all walls should fall within the recommended thickness range for the material used. · Use ribs to strengthen tall walls. · Place radiuses on inside corners to strengthen them and alleviate the stress that causes warping. · Avoid sharp corners, long unsupported areas, and poorly designed bosses. · Keep draft consistent to avoid creating unnecessary internal stress. A good rule of thumb is to use one degree of draft for every inch of cavity depth. Use Coring or Gussets to Avoid Sink Marks and Shadowing Intelligent tweaks to a part’s geometry can alleviate the stress created by suboptimal wall thickness. For example, a manufacturer may use coring for parts shaped like dumbbells. This technique is similar to coring an apple, as it involves removing cross-sections of the material while keeping the sturdy core in place. Coring can help to prevent sink marks and reduces material wastage. Furthermore, using gussets reinforces long and thin walls, such as those required for box lids. This prevents shadowing, which happens if one area of the part cools faster than another. Understand the Material’s Key Properties The material’s recommended injection molding wall thickness isn’t the only material consideration a manufacturer must account for. They must also consider the attributes of the intended product when selecting the material to use. Key questions for these considerations include: · Can the material be painted or can the manufacturer add colorant to the melt before injection? · Does the part need a high ultraviolet light or chemical resistance? · Is the part intended to be subjected to extreme temperatures? · Should the part be able to flex when under a heavy load? · Will the part be used in an electromagnetic environment? Knowing the answers to these questions ensures the manufacturer selects an appropriate melt material. With the material selected, they can then adapt the part’s design to account for that material’s recommended wall thickness. Follow the Adjacent Wall Thickness Rule The adjacent wall thickness rule states that the thickness of one wall should be no less than 40-to-60% of any wall adjacent to it. Going below this percentage range creates thin sections of a part that may be subject to short shots. Furthermore, manufacturers must follow this rule while staying within the melt material’s recommended injection molding wall thickness guidelines. Avoid Wall-Related Problems here are many issues for a manufacturer to consider in injection molding. Wall thickness is among the most important because sudden variations in thickness can create visual and structural defects. Maintaining uniformity throughout is ideal. When that isn’t possible, the manufacturer must design for manufacturability by using the best practices in this article to account for wall thickness variations.

The injection molding process allows manufacturers to rapidly create parts. The process involves using a mold into which a melted material, called a melt, is poured. The design of that mold is critical to the part’s visual and structural integrity. Mistakes in the design of a mold can lead to an array of defects, including warping, sink marks, and flow lines. This article aims to help manufacturers avoid the poor mold design choices that lead to compromised parts by sharing some key injection mold design tips. Tip No. 1 – Maintain Uniform Wall Thickness for Molded Parts Managing the injection molded part’s wall thickness is key to quality design. A lack of uniformity in wall thickness can cause the melt to warp as it cools into a solid shape. This results in sink marks that have a negative visual impact on the part. Maintaining consistency in wall thickness helps to avoid the creation of sink marks. Of course, it’s not always possible to have the same wall thickness throughout the whole part. If a wall needs to be thicker, it should be no more than 15% thicker than the nominal wall used for the part. Additionally, wall thickness varies depending on the material used to make the part. The following are recommended wall thicknesses for the most common injection molding materials: · ABS: 1.143 mm – 3.556 mm · Acetal: 0.762 mm – 3.048 mm · Acrylic: 0.635 mm – 12.7 mm · Liquid Crystal Polymer: 0.762 mm – 3.048 mm · Long-Fiber Reinforced Plastics: 1.905 mm – 27.94 mm · Nylon: 0.762 mm – 2.921 mm · Polycarbonate: 1.016 mm – 3.81 mm · Polyester: 0.635 mm – 3.175 mm · Polyethylene: 0.762 mm – 5.08 mm · Polyphenylene Sulfide: 0.508 mm – 4.572 mm · Polypropylene: 0.889 mm – 3.81 mm · Polystyrene: 0.889 mm – 3.81 mm · Polyurethane: 2.032 mm – 19.05 mm Tip No. 2 – Follow the Guidelines for Avoiding Sink Marks Beyond maintaining consistent wall thickness, manufacturers can prevent sink marks by ensuring the proper placement of ribs, gates, and screw bosses. There are three guidelines to follow: · Avoid placing any ribs, gates, or screw bosses on the rear side of cosmetic surfaces; · Rib bases should be no more than 60% of the wall’s thickness; · A rib’s height should be no more than three times the wall’s thickness. Tip No. 3 – Save CAD Design Files in an Appropriate Format Injection mold design tips aren’t limited to the physical manufacturing of the mold. Even something as simple as the computer-aided design (CAD) file format a manufacturer uses when designing the mold can affect its quality. For example, let’s assume a manufacturer creates a CAD design and saves it in the .STL file format. While this may be fine for 3D-printed molds intended for temporary use, this file format has a problem. It reveals the mold’s surface as a series of triangles linked together to create polygonal shapes. As a result, this file format isn’t ideal if a mold or part has precise curves. This triangular representation can also cause issues when defining wall thickness. In this scenario, using a STEP file created by a CAD program like Inventor or SOLIDWORKS is the better option due to this file type’s increased precision. The point is that even a well-designed mold may be subject to unintentional flaws if an inappropriate file type is used for the design. Tip No. 4 – Try to Eliminate Undercuts The term undercut refers to any part feature that prevents straight ejection of a part at the mold’s parting line. Using undercuts in a mold increases its complexity, leading to a higher possibility of part defects. Ideally, the mold designer should eliminate the use of undercuts. However, that isn’t always possible, especially if the part requires a pick-out, side action, or sliding shutoff. In these cases, the manufacturer may be able to mitigate undercut-related issues by using pass-through cores or by adjusting the mold’s draft angles and parting line to facilitate easier ejection. Eliminating undercuts is also one of the most important injection mold design tips for manufacturers that wish to reduce costs. Using undercuts creates higher tooling costs because the mold requires more pieces. Tip No. 5 – Add Draft Angles for Injection Molded Parts Creating parts that have vertical walls can cause problems with injection molding. The part may get stuck as it contracts upon cooling. This leads to the manufacturer having to apply more force to eject the part, which can damage both the mold and the machine’s ejector pins. Using draft angles can solve this problem. Draft angles allow manufacturers to design the walls of a part with a slight slant, facilitating easier ejection in the process. Draft angles are usually added at the end of part design. Typically, the angle is two degrees for most parts. However, any walls with near-vertical requirements should have a 0.5-degree angle. Shutoff surfaces and faces with light textures need three-degree angles, while any face with a medium texture usually requires a draft angle of five degrees or more. Tip No. 6 – Arrange Polymer Flow from Thick to Thin Sections A manufacturer may need to design injection molded parts with thicker sections, which enhance the strength and structure of the part. In these cases, maintaining uniform wall thickness isn’t possible. The problem this creates is that the melt loses pressure and temperature as it flows through the mold. Improper design can lead to the melt flowing through a thin section and into a thick one, resulting in incomplete filling. One of the simplest injection mold design tips to overcome this problem is to position gates at the thicker sections of the part design. This ensures the melt fills the thick sections before flowing into the thin ones, creating a stronger part. Tip No. 7 – Don’t Forget About Ejection Applying inappropriate ejection force can damage the mold, part, and machinery used in the injection molding process. Manufacturers must balance ejection force over the part’s surface area, taking mass and thickness into account in the process. This prevents the part from breaking or warping during ejection. Furthermore, the manufacturer may have to account for the need to clear plastic from the gate in the event of a short shot. This issue can be remedied by placing stripper plates or extra ejector pins in the area surrounding the gate. Tip No. 8 – Attach Bosses to Side Walls and Ribs A boss is a cylindrical feature that is molded into a part. Its typical function is to receive a pin or screw. Manufacturers may use bosses for parts that come in a collection of parts that require assembly. Bosses shouldn’t be freestanding. It’s good practice to attach bosses to ribs or side walls, which ensures the part’s structural integrity. A freestanding boss could snap or break easily because it doesn’t have appropriate support. Design with Confidence With these injection mold design tips, manufacturers have some guidance on how to design a mold that produces reliable and high-quality parts. Details are critical when creating a mold. Even small design flaws can lead to visual defects and issues that affect a part’s structural integrity.