News

What started out as a routine request from one Plastics Technology columnist to another to review a draft for an upcoming article led to five highly experienced industry professionals collaborating to create this article about something virtually every molder does every day-sometimes many times a day-mounting a mold in a press. A well-trained and knowledgeable setup person understands the importance-and dangers-associated with the job. They have a heightened respect for their safety, as well as the safety of others, and for the molds, machines, and equipment they work with. They are an extremely valuable asset to every molding company. Before digging in, take note: No single procedure is correct for all applications. This procedure most likely will need to be modified to suit your special/unique situation or conditions. Also note that for safety reasons, the general procedure outlined here requires the pump to be turned on and off repeatedly. This and all other applicable safety requirements must be observed. WITH THE PUMP MOTOR OFF: 1. Check that the mold will cover at least 70% of the distance between the tiebars. a. This is a good rule of thumb. Most machine manuals will specify the minimum mold size for a given machine. Some machines even have placards mounted on the frame. b. The smaller the mold, the more the platens will [wrap around" or bow when clamped under high pressure. This can cause flash in the center of the mold. c. If the mold is excessively small, catastrophic damage to the platen can occur. 2. Ensure the safety strap is in the correct position and in good condition. 3. Check that the mold`s eye bolt is secure. a. Only use shouldered eyebolts, or preferably, swivel-type hoist rings. b. Eyebolts must be threaded all the way in and tightened. c. Two eyebolts are safer than one and can help prevent the mold from tilting. d. Ideally, the location of the eyebolt is at the mold`s center of gravity, so it does not tilt. 4. Check the size and condition of the nozzle seat. It will be difficult to check after the mold is installed. a. Write down or find an appropriate nozzle tip type and size before you forget. 5. Ensure the carriage is back and/or the screw is forward. a. Be alert for resin drool or spitting. b. The barrel heats may be on or off, depending on the situation. 6. Check that the resin is not degrading in the barrel from sitting there too long. a. Many materials, such as PVC or POM (acetal), produce gases that can develop high pressures within the barrel. 7. Clean the machine platens and the mold`s clamp-plate faces. a. Check for [dings" or raised areas on the mold and platen-especially the locating-ring alignment hole. Stone flush if necessary. 8. Check for damage to the clamp bolt threads in the platens. 9. Spray a light mist of [overnight" preservative or WD-40 on the platens and the clamp-plate faces of the mold. 10. Check that the clamp bolts have the correct thread type: English (SAE) versus Metric. 11. Check that the clamp bolts are the correct length. a. If the bolts are too short, with insufficient engagement, or too long and [bottom out," you can strip the threads in the platen. 12. Lubricate the clamp bolts. a. If the bolts are not lubricated, 85% of the torque is used to overcome friction and only 15% is available to produce bolt load. If the bolts are lubricated (with cadmium plate, molybdenum disulfide, anti-seize compounds, etc.), the friction is reduced and greater preload is produced with the same torque. 13. Check that the crane can adequately lift the mold over the machine`s tiebars. a. Check for obstructions above the machine, such as sprinkler heads, ceiling fans, etc. b. Check that the robot, picker, or other automation is safely out of the way. 14. Lift the mold up over the tiebars and lower it into the molding area. a. Keep your fingers away from the chain links. b. Make sure no one is in the immediate area during this process. Use safety cones, barrier tape, or other preventive measures. 15. With your hand on the side or top edge of the mold, guide it into the machine and engage the locating ring into the alignment hole in the fixed platen. a. Do not let the edges or corners of the mold hit the platens or tiebars. IN SETUP MODE: 16. This is a good time to check the machine`s safety switches. 17. Advance the moving platen until it just touches the back of the mold. a. You can make sure the locating ring remains engaged in the platen alignment hole by occasionally looking at it from the barrel side. WITH THE PUMP MOTOR OFF: 18. Open the gate and level the mold. 19. Attach the clamps on the fixed-platen side to prevent the mold from rotating or the locating ring from disengaging from the alignment hole, but do not yet fully tighten the bolts to the specified torque value. a. Grade 8 bolts should engage the relatively soft die-cast platens by a minimum of 1.5 times their diameter to prevent stripping he threads. Two times their diameter is preferred (see Table 1). b. Ideally, the mold clamp should be square with the mold and the toe of the clamp be fully engaged in the slot. c. The clamp bolt should be as close to the mold as possible. You want the pressure of the bolt acting on the toe-not the heel (see Fig. 1). d. If the bolt is closer to the heel end than the toe end, switch to a longer clamp. e. It is acceptable for the clamp to be parallel with the platen, but it is preferred that the heel end of the clamp be slightly farther from the platen than the toe end. This puts the front edge of the toe in contact with the face of the clamp slot (Fig. 2). Failure to do either of these two steps may result in the mold dropping out of the machine. f. Forged, closed-toe clamps with [no-turn" washers are preferred. 20. Use only hardened-steel washers designed to distribute the load on the clamp. Soft [hardware-store" washers will deform and come loose. IN SET-UP MODE: 21. Retract the moving platen enough to install the ejector bars-typically 8 to 12 in. WITH THE PUMP MOTOR OFF: 22. Put ejector bars in the holes matching the pattern on the mold. a. Make sure ejector bars are the correct length, the same length, that they are straight, and the threads are in good condition. b. If the mold is equipped with knockout extensions, the ejector bars should be flush or slightly recessed from the face of the moving platen when the machine ejector (aka butterfly) plate is fully retracted. IN SET-UP MODE: 23. Advance the moving platen until it is 4 to 6 in. away from the back of the mold. WITH THE PUMP MOTOR OFF: 24. Slide the knockout bars forward and thread them into the back of the mold. 25. Tighten the knockout bars with a pipe wrench or other suitable tool. IN SET-UP MODE: 26. Advance the moving platen up against the back of the mold. a. Look and listen for the knockout rods binding or bending. 27. Lower the chain hoist slightly to remove any tension. 28. Set the die height to the pre-established clamp pressure. a. If the clamp pressure has not been established yet, use a high pressure value for large molds or large parts, and a medium pressure value for small molds or small parts. WITH THE PUMP MOTOR OFF: 29. Attach the clamps on the moving-platen side (see steps 19 a-e) 30. Torque the clamp bolts on both the fixed and moving platens to the appropriate value (see Table 2). a. [Click-type" torque wrenches help ensure all of the clamps have the same amount of torque. If all the clamps are not torqued evenly, the one(s) with the lower torque value may come lose. 31. Remove the safety strap(s) and eyebolt(s). 32. Move the hoist out of the molding area. IN SET-UP MODE: 33. Open the mold and advance the ejector plate, if needed, to gain access to the back of the knockout rods. WITH THE PUMP MOTOR OFF: 34. Install the hex nuts or socket-head cap screws on the end of the knockout rods with a ratcheting socket wrench or other suitable tool until they are tight. IN SET-UP MODE: 35. Stroke the ejectors forward and backward a few times to make sure they function properly and nothing is binding or squealing. 36. Wipe off any dirt or grease you may have deposited on the machine and clear the area of your tools and equipment. If you want to maintain a clean work environment, lead by example. The above procedure ensures that the mold is securely fastened to the platens and will not shift or loosen during production. But there is one final step to consider, which will help prevent premature tool wear and rejected parts. On occasion you might hear the leader pins hit the bushings when you slowly close the mold. This is not uncommon when hanging a mold that doesn`t have a lifting strap or interlocks that help vertically align the two mold halves. To correct the problem, the mold half attached to the moving platen should be [re-hung" with a slight amount of lift or pre-load from the hoist. This usually helps, but does not solve the root cause, which is platen tilt. Platen tilt will be the subject of a future article.

Sink marks. Weld lines. Splay. Blush. Scuff marks. Everyone involved with developing molded components should know this list very well (and it`s a really long list). The unavoidable truth is that cosmetic factors significantly affect the perceived quality of a plastic part, whether they influence its functionality or not. Many molded parts only serve an aesthetic purpose, making cosmetic defects an even bigger issue. In both cases, the fundamental challenge is that the prevalence and severity of cosmetic defects are difficult to assess using intuition and experience alone. That`s where computer-aided simulation technology comes in. Injection molders are generally familiar with use of such software to predict and optimize mold filling and cooling. But its role in anticipating, troubleshooting, and resolving or-better yet-preventing surface defects is less familiar. In this article, we will show how a combination of good design practices and simulation technology, like Autodesk Moldflow, can help engineers deal with cosmetic defects more effectively. CLARIFYING THE CHALLENGES One of the reasons why surface finish is so problematic is simply the number of decisions involved. The matrix of choices with respect to part geometry, materials, processes, mold design, and mold textures-and how the consequences of each choice affect other decisions-makes cosmetic defects difficult to visualize until you see the molded part. Depending on your role, you may not always have control over these decisions. For example, you may find that the most straightforward way to solve a cosmetic issue would be using a different material color, mold texture, or process type, but that choice may not be available given brand constraints, the project`s budget, or the schedule. A third challenge is the nature of cosmetic defects. They are primarily visual phenomena that are hard to quantify and difficult to simulate. Surface textures and colors are not easy to characterize with data in the same way as mold-filling conditions (such as flow-front temperature, shear, or velocity). Defects may be minimized or exaggerated depending on the lighting intensity, direction, source spectrum, viewing time, angle, and distance. For example, an off-white color will mask defects better than gray or (even worse) black. Specific surface finishes can amplify or reduce the visibility of surface defects. The nature of a defect, such as sink-mark depth or width, may also increase the odds of visual detection. The color of objects around the part influence this effect as well. As a result, even the most sophisticated simulations may not be able to fully represent the end user`s visual experience. The good news is that we`re making progress. Some recent trends are pushing the envelope of visualization: Exporting warped geometry as a CAD file (.sat or .step) for easier comparison with the original model; Exporting sink-depth predictions from simulation tools to visualization tools (VRED or 3Ds Max); High-quality rendering to more closely match reality in terms of color, texture, and lighting (see Fig. 1). Meanwhile, manufacturers are moving ahead with new techniques to combat cosmetic defects, including more sophisticated thermal control of the mold, 3D texturing technologies, liquid silicone rubber (LSR) injection molding, and component integration-such as multi-shot techniques. Nevertheless, engineers will always need reliable ways to identify and manage the risk of cosmetic issues. This, again, is where simulation comes in. FOUR KEY VARIABLES To overcome the challenges posed by cosmetic defects, engineers have four primary variables to explore. Depending on the scenario, simulation can help engineers consider ways to mitigate risks in the design phase or accelerate the troubleshooting process if defects show up in a prototype. 1. Process type: Anytime you have the ability to explore processes, it will change your approach to evaluating aesthetics. For Example, gating thick to thin is a trusted, conventional approach. But gating into a large, thick area can cause jetting, depending on the type of gate (direct drop, tunnel, tab, or lap style). Manufacturing the same part with gas assist, coining or two-shot technologies could eliminate this source of surface blemishes. Another way to do this is to replace the pack-and-hold phase with microcellular foam growth, in which case it is ideal to gate into thin areas to control and contain bubble excitation. Of course, engineers could also vary the mold temperature to create a very resin-rich surface that improves finish quality. An example of this would be the use of rapid heating and cooling or induction heating (Fig. 2). Many of these process choices can be simulated, creating opportunities to see which one is most appropriate for ensuring the desired level of surface finish quality. 2. Material choice: Not all materials are created equally with respect to cosmetics. Simulation allows you to explore how material choices affect process- ability and surface defects. Understanding the properties of different materials can provide a plastic engineer with clues about how to design gates to avoid a defect like gate blush, for instance. Fillers, such as fibers or metal flakes, can also have a significant impact on the product`s appearance, and simulation can be used to get a handle on this. Another area where simulation can be advantageous is in the study of weld lines. It is common for plastics engineers to examine the angle of the melt front as well as the temperature and pressure to identify regions where melt fronts are separated by an obstacle (the part`s geometry or multi-gates) and then recombine. These dynamics affect both the strength of the part and its cosmetics. With simulation, you can try the options available to you and let the software iterate to help you choose the best material, gate location(s), and geometry sooner. 3. Part geometry: Simulation excels at the classic DFM (design for manufacturing) approach, giving engineers a reliable way to examine the impact of thickness variation, such as rib-to- surface ratios, thick-to-thin ratios, and flow phenomena. A quick check of drafts and undercuts can also be useful when evaluating mold cost, manufacturability, texture depths, and the potential for ejection distortion (such as scuff marks). Flow quality and thickness go hand in hand. The cardinal rule for balanced fill is uniformity-whether of melt pressure, temperature, velocity, or volume/ thickness-which is important for cosmetics too. Flow hesitation effects are often visible and are very thickness dependent. Injection molding simulation can quickly help identify problems using contour plots to identify flow-related defects, as well as using flow-front velocity, shear stress at the wall, temperature at the flow front, and other parameters calculated by the software. Simulation software can also ensure that a mold fills easily and uniformly without significant temperature variations, and also help you predict jetting effects, weld-line positions, and air traps. 4. Mold design: Mold design is an extensive area to explore, in particular gate design and blush. Gate area and thickness transitions matter a great deal for cosmetics, and shear rate is a key result to focus on. Simulation offers a proven way to see whether, for example, changing a circular gate to a more rectangular shape can reduce shear rates. Simulation also makes it easy to find the best gate locations and flow rate, then size the gates to minimize the shear rate (Fig. 3). In addition, simulation can help engineers look at new ways to avoid surface defects, such as rapid heating and cooling (aka [variotherm" molding). Simulations can show a transient or dynamic thermal analysis of the mold and the interface of the plastic and tool steel. Induction heating is another approach that can be modeled to optimize temperature distribution without affecting cycle time. Another choice engineers have to make is the type of runner system and gate (cold gate, hot tip, or valve gate). Simulation can capture the mechanics of opening and closing, such as the valve-pin opening speed, as well as create a detailed flow- front profile. This profile identifies potential hesitations that may change flow-front speed and the material melt properties, which have a significant effect on the imprint of the texture and surface finish. A CASE STUDY A quick case study of an actual part can illustrate how all of this complexity comes together to affect the part`s cosmetic quality-and how simulation can help find a solution. In this case, the part was a TP elastomer molded with a two-shot process. It was cosmetically challenging due to the dispersion of the colorant. However, initial runs were perfect. Then the program changed both the material and the colorant, creating a defect in the bottom of the part (Fig. 4). Overlaying various analyses-including pathlines, flow-front progression, and single contour-within the simulation software helped engineers visualize the flow velocity and identify the hesitation near the rim that was causing the flow-front speed to vary and resulted in a visual defect (Fig. 5). This example highlights how the decisions we make as engineers can have unpredictable effects on surface quality. In this case, the hesitation was present in both situations. But one material masked it, while the other material exaggerated it. The part volume in this case was very small, which made it hard to control the molding process. Some process changes did alleviate the defect to a degree, but the underlying cause of the hesitation was part geometry-specifically a thickness variation that resulted in the hesitation and the ensuing racetrack effect. Once the root cause of an issue was identified, it quickly became apparent what to do next. All plastics engineers face similar challenges when it comes to optimizing surface-finish quality, but there is a huge array of options available to resolve problems before they become too expensive to fix. However, the resulting tradeoffs are not always easy to quantify. Judging what is acceptable is often subjective and application-dependent. The underlying causes of surface-finish defects, however, are not subjective. Simulation provides a wide range of analytic tools engineers can use to examine them and understand how choices in process, material, geometry, and mold design might change the look of the final product. Simulation technology, such as Autodesk Moldflow, can provide insight quickly, enabling engineers to consider more options within a tight schedule and reach a satisfactory answer sooner.

Used in all types of industries, plastics provide versatility and strength across a wide range of applications, from automotive body parts to human body parts. Each application requires a special manufacturing process that can mold the part based on specifications. Both thermoforming and injection molding - two of the most popular manufacturing processes for crafting plastic parts - offer unique advantages depending on the particular application. While thermoforming is commonly used for large-scale designs and shorter production runs, injection molding tends to be a better choice for small, intricate parts and large production runs. What Is Thermoforming? Thermoforming is the process of forming a heated plastic sheet to the surface of either a male or female mold. This is a single-sided plastic fabrication process, unlike injection molding; only one side of the plastic sheet is controlled by the mold or tool. Vacuum forming and pressure forming are both popular styles of thermoforming. Depending on a project`s needs, thermoforming can offer several distinct advantages, including: Lower tooling costs compared to injection molding Quick product development and prototyping Bright color and texture options Extreme adaptability and simple adjustments Thermoforming is ideal for smaller production quantities (250 to 3000 parts per year). What Is Injection Molding? Injection molding requires a great deal of upfront engineering to develop detailed tooling or molds. Crafted from stainless steel or aluminum, split-die molds are injected with molten liquid polymers at high temperatures under extreme pressure. The molds are then cooled to release complete plastic parts. Plastic injection molding offers several distinct advantages of its own, including: Detailed, highly engineered tooling with multi-cavity mold options Precise, efficient processing for large volumes of small parts Effective reduction of piece count Efficient material use and low scrap rates Plastic injection molding is ideal for large-volume orders and mass production in projects requiring thousands or even millions of the same part.

Cutting costs while retaining high quality standards has never been more important in manufacturing. Competition is fierce in these difficult economic times, with increasing labour, overhead, and materials costs that make beating the competition difficult. Working in partnership with an injection mold manufacturer can help you cut costs while ensuring product quality and consistency. When each piece must be exactly the same, you cannot afford mistakes or outdated methods. Injection mold manufacturers can provide high quality components at a low cost, which can increase a company's profit margin significantly. Injection Mold Manufacturers Provide Affordable Flexibility Molded plastic has become a highly versatile, durable, and surprisingly strong material, ideally suited to many different types of manufacturing applications, including automotive, electronic, medical, and consumer products. The flexibility of molded plastic makes it a new option for many manufacturers that have, until recently, stayed with more traditional and costly methods and materials. Today, there are thousands of different polymers to choose from, making it easy to select just the right material for your application. A die is engineered to your specifications, and production begins from there. The flexibility provided by reputable injection mold manufacturers ensures that each piece is identical, durable, and resilient to wear, while costing far less than other materials and manufacturing processes. Professional Design Saves Money When considering different component suppliers, it is important to evaluate the design, production, and delivery services that each company offers. Working with a talented engineer can cut the time it takes to design the initial die and that means savings. Professional engineers are able to recognize potential design problems before they go into production. If a product is comprised of several interactive pieces, an expert engineer can help create the best design for high product quality and durability. Find Logistical Leaders Engineering the right components with the best materials does no good if the products do not arrive on time. A reputable supplier must be able to provide seamless logistical support and short delivery times. These efficiencies cut costs and increase profits. Your injection mold manufacturer should be able to provide door-to-door delivery, handle all types of shipments both international and domestic, and keep delivery times as short as possible. After all, time is money. Seek Out Options There is no reason not to take advantage of this possibility for your automotive, medical, electronic or consumer product needs. Cutting-edge technologies can make a huge difference in reducing manufacturing costs. By learning more about the wide variety of applications molded plastic can be used for, companies can reduce unit costs substantially. There are YouTube videos, informative articles, and industry journals that can describe in more detail how working in partnership with injection mold manufacturers can boost company profits by reducing costs while improving product quality. The low cost of fabricating these components, high speed of production, and reliable, fast delivery make it worthwhile to search out and learn more about injection mold manufacturers and how they can boost your company's profits.

If your company has particular components that it uses within its own finished products, it has probably relied on the services of a contract custom injection mold manufacturer to provide specific plastic parts or modules. In some cases, these arrangements are lucrative for the manufacturer while providing your business with precision engineered components that meet your high standards. Sometimes, however, you have to terminate the contract because the fabrication company proves to be unreliable. Late deliveries, missed deadlines, sub-par quality or even unfortunate problems at the plant can all leave your own company in the lurch if the manufacturer can't or won't make good on its promises. If you have to shop around for a new custom injection mold manufacturer, there are five characteristics you should look for: 1. In-House Engineers While you probably have your own engineers, it's always best to work with a contract manufacturing company that has their own in-house engineers who can work with you to develop or improve a prototype for each component you need. These experts can suggest alternative methods of fabrication and offer design assistance so that you end up with a high quality product every time. They are also invaluable as trouble-shooters in the event there is a problem during manufacture, minimizing down time and ensuring your production run won't be delayed any longer than absolutely necessary. 2. A Variety of Manufacturing Techniques, Including Custom Injection Mold Perhaps your company needs an injection molded component for your current project, but can the same manufacturer that's currently providing those parts also produce the thermoset plastics or structural foam parts you'll need next year? While you could work with five different suppliers under five different contracts, it's simpler and more cost effective to get as many plastic components made by the same company as possible. 3. Round The Clock Manufacturing Capability In a perfect world, you will never need a rush job or require additional shifts to meet product demand, but this isn't a perfect world. Your custom injection mold contractor should be able to routinely run three full shifts in the event that you need a rush job or have an unanticipated number of orders to fill. If your current manufacture runs only one shift, what will they be able to do for you when you need more components in less time? 4. Stellar Customer Service Thermoplastics fabrication isn't an industry known for its exceptional customer service support, but that doesn't mean you have to put up with unanswered phone calls, lost messages or any other inconveniences that can slow down production and create problems through misunderstandings. Before you sign a contract with your new custom injection mold supplier, contact their customer service department. Did they answer the phone in a timely manner? Were they able to answer your questions or direct you to the right person to get an answer? Were they personable and pleasant?. 5. Multiple Facilities No one wants to think about what they would happen if their custom injection mold supplier had an industrial accident, a fire or any other problem that would require shutting down the facility, but it can happen. The impact on your own production can be profound and costly. If the fabricating company has another facility, however, they can continue to supply you with the components you need by using a secondary facility and adding additional shifts. If you find a custom injection mold fabricating company that meets all of the criteria above, your company will discover that their plastic component needs will always be met with best practices and excellent support in place.