Material selection is one of the most crucial factors when developing an injection mold design. There are a lot of excellent material suppliers offering quality materials for the injection molding process. Many also offer different grades or blends of materials to choose from. However, one wrong decision can have major effects on the production process and the final product.
Material Selection for Injection Molding
Generally, material selection is dependent on the use of the part being manufactured or fabricated. Although almost every part is unique, there are certain, consistent aspects that you should consider while choosing injection-molding materials. These considerations can help you save both cost and potential headaches for your project.
Some of the most important considerations are as follows:
Raw Material Quantities – Order The Right Amount Try to order enough material at one time. No one wants to be left with surplus raw material, but you also don’t want to be short or run out in the middle of a production run.
Choose The Right Material It may seem like an obvious statement, but different types and grades of plastics and polymers have different uses and properties. Be sure that the material you have selected is appropriate and compatible for the use of the end product. The plastic requirements for a medical part may be significantly different than that of a sub assembly component for an automotive application. Considerations like temperature, biological and chemical interactions, food or animal contact and more must be considered.
Minimize Secondary Processes Minimizing secondary processes like custom inserts, trimming and even pad printing, can help reduce the overall cost of a project. All these processes entail additional costs and setup time. And in many cases can be eliminated based on the end us of the product, or in the initial design of the mold. In some cases, changes in the material used or even the use of different mold release (like Nanoplas’ Nano Mold Coating) can help reduce or eliminate the need for some secondary processes or a tooling modification.
Mold Design This is truly an art and science in and of itself. The design of your mold can have significant impact on the materials that can be used, the secondary processes that will be required and the final appearance of the part, to name just a few.
Material selection is complex process. It’s important to select materials that meet the specifications and the end use while also taking into account cost, design and service conditions. It is also imperative to follow the material manufacturers’ data sheets and performance matrix.
One aspect of material selection that is often overlooked is how the mold maintenance and mold release products that are used can impact the materials selected. The ability to mold through a rust preventative or grease without bleeding or the ability to use an existing tool without modification because of a new mold release technology can save time, cost and hassle.
To learn more about how the integrated family of Nanoplas products can help reduce scrap, increase production efficiencies and save time for your injection molding operation, contact us today!
Time is money in the production business and the more you waste, the more you lose. The Single-Minute-Exchange of Die (SMED) methodology may allow you to successfully implement a lean production process in your injection molding business, and when combined with a progressive mold maintenance program, allow you to reduce the time needed for changeovers.
Why Lean?
Lean manufacturing aims to eliminate unnecessary waste during production, and uncovering ways that will add value by eliminating or decreasing other processes or variables than can adversely effect production.
With the rising cost of transportation and raw materials, it has become increasingly important for injection molders to produce a wide variety of products. With that product expansion, the need for efficiencies and cost reductions has generated a lot of interest in the lean method.
Potential Problems in High Variety Production
Lengthy and difficult set up procedures.
Expensive, high-tech machines are required to increase production capacity and flexibility.
Waste arises out difficult changeovers, lack of adequate maintenance or equipment not being ready when needed.
SMED (Single-Minute-Exchange of Die and Maintenance
Globalization and Just-In-Time models have increased the need for production of smaller lots on a more frequent basis. This shift in format requires accelerated set-ups to maintain flexibility, to meet customer demands, and to remain competitive.
SMED allows you to make the necessary reductions in changeover time to achieve a just-in-time pace. The practices under this system achieve machine changeover in less than 10 minutes (single digit minutes) thus reducing the time during which production is down. The SMED approach does not only just reduce changeover times but also the overall labor involved.
The goals of SMED are:
Reduction in inventory
Reduced changeover time
More efficient changeover process
Flexibility for reduced batch/lot size
Improve flexibility in equipment usage
Reduce impact and downtime on equipment
Meet customer demand
SMED Process
SMED involves certain steps, with a basic overview as follow:
Elimination of Non-Essentials: Observe and record the areas where change outs are required, then eliminate all non-essential activities where possible, especially duplication. By eliminating non-essential activities it is possible to speed things up and reduce waste.
External Set-up: Get all the materials and supplies to be used in place so that they are available when required. Some things to consider for this include: color code all items needed, create checklists and develop and maintain uniform standards and procedures
Internal Set-up: Replace complex tools where possible with more simple equipment to prevent unnecessary waste. Use functional jigs and fixtures, levered or one-turn fasteners, preset guides, pins and notches. Remember the goal is to work efficiently but still but also effectively.
Measure: The SMED approach entails change, but to know if you’re on the right track it is vital to measure business performance every time. It is a successful way of knowing if improvements are being made or not. Based on the results obtained, corrective or proactive measures can be taken. Consider the time lost/wasted as the benchmarks you will need to improve upon.
Benefits of Equipment Maintenance
The SMED system also requires proper maintenance of tools and equipment. When equipment is well looked after, it is more reliable. It will result in production efficiencies and lower costs due to fewer breakdowns and equipment downtimes. Also, with an effective maintenance program, equipment required will be available as and when necessary reducing wasted time and high costs due to idle equipment and staff.
It is also imperative that molds are stored properly to ensure optimal performance and longevity. Instead of leaving it on the floor or on pallets where it can sustain damage, it is best to store molds in a designated storage area or if possible on shelving or racks. Furthermore, it is best to use rust preventatives and grease that require little or no pre-production cleaning for start-up.
Many companies treat mold maintenance as an after thought, and have yet to explore how new products (like the Nanoplas line of mold maintenance products) can have a significant impact on their set-up and speed to press times. These gains in production efficiencies when combined with an approach like SMED can have a real impact on the bottom line.
To learn more about how the integrated family of Nanoplas products can help reduce scrap, increase production efficiencies and save time for your injection molding operation, contact us today!
This is the final installment in a series on flash free molding. [Read Part 1 and Part 2.] In this article, we will get into issues with tool design with shut-offs, parting line maintenance, and where the machine can contribute to flash. First, I would like to briefly go over how to define flash. Flash at times can be difficult to eliminate, and many will give up and accept this defect. Flash also can be miss-diagnosed at times with miss-matched parting lines or feather flash. I have seen miss-match called flash many times, but if it is flash you can see or feel it from both sides, miss-match will only be seen or felt from one side. (more…)
I hope you found the first article on flash free molding interesting. [Read Flash Free Molding Part 1.] I covered cavity pressure versus clamp pressure and will talk tool deflection in this article. Tool design and construction can be a contributor to flash issues. But, if you read the first article and the three conditions are met, flash is not possible. An inadequate tool design can contribute to flash by allowing deflection in line with clamp force and perpendicular to clamp force. Also, on the construction side, improper spotting, timing of components, and fitting of components can be contributors to flash. (more…)
Why should you choose a hot-runner mold system over a cold-runner mold system (or vice versa)? Each type of molding system has unique features that help determine exactly which one is best for you.
Cold-Runner Mold Systems
Called a cold-runner mold system because the runners are the same temperature as the molds, there are two types of cold-runner systems: a three-plate system and a two-plate system.
Three-plate systems allow the part to be ejected from the runner without an ejection system, but are a little more complicated than a two-plate system, which does require an ejection system to remove the part and the runner from the mold. Two-plate systems can handle most molds, however a three-plate system is friendlier when it comes to complex designs.
In a cold-runner mold system, the runner has to be larger than the part. Otherwise, you run the risk of underfilling the mold. One big advantage over a hot-runner system is the ability to use more types of polymers without concern for heat sensitivity.
Cold runners are less expensive than hot runners and are easily maintained as well, but they can create waste unless you can recycle or melt down the extra material.
There are two types of hot-runner mold systems, both of which use two plates heated by a manifold system. Externally heated molds allow you to use more heat-sensitive polymers while internally heated molds generate better flow control. Depending on your materials and applications, you may prefer (or need) one type over the other.
Hot runners are more expensive than cold runners (in initial investment and maintenance), but they can handle higher volumes and larger parts and also don’t generate any waste. In some cases, the lack of waste balances with the higher maintenance cost to actually be about the same net cost as a cold-runner system.
Overall, hot-runner molds produce parts with more consistent quality and do so with faster cycle times, but it’s not as easy to change colors nor can hot runners accommodate some heat-sensitive polymers.
Pros and Cons of Hot Runner System
Pros
Fast cycle time
Consistent quality
Very little waste
Ideal for larger parts and higher volumes
Cons
Expensive to purchase and maintain
Not ideal for some heat-sensitive polymers
Difficult to make color changes
Which System is Right for You?
Depending on exactly what you’re doing with your molds—materials, applications, size, volume, etc.—you may have a clear answer as to the best mold system or it may be more complicated. For instance, if you’re only working with heat-sensitive polymers, a cold-runner mold system is probably your best choice. If you’re producing large volumes and need faster cycle times, you’re probably looking for a hot-runner mold system.
However, those aren’t definite answers and shouldn’t be taken as such. You need to consider every facet of what you’re doing to determine the best system for you. Feel free to contact us if you’d like to talk about which type of mold system is your best option.
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