A Comprehensive Guide to Injection Mold Tooling
Table of Contents
Plastic parts can’t be of high quality even before the resin melts on the inside of the mold. The first thing to consider is the mold itself. In the world of manufacturing, the most important step to the whole process is called injection mold tooling. If there is any mistake during the process, there is no way to salvage the end product, even if the machine is high tech, the molding machine is advanced, or the polymer used is of great quality.
This guide explains all the important parts of the world of ‘Plastic Injection Moulding Tooling’ from picking the right metal, the complicated parts of the design, and the lead times. Product designers, engineers, and procurement managers can optimize and improve their manufacturing strategies and design better products that can be sold on the market to customers.
Choosing the Right Tooling Materials
The mold that you pick the resin for directly makes an impact on the tool. It affects how long the tool will last, how long the cycle will be, and the quality of the finished product. Not all molds are the same, and the ‘best’ depends on how high the production volume is, and what type of resin is used.
P20 Steel
P20 is the most versatile tool material. Because of his moderate pricing and reliability, he is preferred most by industries. It holds up well during long production runs averaging from 50,000 to 500,000 cycles. For general purpose tool steel, there is no greater substitute. Other than doing a decent polish, he works and machines well. Thus he is a great tool material for general purpose and consumable electronic enclosure goods
Stainless Steel
Stainless steel is ideal for molding parts designed for the medical and food industries as well as for corrosive resins like PVC. Example grades of stainless that offer corrossion resistance are 420 stainless that rusts or has resistant degrading steel. Polishing stainless steel is doable to a great mirror, finish, thusimplifying aesthetic high gloss parts.
S7 and Harder Steels
In tool steels, S7 and H13 are the std in high volume production runs, thus bringing in high durability as well. These must be heat treated to extreme hardness as well, allowing to withstand wear and the relentless tear of millions of cycles. The particulates of glass fillers brought a high abrasion resistance to it. High upfront wear and machining are self evident. And thus high costs are to be endured to attain long term low maintenance and investment longevity.
Aluminum
Aluminum is a great material that is definitely worth your consideration. It has a wide variety of applications that can benefit from its qualities. For instance, it is much easier and faster to machine than steel since it is significantly softer. This is why aluminum is the material of choice for production runs of low volumes and for production runs that require a prototype. In addition, aluminum can speed up production cycles because it cools down faster. One thing to consider though, is that it is not good for use in high volume applications involving abrasive materials because of the fact that aluminum wears down much faster than steel.
Essential Tooling Design Considerations
Even the best steel will not create a good end product if the engineering is bad. Ineffective designing s the cause of many expensive mistakes in production and can hinder the functionality of the injection molding tool for the plastic.
Draft Angles
Lack of sufficient draft is one of the things that gets people in the design stage in the most trouble. Draft is a design feature that involves the addition of a slight taping to the vertical walls of the part. This is done so that the part will slip out of the mold without friction that can cause scratches or dragging. In the absence of sufficient draft, parts can get stuck in the mold and poor the tool, in some cases causing damage in the form of ejection pin marks.
Wall Thickness Uniformity
As a part cools it shrinks. If a part has different wall thickness, the thinner parts cool first. This uneven cooling causes internal stress. This can cause warping or create sink marks which are depressions formed on the top layer of the part. Keeping the wall thickness even throughout the design helps with even cooling and the all around toughness of the part.
Gate Placement
The gate is where the molten plastic firsts fills the mold part. Its location can affect the part’s overall design attractiveness and strength. If done poorly, the mold can have weld lines and/orjetting. Engineers have to look at the flow path of the part to help spot the best location for the gate.
Navigating Mold Build and Lead Times
Understanding the timeline for creating a plastic injection molding tool is crucial for project planning. The process generally moves from design approval to machining, assembly, and finally to the first test shot (often referred to as T1).
Factors Influencing Lead Time
There is a multitude of reasons dictating the time a mold takes to build:
- An easily open and closed mold is much more rapidly constructed than one that has complex mechanisms, such as side slides or lifters, to remove undercuts.
- Material Availability. Standard P-20 steel is usually readily at hand, though specialty alloys may take longer to procure.
- Surface textures such as leather grain involve a more time-consuming chemical etching process, which adds to the time on the schedule.
Soft Tooling vs. Hard Tooling
This distinction often determines the schedule. “Soft tooling” usually refers to aluminum or pre-hardened steel molds used for prototypes or bridge production. These can often be ready in 2 to 4 weeks. “Hard tooling,” involving heat-treated steel for high-volume production, is a longer process involving precision machining and heat treatment, typically taking 8 to 12 weeks or more depending on complexity.
Cost Drivers in Tooling
Budgeting for injection molding tool options for plastic parts requires an understanding of what drives cost.
- Cavitation: A single-cavity mold (making one part per cycle) is cheaper to build than a multi-cavity mold (making 4, 8, or 16 parts per cycle). However, multi-cavity molds reduce the unit price of the final part.
- Part Complexity: Features like internal threads, undercuts, or insert molding require complex mechanisms within the tool, increasing both design and machining costs.
- Surface Finish: A standard machined finish is cost-effective. High-polish finishes require manual labor, which drives up the price.
Conclusion
Investing time and resources in the plastic injection moulding tooling phase almost always leads to better long-term results, lower unit costs, and a superior final product.
Ready to optimize your manufacturing process? Contact our engineering team today for a consultation on your next project or to request a quote.
Frequently Asked Questions (FAQ)
Q: What is the life expectancy of a mold used in plastic injection?
A: This all depends on what kind of mold is used. An aluminum mold is likely to complete anywhere from 5,000 cycles to 10,000 cycles. If a Class 101 hardcore steel mold is used, that is likely to last more than 1 million cycles.
Q: Once a mold is created, can it be changed?
A: Yes, it is. But removing metal is a more simple task than adding metal. When a mold is designed with the intention of being able to easily adjust the dimensions by removing metal, it is termed to be \”Steel Safe\”. Adding metal in the form of welding is possible, but is a more expensive task. In addition to that, the integrity of the mold could be changed.
Q: What differentiates a production tool from a prototype tool?
A: In an ideal world, a prototype tool is supposedly designed for speed, low costs, and efficiency. In contrast, a production tool is supposed to be designed for excellence, efficiency in speed and low costs, and of course, a long life span on the tool.
