Hundreds of designers work on injection molded components, but only a tiny percentage of them are capable of designing parts for injection molders. Before all of the pieces are recorded and sent to a molder for manufacturing, an injection molded product goes through multiple stages of development.
This is an essential phase in the development process since design adjustments or corrections can no longer be made without drastically increasing project costs or delays. Unfortunately, flaws of Plastic injection mold makers will only be discovered after the project team has examined and assessed the initial article parts.
Factors you need to consider while choosing a plastic injection molding
You should always create tight cooperation with your desired molder as early in the design process as feasible, regardless of how well you believe you know how to design components for injection molding correctly. Any of the following critical design-related aspects impacting an injection-molded item may be influenced by these subjective preferences:
- Material choices and their implications
Materials are often defined early in the design process, and both parties should agree on them. Molders may be able to get vast amounts of certain resins at a significant discount. Customers may benefit from these offers. Many tens of thousands of dollars may be saved if a designer can choose an ABS grade that matches the qualities of one bought in significant quantities by a molder.
On the other hand, many high-performance resins may not be optimal for molders because of their viscosity, high glass content, or crystallinity. A resin may be selected for specific physical or chemical resistance qualities, but it may be difficult to mold or keep to precise limits. Molders, who will be responsible for molding the parts, should agree with the given resins and overall component specifications.
- Critical tolerances
One of the most challenging tasks for any designer working on an injection molded product is to provide adequate room in the design for tolerance variance. Many factors influence tolerance variation, including the materials used, process management, and tool design. The tolerance ranges that are acceptable in a design will vary substantially from one molder to the next.
Designers must talk to a molder about appropriate critical tolerance criteria and evaluate possibilities for mold changes if necessary. This may need the purposeful construction of additional clearance in some design elements, which will subsequently be tightened by removing steel from the mold.
To solve interference difficulties, no one wants to use welding to add steel. Two shot mold may advise post-machining, fixing, and gate placements to ensure tight tolerance control.
- Marks on the sink
Avoiding sink marks in injection molded products is a constant issue for experienced designers. However, remember that this is only a guideline and does not ensure that the component will pass QC. Gate position, tool quality, nominal wall thickness, material, additives, surface finish, color, and viewing angle influence cosmetic surface flaws.
Production difficulties may be avoided by explicitly defining acceptable surface quality with the molder long before any of these choices are taken. Before manufacturing begins, reputable molders will establish realistic expectations and backup plans. For example, molders may recommend that all features on the interior of a component be removed, while others may recommend using specific coring procedures.
- Steel-based secure zones
We often encounter precise tolerances while developing injection molded components, such as snap fittings, alignment features, and interlocking sections. It’s simple to align and match these characteristics in CAD, but it’s not simple to create them repeatedly in production. Details that a molder can’t reliably duplicate are often meant to be steel safe.
For those unfamiliar with the term, steel safe refers to a design feature that allows a tool manufacturer to easily machine away steel in the mold after the initial test shots have been formed to tighten up clearances. Most molders prefer to take these precautions rather than fusing material back into the mold, which must be machined afterward.
Welding continuously degrades tooling quality, is costly, and slows down production start-up. Early in the design phase, working closely with a molder or toolmaker will reduce design modifications by allowing both of you to agree on essential dimensions that should be made steel safe and the amount of clearance to provide in the design.
Unfortunately, these well-coordinated, well-planned choices often contribute little or nothing to the tooling budget and impact production start-up. On the other hand, some molders like pieces that are created precisely as planned and do not need additional clearance. That’s why it’s crucial to keep in regular contact with the molder you’ve chosen.
- The position of the gate
A designer, molder, and tool manufacturer should all specify the gate placement. The position of the gate is crucial to almost every aspect of an injection-molded item. Particular designers use mold flow simulations to determine gate design and placement.
If the molder agrees with their suggestions, I believe that’s fantastic. I can’t entirely agree with designers who insist on sticking to their gate suggestions to the letter. In any scenario, working closely with a molder throughout the design process will guarantee that the gate has no negative impact on component performance, appearance, or fit.
Molders will also advise designers on the sort of gate to use and any features that may need to be added to the component geometry due to the gate design. Molders will often provide trade-offs between other gates, such as fan gates, edge gates, and sprue gates.
Conclusion
Before being shipped to a molder, an injection molded product goes through many phases of development. Molders may be able to purchase large quantities of specific resins at a reduced price. If a designer can pick an ABS grade that matches the attributes of one purchased in significant numbers, tens of thousands of dollars may be saved. A variety of variables, including the materials used and tool design, impact tolerance variation. The acceptable tolerance ranges in a design will vary significantly from one molder to the next.
