Injection Molding of Thermosets
American Precsion Products can help you save money and greatly improve quality on your compression and transfer molding programs by converting them to injection molding.
| Compression | Transfer | Injection | Comments | |
|---|---|---|---|---|
| Quality | Good | Good | Best | Injection molding's more consistent and repeatable process results in higher part quality and consistency. |
| Cycle Time | Worse | Worse | Best | Injection molding, by feeding the material with injection screw, eliminates the process steps of material preparation and pre-heating which are prone to inconsistencies and slow. Faster mold filling time and cure times speed up the process. Injection units can fill the mold faster and more accurately than transfer molding and compression. The material pre-heats uniformly in the injection barrel resulting in faster and consistent curing. |
| Physical Properties | Best | Worse | Good | A well designed compression mold will typically yield the best physical properties as material alignment and molded in stress are minimized. Injection molding can often come very close to those properties as filling speed can be carefully controlled to optimize flow. |
| Overmolding | Worse | Good | Best | Faster fill rates and more control of the mold filling creates parts with overmolded components with less stress and better weld line integrity. |
| Gating | N/A | Good | Best | Gate size and vestige can be reduced in injection molding. |
| Repeatability | Good | Good | Best | The accuracy and repeatability of injection molding derives from the elimination of the (typically) manual steps of metering, pre-forming and pre-heating the material charge coupled with the computerized control of the mold filling. The availability of multiple speeds and pressures during mold filling allows for precise and repeatable control of the process. |
| Mold Cost $ | Good | Good | Worse | Injection molds often have more components and slightly higher costs which are offset by process speed and quality. |
| Part Cost $ | Worse | Worse | Best | Reduced part cost and increased part quality are the hallmarks of the injection molding process. |
Considerations for Converting:
Material
A suitable injection grade material must be available. Many thermoset materials come in multiple flows (compression, transfer and injection) and the published properties values and approvals are often the identical which makes the transition easy. For other materials, switching to an alternate material may be required.
Physical Properties
You cannot beat compression molding for physical properties when the part and mold are properly designed. If there are flow and filling issues though, injection molding can more easily correct them which can improve the properties. Injection molding can also overcome issues of challenging part designs.
Part Design
In most cases, no design changes are required.
Mold Design
Injection molds are very similar to transfer molds and many times we can convert your existing mold to injection molding. Injection molds allow for more flexibility on injection and gating. For parts with molded in components, we can move to a press with up to a four station rotary table. Components can be loaded into one mold while the other is molding and curing.
Other Options:
For the ultimate in cost savings, moving your program to an engineering thermoplastic material may be ideal. American Precision Products has a vast knowledge of high temperature, engineering materials. While thermplastic materials are often more expesive the faster processing times often overcome the increased material cost.