Custom Injection Molding
Midwest Plastic Engineering is primarily a custom injection molder. We operate 32 injection presses with clamp tonnage from 75 to 850 tons, supported by a maintenance philosophy built around uptime and repeatability.
Press Capacity
Our floor runs 32 presses spanning 75 to 850 tons of clamp force, giving us the flexibility to run everything from small precision components to larger structural parts. Nearly every one was purchased brand new — the only exceptions are two factory-refurbished machines brought in to replace a press lost to a lightning strike and another retired after long service — and each is continually maintained and rebuilt over its life, including control-system upgrades that support complex part production.
To protect your delivery schedule, we maintain replacement screw and barrel assemblies on hand to minimize downtime when maintenance is required.
Materials We Run
Commodity resins: polypropylene, polyethylene, rigid and flexible PVC, ABS, nylon — filled and unfilled.
Engineering grades: polysulfone, PPS, acrylics, polycarbonates, and various alloys.
In short, we process all injection molding material types — filled and unfilled, commodity through engineering-grade.
Molding Capabilities at a Glance
Presses & Shot Size
32 injection presses from 75 to 850 tons of clamp force, with shot sizes from 4.5 to 140 oz:
- 1 × 75 ton — 4.5 oz
- 1 × 120 ton — 7.58 oz
- 4 × 150 ton — 9 oz
- 11 × 200 ton — 14 oz
- 6 × 300 ton — 32 oz
- 2 × 400 ton — 48 oz
- 5 × 500 ton — 52 oz
- 1 × 725 ton — 95 oz
- 1 × 850 ton — 140 oz
Tooling
We run prototype and production tools — single-cavity, family, and multi-cavity — in both cold- and hot-runner configurations. We also run tools built with interchangeable cavities, letting a single mold base produce multiple part configurations for added flexibility and efficiency. We maintain and perform preventive maintenance on the tools we run, with most of that work completed in-house.
Tolerances
We hold dimensional tolerances to recognized industry standards — DIN 16742 and SPI/DME guidelines — with achievable tolerance depending on the resin, part size, wall thickness, and geometry. Tighter tolerances are held on critical dimensions and verified through SPC and in-process inspection. Final capability is confirmed against your drawing during the RFQ and part-approval (PPAP/APQP) review.
Insert & Over-Molding
Yes — we offer both insert molding and over-molding.
Automation
Many of our presses run sprue pickers or robots, and we’re continually adding more automation to improve consistency and efficiency.
Production Schedule
Around the clock — our molding floor runs 24 hours a day, Monday through Friday, across three shifts.
Have a part to quote?
Send your print and resin and we’ll match it to the right press.