Hardware Engineering / Manufacturing
Pneumatic Plastic Injection System for In-House Manufacturing
This project involves designing and building a DIY pneumatic injection molding machine from scratch to create in-house manufacturing capability for plastic products. The machine uses a 12-ton H-frame shop press as the base, with pneumatic injection (SC80 cylinder), PID-controlled band heaters, and a vise-clamped mold system.
The goal is to bridge the gap between 3D printing and professional manufacturing. While 3D printing is great for prototyping, it produces parts with visible layer lines, structural limitations, and slow cycle times. Injection molding produces professional-quality parts with smooth surfaces, superior strength, and dramatically faster production - ideal for selling on platforms like Etsy.
The project leverages existing shop infrastructure (CNC, lathe, compressor) to minimize build costs while creating a flexible manufacturing platform capable of producing a variety of small plastic products.
January 2025 - Ongoing
Designer / Builder
Hardware Engineering
Parts Staging 70%
While 3D printing excels at prototyping, injection molding offers significant advantages for production:
~1,090 lbs injection force using SC80 cylinder at 140 PSI, achieving ~1,388 PSI through 1" barrel. Double-acting cylinder provides both push and pull force without return springs.
REX-C100 controller with 380W band heaters and K-type thermocouple. Targets 200-220°C for HDPE/PP processing with 25A SSR for precise control.
System designed for interchangeable mold components using aluminum plates. CNC-machined cavities enable production of multiple product variations.
6 specialized Claude Code agents track construction progress, inventory, injection parameters, quality metrics, and session logs asynchronously.
Defined specifications, visual standards, and functional testing protocols ensure consistent part quality across production runs.
Leverages existing CNC, lathe, and compressor infrastructure to minimize costs while maximizing capability for custom mold creation.
| Component | Specification |
|---|---|
| Air Cylinder | SC80 double-acting, 80mm bore |
| Operating Pressure | 140 PSI |
| Injection Force | ~1,090 lbs |
| Barrel Pressure | ~1,388 PSI (through 1" barrel) |
| Barrel Dimensions | 5" length, 1" diameter, 4" usable stroke |
| Shot Capacity | 48g per injection |
| Component | Specification |
|---|---|
| Controller | REX-C100 PID |
| Heaters | 380W band heaters |
| Temperature Sensor | K-type thermocouple |
| Power Switching | 25A Solid State Relay (SSR) |
| Target Temperature | 200-220°C (HDPE/PP) |
| Material | Purpose |
|---|---|
| HDPE Pellets | Primary injection material - good flow, durable |
| PP Pellets | Alternative material - excellent chemical resistance |
| Aluminum Plates | Mold construction - good thermal conductivity |
The air cylinder rod serves directly as the injection plunger, eliminating a separate plunger mechanism. The double-acting cylinder provides both push and pull force, removing the need for return springs. The barrel is fixed to the H-frame via U-bolts and angle iron cross braces for precise alignment.
Careful calculation of barrel dimensions ensures adequate capacity for target products:
A multi-agent architecture where semantic events (#milestone, #params, #shot, #defect, etc.) are emitted during work and processed asynchronously by specialized agents. This enables tracking of physical construction, inventory, injection parameters, and quality without interrupting workflow.
Six specialized agents track different aspects of the build:
Tracks construction progress and milestones
Monitors parts, materials, and procurement
Optimizes injection parameters
Tracks defects and quality metrics
Manages product designs and molds
Archives work sessions and decisions
Injection molding involves high temperatures (200°C+) and significant pressures. Proper safety equipment including heat-resistant gloves, safety glasses, and adequate ventilation are essential. The machine design includes safety interlocks and controlled pressure release mechanisms.
The machine is designed to produce small to medium plastic products suitable for e-commerce sales:
The modular mold system allows rapid tooling changes to produce different products with minimal downtime.