Mold Making Tips for APSX-PIM Injection Machine

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APSX-PIM Mold Making Tips (PDF)

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Mold Making Tips for APSX-PIM: Quick Guide

Introduction

Traditional steel tooling requires 6-8 weeks of lead time and significant costs. The APSX-PIM system transforms this process by enabling:
  • Creation of aluminum molds in hours using standard CNC mills
  • Production of parts with production-grade thermoplastics the same day
  • Quick re-machining for dimensional adjustments
  • Use of 3D-printed trial inserts for early validation
This approach eliminates the "too expensive to iterate" paradigm, accelerating product launches while reducing total tooling costs.

Injection Molding Basics

Injection molding is one of the most common manufacturing processes for plastic components. The basic steps include:
  • Melting plastic pellets in a heated barrel
  • Injecting molten polymer into a temperature-controlled mold
  • Packing and holding to compensate for shrinkage
  • Cooling until the part solidifies
  • Ejecting or manually picking up the finished part
The APSX-PIM features:
  • Cartridge heaters embedded in the barrel with user-controlled temperature
  • Mold temperature controlled via an air fan
  • User-adjustable holding pressure that can be set very low
  • An ejector bearing for hands-off operation in multi-cycle mode

Choosing the Right Plastic

Key Rules:
  • You do NOT have to use ABS
  • Select user-friendly, readily available materials for your application
  • Consider melt flow rate and drying requirements
Common Plastic Types:
  • Polypropylene (PP): Lightweight, flexible, versatile, and fatigue-resistant; most user-friendly overall
  • Nylon: High strength and wear resistance; ideal for mechanical components
  • Acetal (POM): Low friction and dimensional stability; good for gears and moving parts
  • ABS: Strong, impact-resistant; used for housings and enclosures
  • Polycarbonate (PC): Transparent and impact-resistant; used in safety applications
Thermoplastic Categories:
  • Amorphous Thermoplastics (ABS, PC, PEI): No sharp melting point, often transparent, good impact resistance
  • Semi-Crystalline Thermoplastics (PE, PP, acetal, nylon): More rigid, higher heat resistance

Fundamental Part Design Rules

Wall Thickness

  • Target 1-4 mm uniform walls
  • Core out thick sections; add ribs for stiffness
  • Gate into thick sections to enable proper packing

Draft and Part Ejection

  • Use draft angles from 0.5 to 2 degrees
  • Increase by 1° per 0.001″ of texture depth
  • Polish cores/cavities in the line of ejection
  • Use bronze bushings to stabilize ejector pins

Weld Lines

Weld lines form when two molten flow fronts meet, creating potential weak points:
  • Optimize gate location for shorter material flow paths
  • Increase mold temperatures to improve fusion
  • Use flow enhancers like additional vents
  • Avoid materials with fillers such as glass or fiber
  • Add overflow wells adjacent to welds

Shrinkage and Warpage

Plastic contracts as it cools, causing dimensional changes:
  • Material-specific shrinkage: ABS (0.5%), Nylon (1%), PP (2%)
  • Follow manufacturer's suggested percentages when designing molds
  • Set holding pressure high enough to compensate for shrinkage but low enough to avoid overpacking

CAD Workflow (Fusion 360)

  1. Design the part in CAD software
  2. Add the APSX blank mold template (cavity and core files) to your project
  3. Position the part in the cavity mold and adjust orientation
  4. Use the combine/cut operation to create the mold cavity
  5. Design runners and gates (typically 1" × 0.15" rectangle, extruded 0.03" deep)
  6. Add 0.001" deep venting lines if needed
  7. Repeat similar steps for the core (B) side
  8. Save both files and proceed to CAM for creating machining paths

Prototyping

Prototyping validates designs and identifies issues early:
Methods:
  • 3D Printing: Fast and cost-effective for initial concept validation
  • CNC Machining: Produces accurate prototypes from real plastic stock
  • Soft Tooling (Level I-II): Low-cost molds for small production runs
  • Bridge Tooling (Level III): Aluminum molds for low-volume production
Benefits:
  • Identifies design flaws before investing in expensive molds
  • Allows testing under real-world conditions
  • Enables iterative improvements for optimal manufacturability

3D Printed Mold Tips

Advantages:
  • Cost-Effective: Entry point around $200 vs. $10,000 for industrial molds
  • Immediate Implementation: Various suitable materials readily available
  • Design Flexibility: Easy updates to CAD models for revised molds
Limitations:
  • Not suitable for large manufacturing batches
  • Requires special 3D printing materials for hot plastics (e.g., Rigid10K from Formlabs)
This guide provides fundamental knowledge to help you reach your first "good" part faster without breaking the budget, using the APSX-PIM system with rapid aluminum or 3D printed inserts.