Injection molding produces high precision parts at volume quickly, making it ideal for prototypes and small production runs. Traditionally only done in factories, desktop injection molding machines now provide compact affordable options for home shops.
In this guide, we’ll examine desktop injection molding technology, advantages versus 3D printing, top starter machines, and principles for successful molding from your desktop.
What is Desktop Injection Molding?
Desktop injection molding machines are small injection molding presses designed for home workshops or lab environments.
They use the same fundamental process as industrial molding machines, just on a smaller scale. Granulated plastic is melted and shot into a metal mold cavity where it cools into the finished part shape.
Popular machines like the MiniJector can produce small plastic parts using molds up to 5 x 4 x 3 inches in size. Clamping forces under 10 tons keep machines compact enough for desktop or benchtop use.
Key Benefits of Desktop Injection Molding
Here are the main advantages desktop injection molding offers compared to consumer 3D printers:
FasterProduction – Make 10-100+ parts per hour once molds are made versus slow layer-by-layer 3D printing.
LowerCost Per Part – Low material cost and fast time-to-part makes overall part cost just pennies each.
ProfessionalQuality – Industrial grade finishes and material properties unlike layer lines of FDM prints.
WideMaterial Options – Mold parts from standard plastics like ABS, PP, nylon, and even flexible materials.
LargerParts – Mold small parts up to 5 inches versus size limits of home 3D printers.
ReusableMolds – Injection molding reuses molds indefinitely whereas prints “destroy” the digital file.
For short-run production, desktop injection molding bridges the gap between prototyping with 3D printers and full mass production.
How Desktop Injection Molding Works
Here are the basic steps to produce injection molded parts with a desktop machine:
1. DesignPart CAD File
Create the 3D CAD file for the desired part shape and geometry.
2. CNC Mill Mold
Use a desktop CNC mill to fabricate mold halves from aluminum based on part design.
3. Install Mold
Secure mold halves into injection press and clamp shut.
4. Insert Material
Pour small plastic pellets into material hopper to melt and inject.
5. Cycle Molding Press
Press cycles by closing mold, injecting melt, holding pressure, cooling, then ejecting finished part.
6. Eject Part
Open mold and eject formed plastic part. Finished parts are ready for use.
The ability to quickly and affordably prototype injection molded parts makes desktop machines invaluable for inventors and small businesses.
Top Desktop Injection Molding Machines
Here are two excellent starter injection molding machines for home or classroom use:
PicoPlast Desktop Injection Molding Machine
At just $699, the manual PicoPlast provides outstanding value with a compact size and 5-ounce shot capacity. It can be mounted on a benchtop or wall. A great budget option.
MiniJector Desktop Injection Molding Machine
The $2,650 MiniJector is an advanced desktop unit great for prototyping, short runs, and R&D. It offers a larger 28-ounce shot capacity and delivers consistent professional results.
Both machines are small enough for use anywhere while packing professional injection molding capabilities. They use standard molds machined from aluminum or even 3D printed material.
Design Tips for Quality Injection Molded Parts
Here are some best practices to follow when designing parts for desktop injection molding:
- Include a draft angle on walls to ease ejection from the mold
- Add a radius to sharp corners to avoid cracking and stress
- Keep wall thicknesses consistent, ideally between 2-4mm
- Include a shallow angle on steep vertical surfaces
- Minimize large flat areas prone to warpage
- Design beefier sections around screw bosses and inserts
- Allow space for injection gates and make them generously sized
Take molding nuances into account in the CAD design phase to maximize results. Simulation software can predict trouble areas.
Materials for Desktop Injection Molding
Desktop machines mold a wide range of inexpensive standard plastics:
- ABS – Tough, impact resistant, handles pigments well
- Polypropylene – Resilient, chemical resistant, low friction
- HDPE – Stiff, hard-wearing plastic great for white/bright colors
- Acrylic – Optically clear parts, shatter-resistant
- Nylon – Abrasion resistant, strong, some flexibility
- Styrene – Rigid, durable, and very low cost material
Avoid highly filled or reinforced resins as abrasive fillers quickly degrade molds. Experiment with various plastics to learn molding characteristics.
Safety Tips for Injection Molding at Home
Here are some basic safety precautions to follow:
- Wear protective equipment – safety glasses, gloves, closed shoes
- Keep hands away from mold area when in operation
- Ensure machine is level on a sturdy surface and fully assembled
- Follow manufacturer instructions carefully during setup
- Never leave a press unattended when hot or under pressure
- Allow molds and parts to fully cool before handling
- Keep flammables away and have a fire extinguisher on hand
With sound judgment and safe operation, desktop injection molding provides a thrilling way to make professional plastic parts at home.
Next Level: Hydraulic Injection Molding
For more advanced users, hydraulic powered machines like the Autoject MJ15 offer:
- Larger shot size and mold capacity
- Programmable process control
- Higher mold clamping force
- Increased speed and precision
- Ability to use liquid colors and additives
- Higher degree of process monitoring and automation
While pricier, hydraulic machines expand the range of desktop injection molding into even more professional territory.
Affordable Short-Run Production
Thanks to desktop units like the MiniJector and PicoPlast, injection molding is no longer restricted to factory floors. Engineers, designers, and tinkerers can easily experience producing real injection molded parts cost-effectively on a small scale.
The ability to quickly test designs, validate prototypes, and produce short pilot runs with professional material properties and finish is invaluable. With a compact injection press and basic mold making skills, your desktop can be a mini-production powerhouse!
