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YOU CAN BUILD AN INJECTION MOULDING MACHINE THAT RUNS A WHOLE BATCH BY ITSELF

A benchtop injection moulder that runs the full cycle without a person — feeds pellets, melts, injects, holds, ejects, and counts down the batch.

by Buster Beagle 3D

FULL CAD BOM FIRMWARE DOCS

WorkshopAutomation

Built withArduino3D printing

difficulty
●●●●○
time
a long weekend-plus
license
CC0-1.0
repo
repo ACTIVE9 stars

WHAT YOU’LL NEED

Videos
1
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COMPAREE VERDICT

This is a benchtop injection moulding machine that runs a full production cycle without a person: a timed auger feeds pellets, two 110 volt 380 watt band heaters melt them, a pneumatic cylinder injects, the vise holds closed while the part sets, then opens, a servo ejects the part, an optical sensor confirms it dropped, and an LCD counts down the remaining parts before the next cycle. It took four generations to get there: a hand-cranked MK1, a larger MK2, a pneumatic MK3, and the MK4, which is an upgraded MK3. The repo is CC0 and includes the Arduino firmware, 3D-printed parts, wiring and pneumatic diagrams, and links to a bill of materials and frame and vise PDFs. The single biggest catch: several of the harder parts (heating chamber, chamber extension, aluminium plates, plunger extension rod, funnel and vise kit) are sold by the maker, so this is an open design that is partly a kit; STEP and IGES files are offered for the plates, but the rest means machining or a longer search if you source it yourself. The bill of materials has no prices. Heat is regulated by three Rex C100 PID controllers with solid state relays and K-type thermocouples, the frame is 2020 aluminium extrusion, and you also need a compressed-air supply for the pneumatics. The most likely failure mode is getting the timing wrong: injection time, hold time and cooling are tuned for the specific mould and material, and there is no lookup table in the repo.

GOOD TO KNOW

  • —Firmware, printed parts (pellet sensor holder, plunger fan bracket, hall sensor mount, auger and feeder, ejection servo, part-drop chute, enclosures), wiring and pneumatic diagrams are in the repo; the bill of materials, frame and vise PDFs and a mould template are linked from the README.
  • —Several of the harder parts — the heating chamber, the plunger, the aluminium plates, and the vise — are sold by the maker. This is an open design that is partly a kit.
  • —The bill of materials does not include a total cost, so actual spend is unclear until you price every line.
  • —Licensed CC0-1.0, which is as permissive as a licence gets — no restrictions on commercial use.
  • —The repository documents the MK4; MK1-MK3 videos are linked in the README for background, and the MK3/MK4 frame PDF is shared.
  • —Frame and vise have assembly PDFs (plus a vise assembly video); the automation wiring and pneumatics are documented as diagrams only.

Parts to buy

12 items

From our check of the build. Exact quantities and part numbers are in the creator’s BOM.

  • Two 110V 380W band heatersFind
  • 2020 aluminium extrusion and brackets for the frameFind
  • Arduino Nano with I/O shield (or the maker's PCB)Find
  • LCDFind
  • EncoderFind
  • Hall and optical sensorsFind
  • ServoFind
  • Auger motorFind
  • Pneumatic valvesFind
  • Regulators and hoseFind
  • Compressed-air supplyFind
  • Either the maker's kit parts or your own machined equivalentsFind

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Can I build this?

PrintPellet sensor mount, plunger fan bracket, hall sensor mount, auger, feeder, ejection servo mount, and enclosures — all STL files are in the repo.
BuyTwo 110V 380W band heaters, three Rex C100 PID controllers with solid state relays and K-type thermocouples, 2020 aluminium extrusion and brackets for the frame, an Arduino Nano with I/O shield (or the maker's PCB), LCD, encoder, hall and optical sensors, servo, auger motor, pneumatic valves, regulators and hose, a compressed-air supply, and either the maker's kit parts (heating chamber, chamber extension, aluminium plates, plunger extension rod, funnel, vise) or your own machined equivalents.
Tools3D printer, basic hand tools, soldering iron, and access to the maker's part sales if you are not machining the heating chamber and vise yourself.
SkillsIntermediate electronics (wiring PID controllers and solid state relays), mechanical assembly (2020 extrusion frames and pneumatic systems), and the ability to tune injection timing for your mould and material — the frame and vise have assembly PDFs, the automation is documented as diagrams plus a video walkthrough.
TimeA long weekend if you buy the kit parts, longer if you are sourcing or machining the heating chamber and vise yourself, plus tuning time for your first mould.
Cost$$$, dominated by the band heaters, PID controllers, and the kit parts if you buy them from the maker — the bill of materials has no total, so actual spend is unclear until you price every line.
SafetyMains voltage (110V band heaters regulated by solid state relays), high temperature (melting plastic), and moving parts (vise and ejection). Use proper mains wiring, do not touch the heating chamber during operation, and keep hands clear of the vise.

This build involves mains voltage — for adults comfortable with electrical work only.

Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.

Videos

The maker's own walkthrough of how the MK4 works and runs a fully automatic cycle.

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Gallery

Start here

Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.

  1. 1.Check the bill of materials (Price every line before starting — the repo does not include a total cost.)
  2. 2.Decide whether to buy the kit parts or source them yourself(The heating chamber, plunger, aluminium plates, and vise are sold by the maker — if you source them yourself, expect machining or a longer search.)
  3. 3.Print the sensor mount, plunger bracket, hall sensor mount, auger, feeder, servo mount, and enclosures (All STL files are in the repo.)
  4. 4.Build the frame from 2020 aluminium extrusion (Frame drawings are in the public drive linked from the repo.)
  5. 5.Wire the PID controllers, solid state relays, and thermocouples (Wiring diagrams are in the repo — this is mains voltage, so check your work.)
  6. 6.Flash the Arduino firmware (Firmware is in the repo.)
  7. 7.Tune the injection timing for your mould and material(There is no lookup table — you will be tuning injection pressure, hold time, and cooling time for your specific setup.)

Resources

Documentation, files and community threads for this build — we link straight to the original sources and never rehost the creator’s files.

KNOWN ISSUES

  • Several key parts — the heating chamber, the plunger, the aluminium plates, and the vise — are sold by the maker. If you expected a fully open-source build, this is partly a kit.
  • The bill of materials does not include a total cost, so actual spend is unclear until you price every line.
  • There is no single manual for the whole machine: the frame and vise have their own PDFs and a vise assembly video, but the automation wiring and pneumatics you build from the diagrams and the main walkthrough video.
  • Injection timing (pressure, hold time, cooling time) is tuned for the specific mould and material, and there is no lookup table in the repo — expect trial and error on your first mould.
  • The repository documents the MK4. The MK3 and MK4 share the same frame and an MK4 is an upgraded MK3, but follow the MK4 parts list for the chamber, vise and electronics; the MK1-MK3 videos linked in the README are background, not build instructions.
  • Mains voltage and high temperature — use proper wiring for the band heaters and do not touch the heating chamber during operation.

Can I source all the parts without buying the kit?

Yes, but the heating chamber, plunger, aluminium plates, and vise are the parts the maker sells — if you source them yourself, expect machining or a longer search.

How much does it cost to build?

The bill of materials does not include a total, so actual cost is unclear until you price every line — it is in the $$$ band, dominated by the band heaters, PID controllers, and the kit parts if you buy them.

Is there a step-by-step assembly guide?

Partly. There is a frame build PDF (shared with the MK3), a vise assembly PDF and a vise assembly video; the automation wiring and pneumatics are covered by diagrams and the main walkthrough video rather than a single step-by-step manual.

What plastic can it mould?

The repo does not specify a material list — injection timing is tuned for the specific mould and material, so expect trial and error on your first mould.

Can I use this commercially?

Yes — the licence is CC0-1.0, which has no restrictions on commercial use.

Community builds

No community builds yet — be the first, we feature the best ones.

Discussion1

FROM THE COMPAREE TEAM

Four generations to get to a machine that runs a batch without a person standing there. If you were building this, would you buy the kit parts or machine them yourself?

CompareeTEAM1mo agoedited

Practical notes from our verification: the bill of materials is a Google Sheet without prices, so actual spend is unclear until you price every line. The heating chamber, chamber extension, aluminium plates, plunger extension rod, funnel and vise kit are sold by the maker — STEP and IGES files are offered for the plates, but the other parts mean machining or a longer search if you source them yourself. The repo covers the MK4 automation: the Arduino sketch, 3D-printed parts, wiring and pneumatic diagrams, and PDFs for the frame and vise. The README also links the MK1, MK2 and MK3 videos for background; the MK3 and MK4 share the same frame, and an MK4 is an upgraded MK3, so follow the MK4 parts list for the chamber, vise and electronics. The biggest upgrade is not the hardware — it is the automation that took four generations to get right. Correction (4 October 2026): we re-checked this page line by line against the project's own repository, documentation and videos, and fixed errors in earlier versions.

Buster Beagle 3D

Built four generations of injection moulding machines to get to a design that runs unattended — the MK4 is the one that feeds, melts, injects, holds, ejects, and counts down the batch without a person standing there.

GitHub

Star the project on GitHub

DISCLAIMER

  • Comparee is not the author of the projects featured here. All rights to each project belong to its creator — every page links to the original source, and we never host creators’ files.
  • Information is provided without warranty and may become outdated as projects evolve. Prices are indicative bands only — always check the creator’s parts list for current costs.
  • Building and operating any project is at your own responsibility. Protective equipment, safe workshop practice and compliance with local regulations are the builder’s responsibility.
GitHub repo