Designing Molds for the INJEKTO 3 Desktop Injection Molder
The INJEKTO 3 is a desktop injection molding machine that takes a standard mold backer. Mold Backer Compatible mode generates molds that drop straight into it: fixed block dimensions, matched sprue position, and a part envelope sized to the machine's shot capacity.
The size envelope
| Parameter | Value |
|---|---|
| Mold half size | 75.6 x 86 x 25.88 mm |
| Max part size | 69 x 80 x 48 mm (24 mm per half) |
| Max part volume | 45 mL |
| Corner radius | 8 mm |
| Sprue diameter | 4.8 mm |
| Vent channel | 2 mm |
Models larger than the envelope are scaled down automatically to fit. Models are never scaled up, so a small part stays small unless you raise the scale yourself. Scale is locked once analysis runs, because the parting plane scores depend on it.
Designing for the shot volume
45 mL is the hard ceiling on part volume, and the practical ceiling is lower once you account for the sprue and runner. Thick solid sections are the usual culprit when a part exceeds it, and they cause other problems too.
- Keep wall thickness roughly uniform. Thick sections cool slowly, shrink more, and sink.
- Core out solid volumes rather than scaling the whole part down.
- Target 1.5 to 3 mm walls for most thermoplastics at this scale.
- Fillet internal corners. Sharp internal corners concentrate stress and resist flow.
Flow, sprues, and venting
In Mold Backer Compatible mode the sprue is fixed at 4.8 mm to match the machine nozzle, and the tool places the runner and gate based on the cavity. For parts with two well-separated lobes it generates a dual, T-shaped runner so both fill at once instead of one filling and starving the other.
The 2 mm vent channel gives displaced air a path out. Without a vent, air compresses at the far end of the cavity and you get a short shot, burn marks, or both. Custom Size molds let you remove the vent if you are casting rather than injecting; Mold Backer molds keep it.
Draft and demoldability for injection
Injection molded parts are ejected while still warm and slightly soft, which makes draft more important, not less. Aim for at least 1 degree on every wall parallel to the parting direction, and more on any textured surface. Run the demoldability heatmap and clear the orange and red areas before you commit to an aluminum mold.
Choosing a mold material
| Material | Typical use | Durability |
|---|---|---|
| 3D printed (PLA/PETG) | Fit checks, low-temperature material, one-off tests | A few shots |
| Printed engineering resin | Short prototype runs | Tens of shots |
| PPA-CF | Functional prototype runs | Hundreds of shots |
| Machined aluminum | Production and repeat runs | Thousands of shots |
Physical molds can be ordered directly from the export step in Mold Backer Compatible mode, since the geometry is already matched to the backer.
Alignment pins
Alignment pins are a Pro feature. They add matching pins and sockets with a 0.1 mm clearance so the halves register to each other repeatably. On an injection mold that registration is what keeps the seam tight under injection pressure; without it, flash appears along the parting line and the two sides of the part offset relative to each other.
Keep reading
- Draft Angles and Undercuts in Mold Design
Why parts stick, tear, or trap themselves in a mold, and how to spot every problem surface using the color-coded demoldability heatmap.
- Parting Lines and Parting Planes Explained
The single decision that determines whether a mold works. How to read the scored plane list and when to override the recommendation.
- STEP vs STL vs OBJ vs 3MF: Which Mold File Format to Use
A practical comparison of the four export formats and the workflows each one belongs in.