Material · injection molding
Polycarbonate (PC) injection molding design guidelines
Polycarbonate is tough, heat resistant and clear in natural grades. It flows stiffly, so it wants generous walls and smooth transitions, and it is sensitive to sharp inside corners, where it cracks under load.
This page gives the wall thickness PartCheck checks Polycarbonate against, the rib, boss and corner sizes that follow from it, and the published processing figures. You can then check your own part, free and in your browser.
Polycarbonate wall thickness
A Polycarbonate part is checked against a nominal wall of 1.02 mm to 3.81 mm. Thinner, and the plastic may not fill the cavity or will be weak; thicker, and sink marks, voids and cooling time all climb.
Polycarbonate is amorphous. Amorphous resins shrink less and evenly, so they tolerate more variation in the wall. PartCheck flags regions more than 25% off the part's nominal wall. Where the wall has to change, step it gradually; published guidance keeps neighbouring sections within about 3:1.
Ribs, bosses, corners and draft
These follow from the nominal wall rather than from the plastic, so here they are at the thinnest, middle and thickest wall in Polycarbonate's range.
| Nominal wall | 1.02 mm | 2.42 mm | 3.81 mm |
|---|---|---|---|
| Rib ≤ 0.6× wall | 0.61 mm | 1.45 mm | 2.29 mm |
| Boss wall ≤ 0.8× wall | 0.82 mm | 1.93 mm | 3.05 mm |
| Inside radius ≥ 0.5× wall | 0.51 mm | 1.21 mm | 1.91 mm |
| Thick section from 2.0× wall | 2.04 mm | 4.83 mm | 7.62 mm |
- Ribs
A rib thicker than this at its root shows as a sink line on the face behind it. Make it taller for stiffness, not thicker.
- Bosses
A screw boss with a thicker wall shrinks harder than the wall it stands on and pulls a sink through to the face opposite.
- Inside corners
A sharp inside corner concentrates stress and makes the plastic turn too hard as it flows. Half the wall is the usual radius.
- Draft
At least 1° on faces along the direction the mold opens, so the part releases without dragging. Textured faces need more, roughly a degree for every 0.025 mm of texture depth.
Polycarbonate processing figures
| Figure | Value |
|---|---|
| Grade the figures are for | PC, unfilled |
| Density | 1.2 g/cm³ |
| Melt temperature | 302 °C |
| Mold temperature | 91 °C |
| Ejection temperature | 127 °C |
| Mean cavity pressure | 59–60 MPa |
Polycarbonate is also offered filled: glass fibre at 10–50% by weight. The filled grade's weight is worked out from the filler; its walls and the other figures are the unfilled resin's.
Check a part in Polycarbonate
Open your STEP file in PartCheck's DFM tab, choose injection molding and Polycarbonate, and every wall, rib, boss, corner and draft above is checked on your part, with each problem marked where it is. The full list of checks is in the injection molding DFM guide.
Questions
What is the minimum wall thickness for Polycarbonate?
1.02 mm is the thinnest nominal wall PartCheck checks Polycarbonate against. Thinner sections risk not filling and are weak.
What is the maximum wall thickness for Polycarbonate?
3.81 mm. Above it, sinks, voids and cycle time climb; core the section out instead.
How thick should a rib be in Polycarbonate?
At most 0.6× the wall it stands on: 1.45 mm on a 2.42 mm wall.
What draft angle does Polycarbonate need?
1° is PartCheck's default for every plastic, and more on textured faces.
Is Polycarbonate amorphous or semi-crystalline?
Amorphous, which is why its walls are held within 25% of nominal.
Try it on a real part
The demo is a moulded enclosure lid in two revisions, drawn in CAD. It opens in the tool with no files needed, or you can open your own STEP files. Nothing is uploaded: the analysis runs in your browser.