The maximum part outline that can be moulded is approximately 480mm by 770mm with a maximum part volume of approximately 967cc. Depth up to 101mm from the parting line with 3 degrees of draft, or up to 202mm total if the parting line can pass through the middle of the part, inside and outside. Deeper parts are limited to a smaller outline.
A taper applied to the faces of the part that prevent them from being parallel to the motion of the mould opening is called draft. This keeps the part from being damaged due to scraping as the part is ejected out of the mould. Recommended draft:
- 0.5 degrees on all vertical faces is strongly advised.
- 2 degrees works very well in most situations.
- 3 degrees is minimum for a shutoff (metal sliding on metal).
- 3 degrees is required for light texture (PM-T1).
- 5 or more degrees is required for heavy texture (PM-T2).
Typically, injection moulding tolerances of +/- 0.08 mm + 0.005 mm/mm are expected and achieved.
With injection-moulded parts, observing proper (and uniform) wall thickness helps parts avoid potential issues such as sink marks and warpage. Recommended thicknesses vary by material:
The table* shows wall thicknesses Proto Labs recommends according to resin. Please note that thin walls only work on small parts and thicker walls are required where the resin has a long way to flow (Proto Labs injection moulding makes parts with dimensions of about 6mm to 770mm or more).
Liquid crystal polymer
0.8 - 3
Long-fiber reinforced plastics
1.9 - 25.4
0.5 - 4.5
* Adapted from www.manufacturingcenter.co
A number of standard finishes are available for injection-moulded parts at Proto Labs. Our current finishes include non-cosmetic, low-cosmetic and EDM finishes; bead-blast texturing; and high-end mould polishing.
Standard finishes (from least to most costly):
*"PM" in the table signifies a surface finish adjusted to fit the rapid injection moulding process, where SPI (The Society of the Plastics Industry) denotes an industry-standard finish.
Non-cosmetic: finish to Protomold discretion
Low-cosmetic: most toolmarks removed
600 grit stone, 10-12 Ra
Protomold texture, SPI-C1 followed by light bead blast
Protomold texture, SPI-C1 followed by medium bead blast
600 grit paper, 2-3 Ra
Grade #2 Diamond Buff, 1-2 Ra
Because Proto Labs employs an automated CNC milling process to make the mould for your parts, some part corners will end up with a radius rather than a sharp edge.
This does not usually require a change to the model, but the designer is made aware of these radii before the mould is made.
The injection-moulding process uses ejector pins of various sizes to push the plastic part out of the mould after it has solidified. The sizes and arrangement of these pins are selected to minimize the impact on your part design. Ejector pins range in size from 1.18mm to 9.53mm, with sizes larger than 1.58mm preferred.
Our moulding process supports simple undercuts in your part geometry. Maximum side core dimensions:
≤ 8.419 inches
≤ 2.377 inches
≤ 2.900 inches
Protomold stocks hundreds of thermoplastic resins that offer a variety of benefits for many different applications and industries. See full list of materials.
- Acetal Copolymer
- Acetal Homopolymer
- Nylon 6
- Nylon 66