The maximum part outline that can be molded is approximately 18.9 in. by 29.6 in. with a maximum part volume of approximately 59 cu. in. Depth up to 4 in. from the parting line with 3 degrees of draft, or up to 8 in. 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 mold opening is called draft. This keeps the part from being damaged due to scraping as the part is ejected out of the mold. 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, Protomold tolerances of +/- 0.003 in. are expected and achieved. Additionally, resin is defined as 25 percent of the shrink rate, or no less than 0.002 in./in.
With injection-molded 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 that Protomold 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. Protomold makes parts with dimensions of about 0.25 in. to 15 in. (6.3 mm. to 381 mm.) or more.
Liquid crystal polymer
0.030 - 0.120
Long-fiber reinforced plastics
0.075 - 1.000
0.040 - 0.150
0.030 - 0.200
0.020 - 0.180
0.025 - 0.150
0.035 - 0.150
0.080 - 0.750
*Adapted from www.manufacturingcenter.com.
A number of standard finishes are available for injection-molded parts at Proto Labs. Our current finishes include
non-cosmetic, low-cosmetic and EDM finishes; bead-blast texturing; and high-end mold polishing.
Standard finishes (from least to most costly):
*“PM” in the table signifies a surface finish adjusted to fit the quick-turn injection-molding 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
Non-cosmetic: Protomold discretion, EDM finish and/or toolmarks permissible
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 Protomold employs an automated CNC-milling process to make the mold 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 mold is made.
The Protomold injection-molding process uses ejector pins of various sizes to push the plastic part out of the mold
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 0.047 in. (0.118 cm.) to 0.375 in. (0.953 cm.), with sizes larger than 0.063
in. (0.158 cm.) preferred.
Our molding process supports simple undercuts in your part geometry. Maximum side core dimensions:
≤ 8.419 in.
≤ 2.377 in
≤ 2.900 in.
≤ 213.84 mm.
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 6/12
- Nylon 66