Insert molding part

Overmolding and Insert Molding

Get custom plastic parts molded with two materials or metal inserts. Upload a part to get an online quote.

Certifications

ISO 9001:2015 | ITAR Registered | Critical to Quality Inspections

Our overmolding and insert molding processes produce custom prototypes and on-demand production parts in as fast as 15 days. We use aluminum molds that offer cost-efficient tooling, producing parts from a range of thermoplastic and liquid silicone rubber materials.

Overmolding and insert molding are frequently used for:

  • low-volume production parts
  • bridge tooling
  • pilot runs
  • functional prototyping and testing

Overmolding and Insert Molding Design Guidelines

Our basic guidelines for overmolding and insert molding include important design considerations to help improve part manufacturability, enhance cosmetic appearance, and reduce overall production time. View our design guidelines page for more in-depth details.

  US Metric  
Maximum Part Size 18.9 in. x 29.6 in. x 8 in. 480mm x 751.8,, x 203.2mm  
Volume 59 cu. in. 966,837 cu. mm  
Depth 4 in. form parting line 101mm from parting line  
up to 8 in. if the parting line can pass through middle of part Up to 203.2mm if the parting line can pass through middle of part  
Projected Mold Area 175 sq in. (plastic) 112,903 sq. mm (plastic)  
48 sq. in. (silicone rubber) 30,958 sq. mm (silicone rubber)  

 


Definitive Guide to Injection Molding Cover

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Definitive Guide to Injection Molding

This complete reference guide walks you through everything from quoting, design analysis, and shipment to best practices that ensure your model is optimized for molding.


Additional Notes

  • Height may be limited if using a silicone as the overmold material, and deeper parts are limited to a smaller outline.
  • Minimum part volume is 0.025 cu. in. (40.98 cu. mm).
  • With substrate molds, we can maintain a machining tolerance of ±0.003 in. (0.08mm) with an included resin tolerance that can be greater but no less than 0.002 in./in. (0.002mm/mm).
  • With thermoplastic overmolds, tolerances remain the same as substrate molds, however, if the overmold is LSR, then tolerances shift to 0.025 in./in. (0.025mm).


green overmolded part

Overmolding Material Bonding

Chemical bonding between overmolded materials is possible, but material compatibility should be considered in order to achieve desired bond strength. Incorporation of an adequate mechanical bond is strongly recommended if bonding is critical to your application. An undercut is a good example of a mechanical bond.

 

Substrate Material
Overmold Material ABS Lustran ABS/PC CYCOLOY C2950-111 PC Lexan
940-701
PBT Valox
357-1001
PP Profax 6323
TPU - Texin
983-000000
C C C C M
TPV - Santoprene
101-87
M M M M C
TPE - Santoprene
101-64
M M M M C
LSR - Elastosil
3003/30 A/B
- - M M -
TPC - Hytrel 3078 C C C C M
TPE-Versaflex OM
1060X-1
C C C M M
TPE-Versaflex OM
6240-1
M M M M M
TPE-Versaflex OM
6258-1
M M M M M
TPE-Versaflex OM
1040X-1
C C C M M

M = mechanical bond (recommended)
C = chemical bond



Insert Molding Capabilities

Instead of a mold that produces a final part using two separate shots like overmolding, insert molding generally consists of a preformed part—often metal—that is loaded into a mold, where it is then overmolded with plastic to create a part with improved functional or mechanical properties. We currently accept inserts from PEM, Dodge, Tri-Star, Spirol, and Tappex. A complete chart of stocked inserts at Protolabs is available here.

One way insert molding is used is with threaded inserts, which reinforce the mechanical properties of plastic parts’ ability to be fastened together, especially over repeated assembly. Bushings and sleeves are another great way to increase part durability for mating components that need more abrasion resistance due to moving parts.

threaded insert injection molding illustration


What is Overmolding?

With overmolding, the production of the substrate parts is a standard injection molding process involving an aluminum mold with no heating or cooling lines running through it. Cycle times are a bit longer, which allows our molders to monitor fill pressure, cosmetic concerns, and the basic quality of the parts. When the total run of substrate parts are molded, overmold tooling is then assembled to the press. The substrate parts are placed by hand into mold where each part is overmolded with either a thermoplastic or liquid silicone rubber material.

What is Insert Molding?

Insert molding is a similar process but instead uses a preformed part—often metal—that is loaded into a mold where it is then overmolded with a thermoplastic resin to create a final component. When the run is complete, parts are boxed and shipped shortly thereafter.


Resources

injection molding press

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