Eliminating 100% CMM Inspection with Precision Insert Installation
Case study · Brass insert installation
By Alex Spurgeon — Published 2026-09-21
A customer installing 1/4-20 brass inserts into polycarbonate needed a finished height of flush +0.010"/-0.000". A manual arbor press could not hold it, so every part went to a CMM for about eight minutes. U.S. Heatstake built an automated insertion system with encoder position feedback that holds insert height within approximately 0.003" and eliminated 100% CMM inspection.
At a glance
| Insert | 1/4-20 brass threaded insert |
|---|---|
| Material | Polycarbonate |
| Requirement | Finished height flush +0.010"/-0.000" |
| Previous process | Manual arbor press, more than 50 lb of force, 100% CMM inspection at about 8 minutes per part |
| Solution | Automated insertion with high-precision encoder feedback on every insert |
| Outcome | Insert height within approximately 0.003"; 100% CMM inspection eliminated |
The challenge: a tight insert height held by hand
A customer needed to install 1/4-20 brass inserts into polycarbonate components with an extremely tight finished-height requirement: flush +0.010"/-0.000".
The existing process relied on an operator using a manual arbor press. Installing each insert required more than 50 pounds of force, creating both ergonomic concerns and significant variation in finished insert position.
Because the manual process could not reliably guarantee insert height, every finished part had to be inspected on a CMM.
That inspection took approximately eight minutes per part, creating a major secondary bottleneck in the manufacturing process.
The solution: encoder feedback on every insert
U.S. Heatstake developed an automated insertion system using high-precision encoder feedback to monitor the position of every insert during the staking process.
Rather than relying on operator feel or mechanical stops alone, insert position became a controlled and measurable process parameter.
This effectively built quality verification directly into the insertion process.
The results
- Consistently achieved insert heights within approximately 0.003"
- Reliably maintained the required flush +0.010"/-0.000" tolerance
- Eliminated more than 50 pounds of manual insertion force
- Removed the repetitive manual arbor-press operation
- Eliminated the need for 100% CMM inspection
- Removed approximately eight minutes of inspection time per part
- Improved process consistency and repeatability
- Built quality verification directly into the production process
The result wasn't simply a faster insertion process. By making insert position measurable and repeatable, the customer was able to eliminate an entire downstream inspection bottleneck.
Common questions
How do you control the installed height of a threaded insert in plastic?
Make insert position a measured process parameter instead of relying on operator feel or mechanical stops. In this application U.S. Heatstake used high-precision encoder feedback to monitor every insert during installation, holding finished height within approximately 0.003" against a flush +0.010"/-0.000" requirement.
Can in-process monitoring replace 100% CMM inspection of insert height?
In this application it did. Because the position of every insert was measured during the cycle, quality verification was built into the insertion process, and the customer eliminated a CMM check that had taken about eight minutes per part.