Preheat & Post heat of old tools for recycling

Application: Plastic Reflow and Heat Staking 

Industry: Automotive & Transportation 

Application Objectives:  

An automotive Tier-1 supplier required a precision induction solution to stake M6 PEM threaded inserts and J-nuts into a glass-filled nylon bolster housing. The system needed to support a one-second cycle time within an unattended robotic cell, with individually addressable recipes managed from a single supervisory HMI. The objective was to achieve clean, consistent joints across two PEM insert brands using the same power supply, heat station, and coil hardware. 

A 5 kW UltraFlex induction power supply, paired with a water-cooled heat station and a custom  helical coil delivers a 60% set-point (3 kW for 1-second recipe) that seats both insert brands into the molded boss cleanly It also leaves substantial headroom on the recipe HMI requirement, and drops into the offline robot-cell architecture without changing the heat station or coil envelope. 

The supplier is an existing UltraFlex induction user. This evaluation extends that footprint into a new vehicle-program part design, where the bolster housing introduced cell-level constraints multi-recipe per part, robot-fed automation and multi-brand insert compatibility. 

The challenge:  

The molded part is BASF Ultramid, PA6 reinforced with 30% glass fiber, a class of thermoplastic that is too soft to hold a thread directly, so brass M6 PEM-style inserts are heat-staked into pre-molded bosses. The process window between “too cold to seat” and “too hot, plastic chars” is narrow, and the production cell runs unattended at the supplier’s overall 80-second-per-part target. 

Two PEM-style insert brands had to be supported on the same hardware. Both are M6 brass with knurled outer engagement, but their thermal mass and surface absorption differ the same supply set point produces different fastener temperatures. The recipe needed to deliver clean joints for both brands without changing power supply, heat station, or coil. The supervisory HMI also had to carry individually addressable insert recipes per part with closed-loop set-point trim per insert location. 

Equipment:  

Materials:  

  • M6 brass threaded PEM-style inserts 
  • M6 brass J-nuts 
  • Glass-filled nylon bolster housing 
  • BASF Ultramid PA6 with 30% glass fiber 
  • Pre-molded nylon bosses 

Key Parameters:  

  • 1-second heating cycle time 
  • Unattended robot-cell operation 
  • Clean joints with no charring 
  • Support for multiple insert types 
  • Individually adjustable recipes from one HMI 
  • Fit within a total tact time of 80 seconds per part 

Process:  

UltraFlex sized the cell around a 5 kW induction power supply (SM-5 series) paired with a water-cooled heat station (HS-4W) and a custom helical coil. The coil is with an inside diameter and length sized so a single coil envelope can accept either insert brand without retooling. 

Surface temperature is monitored with a calibrated IR pyrometer. The supervisory HMI on the SM platform supports per-coil recipes, so each insert cell can run individually tunable recipes simultaneously without operator intervention the headline value of induction in this application. 

Results and Conclusions:  

Six trials were run at three set points (55%, 60%, and 65%) for each insert brand, using a fixed 1-second cycle time. The 60% set point produced the cleanest joint for both brands. 

At 60%, the first insert reached approximately 393 °C (740 °F) at 3 kW. The second insert reached approximately 371 °C (700 °F) at the same 3 kW about 22 °C (40 °F) lower than the first at the same set point but seated equally cleanly into the molded boss with no charring or visible plastic damage. Below 60% the insert never reached enough temperature to melt the surrounding plastic without excessive insertion force; above 60% the joint visibly overheated. 

The 60% / 1-second working point is the recommended starting recipe for production tuning. The 5 kW SM platform leaves enough headroom to run faster cycles in the future without changing the heat station or coil envelope. 

Induction heat staking is the right joining method for M6 PEM-style inserts in glass-filled nylon when cycle time, repeatability, and unattended robot-cell operation are all critical. A single 5 kW UltraFlex induction power supply paired with a water-cooled heat station and a helical lab coil supports both  inserts at one-second cycles, with the supervisory HMI carrying multiple individually tunable recipes per part. 

For evaluation of a similar process automotive structural moldings, glass-filled nylon, multi-recipe automated cells request a complimentary lab evaluation from UltraFlex Applications. 

Reference Info: AR 3463 – 8748 

Pictures:

Induction Heat Staking of M6 PEM Inserts
Induction Heat Staking of M6 PEM Inserts in Glass-Filled Nylon
Induction Heat Staking of M6 PEM Inserts
Induction Heat Staking
Induction Heat Staking
Induction Heat Staking

Frequently Asked Questions:

  • Why use induction heating for heat staking of M6 PEM inserts in glass-filled nylon? 

    Induction delivers selective, deterministic heat into the brass insert in roughly one second per cycle, leaving the surrounding nylon cool enough to flow without charring. The supervisory HMI on an UltraFlex SM platform supports per-coil recipes, so a multi-insert robot cell can run individually tunable recipes per insert location without operator intervention well-matched to unattended PPAP-quality automotive assembly. 

  • What power level is required for induction heat staking of M6 PEM inserts in glass-filled nylon? 

    Approximately 3 kW per coil at a 1-second heat cycle, using a 5 kW induction power supply with a water-cooled heat station. The set point is tuned per insert, the one got slightly hotter than the other at the same supply set point, so a per-insert recipe matrix is recommended for multi-coil cells. 

  • Does heat-staking glass-filled nylon require a shielding atmosphere? 

    No. The residence time on the brass insert is roughly one second too short to drive meaningful surface oxidation. The lab evaluation that informed this recipe was performed in open ambient air with no inert shielding, and the joint quality met the customer’s PPAP inspection criteria. 

  • Can a single induction power supply support multiple PEM insert brands on the same line? 

    Yes. In this evaluation a single 5 kW UltraFlex platform supported both inserts at one-second cycles. The first insert reaches about 393 °C (740 °F) and the second insert reaches about 371 °C (700 °F) at the same 3 kW power different absorption, equally clean joints. The integrator adjusts set point per insert location during commissioning. 

  • What is the failure mode if the heat-staking set point is too high? 

    Above the recommended 60% set point at 65% in the lab evaluation the joint overheats and the molten glass-filled nylon exhibits visible plastic damage that the inspection criteria call out as a reject. Closed-loop set-point tuning during commissioning is the standard mitigation. 

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