How to Determine the Proper Installation of Threaded Inserts in Plastic
The overall performance of a Threaded Insert is highly impacted by the quality of its installation. This video demonstrates how to determine if a Threaded Insert is properly installed into a plastic assembly. The process involves cutting a cross-section of the installed Insert, examining the external features around the periphery of the Insert, and comparing those features to the impression left within the plastic component. Watch the video for more information!
Transcript
00:00:04 Today, we are going to demonstrate how to determine if you have a properly installed a Threaded Insert into plastic. Threaded Inserts, typically manufactured from aluminum or brass, provide reusable threads and secure tight threaded joints in plastic assemblies. Retention of the Insert is provided by displacing plastic from the hole wall into the cavities of external features such as knurls, barbs and undercuts. A sufficient volume of plastic must be displaced to entirely fill these external features in order for the Insert to achieve maximum performance when the plastic solidifies. The very first step of determining if you have a properly installed Insert
00:00:42 is to measure the hole in the plastic component prior to installing the Insert. If the hole is not within the recommended hole size, too little or too much plastic will be displaced and maximum retention will not be achieved. Once the hole diameter is verified and the Insert is installed, take a cross section of the assembly to examine the plastic flow within the knurls, barbs and undercuts. You can do this by fixturing the plastic component and using a handsaw or a band saw to cut through the top of the Insert and plastic molded part. Then use a tool such as flat head screwdriver to pop the Insert out of the plastic and visually compare
00:01:18 the external features of the Insert to the impression left in the plastic. Verify that the features of the Insert are mirrored within the plastic hole. Do they match entirely such as shown in this example? If so, then you have a properly installed Insert. If there is improper plastic flow, the impression within the plastic will not show all of the Insert retention features. When this happens, determine the root cause for the insufficient plastic fill in order to rectify this. Considering that you already verified the proper hole size, likely
00:01:47 potential causes for insufficient plastic fill include: installing the Insert too quickly or too slowly, an incorrect temperature setting, or poor fixturing of the plastic component during Insert installation. Once you identify the root cause and make the necessary adjustments, repeat the installation process, and section the Insert installed with the modified settings to evaluate the quality of the plastic flow. Thank you for watching our video. Visit SPIROL.com for White Papers, Complimentary Application Engineering, and Contact Information for any of SPIROL’s global locations!