|
|
|
 |
Thin coating on thermoformed products improves performance |
 |
|
| |
A new technique that improves surface finish along with reducing cycle time in plug assist thermoforming process has been developed. This innovative coating results in improved surface finish and cycle time of thermoformed parts, and also eliminates cleaning and part rejects.
One type of coating has been used in glass-reinforced injection molded parts that are used in sliding or rotating applications. The coating reduces friction and covers protruding fibers that cause wear on mating parts. The coating acts similarly in plug-assist tooling made of glass-reinforced thermoplastics by providing wear resistance for plug durability, as well as low friction and a smooth surface that would not mar the formed parts. A newer, special two-layer composite coating that is applied as a liquid to the plug and cures to form a strong adhesive bond has been developed. The coating for thermoform tooling is different from those tailored for injection molded parts because the film needs the added capability to release the product. The new tooling coating has a smooth yet ultra-long-wear surface that prevents scratching the plastic sheet. Not only does the coating film cover any reinforcing fibers protruding from the plug surface, it allows formed parts to be removed from the mold with minimal effort and no additional mold release.
The two-layer coating consists of a top layer of PTFE, which provides low friction and release, and an under-layer of specially formulated carbon and ceramic nano-particles in a polyamide or polyamide-imide matrix that bond to the plug-assist. A special silane coupling agent bonds the matrix layer to the plug assist.
The liquid coating is applied and cured on the plug assist using proprietary computer-controlled process. It is applied to the entire plug surface and there is no limitation on plug size. First, the silane solution is applied to the plug and then the matrix layer is applied and then cured at 175-180 degree C for 60 to 90 minutes. The final step is bonding the PTFE top layer using infrared curing. The plug is rotated during curing and reaches a surface temperature of 350 degree C for about 15 seconds. The process creates a permanent film with a maximum thickness of about 50 microns, depending on requirements. No polishing is required.
The coating has a coefficient of thermal conductivity similar to mica, resulting in higher heat resistance than a thermoplastic plug assist. It insulates the tool and enables use of higher sheet temperatures, thus improving formability. Heat transfer to the plug is also minimized. |
|
| | | | | | |
{{comment.DateTimeStampDisplay}}
{{comment.Comments}}