Use the Tape Test to Maximize Throughput in Your Closed Molding Process

Converting from open to closed molding provides composite manufacturers several benefits. Closed molding allows manufacturers to produce higher quality parts by reducing the void content, achieving better fiber/resin distribution, and enhanced surface cosmetics on the B-side. Additionally, closed molding processes also afford manufacturers cleaner work environments, reduced styrene emissions, less scrap, and increased throughput from reduced cycle times. Here, we will focus on the last point, throughput, and how proper mold maintenance tricks like the tape test help to maximize this important metric, and increase your bottom line.

Why use the tape test?
With closed molding, properly designed tooling requires a larger initial investment as opposed to open molding. Use the tape test to predict release performance and protect your investment. It gives you peace of mind knowing that the part will pull off the mold easily and without damaging the mold in the process. How? Unlike traditional paste waxes, semi-permanent release agents such as Chemlease®, reduce the surface tension on the mold when applied. This creates a “slip effect.” As the surface tension decreases, the release performance increases and allows multiple parts to be pulled off the mold before reapplication is needed.

Additionally, it’s often found that composite fabricators apply semi-permanent release agent too often in their molding process. By using the tape test, you can determine whether or not a maintenance coat (touch-up) is necessary. Using the tape test can increase throughput by allowing manufacturer’s to maximize their “pull count” – the number of pulls one can attain between maintenance coats.

How can we measure release performance quickly and easily?
Use the simple but effective tape test. The tape test involves the application of a piece of masking tape onto the mold surface. Once applied, pull the tape off to gauge the ease of removal. As additional coats are applied, you will notice the tape pulling off quite easily. Here are some best practices for employing the tape test in your mold shop:

Tape Test Best Practices

  1. Use the same type of tape each and every time.
    a) Don’t use masking tape one time, and duct tape the next.
    b) We recommend using tape that will not leave residue.
  2. Use a new piece of tape each and every time.
    a)  Every time you use a piece of tape, it loses adhesion.
    b)  Do not reuse tape; rather, grab a fresh piece of tape.
  3. Perform the tape test several times. On a green/virgin mold or stripped (buffed/sanded) mold, perform the following:
    a)  After the mold is cleaned, perform the tape test to create a baseline. The tape should pull off “hard”, which implies that the mold is clean and free of debris.
    b)  In between each application of sealer and release coat, perform the tape test to measure surface tension and release ease.
    c)   As a general rule, you want to reach a level of slip where the tape will completely stick to the surface of the mold. However, when pulled off, it comes off easily such that you cannot hear the adhesive from the tape ripping away from the surface. At that time, you can proceed with molding parts.
  4. Check multiple locations on the mold. Perform the tape test on multiple areas, especially challenging geometries such as low-draft angles, non-skid areas, etc.
  5. Don’t perform the tape test right after applying a coat of release agent.
    a) Wait the recommended amount of time to allow the release agent to cure.
    b) Refer to your product datasheets for recommended cure times.
  6. Check after each molding cycle.
    a)  Monitor the difficulty of de-molding the part.
    b)  After pulling a part, perform the tape test to gauge whether or not a touch-up coat of release agent will need to be applied.

To find a semi-permanent release agent system for Closed Molding, please refer to the Chemlease Closed Mold Product Guide:

Please contact your local Chem-Trend, L.P. or distributor representative for regionally available products for your specific application.

We, The Closed Molding Alliance, hope this information assists you in successfully manufacturing composite parts. Please contact Chem-Trend, L.P. with any questions or comments you may have regarding the tape test or mold maintenance practices in general. We are here to help!

Article written by:
Sam Dethloff
Industry Specialist, Composites
Chem-Trend L.P.
PHN: (517) 376-8582 |
www.chemtrend.com