Knowledge Base

How to Clean Cured Resin and Gas Buildup from Injection Molds

Jul 15, 2022, 18:31 PM by The Stoner Molding Solutions Team
Whether you use plastic injection molding for large automotive parts or smaller, intricate items used for surgery, getting precise, finished details in your parts is essential.

An injection molding machine.Whether you use plastic injection molding for large automotive parts or smaller, intricate items used for surgery, getting precise, finished details in your parts is essential. So, when buildup on your mold surface prevents that from happening, it can be frustrating to scrap the part and start all over again. But when you use mold care products from Stoner Molding Solutions, you can decrease the buildup on your molds, leading to fewer scrap parts and increasing your molding operation's productivity.

We previously answered your five frequently asked questions about how to clean injection molds. Still, we wanted to spend a little bit of time talking about why buildup happens on mold tooling, the issues it causes, and how to prevent it from happening in the future. As manufacturing industry experts for over 80 years, you can trust our team to provide high-quality mold releases and cleaners, as well as the best advice to improve your molding process.

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What Causes Buildup on Injection Molds?

There are two primary kinds of buildup on thermoplastic injection molds. The first is the actual polymer being molded, and the second is the buildup of the gasses released during the molding process. Polymer buildup happens primarily on the mold itself, whereas gas buildup can occur on the mold surface or the vent.

Several different reasons can cause the buildup on molds. Some of the most common reasons include:

  • Using the wrong mold release
  • Not applying mold release as frequently as you should
  • Not following proper cleaning procedures
  • Not cleaning the mold as often as you should
  • If additives are combined with the plastic, such as fire-retardant coatings, which may remain on the mold surface after demolding
  • Thermal degradation from high temperatures
  • Cycle times are too long or too short

Injection molds require specific temperatures and cycle times to operate effectively. Extreme temperatures can create defects in your plastic parts and leave residue on your mold surfaces. In addition, if you’re mold release isn’t performing as well as it should, it can cause resin and gasses to build up on the mold surface and vent. Molding operators need to learn how to clean injection molds properly to help avoid these types of buildup.

What Issues Do Cured Thermoplastic Resins Cause During the Molding Process?

When you have cured thermoplastic resin or gas buildup on your molding tools, it can create appearance and sticking issues when you try to remove the plastic pieces from the mold. The cured thermoplastic resin can transfer to the part itself, creating defects on the finished product. The resin buildup can also make it more difficult to eject the part from the mold. In this case, add more ejector pin lubricant, which helps eject thermoplastic parts from metal molds.

Resin and gas buildup reduce the stability of the finished piece and can shorten your mold’s life. For example, suppose resin or gasses aren’t cleaned properly and left on a plain carbon-steel mold for long enough. In that case, they can attack the mold chemically, creating a caustic reaction that deforms tooling over time. So, the next time you clean the mold and remove that buildup, you will find a defect in your mold surface that requires costly repairs.

A can of Stoner’s A499 Precision Mold Cleaner.How Do I Clean Cured Resins from Injection Molds?

If you’re getting a lot of thermoplastic resin or gas buildup, mold cleaning is necessary. We recommend first trying our 93234 CUT Mold Cleaner. This non-chlorinated, quick-evaporating formula rapidly dissolves mold release and buildup from resins and gasses and leaves no residue.

A can of Stoner’s A595 Heavy Duty Mold Cleaner.For a more precise cleaner that can blast away the resin buildup, we recommend A499 Precision Mold Cleaner. The pressurized spray has more force to remove stubborn buildup from both the mold surface and the vent. It quickly evaporates, so you don’t need to wipe it off, making it perfect for quick clean-up jobs on the production line.

For larger mold surface areas, you can also try A595 Heavy Duty Mold Cleaner for Large Surface Areas. This slow-evaporating alternative to A499 has similar cleaning abilities and the same powerful spray blast to eliminate dirt, grease, grime, and buildup on your molds. The precision spray dissolves and flushes away most resin and gas residues from the mold and prepares it for cleaning before applying a rust preventative.

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How Do You Prevent Buildup from Happening?

To prevent buildup from happening so frequently, here are some tips to try:

1. Optimize Your Production Cycle

Before you start running regular cycles of your injection molding, you should take the time to read the directions from the resin manufacturer to ensure you’re using the right temperature and cycle time for your part. If your temperature is too hot, or you raise the temperature to try to get the resin to flow better to fill the injection mold, you may face more buildup than if you were running the cycle at the optimal temperature.

2. Use Better Mold Releases

A can of Stoner’s E317 Heavy Duty Release & Paint.If you're frequently dealing with buildup on your molds, you’re likely not using the right type of mold release. At Stoner Molding Solutions, we have various formulations of mold releases, from silicone spray releases to heavy-duty releases.

Sometimes the light-duty releases aren’t powerful enough for certain polymers. A release like Stoner’s E317 Heavy Duty Release & Paint Mold Release gives you the ideal release you need for large, intricate, or delicate parts. You may also need to apply the release more frequently to prevent buildup.

3. Clean More Frequently

Our cleaning solutions will take care of the gasses and polymers that build up on the mold surface and vent. Certain polymers may build up quicker than others, so you may need to clean the mold more frequently. You can do a quick inspection, cleaning, and lubricant application for plastic parts on metal molds for a more cost-effective approach to cleaning. This process will only take a few minutes if you're using the correct solutions!

Whenever mold repairs are needed, be sure to clean each part individually, apply good lubrication, and reassemble properly. Following standard cleaning procedures during the repair process is a perfect opportunity for routine maintenance, as the mold will temporarily be taken out of production and disassembled.

4. Check the Vent

Gasses from thermoplastic polymers can easily build up on the vent in the molding process. Check the vent regularly to ensure it’s operating correctly. Be sure to use Stoner’s cleaning products on the vent and teach your operators how to clean injection molds properly, including the vent.

Need More Tips to Eliminate Buildup? Get in Touch with Our Molding Experts!

Resin and gas buildup on injection molds can be frustrating. Not only does it create scrap parts, but it can also deform your mold surface if the issues are not resolved properly. That’s why you need to use the best mold releases and cleaners on the market from Stoner Molding Solutions. We can help you find the right ones that provide the heavy-duty release you need to reduce buildup and produce more parts in less time.

Once your operators know how to clean injection molds with Stoner’s mold cleaners and apply the right lubricant for plastic parts on metal molds, you can reduce the amount of buildup on your mold surfaces and vents. This way, the detailed parts you create are free from defects and ready to go to post-mold applications, like painting or hot-stamping. Contact our team of molding experts for assistance if you need help choosing the right products for your molding operations.


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