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Injection Mold Cleaning Tips

Cleaning a plastic injection mold is greatly simplified and results vastly improved when parts are immersed in an ultrasonic cleaning solution. Here we provide some injection mold cleaning tips and explain why sonication is safe and effective, restoring injection molds to a like-new condition.

An ultrasonic cleaning process eliminates risking damage that can result from manually removing post-molding contaminants such as flashing, grease and other residues. It also eliminates health hazards and disposal challenges associated with solvents used for manual cleaning operations. This is because recommended ultrasonic cleaning solutions are water based and biodegradable. And finally, ultrasonic cleaning action reaches and removes contaminants located in crevices, blind holes and other areas difficult if not impossible to reach by manual cleaning methods.

Injection Mold Cleaning Equipment

Ultrasonic cleaners for plastic injection molds are available in a variety of sizes and cleaning solution capacities. They range from benchtop units to floor-mounted industrial models. Cleaning procedures are basically the same regardless of cleaning equipment size. For purposes of illustration we’ll select the 24-gallon capacity Elmasonic SH2400EL unit and its separately ordered basket with dimensions 21.5 x 17.7 x 9.8 in. deep. Although this is a benchtop unit it can be ordered with a rack mounted on wheels to provide portability, and a lid that helps diminish operation noise.

Note: The basket weight capacity is about 66 pounds. If you are cleaning heavier molds contact us for alternative cleaners and baskets that meet your requirements.

Features of the SH2400EL include

  • Operation at a 37 kHz frequency (37,000 cycles per second), a safe and ideal frequency for removing contaminants from injection molds.
  • A degas mode to speed preparation of fresh cleaning solutions by driving off cavitation inhibiting trapped air.
  • A sweep function that provides uniform distribution of sonic energy throughout the cleaning bath. This avoids “hot spots and dead spots” – areas of too much and no sonic cleaning energy acting on the molds.
  • A heater to bring cleaning solutions to the recommended temperature.

While a variety of cleaning solution concentrates are available ask us for CLN-OM-S27, a high pH concentrate to remove burned-on plastic and other contaminants from molds, dies and other metal surfaces.  This is diluted to about 5% with water.

An Injection Mold Cleaning Procedure

With experience you’ll develop a routine for injection mold cleaning in your shop.  Here is a suggested procedure:

  1. Prepare the cleaning solution by adding water to the ultrasonic cleaner tank fill line.* Add the correct amount of cleaning solution concentrate, turn on the ultrasound and the degas function to mix the solution and drive off trapped air. The time required for this depends on tank volume but 15 minutes should suffice for the SH2400EL.
  2. Set the thermostat to the correct temperature for the cleaning solution formulation you use. On the Elmasonic SH series the control panel shows set and actual solution temperature. Note that ultrasonic cavitation warms cleaning solutions so pay attention to temperatures recommended for the formulation you use.
  3. Place injection molds – disassembled if practical – in the basket and lower it carefully into the solution, making certain all parts are immersed. Put the lid on the cleaner to deaden noise and reduce solution evaporation. Set the timer for 10 to 30 minutes depending on the condition of the parts. On the SH series set and elapsed time are displayed on the control panel.
  4. At the end of the cycle remove the basket and inspect the molds. A low pressure hot water power spray may be required to remove loosened contaminants that remain in blind holes. Once particles and cleaning solution residues are removed allow the molds to dry.

Bath Maintenance

Contaminants removed during cleaning may rise to the surface, and should be skimmed off and set aside.  When cleaning time extends it’s time to drain the tank and dispose of the spent solution along with skimmed residues in a locally approved procedure. Rinse the tank to remove sediments that settled to the bottom. Fill it with a fresh cleaning solution, degas it and you’re ready to continue.

For more information on cleaning plastic injection molds call the iUltrasonic cleaning experts at 973 440-2191.

* Notes:

When filling the tank allow for solution displacement by parts being cleaned. Ultrasonic cleaning should not take place with tanks that are overfilled or under filled.

If rusting is a concern ask us for elma-KS rust inhibitor to add to the water.


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