Maintain Plastic Injection Molds with Ultrasonic Cleaning

Ultrasonic Cleaning Plastic Injection Molds

The global plastic injection molding machine market was valued at $10.4 billion in 2022 and projected to grow to $12.4 billion by 2027 according to a Markets and Markets report.  Unrecognized in such reports are the importance and costs of plastic injection molds that support this growth and the role of ultrasonic cleaning in plastic injection mold maintenance.

Ultrasonic Cleaning and Injection Mold Maintenance

According to Rex Plastics, “A small and simple single cavity plastic injection mold usually costs between $1,000 and $5,000. Very large or complex molds may cost as much as $80,000 or more. On average, a typical mold that produces a relatively simple part small enough to hold in your hand costs around $12,000.”

For cost reasons alone injection mold maintenance should figure high on a list of priorities for companies involved in producing injection-molded parts.  Here you’ll learn how ultrasonic cleaning plastic injection molds preserves investments without causing wear or the use of harsh chemicals.

Injection Mold Maintenance Challenges

Many injection molds are characterized by complex shapes, precision finishes and vents. 

Moreover, different molds have different surface tolerances.  Customer-demanded tolerances for a mold surface can be as precise as 0.0002 inch.  

That’s why longer injection mold life depends on keeping them clean and conducting mold maintenance operations in such a way that extends their life by maintaining surface finish tolerances.

Ultrasonic cleaning avoids damages that can result from manually cleaning plastic injection molds.  No matter how carefully applied, manual methods cannot access complex shapes, vents, dumps and other mold surface configurations. 

Moreover, manual methods such as brushing with solvents run the risk of damaging surfaces, thereby rendering the mold unusable.

These are among the reasons why this is the optimum solution for injection mold maintenance.

Ultrasonic Cleaning Works Best to Maintain Plastic Injection Molds

Ultrasonic cleaning uses a process called cavitation – the implosion of billions of micron-sized vacuum air bubbles – against surfaces immersed in a cleaning solution. 

The implosions blast loose and carry away contaminants on any surface immersed in the cleaning solution. 

Because the bubbles are so small, they penetrate cracks, crevices and machined holes unreachable by mechanical scrubbing – and without damaging critical surfaces on costly injection molds.

An Ultrasonic Cleaning Cycle to Maintain Plastic Injection Molds

The Ultrasonic Cleaner

While ultrasonic cleaners come in several forms and sizes, in this case we describe an industrial ultrasonic cleaner used  by PAM Injection Molding as described in an article published in Plastics Today.

The Elmasonic ST unit has a 15-gallon tank capacity with internal dimensions approximately 20 x 13 x 14 inches deep. 

Note that tank dimensions of the ultrasonic cleaner should be selected based on the size of parts being cleaned.  Many injection molds are constructed as interchangeable modules that can be configured to make multiple parts and can be disassembled for the cleaning cycle.

Operating features that make this unit particularly attractive enable users to select either a 25 or 45 kHz ultrasonic frequency based on the extent and tenaciousness of burned on plastic residues.  

For really tough deposits on plastic injection molds operators can activate what is called the “pulse mode” that sends a more powerful blast into the bath.  Pulse is also activated to degas fresh cleaning solutions in order to quickly remove cavitation-inhibiting trapped air.

A continuous “sweep mode” provides a slight ± variation in ultrasonic frequency that serves to avoid harmonic distortions resulting in areas of high or no cavitation.  Too much intensity can possibly damage highly finished injection mold surfaces.      

In addition to frequency and pulse the control panel allows operators to set cleaning cycle time and cleaning solution temperature.  Set and actual parameters are displayed.  The unit will start when the set temperature is reached and can operate continuously with auto shut-off at 12 hours or if the solution temperature reaches 90⁰C.

An optional insulated or standard lid helps muffle noise during the cleaning cycle and reduce cleaning solution evaporation.

An Injection Mold Maintenance Cycle

Biodegradable ultrasonic cleaning solution concentrates are formulated for specific cleaning tasks.  Ask us about Omega Mold Release Agent concentrate with a recommended dilution rate to 10 to 1 with water.   

Injection mold cleaning cycles are quite straightforward: 

  • After filling the cleaning tank halfway with water the correct amount of concentrate is added then water is added to the fill line.
  • The unit is turned on and the pulse mode activated to mix and degas the solution.
  • Time and temperature parameters are set.  A typical cycle is 30 minutes at a temperature of 50 to 60⁰C.
  • Disassembled modules are carefully positioned in the basket, taking care that they are not in contact with each other.
  • Lower the basket into the tank and close the lid.  Cleaning starts automatically and will shut off at the end of the timed cycle.

At the end of the cleaning cycle parts are removed, rinsed, dried and inspected.  If all is satisfactory the molds are put back in service.

Other Equipment Options for Cleaning Plastic Injection Molds

The Elma xtra ST described above is available in 7 tank capacities from 7.9 to 67.4 gallons.

To accomplish maintenance on smaller injection molds, consider the Elma x-tra TT series in 4 tank sizes from 0.79 to 4.8 gallons. These robust 37 kHz benchtop industrial ultrasonic cleaners are specifically designed for operations that run continuously for up to 8 hours as part of production cleaning cycles.

A sophisticated temperature control system provides an optical alert if the pre-set temperature limit is exceeded.

Cleaning Solution Maintenance

Contaminants removed during the cleaning cycle accumulate in the solution, which eventually must be drained and replaced.  Spent solution should be stored and disposed of following local regulations.  At this time the tank should be cleaned following user manual instructions before being refilled with fresh solution.

Closing Commentary on Plastic Injection Mold Maintenance

There are side benefits to using ultrasonic cleaners such as the Elma x-tra ST and x-tra TT for cleaning plastic injection molds. 

Once a cleaning cycle routine is established personnel simply load components in the basket, set the cleaning parameters and are free to attend to other tasks.  No longer do they have to spend time manually cleaning these intricate and costly molds.  The ultrasonic equipment can do a job in about 30 minutes average – a task that could take hours if done manually.

Contact the scientists at Elma for expert help on selecting and using ultrasonic cleaners and the correct cleaning solutions to add efficiency to your operations.