3D printing, also called fused deposition modeling and fused filament fabrication, has revolutionized and lowered the cost of traditional molding techniques such as the lost wax process. By using two moldable thermoplastic formulations such as ABS for the part itself and PLA for removable mold supports 3-D printing is capable of quickly producing highly complex configurations.
A key to the efficiency of the process is fast, safe removal of the PLA mold support without risking damage to the ABS part. An ultrasonic cleaner is proven far faster, safer and more effective than water sprays or manual scrubbing.
3-D Printing in Brief
Computer aided design files for components are programmed into the 3D printer which uses thermoplastic filaments to create components by successively building up extremely thin layers of plastic. The ABS filament ends up as the product; the PLA filament, deposited at the same time, serves as a support for overhangs or by filling voids and other openings in finished products. Once a component is “printed” the mold support must be removed. It’s here where ultrasonic cavitation comes into play.
How to Remove Fused Deposition Modeling Mold Support
First a caveat: Our example uses ABS for the part and PLA for the support. That’s because PLA can be removed by ultrasound leaving behind the undamaged ABS component. The cleaning bath chemistry is also important as it must be strong enough to work on the mold support without harming the part itself. Other support materials include water-soluble waxes or brittle thermoplastics that can be removed by water and a surfactant. The takeaway is that the more complex the shape the more important ultrasonic energy is for complete support removal.
That’s because ultrasonic cavitation, the implosion of millions of minute bubbles created by generator-powered transducers vibrating at ultrasonic frequencies, reaches all surfaces immersed in the solution. The implosions safely remove mold support compound without affecting the ABS part itself.
Ultrasonic Cleaning Equipment Suggestions
A good selection for this application is the dual-frequency Elmasonic TI-H ultrasonic cleaner series available from Tovatech. These professional units are available in cleaning solution capacities of 1.3, 2.8, 4 and 5 gallons. Make your selection based on the size of products being cleaned.
Ultrasonic frequency, given in kilohertz (kHz) or thousands of cycles per second, determines the size of the cavitation bubbles imploding on contact with the parts. Higher frequencies produce (relatively) smaller and gentler bubbles that penetrate small openings in the 3D printed part. Cavitation bubbles increase in size at lower ultrasonic frequencies and produce more vigorous cleaning.
For our discussion we’re using the 1.3 gallon Elmasonic TI-H-5 with operator-selectable 35/130 kHz frequencies. An important feature of the TI-H cleaners is their heavy-duty cavitation-resistant stainless steel tanks and ability to support the long run times that may be required to remove mold support. Other TI-H features that make it a truly versatile tool for supporting fused deposition modeling include:
- Thermostat-adjustable cleaning temperature from 30°C to 80°C (86⁰F to 176⁰F)
- Controlled ultrasonic power from 10% to 100% output to program cleaning cycles to what is needed to remove mold support
- A degas function that speeds the preparation of fresh cleaning solutions
- A sweep function for homogenous cleaning action throughout the bath
- Adjustable timing from 1 to 15 minutes or permanently on.
Cleaning solution formulations for removing mold support may vary depending on the mold support chemistry. This should be discussed with the scientist at Tovatech. In general, it will probably be a highly alkaline or caustic solution with a detergent serving as a wetting agent. Once the formulation is settled there is a fairly standardized procedure for removing mold support following the formulation directions. Here’s a general outline of cleaning procedures:
Add water to the tank fill line and the correct amount of cleaning solution formulation
- Turn the unit on and activate the degas mode to thoroughly mix the solution and drive off trapped air. (This must be done each time you prepare a new bath of solution).
- Set the thermostat to the recommended formulation temperature.
- Wear protective gloves and use tweezers to place the parts in the bath.
- Set the timer to permanently on* and place the lid on the tank.
- At the end of the cycle remove and inspect the parts. Again: never reach into an operating ultrasonic bath. Wear gloves and/or use tweezers to handle the parts.
- If satisfied thoroughly rinse the parts to remove all traces of solution.
The solution must be replaced when cleaning efficiency drops. Drain and dispose of it according to local regulations. Follow user manual instructions to clean the tank before filling it with fresh solution.
Contact the ultrasonic cleaning experts at Tovatech for information on selecting the equipment and cleaning chemistry best matching your operations. We can also provide suggestions for ultrasonic cleaners used by hobbyists working with 3-D printers.
*Cleaning time varies depending on the complexity of the part and amount of mold support. You will develop your routine based on your own experience.