ActOn Develops Cost Effective Vibratory Finishing Solution for Processing Selective Laser Sintering Parts

The Solution – for Parts Manufactured via Selective Laser Sintering

There are a few options on the market for finishing 3D printed polypropylene parts, including vapor smoothing, shot blasting and mass finishing. Though vapor smoothing gives a visually good surface and a gloss finish, this technique can be dangerous due to the fumes associated and flammable chemicals. Shot blasting most of the time proves to be expensive, as it implies a manual process. Mass finishing tends to be a preferred option to process additive manufactured parts, as it is a repeatable, cost effective solution.

As Ricoh did not have a specific Ra requirement, we carried out trials to show the range of finishes that can be achieved in different time periods. From this the client was able to choose the finish and timeframe that would give them the best result for their customers.

Processing Trials

The polypropylene samples we were provided by Ricoh to test included rotary atomizer head, rotary atomizer hub, adhesion samples, tension rod, VW bumper components, wing mirrors and automotive exterior trim. The initial surface roughness of these parts ranged between 3.6 microns to 13 microns.

As we previously proved that AM parts can be finished using ActOn’s Centrifugal High Energy technology, we processed the components in our CHE 40 machine for 60 minutes. The trial was carried using a highly abrasive ceramic media and a concentrated liquid compound, that acts like a cleaner and polisher. This compound is manufactured by ActOn and we recommend it for processing polymer, additive manufactured parts. Although the surface roughness achieved was between 1 and 3 microns, parts showed signs of damage.

Hence we repeated the same test, but we changed the media with a medium abrasive plastic media manufactured by ActOn. Like in the first trial the Ra results were good, however there were signs of damage on the parts. We knew at this point we had to rule out Centrifugal High Energy finishing.

We continued the next two trials using our Vibratory Finishing machines. Using the same ceramic media and liquid compound from the first trial, we finished the 3d printed parts in our Vibratory Bowl machine, for 20 hours. Visually the finished parts looked good, had no damages and the Ra was between 0.5 and 3 microns.

Proving that Vibratory Finishing is the way to process parts, manufactured via selective laser sintering, we decided to also test the finishing process in an ActOn Trough Vibratory Finishing machine. As Ricoh also manufactures larger and longer parts, the Trough finishing machine would give them the flexibility to process all types of parts, due to the shape of the process chamber. The trial proved to be a success showing an improved surface finish.

The process benefits include:

• In a 4 hour Vibratory Finishing process most of the Selective Laser Sintering parts are smoothly finished
• The process reduces the faceting caused by the printing process and could also be a method for reducing the orange peel
• The mass finishing solution we have developed helps our customer to achieve an Ra value of approx. 3 Micron. This is visually a good result, parts being smooth to touch
• The solution offered by ActOn is cost effective as client can use only one finishing machine to process 3D printed parts of different shapes and sizes.
• The ROI for this project was 34 weeks.

In Richard Minifie’s (senior AM engineer, at Ricoh UK Product Limited) statement, he concluded that:

We worked together to devise a series of tests and these were conducted by ActOn Finishing using a range of technologies employing different media types and a range of run times, to establish the optimised equipment and process to support our application. This was done quickly and professionally with regular updates along the way.

ActOn Finishing’s openness and willingness to conduct trials to establish the most suitable technology and process, was exactly what Ricoh required from a technical partner. As engineers, we like to capture lots of data to prove processes and learn through experimentation. During this collaborative project, we were able to share knowledge with ActOn Finishing to quickly establish a smoothing process for SLS printed parts. This open style learning approach is really important to Ricoh, because the knowledge developed provides value on both sides, which in turn increases the chances of future collaborative projects.

Result

Taking the rotary atomizer head as the example the Ra value started at 7.2 Microns. After the 4 hours process, in the Trough machine, this was reduced to 5.9 Microns and then to 3.681 Microns in 8 hours. There were no sign of contamination and part looked good visually.

We discovered that a finishing process between 8 and 20 hours can result in damaging the thinner wall sections of the part. Therefore, we recommended Ricoh UK Products a finishing process between 4 and 8 hours in ActOn Vibratory TU9 machine using mix sizes of the abrasive ceramic media, the concentrated liquid compound for cleaning and polishing and water.

We suggested that the TU9 finishing machine should be used with a divider plate, to create a chamber for the smaller parts to be processed and a chamber for the larger and longer components. We also included a jog button on the control panel to help bring the parts to the top of the media to make it easier for operators to collect the parts.