Tuesday, November 3, 2015

Post Processing: Step 1 - Obtain Test Items

The more I research the various ways people are post-processng their 3D prints in ways other than vapor treating ABS, the more I realize that getting it right is going to take some serious repetition and experimentation.  After all, for the most part, we are using equipment and smoothing material that are designed for rocks and metal parts.  So, to some extent we are in uncharted territory.

So, I am going in three different directions... epoxy coating, rotary tumbling and vibratory tumbling.

Smooth-on XTC 3D Print Epoxy Coating

I've ordered the Smooth-on XTC.  It should arrive in a day or two.  The total cost, with shipping was around $38.00.  I also called Smooth-on to try to establish some contacts that could give me quick help if I run into difficulty.  I don't want to be unfair to a product due to my own inexperience.  I managed to get through to technical support right away which was encouraging.  So, it seems we are off to a good start with XTC.  But, I will need to purchase a better mask before working with it.

Smooth-on XTC 3D Print Coating

Harbor Freight Rotary Tumbler

If tumbling works, it's probably a good idea to purchase a more robust rotary tumbler.  But, for now, the Harbor Freight dual tumbler is on sale for under $55.  The double tumbler should allow me to test two different media at the same time for the same time, allowing for better comparison.

Harbor Freight Double Rotary Tumbler

Harbor Freight Vibratory Tumbler

Harbor Freight offers both a 5lb version and an 18lb version.  I have purchased the 5ib version at under $55.  Shapeways uses a professional vibratory tumbler for smoothing nylon parts.  While I'm not sure that trying to use a tiny tumbler will perform anywhere close to the monster they use, it was certainly worth exploring.

Harbor Freight Vibratory Tumbler

Starting Materials Selection

Since I'm starting this process from a completely ignorant position... my usual starting place for such adventures, I've simply picked up the most easily available materials for the first tests.
  • Medium Ceramic Abrasive Polishing Tumbler Media
  • Rust-Cutting Resin Abrasive Tumbler Media
  • Rock Polishing Abrasive Set
  • Ground Glass Abrasive

  • Petco Mini White Aquarium Gravel

We'll discuss each material type as we test them. 

I will start the first preliminary tests today.  But, I don't expect to report anything until I know that I am using the right proportions for each tumbling method.  For instance, rotary tumbling usually involves water.  But, how much is not so easily determined by searching the web. The vibratory tumbler that I purchased is NOT intended for using with water.  But, is it still advisable to put the pieces into the tumbler in a wet state?  Again, it's not clear from the little research I have done.  So, I don't expect great results any time soon.  All we can promise is that we're going to give it a good try.

But, it would be VERY helpful if you have any experience at all to share it.  :) 

An Additional Test Item

I should also mention an additional product that I will be testing with Infinity Supports.  Frankly, I'm still not comfortable with washing off the supports directly in any of my sinks where chunks of support might be washed down the drain.  I am more comfortable with ensuring that the Infinity Supports have been thoroughly dissolved first,  I've been using a bucket for this purpose.

But, at the same time that I picked up the vibratory tumbler, I picked up a  portable parts washing station at Harbor freight.  

 It's not at all clear if this is a good solution or not.  But, at under $50, it is certainly worth exploring if it helps us avoid unintended and unexpected issues down the road..


  1. Tom;

    Great post! Some truly interesting ideas!

    I have completed post processing on three projects with the Smooth-on XTC 3D coating material and have definitely learned from the experience!

    1. Do not mix up more than you need - measured mixing cups work great but a single use syringe works much better, allowing you to make up very small batches. ( at 37 cents each it is a no brainer)

    2. A small disposable aluminium pie plate (4”) works much better than the dual layers of foil and allows you to spread a very thin layer which does not harden as fast. It also keeps your workspace much cleaner and prevents unwanted spills.

    3. Don’t forget to use disposable gloves that fit your hands, this stuff is sticky and if they are not fitted you will get unwanted material on your print.

    4. Use smaller (disposable) brushes an clean the detail rides as they run. This will give you a much better result. A set of 20 cheap brushes cost me $3.99 and by using isopropyl alcohol (99%) on a paper towel I was able to clean them between strokes and get multiple uses.

    5. As stated, the material is dry after two - three hours at room temperature but I let a couple of projects cure overnight and found I was able too sand and scrape the surfaces with better results.

    6. As far as painting, I used normal metallic spray (Kroylon) on one and got a great smooth finish. I also mixed some metallic acrylics myself and used a quality airbrush that I had sitting around to apply and got some amazing results (vignetting and blending). A final thin coat of clear (Kroylon) gave me the finished product that I was looking for.

    I am now going to experiment with a Paache Air Eraser (airbrush size sandblaster) that I have and some aluminium oxide material to clean up the fine details of my next prints before applying the XTC 3D product.

    I will keep let you know more as I continue to experiment.

    Keep on keeping on!


  2. Fantastic information. Thanks!

    I am in the midst of the vibratory and rotary tumbling experiments. But, it's going to take some time to get the combinations right. However, I have already determined hat I need the larger 18lb vibratory tumbler. And, I've also learned that (1) the vibratory tumbler CAN help remove Infinity supports with just water and (2) Infinity supports are too sticky for walnut shell media. Not pretty! LOL!

  3. Hi Tom I was wondering if a modified clay trap would work for using a utility sink for your washing needs? Here's a video showing how to make one. I was thinking a screen on the last outlet would prevent floating parts from getting through?

  4. You would think that with a clay studio in my back yard for the past 15 years, I'd know that. But, it's the first time hearing about it!