Thursday, February 5, 2015

3D Printing : Cold Vapor Smoothing

you can click on all the pics for larger views!
So I've been working on this Nexus 7 w/Battery Charger Holder/Stand (Prototype) which originated with this model on thingiverse .

Its an ok design, but the cable goes out the side instead of straight back, the stand itself slides around unless affixed to a surface even with the battery in the mount providing a bit a weight, and the magnet is so strong between the charger and the nexus7 that more than often the charger puck gets pulled out of the stand.  Not to mention that as presented its almost impossible to print on some printers.

So I took the design and tweaked it, I separated it into two sections so any printer can print it, I also placed in a small divot in the back of the charger area for some velcro or adhesive strips, as well as divots on the bottom to hold the stand in place on a surface, and included a "spinner" device so you can orient the viewing angle. 

However this post is really about the "finish" of the stand.  Being that I'm using ABS plastic which "melts/dissolves" in acetone you can use a process called vapor polishing to give your products a injected molded look. (You can't use acetone with PLA or other similar plastics, each plastic usually has its own chemical that similar effects can be achieved however some of those are really nasty compounds and I'd avoid using them in a process like this.)

There are typically two methods to do this and both are similar, one method uses added heat to hurry the vapor process and "melting" of the plastic along with a breif stint in the freeze of the object you want to smooth before you put it in to the hot vapor path.

The other method is using the same process minus the added heat and stint in the freezer.  This is the cold process

The cold process is essentially when you take a air tight or near air tight container, fill the bottom portion with acetone place your object on a non porous "stand" above the acetone and then wait for a period of time for the acetone to "melt" the outer layer of plastic of your object. 

Unlike most setups which involve paper towel lined paint cans, I've opted for a glass jar some metal mesh for the stand and the inclusion of a computer fan run off of a 12v lantern battery. I've never seen sparks from this setup, and while acetone vapor is highly flammable, I feel this is perfectly safe.  There hasn't been any issue with using the computer fan either, but as always you're responsible for your own setup and actions.  

I placed in the nexus 7 stand for about 2hrs in total, (started at 10 min checking, then waited 1 hr and it was shinny at that point and an additional hour made it glass smooth)

Now these were just prototypes while i was working out the issues with the design and printing, as you can see the non shiny one was an earlier prototype and the one section didn't print well.  

Even the shiny one all I did was remove the support material and glue the two halves together, very sloppily I might add, because I was checking clearences of the two ports and the spinner port more than worrying about fit and finish at this point.  

My final model is printed in glow in the dark ABS, so I'll be smoothing it after sanding the bad spots, along with including a light sensor and battery for a small LED that will shine in the middle of the stand when the lights go out to make it be "ultra glow'y" :)

Hope you enjoyed this post and thanks for stopping by!


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