As some of you will possibly remember I upgraded my RapMan to a double extruder some time ago and did some prints with ABS for the object and PLA for support material. I did my first prints like this during last summer and I used Caustic Soda or Lye (NaOH) to remove the support really quite successfully. A couple of months later I tried again and with a dangerously strong mix of NaOH even after 2 days the support was still intact…. I suspected that it was because of the colder weather. I was also very concerned that this was far too risky to do in school, we needed to find an alternative approach!
So I talked with the guys at BfB and thinking around the problem it started to become obvious why the PLA is biodegradable…. It’s to do with 2 things- HEAT and MOISTURE. i.e. the things that make it degrade when buried in a rubbish tip or compost heap.
The guys at BfB then started experimenting and passed on their ideas for me to try out too. And here is the good news…
PLA SUPPORT MATERIAL CAN BE REMOVED JUST WITH HOT WATER !!!
The process is somewhat slower than with NaOH but considerably safer.
As a result of this testing it looks like all you need to do is immerse the part and support into a container of hot water at 80 degrees Celsius for about 36 to 48 hours… after this time the PLA starts to go brittle and crumbly – you can easily and safely crush it (almost to a powder) in your fingers.
The problem is how to maintain a container of water at 80 degrees Celsius for this amount of time… The guys at BfB allowed me to borrow an ultrasonic cleaner tank for a few days and this seemed to work very well… I only used the heater not the ultrasonic part which may or may not help (not tested yet)… I have a feeling BfB might consider supplying these tanks sometime.
So for support materials removal…
Method 1… SAFER…. But slower… Hot water at 80 degrees Celsius for 36 – 48 hours
Method 2… RISKY… But faster… Hot, NaOH (time depends on strength and temperature)
(method 2 is made a bit safer by using a proper tank but don’t forget NaOH is very corrosive and you should carefully assess the risks to yourself and others before you consider trying it)
For those of you who have not come across ultrasonic tanks there is a photo attached (other styles and makes are available) In school why not see if your science department has one of these that you can use.
Essential to have…
Thermostatic control, A lid to prevent evaporation, Safety cut-out (as liquids and electricity don’t tend to work well together), Correct voltage machine, A timer is probably useful, Ultrasonic may or may not help… not tested by me.