[reprap-dev] Printing ABS on stainless steel

Matthew Roberts reprap at mattroberts.org
Thu Nov 10 11:28:01 PST 2011


Yesterday I described my experiments attempting to print ABS on glass (attached far below) – today I have been experimenting with printing onto stainless steel.

I ordered a sheet of 316 stainless (300mm x 210mm x 1.5mm) from metaloffcuts.co.uk
(I chose 1.5mm so that it couldn’t possibly get bend in the post, with hindsight I could, and should, have ordered much thinner)

First conclusion: is that you can, just about, print straight onto stainless steel with a “2B” finish.


As before, I also tried printing on the sheet after sanding (about a minute of sanding, by hand, with 150 grit sandpaper – so the roughness is probably <0.05mm deep).
Second conclusion: You can *easily* print on sanded stainless steel.

Unlike the glass, you don’t seem to need to worry about cold drafts so much, so you can turn the number of “skirt” layers down to 1 (or disable it), and you don’t seem to need to heat the room either.

Also, I think that the “ABS in acetone wipe trick” should work with stainless as well – although I haven’t felt the need to bother.


So, in summary: I think I have a winning build platform.  The main benefit is that the stainless steel shouldn’t deteriorate with use.

--

For reference, I was printing at 250C (although 230C also works) on a bed at ~120C (wild guess: the base of the bed was at 130C).
For amusement, you shouldn’t order such a thick sheet if you wish to repeat this experiment – the extra mass means that my Y axis now has a much lower maximum acceleration!
Finally, a fair time ago I tried printing on FR4 – and like nophead ( http://hydraraptor.blogspot.com/2011/06/fr4-fail.html ) it works for a while and then dies.


From: Matthew Roberts 
Sent: Wednesday, November 09, 2011 12:00 PM
To: reprap-dev at lists.reprap.org 
Subject: [reprap-dev] Printing ABS on glass

I came across this http://www.thingiverse.com/image:78399 that was printed on a http://www.fablicator.com/
My thought was that the build surface looks nice (no tape), and the plastic looks like ABS.  A bit of digging later and I found out that the build surface is borosilicate glass.  Other people have tried to use ABS on borosilicate without success: http://forums.reprap.org/read.php?4,91047,page=2  But I thought that I’d give it a go anyway.
So, I got three microscope slides put them side by side on my bed and attached them (at the edges) with tape – making a ~70mm square glass build platform.
That didn’t work, so I roughed up the surface of glass (sandpaper does work, but I used a dremel).  The idea is that more mechanical grip should be better.  And the result is that it works (ish).
In summary:
On smooth glass, Printing ABS at any temperature (220C-260C) on to the slides at any temperature (100C-150C) doesn’t work.
On sanded glass, Printing ABS at highish temperatures (240C-260C) on the slides at a claimed 125C works.
Also, the first layer needs to be compressed into the glass to maximise the mechanical grip.

--
But... warping is a problem.  Even when it works, the glass doesn’t offer nearly as much grip as kapton – so you need to pull several tricks to reduce warping.  In principle, these tricks work regardless of the build platform – it is just that you need to do that to do them all with a glass bed:
The first trick is to stop cold air causing the object to detach at the edges... I used the skirt in skeinforge with enough layers to reach ~3mm height.  (you can use this trick to your advantage – you can detach objects by letting the bed cool a little and then blowing cold air on them.)
The second trick is to make sure that you are not stretching the ABS too much when printing.  If you stretch the plastic too much, then the plastic you lay down as perimeters is under tension – so after a few layers it will lift the corners and start to peel.  There are two ways to do this:
    extrude at a higher temperature.
    increase either the layer height and extrusion width (and plastic flow rate).
The third trick is make sure that the bed is surrounded by warm air – either a heated chamber or by simply closing the doors and windows in the room.  (This means that the plastic will not cool as far below its glass point, which should reduce the warping due to thermal contraction).
--
More on the second trick: I’ve noticed that printing with the same cross sectional area gives almost the same amount of warp – i.e. a 0.1mm layer height with a 0.9mm extrusion width is very similar to 0.15 x 0.6 and 0.2 x 0.45.  I suspect that to minimise this cause of warping: one should use a cross sectional area slightly smaller that extrusion into air.  (you need some stretching, otherwise bridges will be impossible). 
As an aside,  I believe that PLA swells less than ABS as it leaves the extruder – which means that naturally you’ll stretch PLA less (i.e. using the same layer height and extrusion width) – so this is probably one of the effects that makes printing with PLA on glass work better than ABS on glass.


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