ABS rafts suddenly start lifting off the print table.
I've been printing ABS onto an acrylic print table at 240 C for the past month with great success. This morning, I got up and started a few simple print jobs and suddenly the bloody rafts separate from the print table It's like somebody sprayed teflon on the acrylic.
The rafts seem to have the same characteristics as they did before. They just don't stick any more. I sanded off the acrylic but that didn't help at all.
Suggestions?
In the 'early' days I used Meths to clean the bed between every print but got a lot of cracks. They might start out as hair line but ended up defoliating the bed. I changed to a 'thick' bed and this also cracked up eventually but I did not use meths. My bed is very rough now with bigish chunks missing but the raft sticks well. I bought a spare a long time ago but have not used it yet.
I have found everyso often that the z seems to drop and there is too much of a gap and I have to reset the stop. But I am sure you know all about that though. I did use to use polish to stop static build up on the corners and was careful not to get any on the middle of the bed. For completeness I only use 235 for the raft but again that would not make much difference and you are probably more experienced than me anyway.
Well, I used isopropyl alcohol to clean the table this morning. I might as well not have done that. Afterwards I got mad, removed the table and went over it with my belt sander. It seems to be working right now. :P
I will remember that for the future. What grade grit did you use :o
I wonder why it happens. I have suddenly had rafts not stick and then you go for ages with it sticking OK. You have to wonder if it is like the static thread and temperature and/or humidity related. I have some temp and humidity monitoring and logging devices that I will have to put in to see if there is any correlation.
I will remember that for the future. What grade grit did you use :o
WA 80. Pretty rough.
The sanding only worked for a while. I finally flipped my print table and lightly sanded the new surface. It seems to be working fine now. :)
I realise you are experienced but was it bowed? Or eaten away in the middle or some contamination?
I am glad you found a solution I will keep it in mind for future reference.
It was pitted in a few places. The pits weren't the problem with the separation, however.
As to contamination, I cleaned the surface with isopropyl alcohol and that made no difference. There was no visible contamination.
Mind, I'd printed quite a bit of stuff on the table. It seemed to have just worn out.
I think I finally nailed the problem. I'm using 0.25 mm layers for both raft and print. I noticed that on one corner of the print the raft tended to be smeared a bit and the diagonal corner tended to lift in the course of the print. Mind, I was printing two pieces. I removed the acrylic print surface and put a milled straight edge on it in a variety of orientations. I have some slight warping of the acrylic surface. I used the belt sander on it {WA-120 grit belt} until the straight edge was pretty much perfectly flat. I'm doing prints now to see if that was the problem. It appeared that the bowing of much less than a mm was causing the problem. The fact that I'm using 0.25 mm layers and a 0.3 mm extruder orifice seems to require much closer tolerance print tables. I suspect that I will be sanding warping off of my acrylic print surface rather frequently.
hopefully that is it. Of course come to print today and the bed came unstuck. Strange effect I have seen before but only since 4.0.2 is that, after home, when the head moves to warm up position the z axis very slowly rotates down. This means the gap is very big by the time it gets to the warm up. When it starts to print, it moves towards the start point very slowly and the z axis moves up very slowly?
It also helps a lot if you'll print directly on double sided tape.
I think I got it...
If you're using ABS on an acrylic print table, it's difficult to get the raft to stick properly if the table surface is in the low 20s or colder. When I open my lab window to let out ABS fumes that is quite a common situation.
I have a small heat lamp that I beamed onto the print table that raised the acrylic surface temperature to the mid 30s and the detachment problem disappeared. :-)
Good work Forest.
That is why sometimes the bed does not stick and sometimes is does. Heat lamp on its way. I did buy some bits to make a heated bed but not yet got round to it. I might install one of the pads under the acrylic bed to just keep it a bit warmer.
raised the acrylic surface temperature to the mid 30s and the detachment problem disappeared. :-)
I used an old hairdryer for the same purpose. :-) Got to be careful not to warp the bed though so I alternated between printing on one side then the other. I did that until I switched to using a piece of laminated shelving from Ikea scrap yard for 50 c, abraded with 150 grit. Works great with PLA, don’t even need a raft, not yet tested it with ABS, will soon though. Cheapest print bed yet ;D I think ??? oh and I got two print beds from one piece so cost 25 c
I've done about a dozen small prints since my last post with the heat lamp on all. The surface temperature under the heat lamp is 35-40 C. I've had no further raft separations whereas before I was losing 1 out of 3 to 1 out of 2. :D
I blogged this result.
http://technocraticanarchist.blogspot.com/2010/09/dealing-with-detaching-rafts.html
Nice job Forrest! Thats the spirit!
Off topic: I also have a koala on my RapMan :D, my collegues where laughing about it and now as I saw your decoration, the snake, I was feeling better :). I'm not the only one "friki" around.
Giles reminded me to mention that you can switch the lamp off after the print has built up a few mm off the surface of the print table to a point where the extruder head isn't creating a big temperature change between the raft and the print table. If you are trying to print something small and delicate with very limited layer areas that becomes absolutely necessary as I discovered last night.
Has anyone tried actually printing on to an ABS sheet? I'm pretty sure that nothing will lift then. The model could be changed to have connecting tabs long enough to be cut and not hurt the pieces that is being printed.
I have been printing in my basement and I suddenly developed the raft lifting problem as has been described. The temperature effects could be the reason. I installed a 60 W lamp bulb with a reflector and have it positioned 10 inches under the board, being careful not to heat up the electronics or the plastic rolls. Hope this works! Thanks, Everyone!
I use a heated bed....but in the old days a heat lamp definitely helped!
Not everyone agrees on this one but a quick wipe with acetone has allways done the trick for me. But it might result in haircracks in the long run.