Removing finished prints

Ok, I'm loving my new Prusa and I've got most of the kinks worked out just a few more tweaks in my firmware and I'll be all set.

But the issue I'm running across now is that my prints are so difficult to remove I'm worried about breaking the print, or smashing my hand into the side of the Prusa when the part finally comes loose.

I've had this issue more with abs than PLA, but I do have it with both.

I've tried removing it almost right after it finishes printing, but of course the bottom layer warps as I pull it off the bed.

Letting the bed cool almost makes it impossible to remove, and this morning I destroyed a yoda bust printed with 20% infill when I tried to remove it. I ended up ripping his head off, and then his shoulders, etc until I got all the plastic off. This was the first time I broke a print, and I think it was because it was glow in the dark abs which seems to be quite a bit softer.

So do I need to get the bed to an intermediate temp to remove the part, say around 60c?

I print at 215 with abs and a HBP temp of 120-125c

On PLA I print at 185 with a HBP of 60c.

I am printing on a glass square with kapton tape covering. I also am pretty religious about cleaning the surface with either acetone or alcohol before printing, and I make sure it's dried before I start my print.

I've had almost zero issues with warping while printing.

Any tips would be greatly appreciated

Spraying the part with freezer spray works but is expensive.

Increasing the first layer height slightly will make the parts easier to remove. The effect is quite dramatic.

I use PET tape instead of Kapton because it is easier to get things off.

I use an adjustable wrench to grab the parts near the base, but that would be difficult with organic shapes.

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[www.hydraraptor.blogspot.com]

The best thing I've found is a laboratory spatula, similar to this.


The spoon side is usually thin at the edge (almost sharp), so you can get it under the edge first layer pretty easy and pry it up like the claw end of a hammer. Once the edge is up, i use the flat side to pry up the rest of the part.

There are also spatulas with an angled side, which you might think would be better for prying, but the material is too thin and it just bends (at least with the one i have). the spoon shape adds strength, in this case. here's an example of this type:

I've never understood how people get anything between the bed and the part. I can't get even a sharp knife in with out damaging the part or the bed or both.

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[www.hydraraptor.blogspot.com]

Yeah, I know what you mean nophead. I'm also afraid of either ripping up the tape, or worse breaking the glass.

I did go ahead and order some PET tape and I'll give that a try when I get it.

But first I'll definitely give the first layer thickness change a try, that would rock if that is all it took!!


Thanks for the great feedback guys.

Btw nophead I used your idea of flipping the belt so the smooth part is running on the idler, but I just twisted it halfway and didn't cut it. It's been working awesome so far and Spacexula liked it too when he saw how I did it. I was actually able to do it on both the x and y axis.

Yes I do that on both axes on my Mendel 90 and had no issues with the twist. A pain to model in the scad but it is in there now.

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[www.hydraraptor.blogspot.com]

I clean my kapton tape with acetone regularly, which makes the parts very difficult to remove. For ABS on a 6mm aluminium plate with kapton, I have found that about 10 minutes in the bottom of the freezer helps a lot. The plate comes out ice cold and a sharp smack on the edge of the table gets them off. For very large parts I sometimes have to resort to a knife or ruler under the corner, but this risks damaging the tape.

Thinking this through, the main reason this helps is that the expansion rates of aluminium and ABS are quite different.

Looking this up (Units 10^-6/degree C)

ABS is 50
Aluminium is 23
Brass is 19
Glass is 8.5

This leads me to believe that it would work better on glass.

nophead Wrote:
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> I've never understood how people get anything
> between the bed and the part. I can't get even a
> sharp knife in with out damaging the part or the
> bed or both.

Ah well i'm using blue tape on a unheated glass bed, so yes, it damages the (cheap) tape sometimes but not the part or the bed.

I got a spatula from the artist supply place. It is used to spread paint on a canvas so is too thin and flexible to lever things off the bed. But because it is so thin it is easier to get under the print without gouging it and then I twist a bit to get it started. It is then easier to get my wedge (similar Buback's spatula) under to pry it up.

Ok, I went ahead and ordered some PET tape which I'll give a try.

I also experimented with the HBP and found that if it's cooled off and I cut it on after about 30 seconds when it warms up a bit it will pop off without to much trouble. The other trick is being patient enough to let the HBP cool off enough where I can pull it off without warping the part.

NCBob Wrote:
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> I also experimented with the HBP and found that if
> it's cooled off and I cut it on after about 30
> seconds when it warms up a bit it will pop off
> without to much trouble.

Hmm that's an interesting idea. A heating/cooling cycle would make the HPB "ripple" as it expands and contracts. Maybe someone could program a routine to ramp the bed up to X temp and back to 0 temp for N cycles, to remove stubborn parts?

Buback Wrote:
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> NCBob Wrote:
> --------------------------------------------------
> -----
> > I also experimented with the HBP and found that
> if
> > it's cooled off and I cut it on after about 30
> > seconds when it warms up a bit it will pop off
> > without to much trouble.
>
> Hmm that's an interesting idea. A heating/cooling
> cycle would make the HPB "ripple" as it expands
> and contracts. Maybe someone could program a
> routine to ramp the bed up to X temp and back to 0
> temp for N cycles, to remove stubborn parts?
Actually even better I'm going to add some gcode at the end of the print to do that using the dwell command.

I'll turn the heat off for like 5 minutes, then turn it up to 50 for a bit then shut it off again as the first try and see how that works.

Nice thing about that is it won't require any firmware changes, just a change to whatever gcode generator that you use to add the temp cycle commands at the end of the print.

Thinking ouside the box for a moment, most parts could be remodelled with a little chamfer around the base, say 1mm x 45Deg.

Visually you probably wouldn't notice the change, but it would give you a little gap to get a spatula under the corner to lever the part off.

Really all you need is one corner with the notch/chamfer. If you can get up one corner, the job becomes much easier.

----another idea
For some bed surfaces the main sticking force is atmospheric pressure (van derwaals, right?). Potentially, a model only needs enough surface area to supply enough force to keep the part stuck during printing, which would be x% of an area. You could have the first layer print as a bunch of squares instead of a flat sheet, maybe 60%/cm^2 (or whatever you'd need based on your bed material). So you'd end up with lots of 60mm^2 patches for the first layer, with air gaps between them. Some of the second layer plastic would squish into the gap (or sag?), but i still think there would be enough air gap to reduce sticking force.

This would work best with prints with a large surface area stuck to the bed. On the other hand, those same types of prints are the ones that have warping problems. I suppose you could get around this by having the percentage be lowest in the middle of the part and get 'fuller' closer to the edges.

The major disadvantage is that it would ruin the mirror finish on the part.

I think chamfering the corner will encourage it to lift during the build.

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[www.hydraraptor.blogspot.com]

HBP with 3mm glass covered in Kapton tape cleaned with acetone.

ABS sticks perfectly at 100ºC and pops off when the bed has cooled and zero warping.

I set my fan connected to D9 to turn on for 6 minutes after the build has finished and the pats lift right off.

Mine don't pop of when cooled and they are very difficult to remove. Large items will lift the tape from the glass. There seems to be a big variation in people's experiences of what sticks to what.

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[www.hydraraptor.blogspot.com]

When the parts sticks too much to be removed by hand, I use "bent" pliers like this :


Grabbing the part with the curve of the pliers touching the bed, then applying a down force so that the lever effect will push the part up.

This is with PLA then, ABS might be too soft too allow this method.
Also this is on a cold bed with scotch blue tape.

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Most of my technical comments should be correct, but is THIS one ?
Anyway, as a rule of thumb, always double check what people write.

This is a funny issue, I just changed from PLA to ABS and at first I was struggling to get the parts to stick to the build plate, now that I'm nearing the end of the first roll of plastic, I'm struggling to get them off. I'm now degreasing the Kapton tape with electronics cleaner, then taking a little bit of ABS and smearing that to the surface with acetone. Crazy adhesion! Nothing seems to lift the corners anymore.

nophead Wrote:
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> I've never understood how people get anything
> between the bed and the part. I can't get even a
> sharp knife in with out damaging the part or the
> bed or both.

I have a build plate with a total of 12 sunken screws (4 for mounting and 8 for power resistors) and for bigger parts, at least one is usually at the edge of the object and offers a spot where you can stick something under it. (The screw heads are a little bit below the main surface, not much, but enough.) I recently printed the Y carriage, and when the bed had cooled, used a screwdriver to lift one end so that I could stick a crowbar under it. Yes, I actually used a crowbar, and no, I didn't break anything.

An odd thing actually happened afterwards. Some time later the part had gotten reverse warping: the arms had bent a mm or two downwards. I suppose things like that (190x120 mm size, 69 g of plastic) should have their stress relieved in a more controlled manner. Does anyone have any experience about that?

When I switch from PLA to ABS the ABS comes out a little shiny for a long time. It has some PLA mixed in and that prevents it sticking because it is too soft at ABS bed temperatures.

Yes large thin parts do reverse warp a little. That is because the bottom is kept warm by the bed, so it cools down last and shrinks after the top has become solid. It has never been enough to bother me so I haven't done any experiments to try to reduce it. Keeping the top warmer should help and also cooling the bed quicker. Maybe there is an optimum time to switch the bed off before the print finishes, or maybe drop it to about 70-80C.

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[www.hydraraptor.blogspot.com]

I had some great success today with ABS on copper clad board covered with kapton tape on top of the heated bed.

The board is very flat but is also bendable. I attach it with binder clips and when the print is finished i pull it off an bend the board. The parts come flying off at high speed and the tape is left intact. I also clean it with acetone after every print.