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LePaul

Larger parts pulling tape off bed

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Anyone else run into this?

I was making a piece that was about 7 inches long, 100% fill (geared rack so it needs the strength) As it got about 70% done you could see the part was pulling up on the tape and while not ripping it, it was lifted a half inch, ruining the task

 

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It's common for large prints to warp, as the plastic cools it contracts causing the sides to peel up.

What helps without re-designing is:

-active the brim option

-Clean your tape with some alcohol it'll stick like mad, most likely ruining your tape.. but it will stick well.

-try reducing your active cooling if possible

More effective solutions I find are:

-design relief spaces in your object if possible (little square/pyrimid cutouts) on the bottom if you don't need a perfectly flat surface. good for halfing parts and gluing them together.

-round/chamfer your sharp, convex corners. Sharp corners tend to warp the most.

 

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iv printed tons of big building models..

my best tips would be....

_ print your first layers nice and slow.

- make sure the first layers are really flat and squeezed a little against the base.

- have good tape down..really tight to the print base.

- use lots of brim... i normally have 20 in the expert settings

- turn off the coolng fan for the first layers

- dont print to hot.. 220 should be fine for most pla

that normally gets a good model or atleast a flat model ;-)

Ian :-)

 

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I was printing at a speed of 40 and the temp set to 230

With the printer in the basment and the temp down there about 50, I have had good results with 230 so far.

Let me upload the part, I don't have the mixmesh version but i am really curious how others would approach printing it.

 

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Hello LePaul,

first: it seems large parts will warp, no matter what.

You can reduce the warping though.

Apparently the most effective way is having a heated bed, and/or heated build chamber.

I personally have no heated bed yet. But i am printing on glass now instead of tape. The glass is covered in a thin layer of wood glue thinned with water (so thin it looks like water colours), applied with a soft paint brush. It needs to dry before printing, of course.

I clamp the glass to the original acrylic build platform, so i can swap out the panes. Thus i can have panes prepared and just switch them without waiting when i want to do the next print, and can still use the original levelling screws.

(You need glass panes 220mm * 240 mm, mine are cheap 2 mm thick from a DIY store, although thicker should be better)

I have better adhesion to the glass/glue than i had to the blue tape, and less warping (not none, though, and for very large parts (200mm long), the corners still come off, but less so than they used to on the tape). Plus, i have mirror-like undersides of my printed parts. And finally, the printed parts almost pop off of their own after cooling. that's another up side of having several panes: You can take one out and leave it to cool, swap in the next and print on happily while the first one cools :-)

Hope that helps you a bit?

 

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If the part is pulling off the tape, then the above posts have great advice. But if the tape is pulling off the bed, then use wider tape. Use standard blue tape from the paint department at any hardware or paint store. Get the widest you can. I use about 3" wide tape. Illuminarti uses 6" wide tape he got through the internet.

Also clean the print bed before you apply the tape with windex or soap and water or alcohol or whatever. The point is to get any finger oils off. And push that tape down hard with your fingernail or a putty knife so it sticks well.

printing on glass is a great option also. Google it in these forums but the quick explanation - for about $20 you can have the local glass store cut you a piece to size (make sure it fits inside the screw holes) and get it thick - 1/4 inch. Have them ground the edges so they aren't sharp. Then clamp down with heavy duty paper clips so it can expand when it heats. You will have to lower your Z limit switch by quite a bit - maybe lengthen the slots or build a Z limit switch extender (print it) - read about these things - you pop it on and off when you pop the glass on and off.

Then use wood glue mixed with water on the glass. Heating the glass to 100F (30C) and printing the first layer at 240C helps quite a bit.

Another totally different thing you can do: Move your printer into a warmer room! Just for this one print. PLA shrinking isn't an issue until around the glass temp (around 60C) and a normal room is around 22C. That 40C decrease in temp shrinks the PLA around .3%. In a basement at 50F (10C) you get that much more shrinkage.

Or put a light bulb heater under the bed and enclose the sides with plastic.

 

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Is there a PDF/DXF of the build plate so a glass maker could make one out of glass?

I'd love to print on a heated surface but we're waiting on Ultimaker for that option :)

Any brand wood glue better than the other? What's the ratio/recipe for such a thing

 

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It's just a rectangle, lol. Those glass cutter people know rectangles well. It's pretty much their main thing. Just measure to the inside of the screw heads and then edge to edge in the other direction. Or you could remove the bed from your printer and hand that to the glass guy and say "make it like this please" if you want the screw holes and everything. That will increase the price significantly for something you may only use twice before getting a heated bed.

Again, 3 inch tape works much better than the 1 inch tape UM provides.

The cheap elmers wood glue stuff. I think it might be "PVA". Google it and see what other's are using and what ratio. Personally I use elmers glue stick which also works but is not as dependably spread perfectly even without using a wet tissue.

As for the Z height thing - careful you don't break the glass the first time you home and smash it into the print head:

https://www.youmagine.com/designs/z-material-add-on

Print that with the exact same thickness as the glass you buy.

Also consider cutting a corner off the glass bed where the head homes so the head homes in mid air. You can then extrude in home position and there is some air under the head. Of course this limits the size/shape of the maximum thing you can print.

 

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>That will increase the price significantly for something you may only use twice before getting a heated bed.

Also glass is easy to break and you might break it so getting the cheapest, simple rectangle might be best.

 

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I'm using the 2.83 inch (Scotch brand) painter's tape and that's what got peeled upwards.

I wipe down the surface of the tape with rubbing alcohol and allow a few mins to evaporate.

I have no problems with print sticking...almost too much! I have to gently lift under the tape most times to get the part free. Many times, I have to soak the bottom of the part in rubbing alcohol for 15 mins and gently razor off the tape. Its getting to be a pain!

But I'm certain that big part was sticking very, very well!

The glass looks interesting

 

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I don't know if the glass will work any better. Better to print in a warmer room. Or to make a heated chamber - printing in a 50F basement is part of the problem. Put a light bulb under the bed, enclose 3 sides in saran wrap. Put a box over the top. Let it heat up to 80F before you start printing.

 

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