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SimonIC

Printing multiple small models on 1 bed fails

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We're trying to print multiple small models on one bed. But it just ends up as one big mess. We're geussing the filament gets dragged over from one model to the next at one random moment and from that point on everything which happens next doesn't adhere to the layers anymore?

 

Which setting should I try to tweak? Currently we're just using the default "Normal" setting. 

 

Thanks in advance!

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IMG-20180710-WA0000.jpg

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It would be good if you saw the failure in action however...

 

It looks like the whole mess slid to the right at some point - does it go off the right edge of the glass?

 

So your basic problem is that your parts are not sticking well.  What are you printing?  PLA?  Is that masking tape?  If you use PLA with masking tape it's important to clean the waxy non-stick surface off first - use rubbing alcohol.  If you are printing PP (as opposed to PLA or ABS) then tape is indeed good to use.  Also wash with rubbing alcohol aka isopropyl alcohol.  In USA this is found in any drugstore next to where they sell bandages.  In europe it's a little harder to find.  But you can use ethyl alcohol instead (also known as vodka).

 

However you have a heated bed!  Okay you need to watch this whole video and become an expert at getting your parts to stick to the bed every time:

 

 

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Hi Gr5,

 

Thanks for your reply. Indeed we are using masking tape and we did clean the bed with alchohol before applying the tape. But when we print the models seperately the result is stuck very well to the bed. Do you think there having more models would somehow reduce the stickiness of the entire thing?

 

This particular print was done overnight, so we didnt see the error occur. We assumed that the accumulation of loose filament somehow ripped the entire print off the bed.

 

(I didn't have the time yet to watch the video you attached, but will do so over the weekend, thanks for the extra info)

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No.  Wash the tape.  🙂 

 

Masking tape has a layer of some kind of waxy substance to keep the non sticking side of the tape from sticking to the sticky side of the tape (I suspect).  You need to remove that layer.  It just takes a few seconds with a tissue and some rubbing alcohol.   I can wash a UM2 or UM3 bed in about 10 seconds.  So it's not a lot of work but makes a huge difference to how well things stick.

 

Even better, if this is PLA then use the heated bed without any tape.  Clean it off very well and then put a layer of PVA glue mixed with water.  There's 3 easy ways to get diluted PVA described in the video.

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In addition to printing on glass (without tape) as gr5 says, I would also suggest you put the models closer together, a bit further away from the edges. And then enlarge the brim so that is gets so big that it thoroughly connects all models. Otherwise, thin but high models might get knocked over. Or else, design a thin flat plate in your CAD models, which covers the whole bottom and connects all models.

 

What could have happened to you is that one model started to wobble (for example if the tape was a bit weak in one point, maybe due to air under it, or grease), then the print head crashed into it, knocking it over, maybe caused a layer shift due to the impact, unsettled and threw off some more models, and then a sort of chain reaction started? Just guessing of course, but something must have happened...

 

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It's hard to tell from the photo but I think they *are* all connected together (by brim) and the whole sheet slide over.  But it could be that the original poster purposely removed the "sheet" and looked at it and then put it back on the glass for a photograph and that the sheet did not slide around.

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Yes, I'm planning on doing such a test. (We're busy with other projects)

 

I only suggested retraction as an example, I'm not familiar with all the settings. I only thought maybe the printer head oozes out some filament while moving to the next model, somehow connecting both models and causing a chain reaction. Could this also have something to do with retraction?

 

Many thanks again for all the feedback so far.

 

Greetings, Simon.

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2 hours ago, SimonIC said:

I only thought maybe the printer head oozes out some filament while moving to the next model, somehow connecting both models and causing a chain reaction

You would definitely see such a connection after the fact.

 

But I am wondering if you had just a teeny bit of curl that did get caught. If it did not get stuck down properly, it takes nothing to knock things over. The curling can happen for a lot of reasons, but is very dependent on the material in usage.

 

Once a part gets knocked over, it can just leave an open spot for the part where it is supposed to be deposited on and just leave a giant sketti mess like your first print. It only takes one part to do what you saw.

 

I am still going with bed adhesion as the main culprit. But, definitely post the results of your test. That will provide further information as we go along.

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We ran some more prints. You guys were absolutely right. The problem was bed adhesion. We caught some in the act. 

 

It seems like the bigger the surface area, the more the brim starts to curl up near the edges? Is that common? This feels counterintuitive to me.

 

Anyway, I applied new masking tape and wiped it with alcohol. We also started using a raft instead of brim and are now able to print bigger batches with good results, the pieces are stuck really well to the bed now. There are some strange things the printer does from time to time, maybe I'll open a new topic if those persist.

 

Thanks again all for your help. 

 

 

Edited by SimonIC
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The longer the part in X or Y (or both) the more likely it will lift the corners.  So the smallest part to demonstrate this is a print that looks like a pencil but rectangular.  This is all discussed in very great detail (why it does this and how to stop the curling) in the video above.  I could explain it here but I already explained it in detail in the video.

 

After watching the video and doing the things I recommend you will have a new problem - how to get parts off the glass.

 

I can literally lift the printer up by a tiny 3d print like the ultimaker robot and swing the printer around the room.  I think I do that in the video also.

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