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mike-truly

Lifting Edges of Large Print on UM2

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I have a large, rectangular print of some terrain. It is large but not the maximum build size.

I have attempted to start this print several times today. The last problem had the corner lifting at the beginning of the print so I aborted. I re-leveled the bed and the attempted again. This fixed this problem and the print started fine with all 4 corners and the whole print adhered to the bed. Then I noticed a few, very slight lifts to the west-northwest but inside the outer edge (the outer edge wasn't lifted at all). Then as time went on, bad lifting started occurring on the outer edge of the northwest to the southwest edges. (see attached image).

lifting print 02

I am not at the limits of build volume yet I am not sure why this is happening.

Thanks for any ideas.

 

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Thanks very much for the ideas!

I am printing with white PLA and using glue. I will have to look into 'brims'... not sure exactly what that is yet.

I think one of the problems was that I was using too much glue. I cleaned the bed and re-applied a very light layer of glue (I hope I don't have problems getting the part off the bed!). After doing this, it is now printing much better with all edges sticking down.

The large box idea seems like a good one. I have been wondering if ambient temperature in the build chamber is warm enough. I am located in a very cold environment at 9500' elevation. The room the printer is in houses other computers and equipment, so it stays warmer than other rooms, but I will need to place a thermometer in there to get the temp. Would be nice to have an enclosure box made of plexiglass with an openable door. I wonder if anyone makes something like this for the UM2? Is there an ideal temp for the build chamber?

Thanks again.

 

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An easy trick to get big parts off the glass is to let the glass cool down, remove it from the build chamber and let it come to room temperature. Once it reaches room temperature, put it in the fridge for 20 minutes. Because the glass and plastic cool down at different rates, you will easily be able to remove it from the glass.

In regards to Brims, it basically just increases the surface area of your print, and if the print lifts, it will likely just lift the brim. Once the part is done the brim should be pretty easy to remove. You can turn it on by going to the Basic tab in Cura, and then choose it at the bottom where it says "Platform Adhesion Type". And you can adjust the amount of lines on the Brim by going to Expert>Open Expert Settings and you'll see it in the right column. I would just leave it as the default for now and give that a try.

 

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Sigh... I looks like it's lifting again on the left edge a bit. I may have to abort and retry.

lifting print 03

Because the foundation layers of this model spans the entire model and it's large... I wonder if that is contributing to the pulling/lifting. I may need to try a more hollow model with interior supports.

 

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For PLA, start the print with the bed temp set to 65C with fan off, then after the first layer or two, reduce it to 55C and gradually increase the fan speed to whatever works for the print.

This gives good initial adhesion, but then makes the bottom layers firmer and less flexible, without causing them to shrink much. The net is that they will remain stuck to the build plate, but be less likely to be warped upward by additional layers as they are added and shrink with cooling.

This is good practice for any PLA print.

 

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EldRick,

Thanks for these tips! I understand the concept of what you're suggesting, but as a newb, I'm not sure where to implement these changes.

Are these settings to control bed temp and fan speed put into the gcode via Cura settings or are they something that must be setup on the printer itself?

I have looked at the expert settings in Cura and have found the 'fan full on at height' setting. Is this what you mean by controlling when the fan starts? I did not see any settings for setting the bed temp.

When I look at the Maintenance settings on the UM2, I do see a setting for 'fan speed' and as I adjust it the fan speed is controlled. Am I supposed to adjust this setting by hand while printing?

Sorry for my ignorance.

Thanks!

 

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...

I have looked at the expert settings in Cura and have found the 'fan full on at height' setting. Is this what you mean by controlling when the fan starts? I did not see any settings for setting the bed temp.

...

 

The fan settings in Cura are a good starting point. I suggest to carefully read the tooltips for the other options in this section too.

The presets for temperatures, fan and material flow can be found on the material settings menu directly on the printer.

Some finetuning can be done during a print - just use the options in the TUNE menu.

A good advice seems to be to change only one option at a time and only by a small amount. During this - observe the ongoing printing process and expand your experiences...

I suspect the latter we will do altogether for the next few years or so...

Good luck! ;)

 

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OK, I have done several things that is greatly improving my results. (Not sure if only one of these things is giving the better results).

I used Tweak at Z to adjust bed temp and fan speed and print speed during the first few 'foundational' layers.

I removed ALL glue from the bed! (The only thing that might be left is some invisible residue... the glass looked very clean).

1. The Glue issue. This is somewhat confusing. There was a document that came with the UM2 that basically said 'glue will help your print stick to the bed'. Then there's info that glue 'will help you remove your print from the bed'. This seems contradictory and confusing. (I realize that different materials might need glue or not, just seems that with my current large footprint print where edges were lifting that no glue might help it stick to the bed better).

2. In TaZ (TweakatZ), what does the 'New Speed' number actually mean? It's a percent from 0-100% and I think the normal print speed is 50mm/s. If I put in a value of 50% into 'New Speed', is that going to be 25mm/s or is it 50% of the maximum possible speed the UM2 can do? Confused.

It seems like it would be ideal if TaZ had the option to let the user interface with 'curves' rather than plugging in values at different layers. For example, on Fan Speed if the user was presented a manipulable curve on a graph that the user could edit the curve to define what the fan speed should be. Same for print speed and temp and the other parameters. (I realize this would be a lot of work to setup... but I'm wishing here!).

Thanks again for the tips!

 

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2. In TaZ (TweakatZ), what does the 'New Speed' number actually mean? It's a percent from 0-100% and I think the normal print speed is 50mm/s. If I put in a value of 50% into 'New Speed', is that going to be 25mm/s or is it 50% of the maximum possible speed the UM2 can do? Confused.

 

It's going to be 25mm/s.

 

It seems like it would be ideal if TaZ had the option to let the user interface with 'curves' rather than plugging in values at different layers. For example, on Fan Speed if the user was presented a manipulable curve on a graph that the user could edit the curve to define what the fan speed should be. Same for print speed and temp and the other parameters. (I realize this would be a lot of work to setup... but I'm wishing here!).

 

This is maybe something for Cura 20.01... ;)

 

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Both statements are correct re. the glue. It gives a slightly rough surface that helps adhesion for the first layer, and also provides a sacrificial layer between glass and plastic that permits easier removal.

Once the bed has cooled, put it in the freezer for a few minutes, and the print should come off easily. I find that the glue works best after the first print or two, when it is only a thin layer, and after condensation on the cold build-plate evaporates and seems to somehow reactivate it.

At worst case, you can soak the bed in water for a while to dissolve the glue and soak the print loose, without risking pulling chunks of glass off the build-plate by prying.

 

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OK, my print finally finished successfully. One issue is that the bottom levels have elephants foot a bit. I'll have to work on that.

And I had NO problem removing the print from the bed! Just a gentle push at two corners with my glass scraper and it popped off. Also has a nice mirror finish on the bottom!

print bottom edge issue

Thanks again to all for the tips!

 

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One thing that's very weird regarding the speed in TaZ...

If the regular speed setting is 50mm/s... well I've seen that so I kinda know what that speed looks like. If 50% of 50mm/s is 25mm/s then here's what I did:

I sent the first terrain to print with the TaZ setting started off at 25%. This means it was actually moving at about 12.5mm/s (very slow and printing well). Then later I ramped up the TaZ speed setting to 50% which would mean it was travelling at 25mm/s and it did the rest of the print at this speed. (The results were good but very slow).

So on the second terrain, I set the TaZ setting at 50% and then later ramped up to 100%. The printhead was flying so fast like I've never seen it before. The whole printer was shaking more and the print was coming out poor so I aborted it.

Seems like this speed setting in TaZ is NOT doing 100% of 50mm/s (which would be 50mm/s) but rather something much faster than 50mm/s (when set to 100%)!

Thanks!

 

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