PLA prints on glass are warping

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lukeott
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PLA prints on glass are warping

Post by lukeott » Thu May 15, 2014 1:06 pm

I thought that with the introduction of the new Windows software v2.11 I would try printing with PLA as I often print large models and get warping with ABS.
I've bought a reel of FormFutura premium PLA and am printing onto a sheet of glass with glue stick applied. The bed is levelled to within 0.1mm overall and the nozzle is set to 0.2mm at the centre of the platform.
However, I am still getting warping of the parts on relatively small parts. The first part below is about 30mm long yet the flat base is bending up at the edges by approx 1.5mm.
The warping also means that after a while the nozzle touches the edge of the print knocking the part off the build plate (see 2nd part!).
I have tried with and without a fan blowing over it and with and without preheating. (material obviously set to PLA)
Any tips on what else I can try would be appreciated. If this is the amount of distortion typical with PLA then I may as well stick with ABS.
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D3rax
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Re: PLA prints on glass are warping

Post by D3rax » Thu May 15, 2014 2:21 pm

You could try blue painters tape. Worked well fore me when I was printing with PLA from Formfutura.
Up! Plus

lukeott
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Re: PLA prints on glass are warping

Post by lukeott » Thu May 15, 2014 4:31 pm

Thanks, that was on my list of things to try if I don't get anywhere with the glass. I was just amazed at how much the PLA warped. I would be very surprised if an ABS print of those parts on a perfboard with raft curled up that much.
Are you finding that PLA parts on blue tape are showing less shrinkage than ABS? (As is the conventional wisdom, or so I thought)

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woofy
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Re: PLA prints on glass are warping

Post by woofy » Thu May 15, 2014 4:42 pm

What temperature is the glass?
PLA sticks to glass very nicely without tape or glue but the bed temperature needs to be 60-65C.
Also shut the fan off for the first few layers.
(Experience comes from printing PLA on my Ultimaker, I've not tried it on my UP).
UP plus, Ultimaker2 & Raise N2+ Printers.

lukeott
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Re: PLA prints on glass are warping

Post by lukeott » Thu May 15, 2014 5:07 pm

I think the platform was at 60 deg C during printing.
I'll try your tip about switching off the fan at first, thanks.

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wilsonj
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Re: PLA prints on glass are warping

Post by wilsonj » Thu May 15, 2014 9:17 pm

Try a different brand of glue stick. Glues aint glues. :D
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Jamie
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DrewPetitclerc
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Re: PLA prints on glass are warping

Post by DrewPetitclerc » Fri May 16, 2014 3:52 am

I've been very successful with my UP Plus Pro, I print all materials at ABS settings and adjust the temp of nozzle with a mod from:
http://www2.artaylor.co.uk/pp3dp.html
With PLA I run air injection to the extruder gear to prevent pre-softening/strip-outs and standard picture frame glass with washable glue-stick.
You need a few more mods to have better luck.
Regards
Drew
Drew Petitclerc
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roller
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Re: PLA prints on glass are warping

Post by roller » Fri May 16, 2014 6:55 am

PLA still shrinks just not as much as ABS. So you still need good surface adhesion to the bed to stop curling. As D3rax suggested, blue painters tape is worth a go as it is one of the most reliable surfaces for PLA printing. That said the newer 3M tape with the logo printed on it is nowhere near as good as the old stuff and other brands are a mixed bag. All though are generally better than glass. As for glass ... not all glass is created equal either. I have found some glass surfaces to be much less reliable than others - this is not a matter of cleaning but something to do with the surface finish of certain types of glass - unfortunately I was not scientific about my glass collection early on and once it's all mixed up glass kinda looks the same so I cannot provide useful info on which glass is better.

You might also have curling issues because your bed is too hot. Much above 60C and many PLAs soften allowing the base of your print to "rock" and subsequently rocking the base off the bed.

Make sure your bed heat is even. Let the bed get up to temp and sit there for a while to allow the heat to even out in the glass. I put an insulator (silicon mat) over the glass while it heats as the edges tend to cool off easily especially since I always have a couple of big fans cooling my prints to ensure the best PLA print quality.

lukeott
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Re: PLA prints on glass are warping

Post by lukeott » Fri May 16, 2014 1:29 pm

Thanks for all the replies.
I'll try out some tape and see how that works.
I've also got some different glue stick now (Pritt stick), the one I was using came out of the kids craft box (my wife said "oh that stuff I gave you is rubbish at sticking, why do you think I gave it to you." Thanks! :roll: ).
Incidentally, I tried the same print last night using perfboard and it came out really well with no warping, although the raft removal was more difficult than ABS. So at least I know I can print PLA if need be as is, I'd just like to try it raftless.

rjmorel
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Re: PLA prints on glass are warping

Post by rjmorel » Fri May 16, 2014 7:52 pm

see my post above yours "!$%!@! 3D printing" the enclosure really made a difference, rj

roller
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Re: PLA prints on glass are warping

Post by roller » Sat May 17, 2014 12:51 am

Enclosures are bad for PLA. The melt point is too low for PLA and you will end up with poor print quality.

lukeott - one thing - if you are printing your PLA too hot it will also shrink more. Since you are having issues with raft removal this means you should try a lower temp - try a temp mod. Also, once you have the base down get a fan blowing on your print - try this before your temp mod as it might save you some effort initially.

lukeott
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Re: PLA prints on glass are warping

Post by lukeott » Sat May 17, 2014 9:50 am

So I popped into a decorators store yesterday, they didn't have any 3M blue tape so instead I picked up some stuff from Tesa. It worked really well, the parts were held down fast and I managed to get 3 prints out of it before it tore during part removal. Is that about right for durability?

roller - I think I misled you, I meant that the raft was difficult to remove from the perfboard afterwards. The part comes off the raft OK using the Up scraper.

teamcarlisle
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Re: PLA prints on glass are warping

Post by teamcarlisle » Sun May 18, 2014 2:08 am

What kind of glue stick are you using, that makes a big difference too. On my replicator 2 I do large pla prints all the time with glass now. Normal glue sticks didn't work well, but after reading a few forum posts at maker bot I switched to elmers craft bond extra strength glue stick and it works great. Still washes off with water. Just clean the plate off and re apply after each print. Even though the glue needs to be dry before printing (only takes a few seconds) don't try to print on a plate with old glue. I tried printing on a plate that I applied glue to the day before and the pla wouldn't stick to it at all.

roller
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Re: PLA prints on glass are warping

Post by roller » Sun May 18, 2014 3:58 am

lukeott wrote:So I popped into a decorators store yesterday, they didn't have any 3M blue tape so instead I picked up some stuff from Tesa. It worked really well, the parts were held down fast and I managed to get 3 prints out of it before it tore during part removal. Is that about right for durability?

roller - I think I misled you, I meant that the raft was difficult to remove from the perfboard afterwards. The part comes off the raft OK using the Up scraper.
I was commenting on rjmoral commenting that printing with an enclosure made all the difference... of course it would with PLA too but generally for the worse.

As for durability of blue tape if you can let the plates cool they will often pop off - at least with works for me when i print on glass with a blue tape covering (on my non PLA sticking glass plates). The PLA sticks to blue tape whether used hot or cold but the shrink of the base as it cools can help to loosen them. Of course sometimes I can get the tape to let go at all. So sometimes I used to get 1 print out of blue tape and other times up to 20 prints.

lukeott
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Re: PLA prints on glass are warping

Post by lukeott » Mon May 19, 2014 11:34 am

Wow, printing PLA on this machine is not easy! (unless I carry out some more mods)
I've not had any luck with 2 types of glue stick and variable results with tape. The only method which has worked every time has been using perfboard.
The one thing I've noticed (and I realise most people on this forum know this already) is how easy it is for the extruder gear to slip on PLA. Any back pressure at all makes it fail and a change in ambient temperature makes a difference too. We've just had a rare warm May weekend here in Blighty and a print which worked fine first thing in the morning failed in the evening and I think it might be because my South facing home-office warmed up a lot throughout the day.
I'm still going to persevere and have ordered 2 more different types of PLA to see if that makes a difference.

roller
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Re: PLA prints on glass are warping

Post by roller » Mon May 19, 2014 1:37 pm

Most PLAs soften at 40-50C so all direct drive extruders have a problem with printing unless you can manually wind back the current to keep the stepper cool OR use a system to cool the PLA (see Drew's compressed air mod - I think it's on thingiverse even) or my peltier experiments. Anyway your warm day is going to make that worse.

Many filaments are undersized and the Up doesn't have a spring loaded or other feed tensioner so they are prone to slip. See Drew's mods here too - I think Thingiverse also has these mods (see http://www.thingiverse.com/DrewPetitclerc/designs - Drew I hope you don't mind me posting). The fact that PLA is slippery makes this harder.

Generally getting PLA to stick shouldn't be that hard ... Glue stick (Elmers is the good stuff - I think the Blue one form memory but I don't waste my time on stuff I have to clean up) is not really the way to go with PLA... it's is more an effective ABS technique.

With the Up I have taken the lazy way out. I use Colorfabb PLA (which has a dash of PHA) which has reliable diameter and a much higher softening temp so no fuss using it in an Up even on long prints. I use this on the ABS setting with a -50C (18.5 ohms) temp mod. Works brilliantly, reliably and without fuss... and for the rest of my PLA I just put it through the Brutstruder on my reprap which is also fuss free - once I've spend a month leveling all my axes :)

lukeott
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Re: PLA prints on glass are warping

Post by lukeott » Mon May 19, 2014 2:45 pm

I never even thought to check the diameter of the Formfutura PLA I am using, will do so tonight.
Colorfabb PLA is what I ordered at the weekend, along with some UK stuff by Faberdashery. Hopefully that will do the trick.
Incidentally, it appears that the PLA setting in the new software heats the nozzle to 210 deg C (with the bed at 60 degrees), so that sounds about the same as you have with your temperature mod. I don't know what it was like in previous versions, I'd never tried PLA before.

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DrewPetitclerc
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Re: PLA prints on glass are warping

Post by DrewPetitclerc » Mon May 19, 2014 11:03 pm

roller wrote:Drew I hope you don't mind me posting
I'm always grateful and thank you for asking, it is OK.
Regards
Drew
Drew Petitclerc
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lukeott
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Re: PLA prints on glass are warping

Post by lukeott » Tue May 20, 2014 1:08 pm

I measured the diameter of the Formfutura PLA last night, it varied between 1.6 and 1.8 with a bit of ovality too, so I figure this can't be helping.
Measured the Faberdashery stuff today, much better consistency +/-0.02mm. The same with the ColorFabb PLA which has arrived, although that has a noticeably rougher surface finish so I'm expecting that will be the least prone to slip, as most of you have already discovered.

roller
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Re: PLA prints on glass are warping

Post by roller » Wed May 21, 2014 12:14 am

The big difference with the ColorFabb is the higher softening point. I believe also that Faberdashery PLA has a higher softening point too but it's literally years since I've used their filament. No matter what the filament diameter, once the extruder is hot with a lower softening point filament there is no hope as the filament will soften out of round and also buckle.

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