PLA sticking to raft

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albill
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PLA sticking to raft

Post by albill » Mon Nov 05, 2012 10:23 pm

I've been working with blue PLA lately and I cannot get it to let go of the raft, no matter what I do. Even If I try to pry with the edge of a knife, the raft is permanently bonded to the bottom of my PLA models. (Of course, when I print with ABS, I have the typical curling problems.)

I'd love to print without a raft so I can avoid this problem but the perf board that comes with the UP! makes that impossible.

Do folks have any suggestions?

pleppik
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Re: PLA sticking to raft

Post by pleppik » Mon Nov 05, 2012 10:33 pm

albill wrote:I've been working with blue PLA lately and I cannot get it to let go of the raft, no matter what I do. Even If I try to pry with the edge of a knife, the raft is permanently bonded to the bottom of my PLA models. (Of course, when I print with ABS, I have the typical curling problems.)

I'd love to print without a raft so I can avoid this problem but the perf board that comes with the UP! makes that impossible.

Do folks have any suggestions?
Go to your local hardware store and ask them to cut a piece of plate glass to 5.5" square. This will cost a couple bucks. Use that instead of the perfboard and print raftless.

Plexiglass (acrylic sheet) is also reputed to work well with PLA (I have not tried it personally), and has the advantage of working with ABS, too. But for plexiglass you will need to get at least 1/4" thickness to avoid warping on a heated platform, and your local hardware store might not have that.

roller
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Re: PLA sticking to raft

Post by roller » Mon Nov 05, 2012 11:25 pm

Plexiglass is no good - Your prints sometimes end up permanently bonded. I use glass - it has the advantage that once it cools the print pops off on its own. The problem is the glass needs to be extremely clean - if you leave a fingerprint your print may unstick there. The easier and more popular solution in the reprap community (where PLA is king) is to use 3M Blue painters tape. You can stick it over whatever you have already, it's cheap, doesn't break and sticks really well to the PLA. I prefer glass as a no waste option and I have glass that sticks well.

pleppik
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Re: PLA sticking to raft

Post by pleppik » Tue Nov 06, 2012 1:15 am

roller wrote:Plexiglass is no good - Your prints sometimes end up permanently bonded. I use glass - it has the advantage that once it cools the print pops off on its own. The problem is the glass needs to be extremely clean - if you leave a fingerprint your print may unstick there. The easier and more popular solution in the reprap community (where PLA is king) is to use 3M Blue painters tape. You can stick it over whatever you have already, it's cheap, doesn't break and sticks really well to the PLA. I prefer glass as a no waste option and I have glass that sticks well.
I suggested Acrylic mainly because that's what Makerbot is using for the Replicator 2, which is PLA only. I assumed they had tested it and got good performance. Perhaps I assumed wrong.

roller
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Re: PLA sticking to raft

Post by roller » Tue Nov 06, 2012 3:06 am

They will use it cold or its different to what I've seen used many times.... or they intend you to coat it with something.

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JuliaDee
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Re: PLA sticking to raft

Post by JuliaDee » Wed Nov 07, 2012 1:22 am

albill wrote:I've been working with blue PLA lately and I cannot get it to let go of the raft, no matter what I do. Even If I try to pry with the edge of a knife, the raft is permanently bonded to the bottom of my PLA models. (Of course, when I print with ABS, I have the typical curling problems.)

I'd love to print without a raft so I can avoid this problem but the perf board that comes with the UP! makes that impossible.

Do folks have any suggestions?
- Do not heat the platform when printing with PLA.
- Try a different PLA vendor, they're not all equal. I've had excellent results (and no raft separation problems) with PLA from ultimachine.com.
- Open the fan duct and set up a small auxiliary fan to blow a gentle flow of air across the platform from 6-8 inches away.
- Let the print cool fully before trying to remove the raft or support. Like 5 or 10 minutes.

PLA support removal can be funny - it can seem impossibly gummy and stuck, and then you find that one ideal spot to pry, and *pop* the whole thing comes off.

julia

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DrewPetitclerc
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Re: PLA sticking to raft

Post by DrewPetitclerc » Wed Nov 07, 2012 7:44 am

Julia is right the cooling of the PLA as it is deposited is crucial, when you look around at the other printers (Mendal, RepRap etc.) they all add a ducted cooling fan to the extruder for the PLA, also shooting it at the lower PLA temps on the UP is important too. :D
I print on Glass covered with Kapton tape, raft-less for both ABS and PLA and they seem to like it the same, but you really need to get the build plate trammed to the extruder to a very close tolerance for it to work.
Also keeping the extruder from bobbing up and down as it travels will help keep it from both burying/gouging up plastic and not bonding a line causing the layer separations (replace that bent sheet metal extruder mount bracket) :geek: , But remember COOL the PLA as it is deposited and support will come off easier.
I have a second compressed air source that I turn on to blow across the build surface when I print PLA. :ugeek:

Regards
Drew
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roller
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Re: PLA sticking to raft

Post by roller » Wed Nov 07, 2012 1:55 pm

Using a fan does little to change layer adhesion with PLA ... it mostly improves print quality by getting the PLA reasonably firm before the nozzle comes around again otherwise it will be pulled out of shape by the nozzle. PLA is soft and pliable sometimes at temps as low as 40C. I love PLA and my best prints come from PLA but having printed over 20Kgs of the stuff over the last 18months there is no good way to reduce adhesion to a raft in the way the UP does with ABS does just because the plastic is so runny and wont be so compliant.

With the Up the motor/extruder gear really needs cooling to limit jams. I found my stepper easily hits 60C on a long print and this is conducting out to the extruder gear and softening PLA. A lot of direct drive extruders have this problem.

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DrewPetitclerc
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Re: PLA sticking to raft

Post by DrewPetitclerc » Thu Nov 08, 2012 12:09 am

With all my mods to my Up Plus I print happily PLA and ABS and the support is almost as easy to remove for PLA as it is for ABS, yes I have active cooling of the feeder gear and self adjusting pinch roller (no slipping), and air delivery to the build plate for PLA cooling and my experience has shown it to be what makes the difference, check out my mods, I've offered them all in my posts and on Thingiverse too.

Regards
Drew
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roller
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Re: PLA sticking to raft

Post by roller » Thu Nov 08, 2012 3:54 am

I would pose to you Drew that you don't have an Up printer so much as an Up repstrap. If I ever get an Up with a bed I can level (or is level) then I'll surely do similar.

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JuliaDee
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Re: PLA sticking to raft

Post by JuliaDee » Sun Nov 11, 2012 1:15 am

Please don't take this the wrong way, but it doesn't hurt to double-check: when you print with PLA you do go to the Maintenance window and select "New Spool" and "PLA", right? Otherwise you're printing at the higher ABS temperature and for sure getting support off will be very difficult indeed.

julia
albill wrote:I've been working with blue PLA lately and I cannot get it to let go of the raft, no matter what I do. Even If I try to pry with the edge of a knife, the raft is permanently bonded to the bottom of my PLA models. (Of course, when I print with ABS, I have the typical curling problems.)

I'd love to print without a raft so I can avoid this problem but the perf board that comes with the UP! makes that impossible.

Do folks have any suggestions?

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DrewPetitclerc
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Re: PLA sticking to raft

Post by DrewPetitclerc » Sun Nov 11, 2012 8:23 am

roller wrote:I would pose to you Drew that you don't have an Up printer so much as an Up repstrap. If I ever get an Up with a bed I can level (or is level) then I'll surely do similar.
So do I understand you to mean you never looked at my posts and you believe I do not have a true UP printer?
WOW what a fool I've been to buy so much plastic and to expend so much of my time and energy giving to this community.
I think I have had enough.
Drew Petitclerc
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roller
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Re: PLA sticking to raft

Post by roller » Sun Nov 11, 2012 10:48 am

Drew, sorry my intention was not to offend but that you had innovated upon your printer so much that it really was a evolved to the level of a superior new species and almost unfair to compare your super UP to our mere standard UPs... I compared it to a repstrap because you had much of the inventive hacking spirit of the reprap community and hence my next sentence stating that I aspire to follow in your footsteps, "If I ever get an Up with a bed I can level (or is level) then I'll surely do similar." I'm really sorry this message did not come across to you as I intended.

Please, keep up the hacking and the informing, it's great.

eyUP
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Re: PLA sticking to raft

Post by eyUP » Sun Nov 11, 2012 10:51 am

I took rollers comment to mean that your UP has been modified way past being able to call it an UP printer anymore, in effect you've built yourself an UP! Pro 8-) 8-)

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DrewPetitclerc
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Re: PLA sticking to raft

Post by DrewPetitclerc » Sun Nov 11, 2012 9:56 pm

OK, I'm sorry, I really need to have my keyboard locked up after 10pm as I become a really touchy bitch.
:oops:
That being said,
I don't really think of my printer as that far removed from what is sold today, what really burns me up is that from my perspective these "improvements are really small in cost and effort for the manufacturers to implement to improve the capabilities of this great machine.
There are many ways to "skin the cat" to make these parts and it seems that the manufacturers are ignoring the improvements we offer them, if they think it is too costly I would love to talk to them about it and offer some alternate solutions, If they are just going to try to "fleece" us like other manufacturers seem to be trying (see Cubify, I just threw up a little in my mouth) :evil: it will be a very sad day indeed.

I've been really saddened by the software requests we have over the years asked for and seem to have been ignored, I know these things take time but I for one would like some real assurances of what is being addressed by the software team because competitors have taken notice and are finally releasing and developing software to take on the giant (PP3DP).

I know I've listed a lot of small improvements to my machine and the list seems really long but most of that was due to testing and evaluating and then discarding and really what I've finally developed is a small group of changes that I now know make a significant improvement in all the areas I've identified as needed.

I've done a lot of reading on all the other types of printers and it is my nature to observe and collate and combine these into something that has a greater cycle time and through put, this is similar to my day job, I offered all the improvements I came across even those that I dropped in favor of something better because I wanted those that could not obtain or afford what I ultimately came up with to have at least a minor substitute they could try.

As some may have noticed I have not chimed in on the "Mini" subject, and I will continue NOT to after this, my grand mother and mother always reminded me that "If you don't have anything nice to say, just say nothing."
:cry:

I've had time to think and again I must apologize for my late night of being trollish, I need to lock up my electronic devices (far too many) that can access the internet at late night as this always gets me into trouble.
:oops:
Thank you for being kind with a grumpy person.

Regards
Drew
Drew Petitclerc
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JuliaDee
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Re: PLA sticking to raft

Post by JuliaDee » Mon Nov 12, 2012 2:51 am

I understood Roller's remark to be complimentary, but in all seriousness, Drew's mods make a dramatic improvement to performance but do not change the printer into something other than an Up - they change it into an Up that works properly. I've bought the improved bracket and feed mechanism from his machinist; those mods are akin to doing minor bolt-on hot-rodding to a car, like changing to a better-breathing air filter and exhaust - it's still a Chevy, or whatever.

A rigid extruder mounting bracket and a spring-loaded feed pressure roller are just plain common sense and good engineering, not rocket science. The feeder cooling air jet is nice but frankly I've stopped using it except for PLA, it's just not necessary with ABS and I can do without the compressor noise.

And yes, these improvements could be easily incorporated into the production machine very inexpensively indeed, were it not for pp3dp's "not invented here" issues.

julia

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wackojacko
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Re: PLA sticking to raft

Post by wackojacko » Mon Nov 12, 2012 4:36 am

The new UP Plus have this stronger extruder head mount, large USB connector on the printer main board, thumb screws for levelling the platform.

www.3DPrintingSystems.com
Bruce
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Need help with your printer, check out our Youtube channel.
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albill
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Re: PLA sticking to raft

Post by albill » Mon Nov 12, 2012 7:34 pm

Thanks everyone. I'm using an Up! Plus so I'll try turning the vent so the air blows across the PLA.

I'll also try printing on blue painter's tape raftless, which I used to do with my makerbot. I actually have some PLA from another supplier on order to see if it might be the PLA that I'm using.

(And, yes, I did specify new spool of PLA when I put the PLA on the machine.)

I've been interested in switching to glass as a surface. I didn't realize that I could get a hardware store to cut a 5.5" x 5.5" sheet for me. I do have access to a laser cutter and lots of acrylic so I'm tempted to try the 1/4" of acrylic solution to see if it works.

roller
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Re: PLA sticking to raft

Post by roller » Tue Nov 13, 2012 12:53 am

To Drew ... it's all ok ... I hate text ... so easy to be misunderstood and I must admit also that I have been working non stop for the last fortnight on my folio so very little sleep and the Mini issues have been a major negative contributor ... so happy we have all that sorted. Again, love the hacking/improvement approach you've taken.

Back to PLA ... I love glass for PLA. I print on it exclusively with my other printers. This is raftless of course too. Many do have issues with it and it does seem to come down to a few factors:
- some glass seems more print friendly than others. I use old, recycled (not remelted) glass.
- clean it thoroughly - your fingerprints on glass stop PLA sticking. Also clean it thoroughly before you start.
- use pure alcohol/solvent cleaners not glass cleaner. It seems a number have additives to improve appearance and these are are not adhesion friendly. I use Methylated Spirits
- use it hot - I use 60C but beware some glass will fatigue going hold cold and will crack. Consider getting borosilicate (Pyrex) glass that can survive this but I wouldn't bother with the expense initially if your just trying glass
- use a fan but try not to blow too much on the glass. I find the glass cools easily and can affect adhesion - this may not be a problem for you as I don't have a Plus and so dont know how good your hot bed are.

When the print finishes, unclip you glass and let it cool naturally. I a minute or two your print will pop off. No further work required and you can print on it again.

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