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Mendel-3 warping issues

Posted by cstelter 
Mendel-3 warping issues
October 22, 2015 12:16PM
We've had a lot of success printing, but lately we've realized that the thicker/larger pieces have warping at the bed.

At first I thought it was just ABS, but now I'm seeing we have the same issue with PLA. I first noticed that we had an issue when I tried printing an ABS item that was perhaps 4"x3"x3mm at the base and then some more material around the edges up to about 3/4". I made some print adjustments (I forget exactly which) and the next print did not have any warping. This was about a month ago. That same day I accidentally chose the wrong file on a print job and fell asleep. I was very surprised to find what I had printed-- originally that particular tray had partially failed when I tried printing it in blue ABS. The day of the misprint I happened to have transparent ABS in that nozzle so thankfully I at least had the right material for the badly selected gfile. On this print I noticed that while it completed the full tray, there was a bit of warping. Then I went to the blue version I had printed some weeks earlier and for the first time noticed that it had warped as well. The tray had 3 parts on it each ~3"x3"-- the first time I printed it in blue only one of the parts had failed and then I reprinted just that part in blue. The day of the mistake all 3 parts printed in transparent just fine, but again the warping.

Later I printed a plaque with text on top that was ~5mmx190mmx190mm with about 2mm raised text on top of that base. It came out acceptable, but all 4 corners warped. This was PLA.

A couple days ago my son printed a shelf which had supports of 50mmx50mmx10mm and they warped worse than anything I've seen to date. This was again PLA.

About 1.5 months ago we had printed a large makeup organizer for my son to give my daughter for her birthday and I just looked at it and it too suffered warping that we had not noticed until today. It is ~5"x5"x5" in PLA.

All we've ever used is alcohol cleansed Kapton tape on the glass. I've read hairspray can help, I've read enclosures can help (moreso for ABS). I've read painters tape, and all kinds of cookbooks.

But I return to the first item I mentioned where I was able to get a pristine print after having gotten a warped print. I wish I had taken some notes or knew what the difference was. The item had a top and bottom-- both ~3"x4"x3mm and I think I may have printed both at the same time the first print and then one at a time the 2nd one. I may have played with the speed. I may have just made sure I cleaned the bed more carefully. I really don't know what I may have done.

I'd say 80% of our prints come out fine, but we can now anticipate which types of prints are likely to warp and I'd like advice for the simplest things that can be done to try to minimize warping for such prints. Here are some ideas I've had and I'd appreciate any discussion regarding the viability of such ideas

  1. Building a full on enclosure seem a rather expensive solution in time, effort and $$. I'm wondering if it would be simpler/easier to design snap-on panels that would go on the triangular threaded rods so that they can be folded open and closed. one would have to allow room for the x-carriage and the associated wiring/bowden tubes to freely move through its extents in the x-z plane, so there would be heat escape out the top. Possibly one could partially cover the sides with always-present shields, or just leave it wide open on the sides. I'm thinking of panels possibly with holes in them kind of like these knex pieces.
    • Would this approach even be effective with so much space for air to escape? I'm thinking it might be effective enough, but could be way off base. I'm also thinking *some* venthilation may be required to avoid *too* high temps insde. Possibly using holes in the panels like the knex pieces have would be a way to regulate the chamber to an optimal temp. Then again, solid pieces may still not be enough to keep the heat in with the spaces required for the x carriage.
    • I'd of course use ABS for such shields, but would printing ABS then more than likely soften the enclosure such that it is just an unworkable approach? I could see the joints attaching to the threaded rods softening and falling off due to the temps. But maybe the temps at the corners of the enclosures along the threaded rods be low enough to avoid that issue. Thoughts?
    • I googled around a bit but didn't notice any items on thingiverse or anyone trying this approach. Has anyone read of someone trying this approach?
  2. Are there trick with first layer thickness that can help? Print speed, fans off, any particular trick that works really well?
  3. Have folks used the blue painters tape approach with Reprap glass beds? Can one put it on top of kapton, or would it be instead of kapton?
  4. Hairspray? is this recommended?
  5. Is there a point where too much bed heat has diminishing returns? I've been trying 110 bed for ABS and 70 bed for PLA.
  6. One thing I noticed is that early on we printed 3 universal spool holders and despite the very large footprint of the base pieces they had no warping at all in PLA. Any theories on why that piece would give us nearly zero wapring while the side pieces of this shelf would have had severe warping? Is it a matter of surface area to lenght/width or height ratio?
  7. It seems printing just one piece at a time can improve warping (ex. the single piece I reprinted on the mentioned tray of 3 3"x3" pieces had less warping than the pieces with all 3 were printed at once.). Then again, this could be a heat distribution thing too as single pieces are printed in the center of the bed while the tray of 3 was printed in the corners near the edge of the bed. I believe my son printed the shelf brackets that warped so badly 3 at once so those were also in the corners of the bed rather than near the center.
Re: Mendel-3 warping issues
October 24, 2015 01:46PM
I ll tell you what i have done . First of all i had some wraping with pla but it was from a unlevel bed. Once i got this leved and everything was tight then the pla wraping stopped.
Other than this i printed with some glue on the tape . That help a lot but i wasn't able to take out the part so in fear of a broken glass i haven't done this again. The close chamber will help but it is an expensive solution.
Something that you have to watch is if the wraping happens on the same corners . if it is then i would tell you to check the bed and the z homing well. Also you have to clean the table with aceton. Someone suggest in the net to melt some abs with the help of acetone on the table. ( after you clean the tapble then take some drops of aceton and a small piece of abs and sand it around the table. THis will make a thin film of abs that would work as a glue to your part and the bed table.

Finally for the reason that it was risky as i was getting some wraping every now and then i am using small pads 10mm diameter in the corners of my printed part . That keeps my part strong on the table.

I hope you ll solve it.
Happy printing
Re: Mendel-3 warping issues
November 02, 2015 05:46AM
Hi guys,

Well, wraping can have a lot of sources.

As said above, you need a perfectly leveled bed.
You want a properly degreased bed too.
Some plastics leave some greasy film time after time,
clean your bed with both acetone then isopropanol,
if you use glass or kapton tape.
If you use painter's tape, change it regulary.
You can use a bonding agent, preferabily hairspay (Elnett, Garnier...),
but clean and respray befor each print.

Please consider PEI boads or Buildtak products.
They offer a great bond with no bonding agent.
They only need some cleaning regulary when the bed gets too greasy.

Last, with PLA, you want a part's cooling fan that spread air all over the part.
On some printers, the cooling fan (or if you have just a fan for your hotend),
only cool down a side of the part and that causes some wraping in a single direction only.
If your bed is properly level and you experience some wraping on th same size, it's maybe a fan issue.

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