PA6-GF warping troubleshoot

Bambu Lab X1 Series Troubleshooting
1

Good day to you,

I would like to ask your help. I read all related posts and the ones I could found by google search. I was able to apply almost all useful suggestions and thanks to that, using Bambu lab PA6-GF I was able to get from a completely useless print result to an almost perfect one.

In details, I am:

  • using glue on build plate,
  • lowered speed to ~ 60
  • layer height 0.12
  • initial layer height 0.2
  • wall loops 6
  • internal solid infill rectilinear pattern
  • sparse infill density: 90%
  • sparse infill adaptive cubic pattern
  • ironing top surfaces with rectilinear pattern
  • precise wall enabled
  • precise Z height enabled
  • support on built plate and critical regions only with remove small overhangs
  • raft layers 5
  • raft contact Z distance 0.1
  • support raft base Bambu lab PA6-GF (same as object)
  • support raft interface Bambu lab PA Support material
  • interface rectilinear pattern
  • support top z distance 0.3
  • support object xy distance 0.3
  • skirt loops 1
  • no brim
  • nozzle temp 270 Celsius constant
  • build plate 110 Celsius (textured PEI) constant
  • chamber temp 65 Celsius constant
  • no cooling for the first 5 layers
  • drying 12+ hours at 70 Celsius constant while rotating
  • cooling down after printing, gradually

Thanks to this:

  • i have super great surface quality
  • perfect layer adhesion
  • perfect bed adhesion
  • easy support/raft removal

BUT with larger/longer models (smaller ones are perfect):I have 1.5-2mm warping at the 2 edges. Important, that the bed adhesion is perfect, so warping occurs by lifting up the edges of the magnetic plate from the bed.

I also tried different layer heights, but the change was only to sacrifice the quality, while warping still occurred.

I ran out of ideas what more I could do, except 1 crazy thing I read somewhere: printing the model lifted to 45% angle having support only at the small portion touching the bed. But I am very skeptical bout this, as warping would occur anyway in my understanding, so why would that help and having this angle would cause (again just assumption) surface issue as well as no ironing would be possible I guess.

May I ask if you could help me with any concrete idea I could try as you had success with it ?

Many thanks in advance for your time and help!

2

As additional step tried Bed Clips, helped a bit, but problem still exist.

3

This is due to the bed being heated. The heated contact area is softer, so the cooling stresses build up and find the release at these large soft areas. The small contact causes the build up stress to be more spread through out the print and not likely noticed by users. The risk is if too much stress is present it will pull the small contact area off.

I print with nylons fairly frequently. Some things I do different:

If you are going to use a PEI plate:
Add basic object like a square of cylinder. Make it PETG (cheap stuff as its a throw away print part like a support). Take this object and squish it 1 layer high and place it under your project. It needs to be at least 115% larger the contact foot print. Your wanted object should be set on-top of this 1 layer high object (second layer starts your desired print). Set your bed temp to 84C. It will print the PETG, and 84C it will stay in the beginning region of the glass phase. The nylon will print into this and push slightly down into the PETG. Nylon and PETG when hot will stick together. This will keep your part anchored to the bed as glass transition PETG bonds to a PEI bed like no other. Once the print is done, wait for the bed to cool around 50c, the nylon is easily removed from the PETG then. I do not even get warping during annealing with this method, just the standard shrinkage that I account for in the print.
Example from one of my models:

nylone petg
nylone petg555×505 34 KB

What I actually do with PAx, PPS and others is Garolite:

Get on amazon or what ever your preferred vendor is and get your self a G10 Garolite plate or glued on G10 Garolite plate. I use this one, but its no longer available. Mine came with a 3m sticky and was able to bond it to one of my old damaged PEI plates. It was quite easy, just prep work like cleaning before slapping that sticker on it.

The G10 plate with nylon, run it between 98c and 120c and the nylon will stick quite well. Releases around 60c.

G10 does not heat as fast, so preheat before sending your print job. I have never had a PAx, PPA, PC lift from this plate. You also clean this with denatured alcohol, not rubbing alcohol.

I have no experience with this one, but its available on amazon.

Also, personally, I never use it for PETG or PLA. I quite frankly have tried, and PEI works exponentially better then G10 for those plastics. My test has shown me that below 87c, the bed will not stick anything.

4

Many thanks for your reply, appreciate your time!

Allow me t ask what I am confused about:

Add basic object like a square of cylinder. Make it PETG (cheap stuff as its a throw away print part like a support ). Take this object and squish it 1 layer high and place it under your project. It needs to be at least 115% larger the contact foot print. Your wanted object should be set on-top of this 1 layer high object

May I ask what is the difference between this and using 5 layers of raft? My actual bed looks like: 5 layers raft, then support, then my object. If I understood well of your “separator” layer, rafts basically do the same, isn’t it ?

What is strange, that I have perfect bed adhesion, using bed clips now also prevented PEI plate being lift up, but edge of object still warping/bending withotu any visual gap or detachment from the base:

image
image389×494 56.8 KB

As you can see, my object is a long and relatively narrow, but considered large sized. Based on your explanation and images, I should lift it up, so 45 degree isn’t a bad idea after all?

I have some PLA at home (no PETG right now), so I can print a base layer and follow your advice to test, but whats not clear for me, that I assumed that hot bed require for good layer adhesion (so not bed adhesion, but layer one)?

So for my test with PLA, simplified: I use bed heating temp 50 celsius than I keep using same throughout teh whole print on top of it,. correct ? Also, can I use support as I do now ? Finally, when object is large like mine, hard to achieve 115% larger base layer, it is absolutely critical ?

Many man thanks for time and help!

5

I would not use PLA, I do not believe that plastic works with the method (never tried with PAx, have had it work to help shape TPU and release), only PETG. I also would not use 5 layers, additional thickness is waste and more likely to shift the hot PETG. Run the bed at 84c not 50; 50 is too cold for PAx in my opinion.

I have had some luck with odd shapes holding with the bed running at 100c in my open bed printers. In those cases, you also need to have the printer in a room that is warm and the air is still to help prevent it from warping. If you have to, use cardboard or blankets to build a square wall around the printer. If you have an AC or fan in the room that will make warping worse.

Also if you are printing with those straight parts in line the x and y, is it possible to lay it out so diagonal, like a V shape on the plate, not so much of an L shape? try to put more of the bending stress in the center and no so much on the edge. That may also help stop it from bending the plate.

The base layer at 115% is a rule of thumb. Based off your picture, I would go an extra 5mm out form the edges and of course under it. If it lifts, add another 3 to 5 mm more in that area until it stops lifting.

Have you annealed the part after also? Curious as to if it warps more or relaxes. I would follow you PA manufactures recommendation on annealing. I anneal mine at 215*F for 8 to 10 hours. Personally I have not had warping with annealing, but you will have additional shrinkage; if the tolerance is tight on the parts, this may shrink it too much. I set my print shrinkage by setting the shrinkage to 100% in bambu and print a 20x20x20 cube, then anneal. After annealing, measure the cube and divide that by 20, and that will be your shrinkage value in the print.

6

Many thanks again for your response!

Since I only have PLA and PA6 right now, and I don’t mind to spend some extra PA6 on this test, allow me to summarize again, what I should try (forgive me that I am detailed and may seems to not getting what you say, I promise isn’t the case just want to have full grasp of the concept before I start the test):

  • I am adding a base layer using PA6 to my object using the technique in this video: https://www.youtube.com/watch?app=desktop&v=wQqtQQzrvM0
  • Since Bambulab PA6 bed good adhesion requires 110c bed, I print 1 layer being 115% larger then my object, then I lower bed temp to 85c and print my object with support.(on the bottomm as you can see on my photo earlier, this is critical for nice removal on this part)

Correct?

No, I dont anneal the part, I would like to avoid that due to my technical and space limitation.

Once again, many thanks for your help and patience :slight_smile:

7

Not sure if this would help or not but I have found on my carbon fibor nylon I had to use a smooth plate or it would warp. Good luck and let us no if you get this straightened out. I am planning on trying this filament in the near future.