Printed objects are curved in corners

[didero 0]

Hello everyone!

I recently noticed some strange behavior with the plastic that I can't explain !

During the print, after that a few layers have been printed, the corner of my object became to curve and to unstick from the bed ! However, the print can continue and finish the object quite well (except that problem at the base of the object) .

These photos will explain this issue better than me :

Does someone have experienced the same thing ?

Does someone know what's going on here ?

Thanks in adance for any help !

Best regards,

Didier

[owen 19]

It's fairly common. Warping caused by plastic shrinking as it cools. I found the other day that I got it much worse for a small part when I printed faster than normal so I guess it stands to reason if you printed slower for the first few layers at least you may not get so much warping.

[didero 0]

Thanks Owen for your reply !

It make sens that plastic shrinks when cooling ! But since I never read anything about that I though it wasn't so common !

I switched to marlin and netfabb a few days ago, and as you said the speed has certainly a role in that, because I never saw that happening when I used the basic firmware (which print at low speed)!

I would like to follow your advice, but at this time I don't know yet how to print some layer at a certain speed and the others at another one.

I have still a lot thing to learn !!!

Didier.

[owen 19]

If you're using RepG, click on the live tuning button at the start and turn the speed down to say 50% for the first few layers or so. Haven't tried it myself yet, just deducing that it should work. Please let us know in this thread how it goes.

[Daid 306]

warping also depends on the material. PLA warps much less then ABS for example.

Few other factors that can help:

-Thinner layers warp less

-Lower print temperature warps less

-Pushing the filament into the printer bed during the first layer helps (I press my bed up manually during the first layer sometimes to make it stick better)

[didero 0]

Hello,

So I had another try with thiner layer, (I used for that, PLA Ultra profile in Netfabb). I also decreased the temperature for about 20° in RepG (however, I'm not sure whether it's RepG that set the temperature up, or if the temperature is defined in the Netfabb generated GCode).

Well, below is a photo of the result:

Regarding what Daid said about the first layer that need to really be stuck to the bed, I think that in my case I could exclude this factor as a possible cause, because as you can see in the object's angle, the blue tape is well stuck to the first layer, the blue tape is following the object's warping, remaining stuck to the object when the warping began, while it is unstuck from the platform (the strengh of the warping seems stronger than the ability of the tape to remains stuck to the bed!)

It's not very obvious on the photo, but the warping is less strong than in the previous print !

My next try (currently being printed on my UM) will be using the same profil, but with speed being decreased to 50% (with real time control) during the first layers. Stay tuned !

[didero 0]

Against all odds, the print at half the speed came very badly !

You can compare the different attempts in the photo below.

For information the print are a square about 5cmX5cmx0.5cm (the 1rst and the 2nd print have others stuff on top, but I don't think these stuff had an effect on the result)

So what can we conclude regarding that result ?

- It seems that decreasing the speed has unexpectedly made the warping worse !?! (3rd object)

- decreasing the temperature had a modest impact (should I try even lower?) (2nd object)

- I'm quite lost !

What do you think ?

[falc 6]

I think you need a heated bed

is this PLA or ABS ? this effect is the worst with ABS, but normally should not appear with PLA

[mm_build 1]

Different PLA will warp different amounts, some colours are even worse than others. Changing your temperature in RepG should not work during a print, to actually change your temperature you will have to add the change to the g-code or re-slice your model, I am well familiar with your warping problem, the only suggestion I can give is thinner base layers and infill instead of solid. Or as Falc said, a heated bed.

[owen 19]

Hello,

I also decreased the temperature for about 20° in RepG (however, I'm not sure whether it's RepG that set the temperature up, or if the temperature is defined in the Netfabb generated GCode).

 

In the RepG window where you see 2 lines near the top that start with M109 the next number is the temp that is set by the GCode and is the one you need to change.

I'm liking seeing your experimenting and results. I'm getting very similar results with different variations not making much difference.

[didero 0]

I think you need a heated bed

is this PLA or ABS ? this effect is the worst with ABS, but normally should not appear with PLA

That's PLA ! I heard about a heated bed ! Does that exist for the UM ? What are all the advantages of heated bed ?

[Daid 306]

That's PLA ! I heard about a heated bed ! Does that exist for the UM ? What are all the advantages of heated bed ?

The advantages of a heated bed are less (no?) warping, and that the first layer sticks better.

Funny fact, seems that the Ultimaker is the only printer without a heated bed right now. And still we are producing great results.

There is a "build it yourself" heated bed on thingiverse. And the UM Team is working on a heated bed, but no word about the release date yet.

[didero 0]

Thanks Owen for your comment ! I'm glad if I can contribute even at a little level ( I've been using my UM for about one month and a half, so I'm still quite inexperienced)

I used the netfabb profil (PLA high 3a ultra quality filled object).

When I checked the temperature after the M109 it is set to 190 (wich is quite low comparing to the temperature I used in RepG(220°) before I switched to Netfabb )

I'm quite sure the shape of the object as an effect ! Would I had that much warping with a cylinder ?

One of my very first print with netfabb was the famous YODA where no wraping at all occured !

 

Owen, what was the shape you printed during your own experiment ?

By the way, regarding the different profils in netfabb (standard , high, ultra + [VASE, Filled, Hollow], ect..) Is there a place where they are discribed ( what profil is the best for what purpose and how the machine will behave using a profil or another) ? advantages and disadvantages ?

[didero 0]

The advantages of a heated bed are less (no?) warping, and that the first layer sticks better.

Funny fact, seems that the Ultimaker is the only printer without a heated bed right now. And still we are producing great results.

There is a "build it yourself" heated bed on thingiverse. And the UM Team is working on a heated bed, but no word about the release date yet.

Sure it's possible to have great result without a heated bed (I saw a lot of wonderful print with basic UM ), but If a solution exist that could make thing a little easier for new users (with less frustation also), I think it's a good thing ! I will have a look at the DIY heated bed you mentioned ! thanks for the information !

[Daid 306]

I'm quite sure the shape of the object as an effect ! Would I had that much warping with a cylinder ?

One of my very first print with netfabb was the famous YODA where no wraping at all occured !

Organic shapes have less problems because the stresses put on the model are not all in the same direction. I've printed a 18x18 footprint octopus without any warping problems.

http://daid.eu/~daid/IMG_20111213_232929.jpeg

the bottom one, almost as large as a 0.75kg roll of PLA.

[didero 0]

Ok Daid ! so you confirm that shape matters !

How much plastic was used for the big octopus ?

The squared shapes I tried to print was for a friend that make models for architects, he asked me to try if it's possible to make what he calls a "ground-plane" that could help him in his work (and then considering to build/buy his own machine). It seems like that kind of shape would generate too much warping !

[owen 19]

Ok Daid ! so you confirm that shape matters !

How much plastic was used for the big octopus ?

The squared shapes I tried to print was for a friend that make models for architects, he asked me to try if it's possible to make what he calls a "ground-plane" that could help him in his work (and then considering to build/buy his own machine). It seems like that kind of shape would generate too much warping !

I have been printing cylinders and getting warping. They are feet for furniture to go on carpet.

They are about 5cm across and 4mm thich with a 2.6mm external wall that rises above an extra 2mm

It has been with 100% fill

To make a ground plane you could make a top surface flatter than a bottom surface, probably more so if you have less than 100% fill.

Daid that is some monster squid!!!

[Daid 306]

Ok Daid ! so you confirm that shape matters !

How much plastic was used for the big octopus ?

The squared shapes I tried to print was for a friend that make models for architects, he asked me to try if it's possible to make what he calls a "ground-plane" that could help him in his work (and then considering to build/buy his own machine). It seems like that kind of shape would generate too much warping !

No idea how much plastic is in the octopus, not a huge amount I think. Because it's not that solid.

What might work for a square base is to put circular holes in the bottom. Like this:

Then you might have less stress on the corners causing no/little warping

[didero 0]

Thank you Owen and Daid for your suggestions ! I will try the solution given by Daid !

I also think that I could make a thiner base than the original 0.5 cm height as each layer add his own strengh to the previous one causing more and more warping ! I will let you know !

Didier

[cyclone 0]

This is most likely from printing too densely. Daid's suggestion should work, but you could also

set netfabb to increase the "fill spacing" to 1 or 2 mm, I use 3mm pretty regularly.

Solidly printed things curl badly even if you are using PLA and even if you have a heated bed.

If the object is too thin the profile may still fill it solid, if the number of surface layers in the profile

is greater than the thickness of the object. In that case you could reduce the number of surface/skin

layers, or change the model as Daid suggested.

[didero 0]

I came back with this new attempt using a modification like Daid suggested !

It's better, but it's not perfect !

As cyclone said, I should have another try with less density ! The thing is to find a good compromise between solidity and warping free structure !

Below is a photo (upside down)of the model with modifications suggested by Daid (by adding holes in the base structure):

Ultimaker 2 Go + Ultimaker 2 Extended Press kit.zip

Now a comparison with the previous print :

Ultimaker Logo.eps

Ultimaker Logo.zip

If you are still interrested with those test, I will post my next attempt !

Didier.

[joergen 2]

I came back with this new attempt using a modification like Daid suggested ! It's better, but it's not perfect

Another thing to consider is how well you tape the blue tape down... from your photos, it seems to come off easily, especially if the corner of your object coincides with the corner of the blue tape.

you could try a couple of things:

 

• - press down on the blue tape really hard (i.e. with a putty knife, or even better the plastic back of a snap-off blade knife, maybe even clean your acrylic with alcohol first)

  - rotate your object by 45 deg

  - move your object by half a tape-width, to make sure the edges of your object are in the center of the tape, not on the edge

  - use a wider tape (and press it down hard)

  - raise your Z a tiny bit to smoosh the first layer better into the tape

  - experiment with other kinds of tape

  - experiment with more cooling (additional fans)

  - experiment with less cooling for the first 2-3mm

  - experiment with extending your object with disposable geometry (like a fake raft)

  - add horizontal holes/cavities instead of the vertical punch holes you had previously. See

for a better explanaition

- get a heated bed

- experiment with alternative surfaces (i.e. brushed aluminium or glass or kapton)

 

[didero 0]

Hi Joergen,

Nice and instructive video ! thanks for that ! I also liked the little "debate" in the video's comments about improving the technology or adapting the design to avoid warping !

 

There is a lot of tracks to follow to get better results, you gave me some more !

I specially made a note of your remarks about :

- the edge of the tape coinciding with the edges of my object

- Rotate the object by 45°

- make horizontal holes instead of vertical ones

Others options are also interresting, but I would try the easiest ones first !

Have a good day !

Didier.

[owen 19]

If you are still interrested with those test, I will post my next attempt !

Didier.

Yep, keep them coming.

[didero 0]

My next attempt will be with this design, inspired by everybody's comments and suggestions, but with the idea of keeping the external look of the object !

I will also increase the fill spacing (previous one was 0.08, new one will be 1), I will decrease the temperature about 5 ° from the original netfabb profil (PLA Ultra so min temp will be 175 and max temp will be 185). The piece will be placed on the bed with 45° rotation to avoid the edges of the object to coincide with the edges of the blue tape.

Below is the design:

I will print it tomorrow as by now I have to go to work !

Stay tuned !