Model to Gcode missmatch

[Hotpoint 1]

Hi,

 

New to the site so apologies if I've broken any form norms. Had a search in the forum and didn't turn up anything that looked related, so sorry if I've made a newbie mistake.

 

Have a reoccurring issue when trying to slice models that don't have a suitably large enough flat spot for standard bed adhesion.

Tried with all support options in the settings (standard, experimental, adding user blocks..) and with combinations of bed adhesion options (none, brim, .. but most specifically raft) .
 

Even tried turning off the drop to bed setting.
 

However in all combinations of theses setting I'm still get a distortion in the lower portion of the model!

 

 

Had hoped (since I've already paid for the model) that it could be printed without the need to go to an editor and chop it to more amenable chucks.

 

Note the above is in the case where the model is not dropped  but hovers ~1-2mm above the bed with a raft and tree support enabled.
 

Any other suggestions would be gratefully received.
 

Thanks

 

Again let me know if there's some convention I've tramped on or vital information lacking from the post.

 

 

[GregValiant 1,342]

I wonder if there is something in the model file that is causing it.  To my knowledge, slicers don't make things up.

It looks like you've tried manually moving it...how about rotating it in space.  Maybe a different orientation will help.

If it fits within the build volume you shouldn't need to slice it into smaller pieces.

 

[Hotpoint 1]

Hi GregValiant

 

Thanks for your response.

 

Yes I thought this too. The same problem occurs in other models and regardless of their orientation. The example shown here was just as it caused least noticeable distortion to the final output. The problem occurs where there is not a significant amount of flat surface in contact with the bed. With this, and the other models I have tried, there is always a tendency to pull the detail of the area around the lowest point to a pyramid or ridge (model geometry dependant). Also noted that the sit bones on RHS, under the slicer controls, are not distorted in any way and did not quite come down into the lowest layers.

I had thought that the use of a raft and tree support would be sufficient to preserve the shape of the model but so far this has not proved to be the case.

 

I vaguely recall that in the infancy of Cura it required a minimum flat surface on the initial layer to try and provide stability and bed adhesion during printing. I wondered if some legacy algorithm was the cause of the distortion. May be way off track as this is only speculation.

If you have any more suggestions I bee sure to give them a try

 

Cheers

[GregValiant 1,342]

You need one of the moderators for help here.  Gr5 or Maht come to mind.

I draw my own stuff so if there is an issue like this I add a feature (big circle or something) 2 layer heights tall where I want it to sit in the slicer.  It's a way to fool Cura into producing what I had in mind.  I know, it's a workaround and not solving anything, but it gets the job done.

Edited May 13, 2020 by GregValiant

[Hotpoint 1]

Thanks

 

I had submitted a ticket (1234!) as initially the post received no responses. I guess I will not hear back on that until next week.

 

If I allow models to overlap would co-placing any small flat model in the right location achieve the same as an alternative workaround?

 

I'm new to this forum, is the a way to contact gr3 or Maht direct or hope they pick up on your post?

 

[Guest maht]

Hello @Hotpoint, thanks for getting in touch.

 

Please save a project file (File -> Save...), zip up the .3mf file and attach to this issue so I can try to reproduce the issue with the same model and settings as you.

[Hotpoint 1]

Thanks maht for your kind offer.

Sorry for the delay, work got in the way of having fun!

 

 

DeerSkull_175pc.zip

[Hotpoint 1]

On 5/12/2020 at 12:18 PM, maht said:

Hello @Hotpoint, thanks for getting in touch.

 

Please save a project file (File -> Save...), zip up the .3mf file and attach to this issue so I can try to reproduce the issue with the same model and settings as you.

Hi @maht, I have tried to print a skull with horns, this time without experimental tree support, but I still have the same issue using standard support. It only seems to happen on these deer skulls or skulls with horns. The pulling down of the print to the bed is not something I am able to overcome.

I think I might be doing something wrong, but so far I can't work out what?

Did you get a chance to review the file I attached?

Many thanks.

 

 

Edited May 23, 2020 by Hotpoint

[peggyb 171]

I loaded your .3mf and it looks fine to me, or did I miss something in your message?

If you have trouble locating it on/under the bed, check the z-numbers in the Move section, there is also in the preferences something like 'automatically drop models to the build plate'

 

It is also possible that the graphics card of your computer is the problem, indoor first picture it shows you are in 'compatibility mode'

 

My screen looks different because I use Cura 4.6.1 and the plugin 'Sidebar GUI'

 

[Hotpoint 1]

Appreciate the advice @peggyb,

 

Yes, I'm on old PC which could do with a GPU boost hence I don't get the latest and greatest views, so I'm unlikely to get the same view as you but thanks for sharing.

 

Had the drop to bed selected on prior to the model supplied, but was just trying this to move the print way from the bed to see if it made a difference (It didn't). Also blamed it on experimental tree support but I am seeing similar when using conventional (zigzag) support.

 

The best way to describe the problem, for a simple shape, I can come up with is imagine printing a cylinder. On its end you end up with a circular cross-section. However print the same on its side and the area engulfed in the resultant support becomes distorted and the cross-section is more of a tear drop. Attached image shows the resultant ridge on what would otherwise be a semi circular part.

 

[peggyb 171]

There is something weird with the model. Can you check the .stl in a program like Meshmixer, -> Analysis -> Inspector and see if something shows up.

Cura is creating large triangels towards the bed, filling up the model. 

 

 

[Hotpoint 1]

 

 

Yes @peggyb,

 

Exactly the sort of result I'm seeing. Although it's not restricted to this model, so I had thought there must be something in general I have set wrong.

 

Never tried Meshmixer but will download it and give it a try.

 

I contacted the company I purchased the model from and they have assured me its a 100% correct watertight model (but they have never printed it!).

 

Thanks again.

[tinkergnome 927]

20 hours ago, peggyb said:

Cura is creating large triangels towards the bed, filling up the model.

 

Well, that's exactly what "Make Overhang Printable" is meant to do.

So.... the simple solution may be to switch this option off - if it is not wanted? 🤔

[peggyb 171]

good find, never used this setting, will keep this in mind 👏

[Hotpoint 1]

Good advice @tinkergnome,

 

Not sure how that one snook in there as only experimental one I thought I've tinkered with was the tree support. But it has done the trick.

 

You don't know what you don't know which is exactly why I'd asked for some guidance! 😉

[tinkergnome 927]

21 minutes ago, Hotpoint said:

it has done the trick

 

neat - another mystery solved. You're welcome! 🙂

[Hotpoint 1]

Thank you very much everyone for your help. I thought I must be doing something wrong, but missed it. I'm glad it was me rather than the print, as it is a good one. I clearly have a lot to learn still.