Printing a 200% T Rex; crashing issues  

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Bas Raas
(@bas-raas)
Active Member

Hi,

I tried printing the T Rex model, described in a blog by Jan Olejnik. The model was downloaded from Thingiverse.com and scaled in PrusaSlicer up to 200% as described in the article. I own a stock Mk3s, and used Prusa PLA for the print. As described furthermore, I used a brim of 15mm, no supports, no infill, a 0.4mm extruder and, 0.15 mm layer thickness.

Upon till now, I did 2 attempts; 1) nozzle temp of 205/200 and 2) nozzle temp of 215/210. At the second attempt, I also changed the model's orientation by rotating over z-axis by 90 degrees. In both cases the print fan was 100% on.

In both cases the printer crashed at the point where the PLA tends to raise (warp) from the surface.

On the bottom exterior, in an earlier print stage it is clear that several other layers weren't that pretty as well:

  

Can someone help me out? For me it would be really helpful to get some details upon settings I should use in PrusaSlicer.

Thanks so far

 

 

 

 

Posted : 06/04/2021 9:43 am
fuchsr
(@fuchsr)
Honorable Member

Not sure I understand the specific issue? I get the crash but it seems it's because you're seeing warping despite using a (quite large) brim? If so, my first thought would be imperfectly cleaned steel sheet (use hot water and dish-washing soap without additives) and/or imperfect Live Z calibration.

What you seeing in picture 2 is just the imperfections you'd expect from steep overhangs. The printer can't lay down filament in thin air, so it will sag. Supports may help but even with supports you're likely to see imperfections just like what you have here, which isn't bad. IMHO, your best option for this is sandpaper/dremeling.

You may also want to consider exporting your project as a 3mf file (under the File Menu) and uploading it to this forum. The 3MF contains the model as well as all your settings so folks here can take a look. The forum software doesn't allow the upload of 3MFs, so you will have to first zip it into an archive and then upload the .zip file.

 
 
This post was modified 1 month ago by fuchsr
Posted : 06/04/2021 12:25 pm
Swiss_Cheese
(@swiss_cheese)
Honorable Member

@bas-raas

 

I suspect you are having a cooling issue, if you can try turning the parts that are curling up so that they get the most straight forward exposure to the fan, steep over hanging areas that require a lot of (ensured vertical shell thickness) are especially susceptible to this behavior. with some filaments you can use heat to help this and with other filaments to much heat will cause it, so you have to know your material.

 

A small example of this.

 

 

The over hang on this tree frog model is curling upwards as it prints, it's very thin and flat and the nozzle passes over it many times trying to " ensured vertical shell thickness" in this case it's necessary to do so, however this silk filament (PLA) doesn't respond well to this situation at the temperature I might normally print this Frog (215C) the problem is solved in this case by turning the temperature up 5C to 220C and the problem goes away. (if this was Hatchbox brand I would have printed it at 205C) this can also be accomplished in some cases by reducing the fan speed for a part of the model or re orienting the models position to the fan, or even using a different filament. you will have to experiment with your specific model and filament to get it right. There are many possible fixes to this problem others may include, slowing the print down, turning off "ensured vertical shell thickness" <-- although slicer will still try, it changes the results, and changing the infill type and density can have an effect as well.

 

If it was me, I would try printing it 215C even 220C knowing its prusament, my experience has shown me that prusaments print better at hotter temps.

 

that's all I can think of for now, if I remember anymore I'll pass the info along.

 

Good Luck

 

Swiss_Cheese

Posted : 06/04/2021 8:08 pm
Daryl liked
Swiss_Cheese
(@swiss_cheese)
Honorable Member

something I meant to mention, but forgot to as I was addressing the curling issue your having. whether it's effecting your print or not, in your second photo your Z looks to high it should be lower, and if your using a brim you should turn off elephant foot compensation.

This post was modified 1 month ago by Swiss_Cheese
Posted : 07/04/2021 1:46 am
Bas Raas
(@bas-raas)
Active Member

Thanks for the replies!

I will immediately start implementing some of the suggestions and test again. I'll keep this updated here.

As for the detail I added the project file, hopefully someone can check it and provide me with more insights based upon it.

TRex_Skull

Many thanks again,

Regards Bas

 

 

Posted : 07/04/2021 9:43 am
fuchsr
(@fuchsr)
Honorable Member

Thanks for uploading the 3mf file. 

To be honest, good luck with this. I looked at the original blog post ( https://blog.prusaprinters.org/cool-prints-from-our-office-t-rex-boxer-engine-3d-clocks_8492/) and he makes it sound easy but if I look at the model, I don't see how you could possibly get decent results without supports. But hey, I've seen stranger things happen. I would also go with 10% adaptive cubic infill, to provide a bit more support to all of the internal overhangs. It is a tall model, with a small surface connection to the sheet, so at greater heights, I wouldn't be surprised to see some vibrations that may lead to crashes.

Posted : 07/04/2021 4:24 pm
Bas Raas
(@bas-raas)
Active Member

@fuchsr

Yes I agree. Today I tried increasing temp to 220C, turned off elephant foot comp, calibrated z-axes again, tried with and without " ensured vertical shell thickness", tried filling 5%. All of them resulted in the same failing behavior. 

For now I will try a last time today, with small supports. 

Keep you updated on progress.

Many thanks again!

 

Posted : 07/04/2021 6:20 pm
MichaelK
(@michaelk)
Eminent Member

@bas-raas

I printed the Trex model a few years ago, at 100%, on my Cr10s.

I printed with white PLA with 3 or 4 perimeters and no infill. I didn't want to see the infill pattern through the surface. And I don't think I used supports. I might have used a raft on some of the parts.

My Cr10s was new, and this was before I started "upgrading" it.

I was amazed at how good it came out.

I'm also thinking of printing a 200% version on the MK3, as I now have a Bone coloured PLA.

I have printed the T-rex skull only model at 200% with 4 perimeters and no infill at .15, and it came out great.

Posted : 08/04/2021 4:54 am
Bas Raas
(@bas-raas)
Active Member

@michaelk

Did you use 4 perimeters for the whole build? Can you check for other parameters used, such as: did you use "ensure vertical shell thickness"?

Thanks!

Posted : 08/04/2021 8:15 am
Swiss_Cheese
(@swiss_cheese)
Honorable Member

@bas-raas

 

I got a roll of filament that I hadn't tried yet so I decided to try it out on the 200% T Rex I first printed a temp tower for the PLA because I've never used this type before, I ended up going with 200C it had the best bridging (A quality needed for this project).

 

Note: 190C didn't print at all and the manufacture spec was 190 - 220C.

This is one of the reasons I always start off hot with my temp towers.

 

 

I loaded the original Skull from Thingiverse, downloaded years ago,(I assume it's the same) scaled it 200% rotated it 180 degrees, sliced it for 3 perimeters, I did some selective infill at 20% in areas that I felt might not be supported well otherwise, (can be seen in the photos, its internal only.)

 

 

The following photos were taken under florescent light for the specific purpose of showing the layers and how it printed, they are not very noticeable otherwise.

 

 

(non florescent light photo)

 

(Possible problem areas)

Although I think they printed just fine, the areas are at about 70 degrees or more! and unsupported, however the 3 perimeters allows for plenty of structure in these areas for sanding and post processing. they didn't cause any crashes or offer any cause for alarm during the entire 10 hour 27min print.

(be sure to pay attention to the nostril)

 

printed @ 0.15 quality, No external supports aside from a 15mm brim were used, Ensure vertical shell thickness was turned off, elephant foot comp off, I'm sure I'm forgetting some other info, but that's the gist of it, I really like this color and the model seems fun, I think it prints just fine your not going to get a 100% perfect version of this, although I do think I could tune it feather and get it really close. I may actually try and finish this in this color : )

 

Anyway I hope this helps someone,

 

Enjoy,

 

Swiss_Cheese

 

 

This post was modified 1 month ago by Swiss_Cheese
Posted : 08/04/2021 10:06 pm
fuchsr
(@fuchsr)
Honorable Member

@swiss_cheese

NICE!

Posted : 08/04/2021 10:32 pm
MichaelK
(@michaelk)
Eminent Member

@bas-raas

I think I used 4 perimeters on the large parts. The backbone and skull. Maybe the legs as well.

I used Cura at the time, so I don't think the "ensure vertical shell thickness" was available.

Posted : 09/04/2021 4:53 am
Bas Raas
(@bas-raas)
Active Member

@swiss_cheese

Wow!

Thanks a lot. I will have a go with these settings soon!

cheers

Posted : 10/04/2021 12:32 pm
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