Warping On Underside of PLA Parts

[cmd348 1]

I’m experience warping on the underside of my parts - see attached images.

I’m using an Ultimaker 3, printing in PLA with a heated bed, fan cooling, and breakaway support (1+ degrees). Basically default printer/Cura settings.

Print quality is excellent otherwise. Warping is only present on the underside of the part, nowhere else.

[gr5 1,123]

This is just typical overhang issues.  This is a pretty steep overhang and overhangs are difficult to print.  Combine that with being very close to the heated bed and you aren't getting enough cooling.  Solutions:

 

1) You could print on blue painters tape instead and let the bed stay cold.  If you do make sure you wash the tape with isopropyl alcohol and relevel (or just tighten the 3 screws about 1 full turn).

2) Crank up the fan - make sure the fan is 100% on the very second layer!  Maybe even 100% on the first layer.  Also lower the bed temp to 50C (part may come off the bed if it's too long though so be wary - you might want to add an incredibly thin layer of pva glue - such as glue stick spread around with a wet tissue until it's invisible and also maybe raise the bed temp back to 60C when it's done with this difficult spot - having the part come loose 1cm up is a disaster and can destroy your print head due to flooding of filament in the print head).

3) Change the design?   Can you make the chamfer at 45 degrees and then go into a curve?  Instead of starting with a curve immediately?  Like in this design document:

 

https://support.3dverkstan.se/article/38-designing-for-3d-printing#chamfers

[cmd348 1]

Hey gr5,

Thanks for the response:

Regarding overhang - I’m using support starting at 0deg, with Z & X/Y support distance equal to the filament diameter. The rest of the part overhangs came out perfect - just the lower/right-facing surfaces had this issue.

1) Painters tape is a last option - just spent almost 4K on a UM3 with a heated build plate. I’m looking into dialing in the right settings and get the most out the machine.

2) My fan speed has always been at 100%. Taking your advice - I’m trying a print now with 60deg on the first layer, 50deg thereafter. I’m also using a glue stick to increase adhesion. I think the heated bed might be the culprit.

3) Design change is not an option for this part.

I’ll update once I print the new part. Thanks again.

[gr5 1,123]

18 minutes ago, cmd348 said:

2) My fan speed has always been at 100%.

Even on the bottom layer?  By default I think it doesn't reach 100% until the 8th layer.  By then your getting into the "easier" area of the print.

[cmd348 1]

5 minutes ago, gr5 said:

Even on the bottom layer?  By default I think it doesn't reach 100% until the 8th layer.  By then your getting into the "easier" area of the print.

Thanks gr5,

I just had a closer look at the cooling settings - full cooling was set a the 5th layer. I’ve changed that to the 2nd layer, keeping the 1st for adhesion. Hopefully this will help.

-C