3D Printed Model has blemish

Post here for help on using FreeCAD's graphical user interface (GUI).
Forum rules
and Helpful information
IMPORTANT: Please click here and read this first, before asking for help

Also, be nice to others! Read the FreeCAD code of conduct!
abasel
Posts: 105
Joined: Sun Sep 02, 2018 12:22 am

3D Printed Model has blemish

Postby abasel » Mon Jun 29, 2020 8:43 am

My Model displays as follows in FreeCAD
FreeCAD-NL.PNG
FreeCAD-NL.PNG (21.01 KiB) Viewed 639 times
When printed however (gcode created in CURA), it produces the following:
20200629_203621.jpg
20200629_203621.jpg (150.93 KiB) Viewed 639 times
I have shown the defect with red arrows. I printed this twice and both times it was as such.

Not sure what I might be doing wrong.
Attachments
NewHolder-top-v2-200629.stl
(48.71 KiB) Downloaded 6 times
NewHolder-v2.FCStd
(189.28 KiB) Downloaded 8 times
kisolre
Posts: 2258
Joined: Wed Nov 21, 2018 1:13 pm

Re: 3D Printed Model has blemish

Postby kisolre » Mon Jun 29, 2020 9:46 am

The STL looks Ok, PrusaSlicer slices it Ok. Could it be a problem with your printer at that height? This looks around the hole on the other side - can you show pictures of the other side? Had you printed other models in the mean time?
abasel
Posts: 105
Joined: Sun Sep 02, 2018 12:22 am

Re: 3D Printed Model has blemish

Postby abasel » Mon Jun 29, 2020 8:26 pm

Hi, I did another one that appeared to have the same issue. I will photograph the old one and the back of the new one tonight. I also have another model printing at the moment. I will check that one too.

Once I have the above photos, I will update the post.
kisolre
Posts: 2258
Joined: Wed Nov 21, 2018 1:13 pm

Re: 3D Printed Model has blemish

Postby kisolre » Mon Jun 29, 2020 8:34 pm

Might be some tension in Z axis when the head is under that height (or above it) - something might be touching where it should now. Please inspect closer movement along Z axis in that area.
neildarlow
Posts: 29
Joined: Mon Mar 17, 2014 1:29 pm

Re: 3D Printed Model has blemish

Postby neildarlow » Mon Jun 29, 2020 9:24 pm

Hi,

I have seen this effect when there is a change in infill density - usually when going from solid layers to sparse infill and vice versa. Can you examine the sliced object in layer view and see if this effect does indeed reflect this.

ATB,
Neil
Reynard1066
Posts: 27
Joined: Sun May 10, 2020 7:27 am
Location: Scotland

Re: 3D Printed Model has blemish

Postby Reynard1066 » Tue Jun 30, 2020 7:44 am

After 4mm of height you lay down a wide floor of material. This floor if possible causing a lot of shrinkage at that level pulling in the side walls.

You don't give any details on wall thickness or top and bottom layer count.

You could try a higher density infill to try and resist the outer walls from being dragged in or thicker side walls.

Building an enclosure done wonders for my prints.

Reynard
Syres
Posts: 754
Joined: Thu Aug 09, 2018 11:14 am

Re: 3D Printed Model has blemish

Postby Syres » Tue Jun 30, 2020 7:49 am

I had a similar issue with PETG and 35% infill during the recent UK heatwave, to fix it I just upped my cooling fan from 45% (normal running speed) to 95% which fixed the issue. Normally my prints are all about mechanical strength and couldn't care less about aesthetics. Typically this was an occasional where the customer had the part visible and it was in compression so the reduction in tensile strength wasn't a worry.
abasel
Posts: 105
Joined: Sun Sep 02, 2018 12:22 am

Re: 3D Printed Model has blemish

Postby abasel » Wed Jul 01, 2020 4:17 am

Thanks all, yes I am seeing this when there is a marked change in floor width. Regarding thicknesses and layer counts, I am using the Cura defaults (unless I have accidentally changed them). Bottom and top layers are 8 and wall thickness 1mm.
abasel
Posts: 105
Joined: Sun Sep 02, 2018 12:22 am

Re: 3D Printed Model has blemish

Postby abasel » Wed Jul 01, 2020 10:02 am

Ok so it is doing it whenever there is an inside insert (insert marked by yellow). Red indicates blemish.
20200701_215907.jpg
20200701_215907.jpg (87.68 KiB) Viewed 314 times
Reynard1066
Posts: 27
Joined: Sun May 10, 2020 7:27 am
Location: Scotland

Re: 3D Printed Model has blemish

Postby Reynard1066 » Fri Jul 03, 2020 10:15 am

Try putting a gap in between the inside ledge and the outer wall skin. That way any shrinkage of the ledge will be isolated from the outer wall.

Also, use a higher resolution mesh for your models. Facets on a curved surface is not a good look.

Reynard
Attachments
Image 1.png
Image 1.png (66.72 KiB) Viewed 249 times