REQUEST Rough and loose surface above supports

[jwilliams2 1]

Hi,

 

I am new to plastic printing and have been running into one problem consistently. This is the that the printed surface directly above the supports often comes out loose and rough. Please see the attached image.

I am assuming that I need to play around with the parameter settings in order to improve this surface. I don't ever expect it to be as good as the top or horizontal surfaces but I hope to get it to a point that it is not loose in some areas. Does anyone have common settings they use to improve upon the quality of surfaces printing above supports?

 

Thank you.

[GregValiant 1,354]

When you use a single extruder printer then there must be an air gap between the top of the support and the actual print.  If there wasn't then the support would become part of the print and be near impossible to remove.

Adaptive Layers aside, Cura works with a fixed Layer Height and so the minimum air gap is 1 layer thickness.  You can play with the other settings but you are going to end up pretty much with what you see in your photos (which really isn't too bad).  If your layer height is .20mm and you have a .20mm air gap then you have extrusions calculated for a .20 height that are going into a .40mm gap.  They are not going to squish like they would with full support.  This is a primary reason people go to dual extrusion printers.  Extruder 2 would be for support with a non-compatible material.  That means no air gap and the support interface can be 100% density.

One alternative is to print separate pieces and bond them together.  I use short pieces of filament for locating pins and have matching 2.0mm holes in the mating parts.  Location is very accurate and Cyano-Acrylic glue works very well on both PLA and PETG.

 

[jwilliams2 1]

Hi GregValiant,

 

Thanks you for the information, this is very helpful.

I have a Ultimaker S5 so it is dual extrusion. I am not exactly sure what you mean by a non-compatible support material. Are you suggesting to use a dissolvable support material that allows me to set the air gap to 0mm? Or two materials that allow for 0mm gap but don't bond well?

 

Thank you.

[GregValiant 1,354]

By non-compatible I meant "won't stick".  PVA with PLA, PETG with PLA, that sort of thing.  If you have the same material in both extruders you are back to the single-extruder problem of the support bonding to the print.

[tomnagel 126]

“I have an S5 so it is dual extrusion” is not true, it is perfectly possible to print single extrusion prints with the S5.

Judging from the pictures you have used the same extruder for the part and for the support. Then you get these mediocre surfaces. 
If you find the roughness of the surfaces important, then you should use a separate support material in your second extruder. This can be breakaway material (BAM) or PVA. 
if you are new to plastic printing, don’t use PVA.  BAM seems a good fit since you will be able to literally break aaay the support (in the sense that is not mechanically locked inside the part, it is on the outside).

My most important advice: stick with the default settings in Cura. Do not start tweaking until you have made a lot of parts!
 

[jwilliams2 1]

Tomnagel,

 

I have used dual extrusion on this part however it was was the same material from both nozzles. The support was printed in white PLA. I am playing around with supports shapes (grid instead of zig zag) as I have started to find that this helps create a more consistent surface. I am ok with seeing build failures, it only helps to facilitate learning, along with the this forum of course.

 

Thanks.

[jirodriguez72 19]

Water soluble supports (PVA) are going to give you the best surface finish, because you can set the gap to "0" and the print is fully support. We print NylonX and CFF-PC a lot, but have to use Aquasys-120 because PVA won't stick to PC, and I will say it ain't cheap! $100 for a 1/2 kg roll!