Hobbyist looking for advice on building difficult structures

mark_dutton343

I am a hobbyist and I have been using Onshape for about a year. Loving it and after using Freecad, it is so much more elegant.

Anyway, I am looking for advice, that might be more suitable to a maker's forum, but I thought I'd try here in case there is some funky feature in Onshape to help me directly.

I have drawn a drain leaf strainter. The drawing is here. https://cad.onshape.com/documents/d1c2ce417c4a1ce1929a6f6b/w/3f729b7dc92ed16468f6dc0c/e/2ab2252e7de05181874d4beb?renderMode=0&uiState=62a028878bfb3069d20c7fbf

The problem I have is that when I 3D print this, the fingers are very unstable and move around with the printhead, so the quality is pretty awful. What I would like to do is draw a very thin cylinder inside the structure with small contact points every 10mm or so to stabilise the entire model as it is printed. Is there a trick to doing something like this in Onshape, or do I have to manually create this as part of the drawing?

Cheers

dirk_van_der_vaart

https://cad.onshape.com/documents/f002c23113158c2a02aea4a0/w/e09c7eff9994109f664faa79/e/0ee142dc1a179d1630fd53eb

This?

mark_dutton343

dirk_van_der_vaart said:

https://cad.onshape.com/documents/f002c23113158c2a02aea4a0/w/e09c7eff9994109f664faa79/e/0ee142dc1a179d1630fd53eb

This?

Yes I thought of that and it would improve, but not totally fix the issue as the bars start to move at a reasonably short length. I am going to put a thin cylinder inside the main frame and then put small connectors to the bars every centimetre or so. When it is printed, I will break away the internal cylinder and cut the small nipples from the bars. This should make it a rigid structure to print.

Evan_Reese

I wonder if this might be more of a printer issue or slicer settings issue, than a part design issue. In my experience the print head shouldn't be applying much pressure to the part, and the printer moves shouldn't be vibrating it. If it's a one-off print, then print time matters less, and you might try just slowing down all of your travel speeds.

shawn_crocker

I'm going to have to agree with @Evan_Reese.  In my experience, this type of thing can print out with great quality but with greatly tuned printer settings.  Flow rate probably has to be reduced way more than seems logical for this.  speeds of 5mm/s is what I would use going into the leg sections.  I realize you have mentioned the part moving around a lot but I'm betting on the speed it tool fast and the plastic is remaining too soft for too many layers.  To address the issue of actually adding manually created supports, I think there is something free called mesh mixer or something that will automatically let you place "tree" style supports onto vertical structures like this.  You would import your downloaded mesh file into this other program.

Evan_Reese

you can create tree supports directly in Cura as well

_anton

So the aim is to create this tall dome with vertical slits? I agree with Evan and Shawn here. Couple of thoughts from my experience:

1. Have you tried turning on z-hop in the slicer? Cura has this setting. This lifts the print head between contiguous extrusions so that it doesn't snag on the print.
2. Make ribs going up the outside of the walls as reinforcement (or just make the walls thicker).

I think, combined with Dirk's solution, this should let you print the part fine.