Adjusting for poor designs - disonnected parts

Many models online are designed poorly when it comes to snapping parts together to make a composite design. In order for the slicer (Cura) to print a strong composite design I find that my designs have to intrude the parts into each other rather than just snapping them together. Even though I will tell the CAD program to make the composites one piece the slicer stills sees them as separate and print them as such unless I do this intrusion. Otherwise they will stick together - but not very strongly.
When I download a complex composite i find that prints will show tiny holes between these parts. Is there a way to “smear” the hidden boundaries of these parts so that the slicer will print as one piece?

I hope make question is clear.

Have you checked the dimensional accuracy of your prints? For interlocking parts you design, a .1 - .2mm gap usually allow parts to interconnect. If the part you design doesn’t interlock well, use the flow rate or multiplier to “scale” the part. A lower flow rate/multiplier will reduce the size of the part.

The flow rate/multiplier setting in your slicer can help with online designs also. A higher setting can help with the gaps for interlocking parts.

Unfortunately there is no magic setting and you’ll have to find the right flow rate for the filament. A good start would be 95 - 97%.

Hope that helps.

Hi and Thanx for responding.
My problem is that the printed object breaks apart when it shouldn’t. People use snap-on tools in their CAD program but when it is printed the model prints as separate objects that are held together weakly. Only by deliberately intruding one object into another in the CAD program does it actually save them as one model. Many people use the snap-on tools thinking that creates one object but in reality it doesn’t. Som example of problem prints:

  • a matrix square for bottom of silverware rack in dishwasher. The matrix is put together with snap-on tools and on the screen it looks like a nice patterned single piece. But when it is printed the patterns have tiny holes between them that traps food and stuff. The filament I used was INOVA 1800 which is supposed to be food safe and has great dimensional accuracy but those qualities don’t help if you have tiny holes in the design that traps food and gunk.

  • A toy trebuchet. It has a long arm that has poles sticking out at right angles to serve as the pivot point. But those poles were snapped-on during design so they broke off easily when any measurable pressure was applied to the printed model. I created a longer pole that extended the length of the two poles on the arm. I then replaced those two snapped-on poles with one piece where most of it was embedded in the arm. Then the poles didn’t break off any more.

Got it. So the snap-on tools creates individual shapes with interior walls. And when the slicer sees this, it creates two objects with a common interior wall… which can break off. Are these objects meant for 3D printing?

Well… I don’t know of a slicer that can account or heal these types of issue. Post processing could possibly help… epoxy coatings, acetone (ABS)…

Can you post a STL?

Sure, here is the dishwasher silverware mesh that I was talking about. I even tried to subtract it from a block and then subtracting that block from a solid one in the hopes I would get a single model - but that didn’t work either.

I deleted the file I had uploaded previously. It wasn’t ideal for our conversation. This is a new one.
modified3rect3.stl (1.11 MB)

Hi again,
At the Simplify3d forum below I make a suggestion to control adding comments to the slicers gcode. The idea was that if there was embedded comments between the start of each “object”, layer by layer, then i could programmatically tweek the ASCII gcode with very good control to increase temperature, slow down, extruder faster, etc. on just the specific areas that I want. I believe this ability would allow me some control to strengthen boundaries between objects.


"I would like to make gcode edits to make the printer do things that I normally can’t do within Simplify3D. it would help if there were comments between each process being acted on within a layer (or slice) . Each comment might even include layer number and process name being acted on. For example, If I assign a different process to each object on a bed or a different process to each part of a multipart object then I might have different GCode commands for each object/part/process per layer. If layer number was included along with the process name then I could program different codes for each layer of a object/part/process. It might even help if there was a start comment and an end comment for each process of each layer. Comments at the start and end of support or raft or brim prints for each layer will also add fidelity to the gcode editing that I would be able to do. Basically I am asking for a verbose setting of variable degree for the generated GCode.
Verbose 0 might be no custom comments per process per layer
Verbose 1 might be comment for start of a process with process name included
Verbose 2 might be comment for start and end of a process with process name included
Verbose 3 might be comment for start and end of a process with process name and layer number or height included
Verbose 4 might be comment for start and end of a process or support with process name or support/brim/raft indicator and layer number or height included

Because this will have the potential to make very large files the comments might also be as short as possible:
;CC L:120 MN:LowerJaw PN:LJIncreaseTemp H:115 ST

CC - Custom Comment
L - Layer Number
MN - Model Name
PN -Process Name
H - Height (in mm)
ST -Start

Another possibility is to simply have a comments option screen where you choose what comments you want before and after each process in each layer in your gcode.
Having the comments optionally inserted will make search and replace on the gcode much easier and give a means for maximum control of the print"

I think S3D inserts a layer comment into the GCODE file.