Newbie questions about 3D print results


#1

I could look up the web for answers… but since we’re all a nice friendly and helpful community, I figured I could be lazy and ask here :wink:

Assuming one of these new desktop additive plastic printers rather than a stone or metal one;

  • Is there a recommended thickness of material so that an object’s wall is not too thin to stand up to being handled without damage?

  • how flexible is the material normally used? is it brittle? how much deflection/bend will it take without deforming or breaking?

  • If interlocking parts (like a chain) were printed, how much of a gap do you leave between elements?

  • If printing multiple individual parts, do you fit them all together (like an airfix model) and print them in one run or print each bit individually?

  • If printing some “engraving” like text or a logo, what’s the recommended depth (or height) of the embellishment?


#2

It probably helps if you think in terms of the extruded plastic diameter when analyzing these questions. For instance, my printer extrudes from a 0.4mm nozzle, so you can expect to have a model made from 0.4mm sticky spaghetti noodles, basically.

[quote=“gadget2020, post:1, topic:15965”]
Is there a recommended thickness of material so that an object’s wall is not too thin to stand up to being handled without damage?
[/quote]Depends on the material. I have a wallet that I sit on daily, and I’m not a small guy, and I have 2mm thick sections, and only two exterior layers (0.4 top and bottom with a honeycomb infill) and it hasn’t cracked. I’ve been using it a year.
Cheaper filaments can be super brittle, and at the other end of the spectrum I have some Taulman Bridge Nylon filament that I beat with a 10lb hammer to see where it failed (the layers delaminated, it never tore or cracked).

[quote=“gadget2020, post:1, topic:15965”]
If interlocking parts (like a chain) were printed, how much of a gap do you leave between elements?
[/quote]Again, depends on how well tuned your printer is, and what size nozzle, but half the diameter of the nozzle is a good starting point if you’re not over extruding (but most people are, it’s the most common problem I see in prints and calibration)

[quote=“gadget2020, post:1, topic:15965”]
If printing multiple individual parts, do you fit them all together (like an airfix model) and print them in one run or print each bit individually?
[/quote]Depends on the quality needed. Each part separate makes a better print with less cleanup, but it’s way slower.

[quote=“gadget2020, post:1, topic:15965”]
If printing some “engraving” like text or a logo, what’s the recommended depth (or height) of the embellishment?
[/quote] Totally up to you. It’s common to not print layers more than .2mm-.3mm, so it would show up at that thickness, but it’s good to print deeper for visual effect, and the ability to change filament to have the top layers a different color than the base.

Feel free to keep asking. There’s too much information out there to try to wade through at this point. I do like the 3D hubs forums for info though. Most people on there know how to run their printers well. There’s also the CADSpan extension, for some helpful info and a calculator to help with these types of things.


#3

Thanks for the information; round 2 with the questions:

  • As the print builds up, what is the maximum inverted incline that is recommended to print without support?

  • If a model has a lip or overhang, how far can it project without support? (and without deflection?)

  • What exactly is support and how is it generated? (ie is it the same material?) (should a model be designed with ‘support’ that will be cut away?)

  • How does it print things within other things so that the two don’t touch (like a sphere within a sphere)?

  • If I have one model with 2 (solid) components butted up against each other so that two faces touch, will the printer print it as one?


#4

Now we’re getting serious!

[quote=“gadget2020, post:3, topic:15965”]
As the print builds up, what is the maximum inverted incline that is recommended to print without support?
If a model has a lip or overhang, how far can it project without support? (and without deflection?)
[/quote] I may need an image to know exactly what the difference is between these questions, but the general rule of thumb is that a 45 degree overhang is fine on almost all printers.

[quote=“gadget2020, post:3, topic:15965”]
What exactly is support and how is it generated? (ie is it the same material?) (should a model be designed with ‘support’ that will be cut away?)
[/quote]This is one of the things that is currently the subject of a lot of software development. Support is typically generated in the “slicer” or GCODE generating application that you use. Common ones are “Cura”, “Slic3r”, Makerbot has their own, and there are constant developments. It really depends on the model, printer, filament, cooling method, build chamber, printing speed, etc. as to what is the best support for a given item. This is why so many people work hard to design models that don’t require it! So typically, you should not design the support, unless you know exactly what your printer is going to need.

As far as what it is? It’s a structure that is built up so that the spaghetti strands of filament always have something to lay on until they cool. Unlike the built up layers that make up the finished model, there will be a slight gap between the support and the model, so that it is intentionally easy to “delaminate” or break away the support material.

[quote=“gadget2020, post:3, topic:15965”]
How does it print things within other things so that the two don’t touch (like a sphere within a sphere)?
[/quote] The same technique of leaving a .2mm gap or so so that the material on the inside can easily break free would be a starting point. However, gravity always has to be on your mind when thinking about how your model will print, (unless you use something like a SLA or SLS printer, but that’s not what we’re talking about here). The proper orientation of faces would also be critical when we look at printing things inside of voids of other solids. A image or model for reference would allow me to more accurately analyze this question.

[quote=“gadget2020, post:3, topic:15965”]
If I have one model with 2 (solid) components butted up against each other so that two faces touch, will the printer print it as one?
[/quote] Maybe? Depends on the software being used, but almost definitely it would cause some weaknesses as the slicing software would probably just print them adjacent, and they might split in the middle. Best way to go is to always have “watertight” solids for export to .STL files.

I hope this helps, keep the questions coming, and to sum up, I think Brook Drumm, founder of PrintrBot, says it best “3D Printing is hard.


#5

gadget2020
Check out meshmixer, model analysis tool like Netfabb, it has included how to best orient model to minimize required support structure.
It is Autodesk and just saw in news they have also bought Netfabb which I think was part of Shapeway.