SpiderBot Delta 3D Printer

Design a part for 3D printing, some advises...

Written by Ph. Boichut on Thursday, 30 April 2015. Published in News
The FFF (Fused Filament Fabrication) 3D printing technology used in SpiderBot is a great tool for design offices and engineering companies
- it accelerates the design process
- it improves product quality by enabling a more iterative design and more thorough design evaluations (We designed part in just a few days that would have otherwise taken weeks, if we didn't have a SpiderBot)
- it helps reduce design costs
 
But the technology is far from magical and not everything can be printed, at least without a slight adaptation of parts...
You will find in this article some tips and rules that I use daily to get better quality prints on technical parts.

General:

Besides the traditional STL files problems with duplicate facets, wrong orientation facets etc...
The design of a part for FFF 3D printing is close to the design of a molded plastic part, but there are a few things to modify :
- The first thing to do is to always keep in mind how you will print it when you design it : which orientation, what face will be on the Bed...
- If you need accuracy on the holesalways design the holes with a slightly smaller diameter and plan to re-drill.

Thickness of material:

Try, as far as possible, to keep a material thickness of 2.00mm, your parts will be robust and free of print defect.
It is possible to print walls of 1.50mm or 1.00mm but it is always easier to print 2.00mm walls.
Avoid printing a part like the example below :
 
You will have better results with this :
 
Note: It is also possible to increase the thickness of the part in contact with the printing bed, it gives a more solid basis.

Support :

One of the limitations of the FFF technology is the support management. The slicing softwares (KISSlicer or other) must generate the support material to prevent the layers of the piece of "falling into the void."
Why it is important to try to reduce support volume ?
  • Support increases the print time.
  • Support needs post-processing time to get the final part.
  • Often the horizontal faces in contact with the support are less clean than the other areas of the part (although the prints with our new DualHead are close to perfect, it is true if you have a single head).
Whenever possible, avoid having to use support and always try to see if there isn't any other solution for your part.
For example this piece below requires support:
 
Could this be acceptable?
 
Or maybe this one?
 
Always try to avoid having faces with small angle with the Bed
The part below is very difficult to print with a good printing quality, 45° is generally a good angle value
 
 

Fillets & Chamfers :

Always place fillets and chamfers wherever it is possible, fillets soften the movements of the print head and reduce marks.
 
 
If you cannot avoid the support, try to minimize its volume and place chamfers on the part at the area where the support will be touching it. 
 
 
Then, add fillets and chamfers everywhere:
 
 
 
The only place where there should not be a radius is where the part is touching the print bed... This part has to be chamfered at 45° to reduce marks.
 
Do not draw this:
 
Because the area in contact with the printing bed has a too low angle and the support may not be added on the first layers.
 
Do this preferably:
 
Or better, do this :
A chamfer + a fillet (it is extremely simple to draw that with DesignSpark)
 

Thickness/Height Ratio :

It is very difficult to extrude a part that has a  thickness / height ratio greater than 10:
This part below will be very difficult to print due to the flexion of the blade.
 
That will print fine :
 
or maybe the one below would be better depending on where you need resistance.
 

Some other things :

- One important difference between a 3D printed part and a molded part is that you can print hollow/tubular parts.
Therefore it is possible to integrate multiple functionalities into your part.
For example in the part below, a suction cup support, the vacuum ducts are integrated into the part, they have two functions : support the suction cup, but also act as an air duct.

That's very difficult to do with an injection molded part.

Simply draw the internal ducts with chamfers at the top to avoid having to put the support inside (Just limit the Z level of the support in KISSlicer)

or that part which will print without support...

 

- Second difference is the possibility to easily print parts with negative Draft Angle, there is nothing to do, simply print...

 

I hope this help... If you have any questions, you can contact me by email at : pboichut[at]qualup.com

Happy Printing !
 

Note :

The images in this article were made with DesignSpark, a free software provided by RS Component / Allied.

DesignSpark is, in my opinion, the best free CAD software of the market (for design parts to be printed by FFF, I mean).
 
Fillets and chamfers commands in DesignSpark are stunning for a free product and the export to STL format is simply perfect.
 
Just open an RS Component account if you want to try this product.
DesignSpark is based on the CAD SpaceClaim, a professional and innovative 3D CAD software using ACIS a mathematical kernel of Dassault Système (a world leader in the CAD market).
 
 
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