DESIGNING HOLES, FOR POLYJET 3D PRINTING.
Today I thought I’d talk about holes!
Time and time again I am asked about what size hole we can 3D Print!
So, I thought I’d right an article on it!
In-order to help those designing parts, wishing to have their parts 3D Printed by POLYJET 3D Printing.
POLYJET is an excellent material for those wishing to produce a hole in a 3D Printed part!
Due to it being a solid mass of plastic produced from liquid resin, and not extruded or powder based, it produces outstanding holes with a smooth surface, and no porosity, in comparison with that of FDM & SLS.
This not only allows you to produce holes but gives you the ability to use machine hand taps to produce accurate threads, for bolted connections.
No need to add metal threaded inserts anymore unless you plan on regularly undoing, and doing up your choice of fastener, and wish to reduce the wear it can create.
If you still wish to use threaded inserts, it is not an issue, POLYJET 3D Printing will still accommodate this!
To aid you and show you what can be done! I decided to print you a hole test board, so you can see for your selves first hand, what is possible.
0.1mm -4.0mm in 0.1mm increments.
Looking at the board! The top left hole is 4.0mm and just like you read from left to right, the holes decrease in size, the bottom right hole being 0.1mm in size, when produced on CAD (Computer Aided Design).
All looks ok, Right! Until we get to the bottom row, we have a nice array of holes.
Hopefully you can make out the bottom row in this second image!
This is where the issue comes in!
As advanced as 3D Printing has become, it has its limitations!
You should be able to make out on the bottom row 4th hole in from the left, the white of the paper below, this hole being 0.7mm in diameter.
This is the smallest hole size on a CAD software package that can be produced for a POLYJET 3D Printer!
Now the technical bit!
Due to machine tolerances the 0.7mm hole has a +/- tolerance as do all the other holes of 0.1mm.
So! The 0.7mm diameter hole is actually 0.6mm, and likewise the 4.0mm hole is 3.9mm diameter.
Moving on! If you wish to produce a 4.0mm hole for a pin with a transition or interference fit with no drilling, you will have to produce it in your CAD as 4.1mm diameter.
With tapped holes, since most people don’t design tapped holes below M2, the 1.6mm diameter hole required will be ok as is, because the Tap will remove any excess plastic material and produce an accurate thread.
This Article has been written for vertical holes which will be printed with no support material in them on a gloss setting.
I will go into holes in the side of a 3D Printed POLYJET part next time.
Thank you for reading and please feel free to comment & share the article!