Getting your 3d model which you have painstakingly designed out into the physical world by 3d printing is always exciting. Finally gonna get to see the futuristic cool design come into life! But sometimes, things may take a much longer path than expected due to hiccups in translating a 3d model into a 3d printed piece!
Things tend to crop up along the way, and it is at the end of the day, an iterative processes in going back and forth the 3d design and 3d printed prototype pieces in the quest to get things just right!
So, in order to reduce (it’s hard to be 100% on this!) the common issues faced in getting from a 3d model to a 3d print, here is our compilation of some of the things to consider and watch out for when modelling or preparing a 3d model for 3d printing. We hope it helps some of you out there, and in case we missed out on any nifty tips, do let us know!
Here we go:
Ensure Model is Water Tight/Manifold
For 3d models to be printable – they need to enclose a volume and have surfaces on all exterior parts to form what is known as a water tight or manifold model. You can think about it like this – if you put water into the inside of the model and rotated it 360 degrees all around, would it leak. If so, you’re not going to be able to 3d print it.
In the very simplified example above, the 2 cuboids are identical, except for the fact that the one on the right has its top surface missing. So, only the left model is considered 3d printable.
For some programs like Rhino, you can check if the model is indeed watertight (and has a volume) to it by using the “Volume” command.
If you get hit by an error message like this, it’s a sign to check where the missing surface is which is causing your 3d model to be not water-tight.
Maximum Size for Print
Sometimes when a 3d model can get really large during the design phase, it is worth considering how it can be separated into parts for ease of printing. The reasons for these are many. But primarily to allow the individual parts to fit within the maximum print dimensions of the 3d printer; and also to chunk the 3d printing times of the various 3d modeled pieces into more reasonable times.
Its is largely better to print two 10 hour piece than it is to print a 3d modeled piece in a 20 hour single shot. If the 3d model was intended to be 3d printed on different printers too, it would be sensible to keep things within a 10cm x 10cm x 10cm bounding box as that will fit most consumer 3d printers.
It’s normally easier and more accurate to separate your models into parts in your working 3d software (such as the example above, using BooleanSplit to slice a quadrant out of the model). But this can be done also with PlanarCuts in MeshMixer if all you have on hand are the final STL or do not have access to a 3d modelling tool.
Minimum Feature Sizing of 1mm
It is equally important to note and take care of the minimal features on the model. Generally given that most consumer printers have a 0.4mm nozzle, doubling that and adding a bit for variance – designing parts with minimal feature of 1mm is a good idea. In some cases, the slicer will also ignore anything which cannot be printed – e.g. if you printer has a 0.4mm nozzle and you feed the slicer a 0.3mm wall, the slicer may decide that it is not possible and drop that feature entirely.
From the image above, the model with the 1mm wall is likely to be the thinnest wall printable. The 3d model on the right with a more robust 3mm wall would be a better bet for printing if design-wise, this dimension is an acceptable option.
Another key reason for checking on the minimal features for the 3d print is to ensure that the final print will have a better robustness and strength, especially for applications where the piece supports weight or needs to take some stress.
Combine or Union into Single Model
The next thing to note is a little less problematic with more recent slicers, but may still throw an unwanted curveball if you’re not watching out for it.
Hence, it is typically good practice to combine all your separate 3d solids in your 3d modelling program into a single solid before exporting; and to not have 2 “overlapping” solids as shown in the left side of the below image:
Here’s what may happen in your slicing program if you did export the model on the left as 2 separate solids. The slicers had assumed that the portion of the model with the overlapping solids was meant to be an empty space and rendered the gCode accordingly as such (which is not the design intent here):
Instead, run a command for Merge or BooleanUnion to combine them into one single model, as represented by the compound solid shown highlighted on the right here:
This will ensure that your 3d model is properly interpreted by the slicer.
Check your Tolerances for Connecting Parts
Here’s another common hiccup for 3d models which need to be 3d printed out and then connected to one another – the lack of tolerance for them to fit together. This means is that a 10mm 3d printed peg will not fit a 10mm 3d printed hole, and some give between the two dimensions need to be accounted for, as shown below:
Now the tolerance needed may vary from one 3d printer to the next but a general guide would be to start with something like 0.5mm tolerance on all sides.
So there you have it – these are some of the common things to consider and take note of when 3d modelling parts which are intended for 3d printing. We will probably add more ideas/thoughts of things to look out for when preparing your 3d model as we come across more of them.
For now, go forth and create some awesome things now then! =)