Apr 20, 2016 | By Andre
As someone that has worked in the 3D printing service sector for some time, I always hold my breath when a client comes in and tests the fit of their 3D printed prototype against the circuit board (or whatever else) they designed around. The ensuing reaction is either one of joyous relief or instead a few stumbling moments of “uh-oh’s” and “oh-no’s”.
The culprit behind the unease is often centred around whether or not the designer adjusted correctly for the material tolerances that differ every so slighty for every mode of manufacture; 3D printing including.
Tolerances are, in brief, the difference in size (often only tiny fractions of an inch) of the actual 3D printed item and what the design software suggested. It is up to the designer to be aware of these tolerances and design around them so if your task is to fit a 1/4" bolt through a 1/4" hole, it’s always wise to design the hole a tiny bit larger.
Fictiv, a network of distributed 3D printing service centers, has recently blogged about how to conduct a tolerance analysis check for 3D printed parts and has made available a handy excel calculator to anyone that wants to improve in designing for 3D print related tolerances.
The blog entry suggests how a minor 0.030” positional error during manufacturing can cause alignment nightmares when it comes to fastening screws. It’s minor mismatches like these, from design to production, that can necessitate undesirable and often costly revisions down the line.
To prevent this, the Fictiv explanation goes through rather clearly how to conduct a few tolerance analysis tests with the help of their handy calculator (although you do have to provide them your email to gain access to it).
The first example is based around conducting positional tolerance analyses by defining the manufacturing method (in this case 3D printer) used, and the necessary clearance based on what you’re trying to match the 3D print with by using the below formulas (don’t worry, they’re also incorporated into the calculator if you don't want to do the math yourself).
The second example has instructions on how to conduct a linear tolerance analysis. This has less to do with matching the diameter of two adjoining pieces and more to make sure two interlocking bits fit snug into one another. Just like before, the part that is to fit into the other needs to have its tolerances adjusted accordingly.
But fret not, if you’re designing for 3D printing for the first time and are kept up at night with the thought of your components not fitting together as intended, a little bit of post-production will typically suffice until the next round of changes. Because heck, some sanding, subtractive modifications and even a little bit of guess work is all part of prototyping. If it wasn’t a process, then there would be no need for prototyping in the first place and 3D printing wouldn’t have the traction in the manufacturing sector it does today.
So if you’re a product developer of any kind and are a little bit uneasy of designing around the tolerance considerations needed for different types of 3D printing, I recommend giving the article (and subsequently tolerance calculator) a try.
Posted in 3D Printing Technology
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