Designing a Part That Won't Break

If you're sending us a model, a handful of design choices matter more than anything we change at the printer. None of them are hard and most cost nothing.

Answer three questions first

1. Which direction does the force come from? Pull, push, twist, or impact.
2. What happens when it fails? A cracked shelf bracket is a different problem from a cracked keychain.
3. Does anything screw into it? Threads and fasteners need planning.

These change the shape, not the settings.

Layers are the grain

A printed part is built from stacked layers and behaves like wood. Strong along the grain, weaker across it. Pull along the layers and you have full strength. Pull across them and you're relying on the bond between layers, which is roughly half as strong.

This is the biggest lever available and it's free. Tell us which way the load runs and we'll rotate the part on the plate so the layers work with you.

Round your inside corners

Sharp internal corners concentrate stress and start cracks. A 2-3 mm fillet where two walls meet is often the largest single improvement you can make, and it changes nothing about how the part fits. Find the square corners in your design and soften them.

Thick walls beat dense insides

People reach for "more solid" when they want stronger. In practice the outer shell carries most of the load. A couple of extra wall passes cost pennies and add real stiffness. Filling the middle costs a lot and adds much less. Aim for around 3 mm of wall on a working part.

Ribs, not bulk

A solid block isn't the strong answer. It's slow, expensive, prone to warping, and no better in the direction that counts. Use ribs and gussets instead: thin reinforcing walls running along the load path. Look at the underside of any injection-molded plastic part and you'll see exactly this.

Plan for fasteners

Fine printed threads strip. If something bolts into your part, design a pocket for a heat-set threaded insert or leave room for a bolt and a captive nut. Both need to be in the model before we print. Tell us which fastener you're using and we'll size the hole.

When printing is the wrong process

If a part needs to be thin, stiff and carrying real load all at once, a bent metal bracket may beat a printed one for less money. Better to hear that up front than after it fails on the first install.

What to tell us

Send the model with a note on how it mounts, which way the load pulls, and what it's attached to. We'll flag the weak spots before we print.