Design guidelines

A closed solid fix

A model has to be a solid: every surface joined to its neighbours with no gaps. Surfaces with gaps don’t say where the metal is, so there’s nothing to machine yet. We also count bodies: a file with several bodies prices as one part, but each is a separate part to cut.

Checked

Edges used by only one triangle. More than a few means an open shell.

Fix

Export the part as a solid body. Sew or knit the surfaces first. Send each body as its own file, or tell us they’re one part.

Size fix

The part has to fit the travel of our largest mill. Long parts are also checked for how slender they are, because a part much longer than it is wide bends under the cutter and is hard to hold.

Limit

1016 × 508 × 508 mm (40 × 20 × 20 in). Slender past 8 to 1, length to width.

Fix

Split a big part into pieces that bolt or weld together. Widen a slender one where you can, or add a rib. We may leave stock to support it while it’s cut.

Walls look at · fix

We measure the thickness of the part everywhere by casting rays through it. Thin walls chatter and bend under the cutter, and below a point they may not survive being cut at all. Tough metals push back harder on the tool, and plastics flex, so each needs more.

7075 aluminum gets one more check. Plate of it holds stress, and floors or walls under 1.5 mm can bow 0.1 to 0.5 mm once they’re cut free. Thicken them, or we stress relieve and finish in two passes.

Fix

Thicken the wall past the first limit, or tell us it can be thicker than drawn.

Hole depth look at · fix

A drill wanders and has to peck out chips as it goes deep. Past 12 diameters, standard drills don’t reach.

Limit

Look at past 6 × the diameter. Fix past 12 ×.

Fix

Make the hole shallower or wider. If it goes through, we can drill it from both sides.

Threads look at

A hole the size of a common tap drill is taken as tapped: 5.0 mm for M6, 5.11 mm for 1/4-20 and so on. A thread needs enough length in the material to hold a screw’s full strength, and softer materials need more.

Stainless screws in stainless threads gall: two stainless threads cold weld when tightened dry. Use anti-seize, or a screw of a different material or hardness.

Fix

Deepen the hole, use a coarser thread, or ask for threaded inserts.

Metal round holes look at

A hole too close to an edge or another feature leaves a thin wall that bulges when the hole is drilled or a screw is torqued. The limit is the material’s wall limit above.

Fix

Move the hole in: at least 1.5 × its diameter from its centre to the edge.

Inside corners look at · fix

A round cutter leaves its own radius in every inside corner. A small radius deep in a pocket needs a small cutter that reaches a long way: slow past 4 × its diameter, and past 10 × it breaks. A corner with no radius at all can only be made by EDM.

Limit

Look at when depth passes 4 × the cutter’s diameter. Fix past 10 ×. Sharp corners: look at.

Fix

Open the corner radius to at least 1/8 of the pocket’s depth, or make the pocket shallower. Add a radius of 1 mm or more to sharp corners, or accept the cutter’s radius: we leave about R1.5 unless you say.

Pockets look at · fix

A narrow pocket needs a long thin cutter, which deflects and chatters. We measure each pocket’s width just above its floor, the narrower way.

Limit

Look at past 4 × deeper than wide. Fix past 10 ×.

Fix

Widen the pocket or make it shallower. Depth up to 4 × the width cuts cleanly.

Reach look at · fix

We find the sides a tool comes from to reach every face, which is also the number of setups. Undercuts and faces hidden on every side need a five axis mill or a special cutter, or can’t be cut at all.

Limit

Look at when more than 0.3% of the surface is out of reach. Fix past 3%.

Fix

Open the hidden faces to one side, or split the part.

Sealed hollows fix

No tool reaches a cavity closed on every side.

Fix

Open it to the outside, split the part, or fill it.

Your drawing

Send a drawing, as a PDF or a photo, when the model alone doesn’t say it all. It is read when it arrives for what a machinist looks for first: the title block, material, finish, the tolerance unless noted, the quantity, threads, tighter callouts, GD&T and notes. The quote page then shows anything that differs from what you picked, such as a drawing that says 7075 on a part quoted in 6061. It’s a first read, and your machinist checks it against the print.

Name the drawing like its model (bracket.step and bracket-revB.pdf), or put the part number in the title block, and it’s matched to its part.

The drawing reader and the AI review send your drawings and your parts’ measurements to Anthropic’s Claude to read them. Anthropic doesn’t train on them. On the instant price on the home page, nothing goes to Claude unless you press Refine with AI review. On a quote in your dashboard, untick Use AI under Extras to keep it to people only.

Casting coming soon

Investment casting is on its way. Until it opens, the checks show a casting preview beside the machining ones. Walls need about 2 mm for metal to fill them before it freezes, and under 1.2 mm is a fix. Sharp inside corners crack the shell and the metal as it shrinks, so round them to R1 or more. Holes under Ø3 mm are cast solid and drilled. Sealed hollows need a vent of at least 3 mm.