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Comment by arnado | Hacker News Reader

You might also want to look at the mostly printed CNC, which uses standard conduit/pipe for the frame.

https://docs.v1engineering.com/mpcnc/intro/

Be warned these plans require you to drill a couple holes in the conduit. I managed with just a handheld drill though the holes weren't quite aligned. Definitely use a file or hacksaw to create a flat spot on the conduit where you want the hole so the drill bit doesn't wander as easily.

Or a center punch (helps on flat metal too).

One favorite trick of mine is to print out 1:1 drill pattern drawings and center-punch through the paper onto my metal workpiece for all the drill locations. Fast and accurate.

Basically, 2D printers (you know, those $150 things) are exceptionally high precision and accuracy tools for making 2D drawings. I've been using printers for years and it never occurred to me you could use it to print a (for example) 10cm square.

You can if you are really nifty do limited scale PCB manufacturing this way.

https://www.instructables.com/Creating-Printed-Circuit-Board...

Fusion360 seems to try to prevent you from exporting PDFs with the free hobbyist version. One tip that I discovered was to create a CUPS printer on a Linux VM that saves PDF files.

(I found it printed slightly off sized if I sent a 2D drawing straight to the printer.)

Yeah, you have to correctly configure the output to get dimensional accuracy. but it shouldn't involve finding some magic scaling factor for X and Y that makes things accurate.

I've used Inkscape to make basic shapes, and pay for Fusion 360. TBH I've never actually thought to take one of my 3D Fusion models and use it to make a 2D template for drilling. That makes sense...

Inkjet yes, laser no.

My favored approach to offset drilling / drilling on curved surfaces is to use an endmill. Doesn't wander, goes straight in. Of course, you need an endmill for that approach, but id you're building a CNC those should be in ready supply.

interestingly you can also mill a flat or indexes to mate tubes together. I’ve also contemplated making one-piece saddles to mate extrusions, filling the gaps with zero-expansion epoxy.

Tubes and extrusions you buy cheap rarely have dimensioning and tolerance you’d want to accept out of the box. To get what you need, best just to use geometry of hole centers, and adjustable fine parts.

I set a limit of 1/128 inch on any garage woodworking projects. This is 8 mil (thousandths of an inch) or 0.2 mm. Wood and plastics (and even aluminum) fluctuate from moisture and temperature enough to make this a lower limit of reasonable value, though I’m getting closer to 5 mil in router precision. It’s not a fine carpentry shop and I’m not making anything that really needs better than eyeball precision (hand marking) which would be about 1/32 inch.

Applying geometric dimensioning and tolerance to design has been a liberating experience. I’m not a mechanical engineer or even otherwise anywhere close to the industry so I really had no idea how to assess or compare designs.

Since the mostly printed CNC already requires a 3d printer, you might as well print a jig to help drill those holes. https://play.fallows.ca/wp/tools/3d-printer/mpcnc-drilling-j...

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