Commercial Metal Cutting - The Process

[rwanttaja]

Fifty years ago, if one were building a typical homebuilt design, there would long sessions with a steel-cutting bandsaw (or, gawd help you, a hacksaw) to cut out steel components out of flat sheets of 4130.

Nowadays, of course, there are companies that will take a digital file, and in a week or two, ship you a stack of the steel pieces you need.

My question is: What do I need to make this happen?

1. How do I find a company that does this? Any magic search terms?
2. What file format do they expect to receive?
3. What limitations should the drawings reflect (e.g., adjacent parts no closer than 1/4" to each other, etc.)
4. Do I need to supply the material myself? SHOULD I supply the material myself?
5. How precise will the work be?
6. How much post-processing (grinding, filing, etc.) are going to be necessary?
7. What's the usual turn-around time?
8. Minimum/maximum part thickness?
9. Restrictions/warnings on material (e.g., can't do aluminum, or steel must be re-tempered afterwards).
10. Any other cautions for the CAD-CAM-Curious?

Ron Wanttaja

[lathropdad]

I use a company that does water jet cutting. I would recommend this over laser cutting because it leaves a cleaner edge. I have used water jet cutting for both aluminum and steel parts. I do not use water jet cutting for thin sheet metal parts, .050 and thinner.

I do the drawings for the parts and send them to the water jet cutter in either DFX or DWG file formats. I always include a few dimensions so they can check the parts sizes they cut. It is too easy to have a drawing scaled incorrectly.

I use water jet cutting for materials in aluminum from 1/8 to 3" thick. I have several designs that are built up from many parts that bolt together. I have found it satisfactory to have the water just cut the bolt holes and only ream them as a secondary operation. Accuracy is within .005 and more like .001. But thick parts will have taper on the sides. And for parts 1 inch or more in thickens, the taper might be .010 top to bottom. The newer machines are capable of tilting the head so the taper is minimal. The quality of the cut though does vary with depth. If I am going to bolt a part to the a water jet cut edge, I do true that edge before I use it as a bolting surface.

With water jet cutting, there is a bit of sand blasting of the edges but it minimal and I usually finish that with a buffing wheel.

I find that with water jet cutting I can nest a bunch of parts that are cut from the same thickness and the material savings goes a long way to offset the cost of water jet cutting.

The shop I use is usually 1 to 2 weeks max for a job depending on complexity and quantity.

[rwanttaja]

Thanks!

Ron Wanttaja