Working With Plate Scans To Make Them Producible?

[morrisey0]

I am trying to work with a few chassis plates that I have, and get them to the point where I can send good files to a fabricator for cutting. This seems so simple in theory to me; place the flat plate in the hi def scanner, hit the button, and Wala you have a fantastic 2D image you can work with to made a dwg, and share it to get made. But I have found that my scanner makes shadows as the plate has depth. And the more dpi you add to the image, the more bumps and unevenness the scan picks up, making seeming straight lines into quite rough routes. So, I end up with something that looks great from 6" away, but when you get down to the pixel level, it is like a war zone. My first below is the first scan, and the second pic is after some manual cleaning up.

I have tried tracing also, but really haven't had great results with that method either once you really get down to the pixel level.

I know people have spoken about getting plates made from scans, so I am just figuring out how to get to that point. Nothing I am doing so far seems like it would be clean enough to create a decent part from. For those that have done it, can you help an idiot out?

[GoMachV]

I will scan the item as a pdf which retains the scale. Then I import it into cad as an overlay. Then I start by picking a hole to base everything off from. I measure the actual part hole to hole, triangulating it as much as possible. Then in cad you can draw circles with those lengths, and where they intersect is your third hole. It *should* line up remotely close to the overlay (er, I guess underlay). The scan, for me, is just a guide to ensure you are headed the correct direction. Without it, you can get pretty far off and not know it until you are too late.

When finished, I make a print of the drawing and lay the original part on top. I use a fine tip mechanical pencil to carefully draw all the holes and shapes on top of the print. This verifies that your holes are going to end up in the right place once you cut the final part.

It’s also important to consider if the company created the part in metric or imperial. If metric, most everything will be on a .5mm grid. If imperial, you then have to figure out if they went with fractional or decimal. AE for example is usually decimal.