Closer… Grazer

As I’m typing this, I’m looking on at a CNC machine with a very long, 23 minute program to run. After a previous week of inconsistencies and mysterious errors, I’ve made some changes to the cut.

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By changes, I really just mean that I slowed it down. For every other part of this design that I have cut, the end mill was set to cut at 30 inches/minute and plunge (a rapid change in the height of the end mill) at 50 inches/ minute. These are pretty standard rates for a machine of this lowly caliber — some of the big ones can cut up to 1200 inches/minute — so I thought that it wouldn’t cause any issues. But after I did everything in my power to make everything level, confirm that the machine is level to itself (although not to the ground), and check the code, to get a result that was still inconsistent, as well as nonsensical if it’s a leveling issue, I was lead to conclude that the part was moving around in the vice. The only way this could happen, is if the part was forced down by the milling action.

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Top ridges are lower than the bottom ones. 

To reduce the impact, I slowed down the feed rate to 17 inches/minute and let the program run. What I got back was more of the same, but to a lesser degree. It’s still not perfect, and I still think it’s because the part isn’t securely clamped in the vice. Steps from here are going to be manually milling out this piece to have each pocket be as similar as possible. I realize that this aspect has spanned quite a bit of time, but hopefully it will pay off in the end.

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