In-Machine Marking & Engraving
In this trick we show the trials and tribulations we went through just to mark and identify our CNC machined products.
KISS (Keep It Simple Stupid)...
We wanted to engrave part numbers and port identifications on the manifolds we were making. Tool pathing the letters was a big enough challenge (I'll post something on that at a later date) but being able to cut the letters turned out to be way tougher than we thought. Actually cutting in letters and markings isn't that difficult, it's doing a good job of it that's tough.
So our next attempt was a high speed air spindle. The 22,000 RPM from this tool was more suitable but it was tempermental to get consistent results. For making nice fine text, it is best to keep the plunge shallow (I liked 0.005" below the surface best). Deeper means bolder and this forces larger text to keep it legible. The problem with very shallow cutting is that you must have very precisely offset tools (which we now do with a Kelch presetter but didn't have at that time) and you have to know the exact deck height you are writing to on the part... the whole deck height. If the part is off level at all it will cut deep at some places and not touch at others. Going deeper is only a partial solution as the text get rather ugly when the depth is inconsistent.
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The last problem I can't really say that I know was a problem but I didn't like it. And that was the 20,000 hits/minute of impact acting on the spindle bearings while they were sitting stationary. It seems like a little pencil shouldn't be able to do much damage but that's because when we use it by hand, our hand makes a lot of compliance. When it is mounted firm in a tool holder and spindle with no give, it actually impacts very hard.
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By the way this is what the engraving looks like in aluminum:
...and here is a close up of 0.060" tall letters. Note that the end mill was run a second time to clean off the burrs raised by the engraver. Normally we don't do this but the letters were so small, they just finished nicer. And I threw it in because I just like this photo!
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