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| Diamond Drag Engraver |
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| awemawson:
This is my take on a spring loaded 'drag engraver' for my CNC mill. Nothing particularly unique, just my take. I wanted a co-axial design that would fit in a collet, so that it could just be one of the tools to select from the 16 way tool magazine. I made an air turbine driven engraving spindle years ago, and that can only be mounted manually as the airline needs connecting so cannot easily be part of a tool selection sequence. Searching around, the diamond tips sold for Dremel engravers seemed the cheapest for experimenting. they are about 1/8" and 1" long. I had some phosphor bronze 3/8" bushes left over from a project many years ago, so they were pressed into service. The housing is a piece of 5/8" re-bar turned down to 15.5 mm and bored 1/2" for the bushes. For what it is, the re-bar machined remarkably nicely. |
| awemawson:
So how well does it work? Not bad at all for a quick cheap and cheerful projectette :ddb: The armature that holds the diamond point is currently mild steel, and measuring 0.373" is a '2 thou lose' in the bronze bushes. I've got some precision ground silver steel on order to replace it however with a non rotating spindle you would hardly notice it. |
| awemawson:
I'm using FeatureCAM to generate the tool path, and had to iron out a few quirks. For the engraver not to rotate, in the tool definition I was putting RPM = 0. It turns out if you do this, FeatureCAM automatically overrides the feed rate to zero :bang: Also the TNC355 controller on the mill strongly objects to spindle speeds below 50 RPM. Now FeatureCAM always issues an 'M03' (Spindle start) after it has called for a tool change. What I've had to do is re-code a bit of the FeatureCAM post-processor, so that if the RPM is less than 50 it outputs 'M05' (spindle stop) instead of the 'M03', then define the tool RPM as 30. Now both the controller and the CAM package are happy - it's just like quarrelling children :lol: Andrew |
| RussellT:
Hi Andrew That looks really useful. :clap: How big are the letters you've shown? Russell |
| awemawson:
Those are about 8mm high. Andrew |
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