This makes sense. Thank you for sharing your own insights and techniques, Bryan
I do a lot of complex micro-engraving (0.002-0.004 tip engravers). I've had good results on gold, silver, copper, and aluminum.
Here are some general guidelines for micro-engraving:
- Use the largest tip and widest angle you can get away with to keep up the strength of the engraver (ie: 60-degree tip is better than 30-degree tip, 0.01 tip is better than 0.005 tip, etc.).
- Use ball mills when possible, they're stronger.
- Not all carbide is the same! I've used "China carbide" and Bits & Bits carbide, same size, same speeds and feeds -- Bits & Bits lasts 5 times longer.
- When you need to go narrow & deep, clear out the engraving using progressively tighter bits - start with a 60-degree, then go to 30-degree, etc.. I've gotten down to 6-degree cutters 0.03 deep with 0.004 feature sizes using this technique, this is the limit I have time for with the 770's 10k spindle.
- When you want sharp features, but don't have time for the speeds and feeds of a 0.002 engraver, use a larger tip to clear out the majority of the engraving, then use the fine tip engraver to trace the outline of the feature just a few thou deep (0.002 - 0.004 deep). Visually this will have the same impact as if the entire engraving was done with the 0.002 tip engraver. A fine eye or magnifier will see the slight shelf left by the higher resolution tip, but for most purposes this works just fine.
If you use SprutCAM, there are a few specific issues to watch for:
- The engraving operation works well for some tool geometries and just goes wonky with others. Check the cut path it generates!
- The engraving operation sometimes skips 'levels' (ie: 0.002 deep, 0.004 deep, 0.008 deep ... wait, what?).
- I often use the Pocket operation instead -- setup the tool as a cylindrical end-mill with the appropriate tip size, then program the side-angle for the engraver you're using in the pocketing op (not the tool geometry). [NOTE: my version of SprutCAM 10 will not save the side-angle parameter when using the wizard view (double clicking the op to get the parameters), I have to use the operations tabs below the operations list to set it]
- For some reason, after many tweaks and re-computes on an operation (engraving or pocketing), the tool paths start to get sharper, like the compute engine is loosing resolution every time I hit the run button. For micro-engraving this totally destroys the features. I have not found any way to correct this, even copying the op and reset/run on the new op does not fix it. The only workaround I've found is to delete the op and program it again from scratch. Works fine this way, but I have to check & re-check the generated paths to make sure it hasn't started to lose resolution.
--Bryan