Wednesday 24 April 2019

First cut on the Bridgeport CNC conversion!!

Just do it:
Let's not fuck about here. It's taken me a couple of weeks to design and make a pneumatic actuator just to enable me to change the tool, what with Easter break and other house works (the Domestic Manager was also present). The least I can do is get on with cutting some swarf now that I've fixed that.

Before I realised that I had no means of changing the tool, I'd fitted a piece of engraving (laminated) plastic to the table. That still seems like a reasonable starting place, so let's make a simple CAM file to try out engraving.

CAD and CAM: Using the text tool in the sketch environment, then extruding it 0.5mm down into the stock should do the trick here. Never done engraving before and I've not bothered to see how thick the layers are - I am assuming 0.5mm will do the trick.



I'm using a 2mm carbide PCB milling cutter because I have a (small) box full of them, mostly in a usable condition. That should make a reasonable job of the corners without taking forever to complete the job. 

Using a 2D adaptive toolpath won't give a perfect profile but I'm just looking for proof of function initially. 


Post this, using the custom Newker post processor I made a couple of months back. Then try to remember how to set machine and work coordinates - and tool lengths. Then finally hit the green tit. And....nothing happened. Needed to remember to press and hold the button on the MPG pendant. Doh.

Pleasing action resulted:

The cutter survived and the end result is OK once I'd lowered the tool another 0.25mm. Seems the stock wasn't very flat and / or the thickness was greater than I'd expected. 



Unlucky for some but it's also our house number. Happy with that. And so is Rufus, although he seems to have gravitated towards the bigger machine. Good boy.



A couple of things:

  • The VFD took forever to ramp down. Needs the parameter sharpening up somewhat. No point forking out for a proper braking resistor if you aren't prepared to actually use it.
  • The ramp feed rate is miles too slow. That needs looking at.
  • The retract and top heights are too high, particularly with the current feed rates. I have a life to live.
  • I need to calibrate / configure the VFD. Currently I haven't much of a clue how fast it is spinning.
  • I just pulled the speeds and feeds for the cutter and laminate out of my ass. I should really work out a sensible set of values for next time.
  • I need to dig out the manual and set up the tool length offset table. Ideally I'd fit a touch off pad thing to do it automatically. I had to set the tool length offset to zero to get it to work, as the previous values (from The Shiz) resulted in illegal Z values when it loaded the values for Tool 2 called up by the program. A bit of MDI to set G54 and some messing with the values in the tool table ("redeem") did the trick.

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