Servo Driven 4th Axis for CNC Mill

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Hazel:
Hi Andrew,
I'm just installing my Z15 Servo card, and just discovered that the card does not have screw terminals on it, but takes another connector with screw terminals on it. I found something in Farnell, but the pins are much thinner than the other ones in by axis cabinet, which are more like 1.5mm thick. The farnell ones are only 0.9mm thick according to the datasheet. I don't suppose you recall where you got yours from?

I Just realised the same connector system is used on the rear of the TNC151. Which is anooying, as I removed the interface PCB and ribbon cable to avoid disturbing the cabling - and all I needed to do was pull the connectors out - D'oh... Oh well I only did that about a dozen times while I was repairing the 4th axis encoder interface.

awemawson:
Hazel,

I used these from Rapid:

http://www.rapidonline.com/Cables-Connectors/CamdenBoss-CTB1050-12-12-Way-24A-90-Interlocking-Terminal-Block-5mm-Pitch-21-4625

They are not a perfect match, and infact I have put a dab of 'hot melt' glue bridging the male and female housings to ensure that they don't vibrate loose. They've proved ok in practise.

Hazel:
Ah, those are the same as I discovered in Farnell. I think my plan is to get some of the 5mm pin header stuff which has 1.5mm diameter pins and solder it to one of the Camden thingies. Many thanks ! Now I have to wade through all the din terminal blocks to find some 35mm rail ones to fit the 3R3 motor brake resistor. Fun Fun Fun!

awemawson:
Well it's been a LONG time in the gestation, but at last, as it hasn't stopped raining for days, I've found a bit of time to sort out a suitable 'Post Processor' to allow me to engrave text on the outside of a cylinder mounted in the 4th Axis. :ddb:

So what's the issue :scratch:

Well, if you use a CAD/CAM set of programmes to generate the bits you want to make on a CNC mill or lathe, the program has to spit out code that meets the specification of the controller that drives the machine. So most CAD/CAM set ups use an intervening set of definitions and code that take in the symbolic actions, and translate them to actual code that the controller can understand. Once defined and installed, from then on the CAD/CAM should (hopefully) produce the right stuff for the controller.

Now there wasn't a 'standard' Featurecam Post Processor suitable for the TNC355 controller in my mill that understood the 4th axis. There were ones that drove 4th axes. And there were ones that were close to the TNC355 (as the TNC150/151/155 is very similar, so it was a case of making a Frankenstein version, with a few tweaks of my own.

It didn't help that some of the 'standard' Post Processors made mathematical errors when wrapping stuff round a cylinder :bugeye: All sorts of Gotcha's appeared - like the one that made moves all the way round the bar backwards to get to somewhere close to where it started, cutting a nice groove as it did it :( Anyway much :coffee: :coffee: and rather a lot of :med: got me there in the end.

So what are we talking about: well the first picture below is a screen shot of a very small fraction of the program like structure of the Post Processor, and the second picture is code suitable for my Heidenhain TNC355 to obey

awemawson:
Now there is still quite a bit of tidying up to do to generate more compact code - but hey - it works :clap:

The 32 mm bar in the picture below has been engraved with my initials 'AWEM' using a diamond 'drag engraver' - quite hard to photograph curved surfaces but I'm sure that you get the general idea.

If you look at the over view picture, you'll see several failed attempts along the way :bugeye:

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