Lathe - X axis positive/negative?

[sansbury]

I recently finished converting my lathe to CNC so starting to try out the lathe module in V23. I watched the training video for the turning feature and threw this little doodle (BBCD fle attached) as a test but when I loaded it on the machine, it looked like the X axis was reversed. Basically it tried to position the tool at the back side of the stock, almost like it thought I was on a slant-bed turning center.

My lathe is a standard manual machine and I've set it up with X=0 as dead center and Z=0 as the face of the stock. A positive X move is backwards away from the center, so for instance X=1 would position the tool at the outside edge of a 2" circle.

I've never programmed or setup a CNC lathe before so I suspect I may be going about something the wrong way here. Should I be reversing my X axis direction, or did I just draw the part wrong? Thanks in advance!

[The Engine Guy]

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Because you did your drawing in the lower left quadrant you have set it to be all - (Minus) values so will work the wrong way round.

Do your drawing in the top left quadrant as per the image below and check the attached bccd file where I have re-done it in the positive.

Now working from the outside diameter of the stock towards the centre (X0) will be reducing numbers and moving out from the centre will be positive numbers.



Don`t worry that the drawing looks to be for a slant bed lathe it doesn`t matter, the numbers will work the right way for you.

You have to remember that on the slant bed the tool is upside down compared to a traditional front toolpost but the slant bed is only the normal toolpost rotated around the Z axis so is in effect exactly the same!! Nothing magical about it to learn

Hope that helps

Regards
Rob

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[sansbury]

Ah, yeah, that makes MUCH more sense. Thanks!

And yeah, I get your point about the slant-bed setup. Visually it looks backwards but I can see how it makes the numbers work properly.