PP for rotary axis (not wrapped)

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Curran
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Joined: Wed Sep 22, 2021 6:53 pm
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PP for rotary axis (not wrapped)

Post by Curran »

Hello,

Is anyone able to help me modify a PP for use with a rotary Y/A axis?

My machine setup is as per the diagram below. Its only 2D/2.5D machining so VCarve Pro can create the tool paths.

Is it a case of converting cartesian into polar coordinates?

Any help would be much appreciated!

Thanks,
Curran
Picture.jpg

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Rcnewcomb
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Model of CNC Machine: 24x36 GCnC/WinCNC with ATC
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Re: PP for rotary axis (not wrapped)

Post by Rcnewcomb »

Send an email to support@vectric.com to see if they can help.
- Randall Newcomb
10 fingers in, 10 fingers out, another good day in the shop

Curran
Posts: 5
Joined: Wed Sep 22, 2021 6:53 pm
Model of CNC Machine: Lots!

Re: PP for rotary axis (not wrapped)

Post by Curran »

I have tried contacting support, they replied saying it's not possible but I'm not sure they fully understood the question.

All that's required is to convert the X and Y co-ordinates to Radius and Angle using the following formula.

R=SQRT((X^2)+(Y^2))
A=ARCTAN(Y/X)

What I'm not sure about is if or how these calculations can be embedded into the post processor.

I could create a macro in excel to do it for me but it would be easier if the post processor did it.

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Rcnewcomb
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Re: PP for rotary axis (not wrapped)

Post by Rcnewcomb »

The post-processor engine only supports multiplication, so there is no support for square root and arc tangent. Some control software like ShopBot do support some math functions. Do you know if your control software can evaluate math functions? Otherwise you will need to run it through Excel or some other program to evaluate and output the results.
- Randall Newcomb
10 fingers in, 10 fingers out, another good day in the shop

Curran
Posts: 5
Joined: Wed Sep 22, 2021 6:53 pm
Model of CNC Machine: Lots!

Re: PP for rotary axis (not wrapped)

Post by Curran »

Thats really helpful, thanks!

I use Mach3. I believe it supports math functions. I'm not sure how they should be embedded in the gcode though. Might it slow down the machine if making calculations on the fly? I'm assuming it would be better just to have the correct values in the gcode ready to go.

I'm starting to think excel might be the best option.

Curran
Posts: 5
Joined: Wed Sep 22, 2021 6:53 pm
Model of CNC Machine: Lots!

Re: PP for rotary axis (not wrapped)

Post by Curran »

Thought I'd give an update on this for anyone who might be looking to do something similar.

I ended up creating a spreadsheet to convert the tool paths from cartesian to polar coordinates. It wasn't quite as simple as I first imagined as the formula falls over at certain points (when dividing by 0) so a reasonable amount of logic was required but anyone with basic excel skills (and google) will be able to achieve the same result as I have.

I wrote a basic PP which creates a txt file with all the raw data instead of the usual g code to make it suitable for importing straight into excel. Excel then converts the data and formats it into g code suitable for Mach3.

I ran a dry test last night and it works really well.

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Rcnewcomb
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Re: PP for rotary axis (not wrapped)

Post by Rcnewcomb »

Thanks for the update. Sounds like an interesting machine.
- Randall Newcomb
10 fingers in, 10 fingers out, another good day in the shop

Curran
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Joined: Wed Sep 22, 2021 6:53 pm
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Re: PP for rotary axis (not wrapped)

Post by Curran »

Basically I've just attached a spindle to the cross slide on my CNC lathe so I can mill on the end face. I can also rotate the spindle 90 degrees to machine keyways, flats etc. It really expands the capability of the lathe.

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Rcnewcomb
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Re: PP for rotary axis (not wrapped)

Post by Rcnewcomb »

attached a spindle to the cross slide on my CNC lathe so I can mill on the end face
I was trying to understand why a CNC manufacturer would make Y as a polar coordinate, but now that you describe the setup it makes perfect sense.

Please share some photos of the machine, or better yet, a video of the machine in action.
- Randall Newcomb
10 fingers in, 10 fingers out, another good day in the shop

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