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FRAX mode with vector & non-vector axes


Raghav
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Dear All,

I'm working on a three axes system with two vector feedrate linear axes (X&Z) and one rotary C axis. I would like to know how to set the three axes to move synchronised based on a given feedrate?

Currently if running C-axis alone, provides a max feedrate of 1 motor unit/ min. Can anyone suggest the best practice to assign and synchronize axes motion?

Thank you.

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Not 100% sure of your application, but I guess you’re machining or engraving on the surface of a cylinder???

 The cylinder has a circumference, so you could scale the rotating axis units to match the circumference.

 For arguments say your linear axes have 1000 counts per unit (mm for arguments sake) and your cylinder is 100 mm diameter, then it’s circumference is 100 x Pi = 314.159mm

 If your motor moves it 1 rotation in 100000 counts then you would scale the C axis as 100000/314.159 = 318.31 counts per mm at that diameter

 So

#1->1000X #2->1000Z #3->318.31C

Then you can use FRAX(C,X,Z) and any motion program move will be able to use F1000 etc. to specify the feed rate in any combination of those axes.

 It gets a lot more tricky if you are dynamically moving at varying distances from the center of your C axis.

 

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Hi David,

Thank you for the advice. FRAX(C,X,Z) works fine. Now I'm facing issue with the C feedrate. I would like to provide a Ffeedrate F72000 corresponding to 200 RPM, but the C feedrate is struck at 54000... Seems the problem is due to some settings with Segmove or lookahead. Any advice on the same?

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On 6/19/2022 at 6:48 AM, Raghav said:

Hi David,

Thank you for the advice. FRAX(C,X,Z) works fine. Now I'm facing issue with the C feedrate. I would like to provide a Ffeedrate F72000 corresponding to 200 RPM, but the C feedrate is struck at 54000... Seems the problem is due to some settings with Segmove or lookahead. Any advice on the same?

With frax on it will use the X and Z moves to calculate the feedrate for the C-Axis as well. So if X/Z were not moving you would get 200 RPM.

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How do you want the speed of the rotary axis (C) decided?
Should it be running at a constant speed?
Should it slow down to maintain a constant overall speed when X and Z speed up?

How do you want the speed of X and Z to decided?
Should they follow along to draw on a rotating cylinder?
Should they maintain a fixed combined feedrate (ignoring C)?

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