Author Topic: helical gear with cnc  (Read 1330 times)

Offline michelko

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Re: helical gear with cnc
« Reply #15 on: January 22, 2019, 05:07:02 PM »
I am using linuxcnc and it worked right out of the box on the simultanious moves.

Offline kvom

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Re: helical gear with cnc
« Reply #16 on: January 22, 2019, 11:31:30 PM »
For a 45 degree helix the length of cut is the hypotenuse of the triangle or 1/cos(45) * linear length.  The rotation is the wrapped length of the opposite side or (1/sin(45))*L*360/(pi*D).

Feed rate for the linear cut depends on the material and the form of the cutter.  It seems to me that circular gear cutter cuts more like a saw than an endmill for initial calculations.

PathPilot is linuxcnc under the covers.


Offline jadge

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Re: helical gear with cnc
« Reply #17 on: January 23, 2019, 07:47:55 AM »
It seems to me that circular gear cutter cuts more like a saw than an endmill for initial calculations.

Correct. To calculate the spindle speed simply take the OD of the involute cutter and use that to calculate in the same way as for an endmill. It works the same for side & face cutters and slitting saws. Feedrate is simply cutter rpm times number of teeth times the chip load per tooth. Both spindle speed and chip load depend upon the material, but I don't take the cutter form into account.

Andrew

Offline jadge

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Re: helical gear with cnc
« Reply #18 on: January 23, 2019, 07:51:36 AM »
I am using linuxcnc and it worked right out of the box on the simultanious moves.

Did you measure the actual feedrate? I only twigged I wasn't getting the correct feedrate when I cut my first worm in steel rather than plastic. After roughing out with 6mm and 4mm carbide endmills the final cut was with a tapered HSS endmill at a significantly reduced spindle speed and feedrate. I got chatter and poor finish which is what made me look into the motion in more depth.

Andrew

Offline michelko

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Re: helical gear with cnc
« Reply #19 on: January 24, 2019, 08:22:11 PM »
I didn't measure it but linuxcnc shows the programed feedrate in the display.

Michael