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Old 06-28-2017, 09:34 AM
cekonecky cekonecky is offline
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Join Date: Sep 2016
Location: Brooklyn, NY
Posts: 3
Default Rotary Feedrates

I'm getting into using the rotary axis on my cobra and have some questions. I have been writing a code to cut tapered spindles for a stool. I've been testing my codes without any stock to see if they're looking right, and I've almost got it, but I'm having issues with feedrates. I'm not sure what controls the feedrate of my Y and A axes. My most recent code ran almost perfectly, except for my A was spinning too slowly relative to my Y - would've ended up with a spiral flute rather than a smooth spindle. To adjust this I upped the number of rotations of the A axis in each move relative to the Y movements. When running the second code my A was spinning fast enough it seemed, but my Y had slowed down to about .001" every 2 seconds. Do you know why my Y would have slowed down even though I didn't alter it at all? Any other useful tips regarding feedrates for A and Y when doing this type of work? Attached are my two most recent codes, the first link being the code where Y was fine but A too slow, and the second link is the code where I attempted to speed up A but in turn also slowed Y way down.
Thanks so much,
Christopher Konecky
Attached Files
File Type: tap Rotary Test Parent File (YZ).tap (4.0 KB, 13 views)
File Type: tap ROTARY TEST 1.tap (4.1 KB, 8 views)
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Old 06-28-2017, 10:16 AM
de5 de5 is offline
Cobra Owner
Join Date: Jan 2011
Location: Honea Path, SC
Posts: 917

When I did rotary work, my feed rates looked like this:

N18 F200 XY
N19 F150 Z
N20 F 10000 A

I'm no expert on rotary, but this seemed to work well.

Charlie Hind
Cobra 404 ATC with 12 tool positions & 4th Axis (2012-present)
(2006-2012 - K2 CNC... sold in 2012 to buy the Cobra)
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Old 06-28-2017, 12:00 PM
eph210 eph210 is offline
Camaster Owner
Join Date: Feb 2013
Location: southern Alberta
Posts: 169

Each G code instruction gives the destination point for all of the axes (A,Y,Z). All three axes have to arrive at the destination point simultaneously. When you increase one axis distance the other two axes must slow down to still arrive simultaneously. Increasing the A axis movement from 90 to 1350 degrees will slow down the other two axes by the same ratio.
By the way, WinCNC from the factory is limited to 99,999 degrees of rotation.
Euan Hanchard
Serrano Studios
Stinger I FTC
Wincnc vcarvepro
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Old 06-29-2017, 08:49 AM
Mick Martin's Avatar
Mick Martin Mick Martin is offline
CAMaster Cobra Owner (MOD, KOTR)
Join Date: Nov 2009
Location: Snohomish, WA
Posts: 3,413

"XYZ" axis are measured in inches the "A" axis is measured in degrees.
N18 F200 XY
N19 F150 Z
N20 F 10000 A
I was just reading your tap files and you have a lot of lines you should be able to greatly reduce that to a few lines of G-Code

Start Position/Start Diameter -> Finish position/finish Diameter = this will give you a taper.
Mick Martin
CAMaster Cobra 508 ATC + Recoil + Popup Pins
Digitize Touch Probe
Wincnc Handheld Serial Keypad + Wireless Pendant
Hurricane vacuum
WinCNC + Aspire 9.5 + PhotoVCarve + EnRoute 5

The search function on the forum is your best friend!

Last edited by Mick Martin; 06-29-2017 at 08:57 AM.
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