Setting up a 4th axis travel

[Scott Pancheau]

I am having difficulty adding a 4th axis. The only way I could find to get the correct distance and speed range I liked was to enter the steps per rev real low and then find the ratio to get the proper distance. I then read that you are not to do this. I then set the steps to 1600 per the setting on the drive. My real ratio for pulley is about 2.5 to 1, but had to set this to a tiny amount to get accurate travel and the use gigantic feed rate to get reasonable speed. With either of the setting shown in attachments I can get 3600 degrees of rotation and come back to 0 start. My normal range of cutting speeds on my XYZ are betwwen 10 to 50. If I tried to run this speed with the second set of parameters the A axis would barely move. What am I missing?

[tblough]

https://centroidcncforum.com/viewtopic. ... eed#p51189

[Scott Pancheau]

Thanks for the reference to other users with the same problem. Sounds like I just ignore the admonition to only use the steps per that your drive is set to and figure out what may work for your particular rotary set up. I did not see where anyone from Centroid offered any help or advise on the place you referenced. I looked for a U Tube from Centroid Keith and all I found is the one about how to set up a on-off button for a 4th. Now that I know it is a degree reference rather than distance, perhaps my speed concern will not be significant.
Thanks,
Scott

[tblough]

No, you read that wrong. You use the correct steps per rev. You just have to realize they rotate axis feed rates are in degrees per time and not inches or mm per time.

Steps per rev should be set the same in CNC12 and the motor driver. For a rotary axis turns per rev is determined by the worm gear ratio of your rotary. These are not arbitrary numbers.

[Scott Pancheau]

Still does not make sense to me. My rotary does not have a worm drive. It is direct belt driven with about a 2.5 to 1 ratio. If you see what I have entered in the ratio on my first post it is a tiny fraction to make a 360 turn to match the commanded 360.

Thanks again
Scoott

[Gary Campbell]

2.5 to 1 is seldom enough reduction to return good results. That said, you need to know exactly what the reduction ratio is. Divide that number by 360 and you will have your turns per degree.

For example for 2.5 to 1 reduction: 2.5/360 = 0.006944

[Scott Pancheau]

Thank you for your input. Can you tell I took a remedial math class in high school? I get it now. I am just wanting to use this for gearotic as a hobby. I will see how it goes and if I need to go to a worm drive I will. I tried a 4th axis gear cutting air and it took forever because the rotary is so slow, I cant' imagine how slow it would be with much more serious reduction.

Thanks,
Scott

[cnckeith]

its running slow since you have max rate set to 4000 degrees per minute for the rotary axis

[Scott Pancheau]

Ok, Thank you Keith. I cannot seem to get through my head how high you have to set when talking degrees. I will give it another try. You people are really patient.

[Gary Campbell]

This may help a bit...
1 rev per minute = 360°/min
1 rev per second (60 rpm) = 21,600°/min

Depending on your hardware neither one of the above are considered very fast. I routinely set my max rate at 144,000°/min for low reduction wood cutting, with fast jog at 7200 and slow jog at 720