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Thanks Ray, I'll have to check this out this weekend. The macro I posted did need a few tweaks.
Brett
Yes, belt pitch makes a big difference. As I said, I used XL, which is 5-pitch. Again, with a stepper, you'll be hard-pressed to get better than *maybe* 25 IPM. A large stepper is NOT going to go fast (maybe 1000RPM at the very best), and torque falls off rapidly with speed, so you'll likely become torque-limited long before you reach that max speed. With a 3:1 reduction, 750 RPM would give you 25IPM. If you have to go to 2:1, you'll likely be looking at 15-20 IPM max.
Regards,
Ray L.
Its not a pretty picture, that I agree. I see you used a pair of 200lb gas springs which seems to be common. I was looking at them tonight at McMaster and see they also make them 225lb and 250lb fairly cheap. Do the 200lb ones fully counterbalance the knee? What do you think of using stronger ones? Who knows what a 42 inch BP table, saddle and knee weigh other than a guess?
Is it Possible to make the G91 temporary (for just the one move)?
SS
I seen your posts and that sounds like great performance. Unfortunately, you are using servos and mine is a stepper system. I am not sure how servo vs stepper rated torque would correspond. Servos like more rpm's so that would explain your 4.8:1 drive ratio. Right now, I am leaning towards 1810ozin stepper and a 3:1 belt drive. I'd like 4:1 but using a online calculator the smaller pulley would not have enough teeth engaged at any reasonable center distance. I could use idler pulleys to increase the belt wrap on the small pulley but I want to keep it simple so 3:1 at about 12-14 inches center distance between the pulleys is about as good as I can get. Its looking like air springs are going to be necessary to get any reasonable speed.
As I mentioned, the knee is only going to move during tool offsets at tool change time so speed isn't terribly important.
However.... going from a 1" long endmill to something like a 6" long drill and chuck would mean a 5" move which at 15ipm would take 20 seconds....... pretty slow and that would no doubt get aggrivating fast! 30-40ipm would be quite satisfactory.
Yes, I used a leadscrew. I replaced it with a new higher precision one but stuck with the screw so I wouldn't have to use a brake to keep the knee from drifting. I did add oilers to the gears and nut but it still works on it pretty good. I'm using 1850 oz in steppers and the final gearing is 6-1. I added gas springs and that helped my rapids some but 30 IPM is about all I can get out of it with this set up.
Brett
I am in the process of considering what stepper size, belt drive ratio etc. Can you elaborate on your setup and how the 6:1 final ratio is reached? I am thinking of the stock screws with a 1810inoz stepper and 3:1 belt drive. Speed isn't terribly important as it will only be active during tool changes but more is better of course.
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