[tkms002]

ok Ger,
What about preload on the bearing blocks? What is recommended?

[ger21]

Light preload should be fine for what you are doing.

[tkms002]

ok one more question. Will a pair of 570 in/oz nema23 steppers move that 150 lb gantry at a reasonable speed? Again, not looking for anything quick but I think at least 200 in/min cutting?

[ger21]

What are you using to drive the gantry? Rack and pinion? What components?

What stepper drives do you plan on using?

[tkms002]

I am going to try a Bell-Everman belt drive using T5 belts and a 3-1 reduction.
KLL-5056E drives and a 48V PS all from Kelling.

[ger21]

On a machine of the size you are doing, I'd be looking for rapid speeds of at least 400-500ipm. If you can do that, cutting at 200ipm won't be an issue.

Those 570oz motors don't have a lot of torque over ~600 rpm. So you need to do the math with the pulley size you'll be using, and calculate how much force you'll have available at the max speed you'll be looking for. I think all of that math info is in the big Servobelt thread.

Speed alone is pretty easy to attain with any size motors. Acceleration is what you really need to account for, and the acceleration rate will tell you how much torque you need.

I was originally going to use those for a similar size machine with a servobelt system, so they should work.
I'd spend an extra $100 and go with the 8060E drives, and run the motors at 60V. Should give you about 20% more speed.

I've been testing the 570oz motors with AM882 drives and 60V and they work fine. (I'm using them for my Z axis)

I'm assuming you are talking about the 5amp version of the 570oz motors. I think there are 3.5 amp versions, and I would not use those.

[tkms002]

On a machine of the size you are doing, I'd be looking for rapid speeds of at least 400-500ipm. If you can do that, cutting at 200ipm won't be an issue.

Those 570oz motors don't have a lot of torque over ~600 rpm. So you need to do the math with the pulley size you'll be using, and calculate how much force you'll have available at the max speed you'll be looking for. I think all of that math info is in the big Servobelt thread.

Speed alone is pretty easy to attain with any size motors. Acceleration is what you really need to account for, and the acceleration rate will tell you how much torque you need.

I was originally going to use those for a similar size machine with a servobelt system, so they should work.
I'd spend an extra $100 and go with the 8060E drives, and run the motors at 60V. Should give you about 20% more speed.

I've been testing the 570oz motors with AM882 drives and 60V and they work fine. (I'm using them for my Z axis)

I'm assuming you are talking about the 5amp version of the 570oz motors. I think there are 3.5 amp versions, and I would not use those.

Yes, the 5 amp version. I have already bought the drives and the PS. I may build the lighter version just to prove I can make it work. If it does not do what I want then I will go back and do it "right" if I see I can make some money at it.
Thank you so very much for all your input.

Please feel free to add any info you feel I may need to this thread.

[tkms002]

I want to wish you all a very merry Christmas. You have all been most helpful as always on "the zone".

[tkms002]

ger21 I am not sure how to go about doing all the calculations to determine if these motors will move a 150lb gantry at a reasonable speed. If you think it will I may decide to go with the heavier beam and profile rails. Will that 6x4 beam do what I need or is that undersized as well? I am looking for woodworking accuracy, not metal working accuracy. I want inlays to fit woodworking good, if you know what I mean.
If I need more speed in the future I wold add an additional PS and those other drivers you mentioned.
Thanks

[ger21]

I just looked at the torque curve for those motors.
https://www.automationtechnologiesin...100-50-4BT.pdf

At 400 rpm, those motors have about 350oz of torque, but at 500 rpm, it falls to about 150oz of torque. At 600RPM, it's under 100 oz.

Say you use a 15 tooth T5 pulley, which has a pitch diameter of about 24mm. Call it 1 inch to simplify things. This gives you about 3" of travel per revolution. With 3:1 reduction, you get 1" per revolution of the stepper. So RPM roughly equals ipm. 100RPM = 100IPM.

If you stay under 400IPM, you have 350oz x 3 = 1050oz, or 65 lbs. You double that with the 1" pulley, and you get 130lbs of force from each motor. This is more than enough to move very quickly.

SO, if you stay under 400ipm, you should have plenty of power. If you need 500-600 ipm, you'd probably need to reduce your acceleration a lot.

I don't think there would be enough benefit to justify the cost of upgrading the drives and PS.

[tkms002]

I just looked at the torque curve for those motors.
https://www.automationtechnologiesin...100-50-4BT.pdf

At 400 rpm, those motors have about 350oz of torque, but at 500 rpm, it falls to about 150oz of torque. At 600RPM, it's under 100 oz.

Say you use a 15 tooth T5 pulley, which has a pitch diameter of about 24mm. Call it 1 inch to simplify things. This gives you about 3" of travel per revolution. With 3:1 reduction, you get 1" per revolution of the stepper. So RPM roughly equals ipm. 100RPM = 100IPM.

If you stay under 400IPM, you have 350oz x 3 = 1050oz, or 65 lbs. You double that with the 1" pulley, and you get 130lbs of force from each motor. This is more than enough to move very quickly.

SO, if you stay under 400ipm, you should have plenty of power. If you need 500-600 ipm, you'd probably need to reduce your acceleration a lot.

I don't think there would be enough benefit to justify the cost of upgrading the drives and PS.

I have a 16 tooth motor pulley driving a 48 tooth reduction pulley and that drives through a shaft a 16 tooth drive pulley. I understand all your math up until "You double that with the 1" pulley, and you get 130lbs of force from each motor.". Where does the double that with a 1" pulley come from? Are you saying double it because of 2 motors?
If I understand you correctly I have to stay under 400 ipm to get much torque. But that gets me from one end of an 8 foot table to the other in something like 14 seconds. Is that a reasonable speed?
Thanks again.

[ger21]

Torque is measured in oz-inches, so 300 oz-in of torque is 300oz of force, 1" from the center of the shaft. The belt on a 1" pulley is 1/2" from the center of the shaft, so you divide 300/0.5, which doubles the force. With a 4" pulley, you'd divide by 2, and have half the force.

that gets me from one end of an 8 foot table to the other in something like 14 seconds. Is that a reasonable speed?

I have no idea what you'd find acceptable. At work, I use a machine that moves 12ft in about 3-4 seconds. So 14 would be an eternity.

[wizard]

I have a 16 tooth motor pulley driving a 48 tooth reduction pulley and that drives through a shaft a 16 tooth drive pulley. I understand all your math up until "You double that with the 1" pulley, and you get 130lbs of force from each motor.". Where does the double that with a 1" pulley come from? Are you saying double it because of 2 motors?
If I understand you correctly I have to stay under 400 ipm to get much torque. But that gets me from one end of an 8 foot table to the other in something like 14 seconds. Is that a reasonable speed?
Thanks again.

Reasonable speed is up to you.

At work we have extractors that pull parts from mold machines literally in the blink of an eye. They make use of linear motors and have a tendency to ruin a set of linear bearings once a year. I do mean ruin as the linear bearing end up so torn up they aren't even worth taking home as scrap!!! (i throw out more linear bearing rails per year than I carte to admit to -sobs-)

So speed is really subjective, given enough money you could move that gantry at some really incredible speeds. Now here is a little gotcha, the ability of your CAM software to optimize moves minimizing the need to use high traverse rates is an important aspect of the impact of slow rapids. Or to put it another way the more rapid moves, that are unjustified, the greater the impact of slow rapids. The type of work you are doing is also a factor as is your ability to manually adjust G-Code if the CAM software really fumbles.

I feel I'm not relaying this idea well but if your cutter is in contact and doing work a good portion of a run, slow rapids don't really matter. On the other hand if you have G-Code that takes the tool out of contact constantly and jumps around the work piece, then slow rapids can have a huge impact on run times.

Beyond all of that we can hope that your cam software does not generate many full length rapids. Generally that seldom happens so your actual rapids will generally be covering less than 8 feet. Beyond that a return to home after the end of run generally isn't a big factor either as that is also a time to cleanup, get ready to remove the work piece and what ever else needs to happen. 14 seconds might sound like a long time but sweeping or vacuuming the work piece can easily cover that time.

Perhaps the most important thing here is to realize that you now have a robot working for you. A robot that works dirt cheap really. A slow rapid might look sad to you but frankly you should NOT be looking at the robot, instead you can leverage that time to do something else.