Messages

341

General Mach Discussion / robot input with encoders

« on: June 06, 2006, 06:03:28 PM »

I might be getting ahead of myself, but bear with me for a while.
Imagine you build a 3, 4, 5 or 6 axis robot (abb and fanuc like) i know the difficulty here lies in telling the robot what to do (generate the toolpath). Ok now imagine making another robot, with the same dimensions (or scaled down) and instead of fitting the robot with servos, you just put the encoders. Now here is what I am getting at:
Is it possible to move the motorless version of the robot and have the motored robot make the same moves? Better yet, can those moves on the motorless robot be recorded, and then played back by the motored robot?

Come fly with me!
Regards
Fernando

342

General Mach Discussion / Re: Acceleration calculations

« on: June 02, 2006, 12:42:31 PM »

ok, now I get it... makes more sense now.
Thanks
Fernando

343

General Mach Discussion / Re: Acceleration calculations

« on: June 02, 2006, 12:18:05 PM »

I didnt understand your suggestion of the spring at first, but now that I think of it, I beleive this is what you meant, and it makes sense.
Thanks, yet again

344

General Mach Discussion / Re: Acceleration calculations

« on: June 02, 2006, 11:52:34 AM »

Thanks Brian,
I had thought of putting a torsional, (rotational??) spring on the shaft of the not driven sprocket. Let see how it all goes.
In your expert opinion what would be better in terms of wear and tear, and design considerations?
A shuttle traveling at:
10,000 ipm and 300 in/s2 or
2,500 ipm and 800 in/s2?
Thanks again
Fernando

345

General Mach Discussion / Re: Acceleration calculations

« on: June 02, 2006, 11:20:54 AM »

I am thinking that the slack of the chain (its a long chain, about 4m between sprocket centers) will make the shuttle move even when the servo is stopped, specially with those accelerations and impacts, any suggestions?
I was thinking maybe to use two servos, one on each side of the chain drive as to keep the top side of the chain as taut as possible.
Ill try it out anyways.
Regards
Fernando

346

Post Processors / Re: ArtCam

« on: June 01, 2006, 11:55:50 AM »

I think Art cam comes with a mach 2 post processor, if it doesnt use the "G code (inch)" or "G code (mm)" thats how I remember them to appear on the list.
Not sure though, i dont have artcam.
Regards
Fernando

347

General Mach Discussion / Re: Acceleration calculations

« on: May 30, 2006, 08:28:46 PM »

correction... scary machine.
I kind of need the most acceleration possible, on the small moves it is going to make speed doesnt make much of a difference as acceleration would.
If the machine just tries to run off with the moves, or destroy itself, i will just have to lower the acceleration. But the goal is to lower the cylcle time as much as possible. trying to keep that gcode i posted under 20 seconds. If I can make it 15 or 10 seconds... WOWW!!!
Tell you how it comes out
Fernando

348

General Mach Discussion / Re: Acceleration calculations

« on: May 30, 2006, 03:18:07 PM »

ok, why set it to 500? when the continuous torque can get to 800? the max torque is far more than the 14Nm.
Are the calculations I made correct?
what acceleration do you have on the automation direct 1kw servos you have?
Another question off topic about your servos, is it possible to lower the encoder count on the driver electronically? If resolution is not an issue in this application, instead of having a 2500 ppr encoder that wouuld translate to 10,000 steps per recvolution, can the driver be programed to lower that count?
Regards and thanks for your comment
Fernando

349

General Mach Discussion / Acceleration calculations

« on: May 30, 2006, 12:18:19 PM »

Hello,
I dont know if it is pertinent to ask this on this forum, but here we go.
I am building an OEM machine which has a shuttle that weights 220lb. I want to size the servo to be used to move that shuttle as fast as possible and with as much acceleration as possible. This is to reduce cycle time as much as possible. The shuttle would make moves like the one at the end of the post (in INCREMENTAL MODE).

I am trying to come up with the max acceleration that a servo would be able to get me.
If I use a 3Kw ac servo, which has a constant torque of about 14Nm going trough a 4:1 reduction and a 2"sprocket (chain drive) gives about 2240N of force on that shuttle. Now If I want to find out the max acceleration I could get I would use F=ma, so 2240N=100Kg*a[m/s2] which solving for "a" gives a=22.4[m/s2] which converting to in/sec2 gives out 881 in/s2. Is that what I should use when tuning my servo? and should I expect that to be the acceleration i should get?

Hope I made sense.
thanks
Fernando

(shuttle movement test in incremental and inches)
G61
G91
F1500
G01 X10
G01 X1
G4 P.1
G01 X1
G4 P.1
G01 X3
G4 P.1
G01 X1
G4 P.1
G01 X1
G4 P.1
G01 X3
G4 P.1
G01 X1
G4 P.1
G01 X1
G4 P.1
G01 X3
G4 P.1
G01 X1
G4 P.1
G01 X1
G4 P.1
G01 X3
G4 P.1
G01 X1
G4 P.1
G01 X1
G4 P.1
G01 X3
G4 P.1
G01 X1
G4 P.1
G01 X1
G4 P.1
G01 X3
G4 P.1
G01 X1
G4 P.1
G01 X1
G4 P.1
G01 X3
G4 P.1
G01 X1
G4 P.1
G01 X1
G4 P.1
G01 X3
G4 P.1
G00 X-50

350

General Mach Discussion / Re: Motor tuning question

« on: May 27, 2006, 02:42:48 PM »

I think running your steppers at 500rpm, with 12 or 24 volts, might be pushing it a little, I could be wrong.
Most laptop paralel ports output 3 volts, instead of the usually needed 5 volts, try your desktop, unless you have a breakout board that takes care of that voltage difference.
You dont have to restart Mach everytime you tune the motors, but you do need to save the axis settings with each modification for it to work.
You could try out Sids suggestion, steppers have the most torque at low speeds, so if you add a 1:2 pulley system (1 turn of the motor=2 of the leadscrew, not the other way around) it just might have enough torque to run your cuts without loosing steps, and increase the speed in the process. You could check the torque speed curve of your steppers to see what would happen to the available torque and speed with the 3 scenarios (1:1, 2:1, 1:2 ratios).

Dont give up, have patience.
Regards
Fernando