[obscurity]

I have finished building the driver boards and the x-axis and hooked it all up to see it go and it was slooooooooow. This is waht I have

L297/298 driver board (from the book CNC robotics)
276 oz.in 4 wire motor 2.8A 1.8 deg/step
Computer Power supply so 12 volts
the x-axis is a larger gas pipe and skate bearing set up
5/16-18 threaded rod for the screw
tested using KCam

When it worked it was very slow. I upped the jog IPM and it got slightly fasted but I couldn't get that number above 15 or so without it just making a loud buzzin sound and not moving at all. I understand that the cutting speed needs to be slow but shouldn't this thing jog reasonably fast.

Speed aside the set up is spotty at best. Sometimes you turn it on and nothing happens sometimes it works fine. I am not sure why because this same driver turned my earlier motor(much smaller) with no problems at all.

Any help would be apreciated,

John W
http://home.comcast.net/~pwprojects

[ViperTX]

I suspect the problem is the 18 threads per inch screw....what is the max. RPM of the stepper?

[joecnc2006]

5/16-18 is what i have on my current machine 60" long, Cut at 30ipm, anything faster it might whip on you, so i would suspect it maybe k-cam, try mach3...

do you 1/2 or 1/4 step? mine is 1/4 so i set it to 14400, 30, 30 in motor tunning.

[obscurity]

I'm not sure but this is the motor

http://web6.automationdirect.com/adc.../STP-MTR-23079

There is a graph in the specs that shows at least 1200 RPM which should be ~66 IPM. That should be more than I had hope at this stage

john w

[obscurity]

5/16-18 is what i have on my current machine 60" long, Cut at 30ipm, anything faster it might whip on you, so i would suspect it maybe k-cam, try mach3...

do you 1/2 or 1/4 step? mine is 1/4 so i set it to 14400, 30, 30 in motor tunning.

I have tried full and half steps but it hasn't made much difference.

[eman5oh]

The 12 volt power supply is the limit to how fast you will be able to drive your steppers and the 18 tpi screw is the limit to how fast you machine will move. Is the driver a chopper style? A chopper style drive with a 34 volt supply would be a good start to speeding things up, then some lower pitch screws.

[pminmo]

I think if you upped your power supply to 40V you would see big improvement. 40V gives you 6V headroom for back emf as the L298 is rated at 46V.

[obscurity]

So it is starting to sound like the power supply is the culprit. Anyone know of a cheap power supply to test this theory with? I really haven't researched power supplies at all since I thought I had that in the bag with computer supplies.

[whateg01]

John,

It is a relief (at your expense) to see that I am not the only person who is fighting this issue. My project (log just started) is progressing slowly, due in part to the same thing. I started out at about 4IPM. Talk about frustrating! I am up to about 16IPM right now with a 12V supply, so I am hoping that when I get around to using a 35V supply and PWM, that will go up immensely.

I also want to say that Phil from PMINMO.com has been a great help so far in getting me this far. (He is probably secretly bashing his head against the wall for having replied to my post for help. ) There have also been others who have helped, and I am also thankful for them, but Phil was the one who kept this project from the dumpster.

Dave

[ger21]

You should try either TurboCNC, or Mach3. Either one is capable of more speed than KCAM, but, like everyone says, you won't get much speed with 5/16-18 and 12V.

[obscurity]

Thanks for the help everyone!

I will definitely try Mach3. The only reason I havn't used til now is that it seems very difficult to get proficient. It took me 20 minutes to figure out where to go to jog the motor while kCam was pretty straight forward. On the other hand Mach3 has a set of features that far more complete.

The only reason I am using a 5/16-18 screw is cost. Long term I hope to move to Acme screw but the machine needs to make something with a resonable degree of proficiency before I go pouring more money into it. This is also what led me to the 12V PS (I already had one)

Another slightly depressing event is that I realized that the motor I got from Automation Direct is 2.8A while the L297/298 driver board is only capable of 2A. I knew my complete ignorance of electronics would bite me in the ass. This would explain why the 298 was getting so hot even with a heatsink So now I have to decide whether I should find a different motor or a different set of drivers (which I had planned to do eventually (maybe the fromorbit.com board) but like I said before not until the machine proved its worth)

John W.

[ger21]

Thanks for the help everyone!

I will definitely try Mach3. The only reason I havn't used til now is that it seems very difficult to get proficient. It took me 20 minutes to figure out where to go to jog the motor while kCam was pretty straight forward. On the other hand Mach3 has a set of features that far more complete.

Jog with the Arrow keys on the keyboard, page up/down for the z-axis. Hold down shift first to jog fast.

The only reason I am using a 5/16-18 screw is cost. Long term I hope to move to Acme screw but the machine needs to make something with a resonable degree of proficiency before I go pouring more money into it. This is also what led me to the 12V PS (I already had one)

1/2-10 for $4.59 http://www.use-enco.com/CGI/INSRIT?P...&PMPXNO=941030

Another slightly depressing event is that I realized that the motor I got from Automation Direct is 2.8A while the L297/298 driver board is only capable of 2A. I knew my complete ignorance of electronics would bite me in the ass. This would explain why the 298 was getting so hot even with a heatsink So now I have to decide whether I should find a different motor or a different set of drivers (which I had planned to do eventually (maybe the fromorbit.com board) but like I said before not until the machine proved its worth)

The drive should have a way to set the current. The drive dictates the current, not the motor. Driving a 2.8a motor with 2a will give you 71% of the rated torque, but shouldn't have any effect on the drive.
I'm not familiar with the drives your using, but don't need different motors. You really need more voltage, though. If you want to purchase a ready to run drive, check out the Xylotex, www.xylotex.com If you want to build your own comparable board, check out the 3977 drives at www.pminmo.com

[obscurity]

Like I said I am electronically ignorant. I guess I always assumed that the motors pulled a certain amount of current and you had to be careful not to exceed the capability of the drive

The only way to change the current on the drive would be to change out components. It is a very basic drive

[pminmo]

obscurity,
Motors have coils, they are inductive. In simple therm there is a charge time consant, all else being the same a higher applied voltage decreases the time constant, thus faster.

[obscurity]

I'm sure this is the wrong forum for this question but in keeping with the theme of electronics and this thread can anyone suggest a good book or web site for the electronically challenged?

Thanks
John W.

[obscurity]

So I need a power supply that is in the 40V range. What does it need for amps 6+A based on the max for the L298 (3 axis X 2A) or 8.4+A based on the motors (3 X 2.8A). I guess what I'm asking is does the power supply match the drivers or the motors?

Thanks again
John W

[pminmo]

Phil from PMINMO.com has been a great help so far in getting me this far. (He is probably secretly bashing his head against the wall for having replied to my post for help. )
Dave

whateg01, glad to be of help. I can't say that I run into to many frustrating people needing help. I've had a couple of communications issues with people that admittedly (their admission) don't speak english well.

[pminmo]

So I need a power supply that is in the 40V range. What does it need for amps 6+A based on the max for the L298 (3 axis X 2A) or 8.4+A based on the motors (3 X 2.8A). I guess what I'm asking is does the power supply match the drivers or the motors?

Thanks again
John W

John,
Depends,
The steppers you refer to work well at 2.5A at 30V. But no stepper works to it's maximum performance at less than the rated current. I've had people driver them with my A3977 board, and people use them with their Xylotex boards. If you want to get the most bang for the buck out of that motor, use a Gecko 201. If that is out of your price range, a PICstep is another good option. You can run a PICstep at 40ish volts.

Geckodrive has an excellent primer on motors and power supplys and getting performance. This will answer some of your questions:
http://www.geckodrive.com/photos/Step_motor_basics.pdf
:banana:

[obscurity]

OK I switched to Mach3 and played around with the motor tuning config and got the motor up to 37 IPM on the 12 V supply according to Mach3 but the moter is not on a machine so I have no good way of verifying that. If that is correct then I am much happier for now. Ultimately faster is better but I can leave that for later once I have 3 functioning axis

Thanks again to everyone for your help
John W