AC or DC Gearmotor?

Look up stepper motors.

If you want to vary it, use a stepper and a controller. You will get precise control, but it costs more.

If you just need it to run at that one speed, us an AC gearhead motor and some pulleys. You can get some speed ratios by stepped pullies or by changing them as needed.

AN AC motor will have a contstant speed as with little load the 60/50 Hz frequency determines the speed. Stepper is also constant speed that you adjust to suit.

If the stepper breaks down, it costs more to fix and fewer can fix it. Simple AC motors are fixable more easily.

Greetings,

Look at putting an indexing window on the conveyor or rollers.

Use an optical sensor along with a small VFD on an AC motor. The AB power flex7 is a good place to start.

The 30 sec timer input would trigger the VFD to advance at a set rate with accel ramp until the optic is tripped by hte indexing windows indicating the conveyor is in position. The vfd would apply a DC brake to stop the motion and standby until the next timer input and start the process all over agian.

Also the Power Flex VFD has a feed back loop that can be tie to the motor with another optic coupler to control the speed even with load changes to the conveyor system.

1000 ways to skin a cat, none wrong and none right, just different.

T.

Depends if you're only after speed control eg - move this fast, or this fast then a gear or pulley system with a clutch to go between the two should be fine - but if you also need accuracy in positioning, then you really can't go past a stepper (and gears if the load requires it).

ALLENAIR, makes Rotary Index Tables that I have used to drive conveyors that need to move x inches per cycle.

They are reasonably priced and last forever.

Go here to see exactly what you need for your application.

http://www.allenair.com/Indextables.htm

IMO, the ac gearmotor is fine with a variable frequency drive as Crossfire suggested. If you are actually indexing, consider how critical the stop location is. At the speed you are moving and the gear ratio you will be at, you may not need a brake.

The one thing to watch is the rpm of the motor. Some motors are cooled via a direct drive fan. Your motor should run at no less than 50% of it's rated r.p.m., preferrably a little higher. If you run it too slow it may overheat.

What if the conveyor has to move at a speed of 1 ft/minute for 20 secs and then accelerate to a speed of 60ft/min. in 1 sec. and then go back to speed of 1 ft/min instantly and keep repeating. We donot need to have any feedback. but speed control and acceleration is very critical. We also need to vary the slow speed(manually) from say 1ft/min to 3 ft/minute depnding upon the parts the conveyor is carrying.

Hook it up to a computer and VFD. Used a tacho generator to gauge the speed and optical switches to apply and other restrictions.

If you are looking for accurate positioning of a part on the conveyer, the optic coupling and position window on the conveyor is the way to go. if you are looking for rate of SPEED or rate of FEED control, an encoder on the drive motor will provide the VFD with the the true speed of the motor. All motors will have some SLIP and will lag a small % of speed based on the amount of load applied. The encoder will let the VFD see the true speed of the output shaft and control from that.

The main concern is we need to run the conveyor at a slow speed of .3 in/sec for 15 secs to 25 secs. We are doing this to stack the parts with one part on the top of another with an offset of 1/8". So one part will fall from the press on to the conveyor, as the conveyor is still moving at the slow speed the next part will fall on the top of another but not exactly on top of it but with the offset. the parts are flat and about 0.030" thin light parts. After 25 parts are stacked like this the conveyor has to accelerate in 1 /2" a second or so to a speed of 6 in/sec to create a gap between stacks and then slow down again right away to repeat the procees again. This way we will have batches of 25 parts and then a gap, 25 parts and then a gap and so on. The 1/8 offset is not critical at all. But there has to be an offset so that the parts donot stack exactly on top of each other but have a spread basically like with the playing cards in a fanned fashion. We are trying to position but to have a spreaded batch and the operator will pick up each batch and put in a box.

Greetings,

Given the info on the process you are running, look at having the press trigger a counter to trigger the advance speed. Advance to optic window and then switch back to the loading speed.

Press makes 25 parts and triggers the ADVANCE SPEED (1/2"/SEC), Optic sensor triggers LOAD SPEED (.3 in/SEC) while press and counter are busy making parts and counting back up to 25.

T.

What kind of motor should be used to accelerate the speed from .3 in/sec speed to 5 in/sec. This change of speed from 0.5 in/s to 5 inch/secs and from 5 to 0.5 inch/sec should occur in .5 secs.

Greetings,

I would look at the Allen Bradley Power Flex 4,40 or Power Flex 7,70 VFD.

Look at the Ratio in the gearbox that drives the conveyor.

The higher the motor speed the better control you will have. 3700 would be nice.

The AB VFD can over speed the out put, greater than 60Hz for the advance speed and less than 60Hz for the load speed. Try to get the speed of the motor above 30Hz during the load cycle of the process.

It looks like you are looking for a turn down of 10:1. That may be a challenge. I believe one of the two AB VFDs will go to 120Hz. That would give you a 4:1 speed turn down.

Shaft speed 1850 Low

Shaft speed 7400 Hi

T.

The main concern is the slow speed of .35 in/sec and acceleration of about 5 in/sec² or even higher actually. You think Allen Bradley power flex will do it for sure?

We donot have the gear box . We are ordering the conveyor with rolls of 1.5" dia on one side and other side roller being 2.5". I am not elecrical engineer so please let me this power flex is just control, right? we still need a motor?

Greetings,

Yes you will still need an AC gearmotor to drive the conveyer.

The circumferance of the small roller at one end of the conveyor should be 4.1723in, the larger roller has a circumference of 7.853in.

For the loading speed the 1.5 in dia roller will need a speed or 7.19 RP/M or .1198 RP/Sec to achieve .5 in/sec.

That could be done at 30Hz or 50% speed based on motor speed given in RPM.

http://www.bisongear.com/specs.asp_Q_catID_E_1_A_subCatID_E_8_A_prodID_E_11_A_skuID_E_212

This gearmotor has a speed rating of 6 - 90 HZ.

At 30 Hz it would be the .5 in/sec you are looking for driving the 1.5 in roller.

What ever motor you end up with, be sure get one that in inverter rated.

T.

The 1.5" dia roll cannot be changed to a bigger dia because of the limited space we have where the conveyor has to go which is under the die. On the other side we have the flexibity though. Can u let me know what formulae are u using?

Greetings,

Dia X Pi = circumference.

To find the REV/Sec needed for the .5 inch/sec,

DIA(1.5) X Pi(3.14159) = 4.7123

This means that the 1.5 roller at 1 REV/Sec would = 4.7123 In/Sec

To achieve .5 in/sec divide .5 by 4.7123 = 0.1061 REV/Sec. X 60 = 6.366 RPM.

To achieve 6.366 RPM at 50% speed or 30Hz, 6.366 X 100 / 50 = 12.732 .

So a gear motor with a rated speed of 12.732RPM @ 60Hz will have a speed of 6.366RPM @ 30Hz.

The same gear motor will have an RPM of 19.059 at 90Hz or 150%.

My previous post was in error. Dyslexia is a pain. I moves a few digits around during the first go around.

After looking at the specs on the Byson Inverter rated motors with a 6- 90 Hz rating, you should be able to calculate the ADVANCE Speed at 90 HZ RPM and use the turn down to get the .5 in/sec or 6.336 RPM.

T.

The drive is going to be on 2.5 in roller though