I don't have the encoders on my ballscrews right now.  I use 1000 CPR
encoders on my motors.  I am just warning that if you have some backlash
in your system,  having the encoders on the screws can cause serious
dithering problems.  The system has to be tight.  Some used machines can
get a bit sloppy.

Having your encoder on the ballscrew will help you with the 128 count problem
that the Gecko drives have.  The 4:1 reduction you have between the motors
and the encoders will actually cause the system to see the encoders as 250
line units which is more ideal for Gecko's. 

Just the inertia can cause these drives to trip if accelerated too high. 
Once the commanded position is 128 counts out of sync with the encoder
position, the drive will trip.  I can trip my drives by just spinning the motor
too fast. (over 2200 rpm or so).

Dennis,  I looked into the Viper drives and was not really impressed with their
construction.  I would like to hear some feedback from someone who owns one.


Good luck.

  That drive motor looks like the ones I have - 4HP and you need a Focus 5hp dc driver for it. There also is a 90v dc brake that you have to release before turning it on. Grab the spindle and try to turn it, make sure the lock pin isn't in and you'll see. The little rectifier in the original cabnet is used to operate this.

  The alernative is replace the dc motor with a 5hp AC motor with an inverter contol. About $1200 job but will be easier to control and they last a lot longer than the dc job in there now. Also, no brushes to deal with and you eliminate the brake release control and timing problem.

  Has anyone solved the turret indexing operation control and encoder feedback to artsoft control?

  For some pics of my project http://www.janick.com/cnc/

Thanks.
I looked at their site, but it says up to 2HP in all places except one.
In any case, I'm sure there's a lot of DC speed control drives out there, just a matter of finding one that I can drive with PWM and that is within my very limited budget.

The Gecko G320 drives arrived yesterday.  I have to get some encoders and then I'm off to making things move.
I'm still waffling on what resolution encoders to go with.
I'm thinking 1000 CPR.

I found some stepper motors that have the encoders mounted on them, so I pulled them off.
One is a US Digital E2 500 CPR (upper picture), which is perfect.  The bore is even .250", which is the machined shaft size on the Hardinge ballscrews.

The other encoders (bottom picture) I have are anonymous.  I counted, and they look to be about 500 line.
They have 8 wires on them, so I suspect they may be differential, but I don't know for sure.
Anybody recognize  these encoders (bottom/lower picture)?  They came off some small Vexta, NEMA 17, 2 phase stepper motors.

Unfortunately, the bore size on the other/anonymous encoder is only .190", and I don't really want to bore it out, so I think I'll just get a shaft extender of the right size and mount it on the ballscrew shaft and mount the encoder on a riser block.

Might take a couple days to get the time to do this.
Weekends with 18 month old twins and a 3 year old are kinda chaotic :-)

More to come...

I don't have the encoders on my ballscrews right now.  I use 1000 CPR
encoders on my motors.  I am just warning that if you have some backlash
in your system,  having the encoders on the screws can cause serious
dithering problems.  The system has to be tight.  Some used machines can
get a bit sloppy.

Right.  I'm worried about it as well.  We'll see once I get things wired up what happens.

Having your encoder on the ballscrew will help you with the 128 count problem
that the Gecko drives have.  The 4:1 reduction you have between the motors
and the encoders will actually cause the system to see the encoders as 250
line units which is more ideal for Gecko's. 

Hmmm.... I think that your numbers are reversed there.
With a 4:1 reduction, 1 turn of the motor is .25 turns on the ballscrew, or 4 motor turns=1 ballscrew turn.
So, with a 4000 PPR encoder mounted on the ballscrew, every motor turn is 1000 pulses.
Or is that what you mean, that it gives more leeway/slop on the motor?

Hi, This pdf file of the HEDS encoders may help.



Regards

I have a Hardinge CHNC that I would like to replace the GE Mark 550 with the Mach3. Has anyone actually done this and if so, did you keep your documentation?
Any help would be appreciated.

hi i just got a hardinge chnc 1980 model Allen Bradley 7360 cnc control, serial #ncn-367-n/c chucker.
Its in really good condition.
i was offered 1200 for the control, so I'm thinking of switching to a mach 3 w/x15-255 monitor.
does any one know how to use the tack and resolver?
I'm also thinking of going with a D0-06DR for my plc ya or no?
got to go for now any help will be GREATLY APPRECIATED
Brians machine shop

I say take the money for the control!  You can't use tachs or resolvers you will need encoders if you plan on using servos.  As for the PLC ise one of these: http://cubloc.com/product/01_01.php,   very easy to program and cheap.

thanks Dennis,
Ya i think i will take the cash.
On the cubloc what one do you recommend?
and what else will i need to get the cubloc going?
The motors are still good on this machine and i have extras so i would like to use them.
machmotion tells me there is a gizmo i can hook to the tac/resolvers that will translate the signal. butt I'm not sure what it is called.
my biggest problem with this retrofit is that i have an order do next week and that job was suppost to pay for this machine so right now I'm looking for the fastest and cheepest way to get that job out.
It's like retrofit 911 lol.
thanks again
Brian's machineshop