Geckodrives aren't rated high enough...

[Jasonixo]

I need to drive the 112V 65A SEM Servos on my V2XT. I was looking at the Gecko G320X but it isn't rated high enough to run the servos at full rpm and torque. I am not familiar with any good alternative brands. I am planning on using a Smoothstepper USB M.C.I. in my retrofit. Any thoughts or experience with a setup like this? I am planning on replacing the encoders too.

Thanks!

Jason

[judleroy]

Viper Servo Motor control maybe?
Judleroy

[cholder]

I used Viper 250's on a Bridgeport R2E4 retrofit. They worked very well.

[Steven Martin]

We're looking at the Viper 200 for our R2E4 retrofit. Out of curiosity, what influenced you to select the 250? Also curious what control hardware/software you used.

Thanks,
Steve

[cholder]

I'm mistaken. They are 200's. At the time that was the only unit they had. I used a Bob Campbell breakout board and a MODIO board. I was going to use a smoothstepper as well, but they were out of stock when I started the project. I removed the manual backgear shifter and added a pneumatic unit and I also installed a VFD. When I was finished, the machine could run on single phase or three phase power. I also left the variable speed pulleys in place. I ran the feedrate override pot to the MODIO board. I also ran the variable speed pot and the VFD analog out to the MODIO board so I could do a rough spindle speed display. It also has a MPG running to the MODIO board. I removed the original CRT and closed the hole with enough structure to support a 15" LCD touchscreen.
The PC in the picture is a Dell GX260 running Mach3. The MODIO board was mounted in the enclosure behind the monitor.

I used Mouser Electronics 651-1688379 to connect the encoders. I kept the existing servo wiring in place. Some of the original encoder wires are quite large and that connector made it easy.

[Steven Martin]

Thanks for all the detailed info!

The R2E4 in question belongs to the FIRST Robotics team I help Mentor. We were looking to replace the old Boss 9 control (it died) with the Viper 200's and a MicroKinetics motion control and MillMaster software.

Anyone looking for some Boss 9 boards? Got three good servo drivers and most other boards. Timing chip in the main CPU card seems to be the problem. Other diagnostics pass.
Steve

[Jasonixo]

The Viper 200 lists 170V, 42A Peak/20A Cont. The SEM Servos on my BP V2XT indicate 112V, Pulse Amps 65A. Does this indicate a torque problem?

Cholder- your retrofit is very interesting to me- I have a solenoid-controlled pneumatic vari-speed and spindle brake to either incorporate or replace with a VFD. It looks like you have a nice setup and one worthy of emulating. The Viper 200s look the most promising out of the drives I have come across.

As far as controller boards, I'm told the Smoothstepper will only run the servos like steppers, not with continuous DC that makes servos what they are. I'd love to use a USB Board but it looks like I need to scrounge up a computer with a parallel port. Any recommendations on a continuous DC servo breakout board?

Next can of worms- auxiliary functions. I need operate coolant, vari-speed, and spindle brake. If I can run the factory spindle systems now and install a VFD later without rebuilding the control, I'll be a happy button-pusher!

Thanks-

Jason

[cholder]

Jason,

I have not seen any torque issues. I don't think the original Bridgeport drives output 65 amps, that is just the motor rating.

You are correct in that the original servos were analog controlled, but the equipment sending the analog signal was taking in the encoder steps and deciding how to change the analog command, also in discrete steps. Using the Viper drives you have just placed the responsibily for deciding what the analog command should be on the drive and not in the PC. If I remember correctly the original Bridgport stepper systems at their best were 0.0005" per half step. The servos are 0.0001 per encoder step if you use the original encoders. The tuning of the drive is what ulimately makes the servo behave as it should. What I'm trying to say is that there is really nothing to be gained by trying to stay with an analog command system.

I have not used a smooth stepper board but it should work well with the Vipers. If you use the smooth stepper you do not need a parallel port, it is USB so it can be used with a laptop if desired. As far as I know the parallel port is only step and direction as well.

If you want true analog command you will need to go to a higher end motion control board and find software to support it.

The only real difference from the original equipment has to do with homing. The original equipment homed from the limit switch and the zero marker pulse from the encoder. I have not worked that out yet so my homing is limited to the repeatability of the switch. Which is OK for softlimits but not for a repeatable work offset at power up.

On a side note for you and Steve, Rutex offers a R2040 unit which would allow you to use the original Bridgeport drives. You would need to leave the tach signal going to the drive intact and run the encoder to this board. They generate +/-10V to command the drives. I don't want to take a sale from Viper, they are great drives, but it is another option. It was not available when I did this rework.

I left the variable speed pulley arrangment and added the VFD. I can now overspeed the spindle for small bits.

I used more hardwired control than I needed to on this machine but I had the switches and relays and would have had to add a PLC or another MODIO board otherwise. I have a reasonable schematic of this sytem if you are interested (No Warranty Implied or Expressed) send me your email.

[Jasonixo]

I looked through Mach3's plugins and I came across the DSPMC.

8-Axis Ethernet Motion Controller, Mach3 CNC Controller, .Net C# CSharp Library

If I went this route, does this determine the type of servo drive I use? Are there analog servo drives to go with analog controllers?

The more I research, the more I realize I know little about CNC systems!

Another I've come across- thoughts?

http://www.adlinktech.com/PD/web/PD_detail.php?pid=684

[cholder]

Jason,

Almost all servo drives can accept an analog command signal. If you use Mach3 the least expensive option is the parallel port with a step and direction servo. Most modern digital servos will also accept step and direction as well as analog but not all will accept both so you need to determine which drive you are going to use. If you are using the original Bridgeport DC servos (I'm familar with Boss 8 or 9) and the drives are in good shape you could use the Rutex 2040 to provide the analog command to the Bridgeport drives. This would work out to around $420 for 3 axis. If you use the Viper 200s it works out to around $660. You could change the encoders to get more pulses per revolution but I'm not sure you would see alot of difference in performance but it does step up the computer needed to drive it. You would most likely need to step up base frequency in the Mach3 in order to generate the faster pulse train which would require a fairly fast machine. The Ethernet Servo package you mentioned could provide the analog command for the Bridgeport Drives as well and it has a lot of I/O. I kept things fairly simple using the hardwired controls for spindle, coolant and backgear so I did not need alot of I/O. It gets simpler if you don't have the pneumatic backgear selector. The board you list will also provide analog command signals.

Cliff

[Jasonixo]

Thanks Cliff-

So which component in the system determines the drive format (step/dir or analog)? The motion controller the servo drives, or both? Is one component more apt to handle either? For example, if I chose the DSPMC and the original drives, will that provide the original servos with a smooth analog feed and a mach3 capable system??

Regarding encoders, a higher resolution encoder equates to greater accuracy, correct? I'd rather achieve a high level of accuracy (for the machine) than high metal removal rates or movement speed.

Initially I looked at the packaged kits like Ajax and Mach Motion, then decided to look into scratch-building a retrofit. Now I'm concerned this is over my head and the extra money for the kit is warranted. Still, throwing someone else's IQ into my machine is against my nature and I want to learn more about these systems. I don't have the luxury of time to piddle endlessly with this thing. Cut chips need to arrive really need to arrive within the next month or so. Is it feasible to cobble this together and get running while learning the ropes?

Thanks-

Jason

[Al_The_Man]

Have you looked at Kflop and Kanalog? these are PC/USB connected and together with the Dynamotion Kanalog board you have a fairly high I/O count PLC as well as ±10vdc analog ouputs.
The unit runs with the built in software also a Mach plug in is available.
BTW, it will run non-intelligent drives as the PID loop is tuned in the Dynamotion boards.
Al.