Need Help with old Controller Change

[Todd Zuercher]

Hi.

I just picked up a Gerber 408. I saw the colossal controller box and only being familiar with small stepper machines and mach3; I am unsure on how to proceed. It did not come with the software. I contacted Gerber to see what I need to do to get the software, but no response thus far. I will try again.

Will converting the machine to steppers have any negative effect on accuracy/speed?
Why convert to stepper rather than a servo controller like G320X DC Servo Motor Controller?

Since I have always looked at the more budget attainable machines with steppers and mach3, I am just at a loss as to what would be the wise direction to go.

Thank you for your advice.

-Mike

Personally I am not a fan of Mach3. If I were to retrofit one of our Gerber Sabres I'd use Linuxcnc and keep the old servos and drives. We just updated to the latest Gerber software, and it seems to be significantly better than the ancient Windows 95 era version we had been using. But it is still way too expensive for it's capability. We only went through with the upgrade because, it was next to impossible to get our old software to run on a new pc, and we have a huge library of old machine files we did not want to loose. That said these routers are treated like an unloved stepchild by Gerber and their support is abysmal, and almost non existent. I have already converted one of our old Greber routers to Linuxcnc (A Dimension-200) I have that one set up so I can run it with both Linuxcnc and the old Gerber software. That would not be possible with the Sabers though. Those would have to be a one way conversion, because too much would have to be changed.

I think there are a few other router software solutions that can run these Gerber routers. One that I know works is Enroute, by SAI (I use it too). But it is almost as expensive as Gerbers Omega software. But Enroute is much more capable for running CNC routers. ArtCAM might be another option. It can also be possible to send generic G-code to the Sabres, but it this feature is purposely crippled by Gerber and doesn't work as well as it could/should.

The biggest barrier to converting one of the Sabres to Mach3 would be the analog servo amps. (Linuxcnc can use/run these though.) You would need to at least replace these with digital servo drives that can accept step/dir signals. That or replace all of the servos with step motors and stepper drives. A third retro fit option would be WinCNC (that would cost you about $5000.)

Another Achilles heal for the Sabres is their lead screw drive system on the axis. The nuts wear out surprisingly fast (especially the Y-axis on 408s.) And when they start to go bad they will start to bind up and cause the control to set servo alarms. I bet 75% of Sabres that get converted because of servo alarms simply needed the lead screws replaced. We used to have to change the Y screw on our 408 about every 2 years. Then I converted it to a Hiwin ball screw about 7 years ago. That screw cost about half as much as the lead screws from Gerber, and the Y-axis has been trouble free since.

[fdarling]

Another Achilles heal for the Sabres is their lead screw drive system on the axis. The nuts wear out surprisingly fast (especially the Y-axis on 408s.) And when they start to go bad they will start to bind up and cause the control to set servo alarms. I bet 75% of Sabres that get converted because of servo alarms simply needed the lead screws replaced. We used to have to change the Y screw on our 408 about every 2 years. Then I converted it to a Hiwin ball screw about 7 years ago. That screw cost about half as much as the lead screws from Gerber, and the Y-axis has been trouble free since.

I agree that the main problem with these machines are the leadscrews, and secondly the reliability of the home/limit switches. I am interested in learning more about this Hiwin ballscrew upgrade... Do you have any details on the part numbers, and any machining you needed to have them do?

I have retrofit two Gerber Sabre 408's with LinuxCNC, and I used the original servos/drives. With one machine we kept the same Yaskawa VFD / "high frequency" spindle, and with another we didn't have a spindle so we put a CNC Depot S30C spindle with Hitachi VFD. In both cases, we used Modbus (either over RS-232 or RS-485) via a USB-to-serial adapter to control the VFD. I wrote a custom "user space" component for LinuxCNC to speak RS-485 to the spindle and manage state. If anyone is interested in learning more about this, feel free to message me (or this thread).

[Todd Zuercher]

Hiwin did all of the machining for us. I cut the mounting flange off of one of the old plastic leadscrew nuts and used that to make a mounting adapter plate for the nut on the ball screw. The only other modification I had to make was to cut a slot in the crossbeam of the gantry under the table for clearance to the grease zerk on the ballnut, so that it could spin without hitting it. I'll try to attach the PDF drawings from the ball screw quote.

C-PGD-09-01_NC.pdf

doc10052009113215.pdf

[mmccracken]

Has anybody successfully successfully converted the Gerber 408 to linuxcnc using the original Servo motors and encoders?

My PC running the gerber software died so I decided it was time to upgrade. With the mesa card shortage, I was able to get a 7i96s and gecko 320x servo drives.

I got the spindle working but am having a heck of a time with the servos. Not sure of the dip switch settings on the drives or any of the info in linuxcnc. I have tried many different settings have had success getting the motors to move but I know the settings weren’t right.

Any help would be greatly appreciated.

-Mike

[fdarling]

Has anybody successfully successfully converted the Gerber 408 to linuxcnc using the original Servo motors and encoders?

I have done several conversions, and recently finished making a drop-in replacement motherboard so that you don't have to do any re-wiring whatsoever, just replace the motherboard and run an Ethernet cable from it to the new controlling Linux PC. You can read more about it here:

https://forum.linuxcnc.org/39-pnccon...tart=20#294504

[mikeysp]

Very interesting. i will have to check those links out later.

I have done several conversions, and recently finished making a drop-in replacement motherboard so that you don't have to do any re-wiring whatsoever, just replace the motherboard and run an Ethernet cable from it to the new controlling Linux PC. You can read more about it here:

https://forum.linuxcnc.org/39-pnccon...tart=20#294504

[andinoag]

This is amazing. How can I purchase a card like this? Could you send me more information please? I have a Gerber 408 and at the moment it is sitting in a corner due to lack of an update. My WhatsApp is +1 778 692 5999. Thanks in advance

I have done several conversions, and recently finished making a drop-in replacement motherboard so that you don't have to do any re-wiring whatsoever, just replace the motherboard and run an Ethernet cable from it to the new controlling Linux PC. You can read more about it here:

https://forum.linuxcnc.org/39-pnccon...tart=20#294504

[arturod]

You could get this working with these servos:
https://cnc4pc.com/dg4s-16035-dc-servo-drive.html
But considering the cost of AC servos or closed loop steppers and the high maintenance cost of the brushed servos, it may be a better idea to replace the servos.

Arturo Duncan
https://cnc4pc.com

[fdarling]

You could get this working with these servos:
https://cnc4pc.com/dg4s-16035-dc-servo-drive.html
But considering the cost of AC servos or closed loop steppers and the high maintenance cost of the brushed servos, it may be a better idea to replace the servos.

Arturo Duncan
https://cnc4pc.com

The CNCDrive DG4S, Machdrives BRD/BRE/BRF, and Gecko G320X are all brushed DC servo drives that present a step/direction interface for the upper controls. They do not repeat the encoder signal, you have to "tee" it off yourself if you want that. You also have to tune the position/velocity loop on the drive itself, sometimes in analog with potentiometers.

Most people doing retrofits of Gerber Sabres go with the simplest path of replacing the motors with steppers, closed loop steppers, or step/direction interfaced servos like Teknic ClearPath (which look like steppers). Most do not get "proper" servos with separate drives from the motors, because typically they are expensive (Yaskawa, Delta, etc.) or have a difficult learning curve to configure/tune (AliExpress Chinese ones). With step/direction being the lowest common denominator, you have a lot of flexibility on which control package you can use: Mach3/Mach4, GRBL, WinCNC, UCCNC, Masso, etc.

Most of those controllers do not support encoder feedback coming from the motors/drives, only an alarm/fault signal. Having the encoder feedback gives you two advantages: 1) you don't lose position if the motors turn off (E-stop, fault, etc.) 2) you can tune the motors "live" because you can see the real-time position error from the controller's perspective

LinuxCNC is one of the few affordable controllers that actually supports encoder feedback, similar to what you'd expect from industrial strength controls from Fanuc, Mitsubishi, Siemens, etc. This is the reason I didn't have to change out the original servo drives (which are usually still working), and I can do all of the position/velocity loop PID tuning directly in the control software.

In theory, the outdated brushed DC servos might be high maintenance, however in practice I have not had any trouble from them. Their encoders are ~$180 to get replaced (never had to do it, I thought I did but it was a bad cable instead), and the carbon brushes are ~$20 to replace (also not yet had to do it, but I'm sure the time will come). If the motor burns out, it can be expensive to get serviced and even more expensive to replace, and at that point you'd want to explore upgrading to newer technology.

The LinuxCNC motherboard I created has servo expansion connectors on the motherboard to support any type of stepper/servo drive you might want to hook to it. The main advantage of my solution is that you don't have to change anything else in the setup, so it's easy to set up and easy to revert.