Kern laser retrofit

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atrueresistance
Posts: 3
Joined: Mon Mar 05, 2018 5:01 pm

Kern laser retrofit

Post by atrueresistance » Mon Mar 05, 2018 5:06 pm

So I'm attempting to retrofit an older Kern laser. This guy:
Image

So the motors on this thing are quite different than what I've normally seen. They are a Pacific Scientific Powermax II (M22NRXA-LSS-NS-02). Pacific Scientific is out of business and was bought by Kollmorgen. The closest spec sheet I could find to this model number is here.

So I'm just guessing this is the right wiring.
Image

So my question is can I wire these two motors to all four of the drivers? So like Driver Connection A connects to the X axis and Driver Connection B connects to the Y axis of the Buildbotics controller? Here is a video explaining.


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Doug
Posts: 239
Joined: Fri Feb 02, 2018 4:56 pm

Re: Kern laser retrofit

Post by Doug » Mon Mar 05, 2018 8:42 pm

You will only need to use two of the four ports on the Buildbotics Controller. Most likely, you will want to connect your X axis to the port labeled X and the Y axis to the port labeled Y.

Your motors have eight wires coming out of them because each coil has a separate pair. I noticed from your video that the motors are classified as bipolar series, so I'd recommend configuring them as bipolar series.

If you look at Appendix III in the manual, there is a nice article that explains how to wire up stepper motors. It says that you need the motor data sheet to hook up an eight wire motor.

I read the model number off of the motor and looked around on the web for the data sheet and found the same documents that you found, but did not find one for the exact model number. Having said that, I am guessing that your picture is correct. You could just wire it up as bipolar series and see what happens.

To do that, connect white/black (pin 2) to white/orange (pin 5) and white/red (pin 4) to white/yellow (pin 7). That configures the motor as bipolar series.

At this point, you can check your work with an ohm meter. The black wire (pin 6) should show a low resistance to the orange wire (pin 1), and the red wire (pin 8) should show a low resistance to the yellow wire (pin 3). These two pairs will make up your coils. Then confirm that you have a high resistance between the two coils, say from the black wire to the red wire. This doesn't completely confirm that it is right, but if you don't pass this test, then it is wrong.

Then make the following connections from the motor to the pre-made cable:
* black wire (pin 6) from the motor to red wire on the pre-made cable (this is A+)
* orange wire (pin 1) on the motor to the black wire on the pre-made cable (This is A-)
* red wire (pin 8) on the motor to the yellow wire on the pre-made cable (This B+)
* yellow wire (pin 3) on the motor to the purple wire on the pre-made cable (This is B-)

Once you get one motor wired up, plug it in to the Buildbotics Controller and try it out. Go to the motor configuration page for that axis and set the power mode to "when moving", the drive current to 3.3A (I read that off of the label on the motor), and the idle current to 0. Then try jogging the motor on that axis with the game pad. If the motor moves smoothly, you probably have it right. If the motor doesn't move, you probably have the wiring wrong. If the movement is rough and jumpy, you probably have the coils partially wrong or you have a bad connection.

If you want to reduce the likelihood that you wired it wrong before hooking it up, you can confirm the pairs with an ohm meter before making any connections. My wiring suggestions make the assumption that black and black/white make up the A coil, orange and orange/white make up the A' coil, red and red/white make up the B coil, and yellow and yellow/white make up the A' coil. If this is true, then you should measure a very low resistance between each of these pairs when nothing is connected. And, the resistance between any two coils should be very high.

If this doesn't get you there, you'll probably have to start reconnecting pairs through trial and error. This could get tedious, but eventually you will find a combination that makes the motors turn smoothly. If the motors turn smoothly, but backwards, just switch A with A-, or B with B-, but not both.

I hope this helps. Let me know how it goes.

atrueresistance
Posts: 3
Joined: Mon Mar 05, 2018 5:01 pm

Re: Kern laser retrofit

Post by atrueresistance » Tue Mar 06, 2018 5:29 pm

Hey that worked out pretty well. Once I had spliced the wires back Kern had the 8 wire combined down to 4 so it was a straight forward solder and plug in. Here is a video of it in action.

I still have to wire the limit switches for homing. That looks easy enough, just a matter of connecting to the right pins on the DB25 Breakout board. Good job on the documentation of that!

That and I need to order a pair of glasses before I even dare touch the laser. I'm guessing these are good?

I'm really nervous to dig into the laser portion as I've never used or let alone attempted to rebuild one. 2 things I know are, they WILL make you blind without glasses and they use HIGH voltage.

So it's a Synrad CO2 laser. I'm guessing the 48 series? With that in mind how would you go about connecting this thing?
Image

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Doug
Posts: 239
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Re: Kern laser retrofit

Post by Doug » Wed Mar 07, 2018 9:02 pm

It looks like the movement is working well.

I think you are asking me questions about laser safety. I must tell you that I have no personal experience with lasers. I do know they are dangerous and can blind you. The glasses that you wear must be designed for the wavelength of the laser. I don't think glasses alone are enough safety. What if someone walks into the room while the laser is running? What if you forget and remove your glasses for a second?

You can use the Load outputs (L1 or L2) on the Buildbotics controller can be used to control a relay that, in turn switches power. Having said that, I would not trust any computer (that includes the Buildbotics Controller) with the single ability to turn the laser on and off. The one laser system that we upgraded had a cover over the box with glass that supposedly blocked the wavelength of the laser. Joe and I added a hardware interlock that prevented the power from being supplied to the laser unless the door was closed. This hardware interlock was completely independent from the controller.

It appears that your laser is not covered at all. Given that, it seems like an interlock on the room would be appropriate. Such an interlock would not allow power to be applied while people are present. Keep in mind that the laser can reflect off of metal surfaces and that reflection could be dangerous as well.

atrueresistance
Posts: 3
Joined: Mon Mar 05, 2018 5:01 pm

Re: Kern laser retrofit

Post by atrueresistance » Fri May 25, 2018 8:47 pm

How long does the update procedure take? I clicked update and it is stuck at upgrading firmware. The controller still moves the motors.

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Doug
Posts: 239
Joined: Fri Feb 02, 2018 4:56 pm

Re: Kern laser retrofit

Post by Doug » Sat May 26, 2018 3:26 pm

It only takes a minute or two. Your computer needs to be connected to the internet. Once you click Upgrade, you get a dialog that asks for a password. The default password is 'buildbotics'.

Doug

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