Motor/driver upgrade

[gc3]

Is the 4g shopbot upgrade the best way to go to upgrade a pr machine. I have a older pr tool that was upgraded to a prt style z axis along with the motors and control box. What other options are out there?


Gene Crain
www.plantasymaderas.com

[taskins]

Gene-
I am updating an early PRT 2000 vintage. Take a look at which motors you have installed. I found out that upgrading to a 4g board would do little to improve performance due to the high inductance rating of the motors-PK299-01AA on my machine.

I settled on the new shopbot RBK board and had it wired for the gecko G203v drivers and am pairing that with the PK-299-03AA motors and 4:1 belt drive transmisions. I hope to have it up and running by the end of the month.

[ken_rychlik]

Gene what do you want the machine to do? Cut faster, cleaner, run smoother, ect...

What motors are on the unit now?

My prt was helped the most by welding up all the joints of the errector set machine to make it tight. I think the PR is even more sloppy than the prt from what I've heard.

Looking at the wiggle points and finding a way to either weld or bolt bracing to take the slop out of it would probably be your best cutting improvement.

Making it faster without improving the frame may hurt more than it helps.

Kenneth

[billp]

Gene,
One of the best "upgrades/modifications"I have seen for the PR units was to rotate the wheels on the Y axis 45 degrees. I owned a PR for years and always had "issues" with the way the wheels rode on the outside edge of the X rails. And I am sure that by now you have had the fun of having to lever your entire Y carriage back on to the rails after some sort of unforeseen "collision" with a clamp, etc.
Here are two shots of one such upgrade. Yes you will have to re-rig your motor mount, but that's an easy fix. Once you've done this there is much less of a chance for the machine to bind or jump the tracks. You also won't have the issue of wearing a deep groove into your X rails anymore as well.
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[rb99]

What did you have to do with the motor mounts and what i that rail the V is now tracking?

Thanks,

RIB

[billp]

Richard,
In retrospect this all went on awhile back, and my memory may be cross referencing two different scenarios. It may not be necessary to do anything with the motor mounts at all. I was probably thinking of when some of us did the original upgrade from a cable drive to the PR. Then we HAD to do something with the way the rails worked because we were moving up to the original rack and pinion setup. If someone were starting with a PR the mounts might be fine.
The V rails you see the rollers riding on can be bought from a number of sources ( maybe even Shopbot themselves?) . I know that Bishop Wisecarver was one vendor, and places like McMaster Carr, or Reid Supply might also stock them.
Guys like Bob Dodd, Ed Coleman, and Jimmy Arneson all made some sort of modification to this kind of setup, so maybe they can chime in here. I'll add another picture or two of how one upgrade was done. New rails can be bought that fit along the outside of the existing frame, or with a "lip" that bolts directly to "C" channel. If I remember correctly there was the option to buy them undrilled, or pre-drilled. Unless you really like laborious work, I'd go with the pre-drilled.


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[gc3]

Looking for a little more 3d cutting speed...

Here is a cheap but very effective rail upgrade(?) I did that works very well I still have not put the hold down rollers back on and have not had any derail issues jogging or cutting as fast as the machine can go, the problem has that I am loosing strps when cutting above 4in/sec or jogging above 5in/sec


Gene Crain
www.plantasymaderas.com
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[rb99]

Gene I think your speed issue jogging over 4" per sec is from the motors being under powered. I have taken the motors off and run them at higher speeds and at a certain point under no load they choke. They also get very easy to stop with bare fingers. (with the old original controller)

Mike Richards is the "man" with the motor knowledge. He has told me lots of info about the motors, (only some of it soaks in!) but my old motors where wired straight, and when they get wired bi-polar they run on 1/2 the power, and get stronger and faster.

I bought a new G4 controller with Gecko 203's. I have not installed it yet but it wires the motors bi-polar.

RIB

[ken_rychlik]

Gene, the 4G will give you more jog speeed without loosing steps, but by it's nature 3d cutting will not reach those speeds anyway. It is either ramping up or ramping down in speed at all times and never reaches full speed anyway from the 3d stuff I have ran.

I can jog at 8 ips without loosing steps with the 4g on my prt, but as far as cutting 3d stuff it will still be under your current 4 ips place where you are now.

Do you know the voltage to the controller for your steppers? Mine has a 48 volt meanwell power supply in the box. If your voltage is below that, a 4g board and upgraded power supply would help quite a bit.

Still the 3d stuff is going to take a long time to run unless you use a large step over and then you will have lots of sanding to do. This plaque is a 10 hour run with a 1/16th bit and and a 10% step over.


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[gc3]

I have some 36X70 signs to do for a local restaurant similar to the photo. I am hoping to find a low budget way of upgrading the speeds. Have you seen a better cut with the 4g box?

Kenneth I wish I could afford your machine, but we have been crunched this past year so the play $ is gone...

Thanks for the responses

Gene Crain
www.plantasymaderas.com
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