Looking to upgrade my PRT Standard 96, seeking advice.

[mjindustry]

Hi,

I purchased a used PRT Standard 96 with PC router a few months ago. It was originally purchased from shopbot in 2006 by a custom speaker box outfit. They used it frequently for cutting rectangles and circles out of mdf. It has not had any upgrades as of yet.

My biggest problem so far since setting up the bot has been accuracy. It seems like it if it isn't the X or the Y, it's the Z. One minute you think you have X and Y under control, but the Z is doing goofy things like cutting too deep or not deep enough. Then, I was pretty sure I had the X and Y tuned in perfect but ran a more complex vcarve file (but still very light duty for the router) and it goes way off track. X and Y seem to work pretty good and maintain accuracy when cutting rectangle profiles (albeit at very slow ips rates, plunge rates, etc). Then, when I load a little more complex design it loses it's position, even under light duty tasks. For instance, I tried to just lightly engrave (.1" depth) a little more complex path with a brand new vbit and it goes way off coarse every time. (up to like 2 inches off coarse)

I have spent countless hours troubleshooting, searching and reading the shopbot forum. Testing, cutting, testing, air cutting. Checking pinion for tightness. Grounding, un-grounding. 3 Different computers. Believe me when I say I have pretty much tried all of the usual suspects to get this thing to do things accurately, but no avail. I'm to the point where I don't want to troubleshoot anymore, and am willing to spend money to make things better!


See, when I purchased this thing for $5500 (around half of a new PRS) I knew that some things, if not all moving things would be worn out because of the heavy use that was stated by the previous owner. I knew this going in, my expectations were very low. I was prepared to pretty much completely purchase and replace all moving parts. Now, I just want to do it in the correct order...

Is there a CHANCE that the 4G upgrade alone would make this thing work right and fix my accuracy issues? Well, how about the 4G upgrade and some new pinions. Would this be a good place to start? I'm willing to go beyond that, but maybe I don't need to just yet. However, what would be next...stepper motors? I really don't want to spend a nice load of money and be disappointed again...maybe I should get new motors right off the bat as well? I dunno. The previous owners used it in basically a commercial production environment. They said they used it 6-8 hours a day for the whole two years of owning it. So my guess is that the pinions need to be replaced, if not the motors. I just don't know the life expectancy of the motors.

Maybe I am completely out of my mind and need to be looking at something else? Currently, I have a budget of about $3500 for any improvements. Eventually, I want it to be all it can be...Can you help me get there in the correct fashion? If so I would really appreciate it.

Here is a picture of my PRT Standard 96 before I hooked it all up...It looks good doesn't it?



8163

[myxpykalix]

I had some similar issues when i installed my indexer to my table. I had issues trying to make it parallel and plumb to my rails and carriage.

I would start out with some low tech trials before you go spending a bunch of money. You have to verify that the table, rails and carriage are plumb and square to the table.

First take your level to the bottom struts on your table down low so you can make sure that that part is level to the floor.

Go to lowes and get a couple "string levels" the kind you clip onto string when laying a stringline for a form, and some string.
I used a couple of microphone stands to run a string along the X (not attached to the table)to check the level of the tabletop.
I did the same thing along the rails in the X.
Then I did the same thing in the Y direction at various spots along the rails from one end to the other.

Then check the level of the carriage in the X and Y with your level.
Once you know it is level, square and plumb to the carriage and tabletop then you can go start spending money.
It does sound like there are other issues going on and you probably have some worn parts but since this is a "new to you" machine you will need to do all the things i mentioned anyway regardless of whether you start replacing parts.

[jerry_stanek]

Make sure your values are correct. Also make sure that your ground wire is making god contact.

[richards]

Solving any problem starts with defining the problem. Most of us have had problems that seemed totally random while they were happening, but later turned out to be caused by something specific.

I would start with repeatability. Run each axis back and forth a specified distance. MEASURE the move carefully to verify that the Unit Values are correct. If some moves are exactly on and some moves are erratic, then carefully check everything for tightness and wear. If everything is tight with no apparent wear, then start to suspect electrical noise.

Stepper motors should last for years and years and years. Some of my process control customers are still running stepper motors that I installed more than fifteen years ago. Some of those machines run 24/7.

Every PRT standard SHOULD be upgraded to the 4g level, but that upgrade won't cure a problem that has nothing to do with stepper drivers.

[curtiss]

Maybe mount the 110 for the router on the top side of the arch and the y & z wires below.

Not sure what is below (or if you want to drill into) your concrete floor, but I went into the crawl space under the house and pounded a 4' copper rod into the ground. The rod is just a few feet from the edge of the machine. Took about 4' of copper wire to ground the machine.

I heard some rock salt next to the copper rod heard makes for a better ground.

[mjindustry]

Wow, thanks guys!

You've made me rethink the spending spree. I simply put an order in for replacement of all pinions. I changed those out & did a much better job of grounding the shopbot right after words. For the grounding I followed the shopbot wiki write up by Gary Cambell to the T. Thank you for that Gary, and Curtis, Jerry and Mike for recommending that! I also leveled and squared as best that I could Jack.

I then also tidied up the power supply running the control board and PC. I realized that I had been using an extension cord to power those, thought better of it and eliminated the extension. I also cleaned up the PC as best I could.

After all that, initial test results are really good! Oh, one thing I haven't done yet either is glue a spoilboard down, but I will be doing that very soon. I plan to use 3/4 Trupan glued over MDF and then plain that down to level. I still also intend to do the 4G upgrade ASAP!

<End Shopbot Inaugural/victory speech>