PRT upgrade to PRS

[JDaVinci]

I've got an older (2003 I think) PRT machine with the 4G controller upgrade.
I've installed the retro-Z 18" z axis, and can cut up to 8" thick material reliably. (limited by available tool length.

We almost exclusively cut EPS foam. The fastest I can cut without getting errors is 4.5 ips (x and y) and 3 ips (z). The ramp in and out movements have been tweaked a little to speed things up, but I'd still like to get more speed out of this machine, as it cuts through the foam like butter... the traveling is the only limiting factor as of now.

I have 3 questions..

1.) First, is there anything else I can do to gain more speed in all of my z heavy machining?

2.) Does anyone have a source they can share for 8" or longer ball end mill tooling?

3.) What would an upgrade to the newest PRS machines do for me? Would I increase my speeds and processing power by that much that It's worth the upgrade?

[jerry_stanek]

What is your speed test showing. My old PR can cut at 5 IPS with no problems. I did the upgrade to the 4G a while ago before that I could only cut at 1.79

[JDaVinci]

I didn't know you could do a speed test? We had a few glitches at 5ips (before retro z upgrade) so we slowed down a little at a time till the glitches went away... 4.5 was the most stable speed. I suppose we could try speeding up again, as it might run better with the new z.

[jerry_stanek]

The speed test is in the Shopbot software. It tells you how fast the transfer rate is and if it is too slow there are tricks to get better rates.

[JDaVinci]

Would love to hear more about these "tricks"!

[Brady Watson]

What is your speed test showing.

Bingo...Get a 2.0 USB hub in between your computer and the bot. Search on this board...there are a gazillion posts about this. Run the SpeedTest.exe in the ShopBot/Diagnostic folder with & without the hub. Communication is most likely not fast enough, which is restricting your speed.

In the future, if you mainly cut larger reliefs with large tools, you can trade out some resolution for speed with larger pinion gears. 30 or 36 tooth would do nicely and would give you a substantial speed increase.

-B

[danhamm]

I think he is talking about USB from computer to controller transfer rate,

and if you have a 2003 prt it probably uses computer to controller serial or parallel connection..

[jerry_stanek]

He posted it had the 4G upgrade

[JDaVinci]

Brady,
I've got usb 2.0 ports on the computer. I upgraded to a brand new PC after finding the old one was a weak link.

The gear change sounds very interesting... I've got a 20T on my z-axis, and 25T on X and Y.
Is it really as simple as putting new gears on the steppers? I've got the gearbox style steppers. Would the internal gears require changing? I wouldnt want to overwork them And with most of our cutting, resolution is not a factor, as it is so large, we are maintaining as much detail as we need. So our tolerances are pretty broad.

Dan and Jerry,
I do have the 4G upgrade...But my controller still has the com port connection. It has a USB adapter plugged into that. Am I getting a data restriction there? Is there a way to upgrade the control box connection to USB and loose the adapter all together?

Thanks for all the help!

[Brady Watson]

JD - The SpeedTest.exe is the yardstick on communication efficiency. You MUST close SB3 before you run it or it won't work. Run it & post your number. Make sure your USB cable is under 12 feet long.

Yes - it really is that easy. You can run a 30 tooth or 36 tooth pinion gear on X and Y axes. You could bump the Z axis up to 25 tooth. You will have to put in new Unit Values (UV), but ShopBot can give you these numbers when you order pinions from them. Just for comparison, a PRT Alpha with 7.2:1 Alpha motors ran 30s on the XY and 25 on the Z. Some ShopBots with plasma cutters ran 36s on the X & Y axes with your exact motors, with and without 4G upgrades.

Call SB and tell them what you want to do.

If we do the math, here is what you can expect with 30T on the X&Y:

You will lose 17% of your step resolution & gain 17% more speed*

With 36T on XY:

You will lose 30% of your step resolution & gain 30% more speed*

*Provided that you are cutting foam and don't ask the motors to make more horsepower than they are capable of.

By going to larger pinions you also drastically increase pinion life since you have more teeth engaged in the rack at any one time. The forces are spread across more teeth.

-B

[JDaVinci]

Wow... great info!
I'll sure consider this.
Here are the results from my ShopBotTest:

http://dl.dropbox.com/u/2327513/ShopBotTest001.JPG