I Want To Share This With You!

Hello,
My name is Mark John. Some of you may know me as a long time ShopBotter, while others may not have heard of me as I am not a regular poster here on the forum. I have been using ShopBot's for years to produce entry doors and various casework and millwork. You can check out my site at: http://www.distinctivedoorsofdallas.com for a sampling of what I do.
Anyhow, I just recently had a demo of the most amazing modification to a ShopBot I have ever experienced (it was a PRT model). There is a company in Dallas called Custom CNC Inc. (http://www.custom-cnc.com) that is producing replacement controller boxes for both the PR and PRT models. The performance difference that this new control box offers is nothing short of PHENOMENAL! You know how when you make a move or jog with the original box hooked up - and it is jerky and the motors growl and make all kinds of vibrations? Absolutely all of that is gone with this new box! In fact you can't even hear the motors run at all when you move or jog it around, and there are virtually no vibrations what so ever. And the cuts that were produced were equally impressive. I should add too that this new box made the system both faster and it was much more responsive (it didn't seem sluggish like what I am used to).
I've been a long-time ShopBotter and own both a PRT and a PRT-Alpha. The smooth cuts that I saw this old PRT do completely blow both of my systems right out of the water! This new box did not have the cut speeds that my Alpha has BUT it's not just cut speeds that I have to consider in my line of work - I also have to figure in the sanding/cleanup times too. I mainly do 3D work on entry doors, so I took a file with me for the demo to see just how much this new box would help me. All I can say is wow, no more sanding. The relief that was cut required almost no sanding at all!!! And the file executed 20-25% faster than on my PRT. I used to base my jobs on both cut time AND sanding time. Not any more - it's virtually just cut time only from here on out (I already have a box on order with these folks).
Also, the case isn't some 'hacked-up' PC case either. It has been made specifically for this application. The original motor cables plug right into the back so no wiring modifications are needed. These folks also put the other wiring connectors right on the back of the box for the ZZero plate and remote pause switch. They were also using a different software package called 'MACH'. In the brief time I saw it, it looked very easy to use, and has quite a few more capabilities than my ShopBot software does. It runs ".cnc" files instead of ".sbp" files, but once I saw how to make the ".cnc gcode files" it looks pretty simple too.
I just wanted to share this info with my fellow 'Botters. Thank you and have a wonderful day!
MJ
PS. The people at Custom-CNC have never had the Mach software crash in over 18 months of using it.

Mike,
They're both right. Ted is absolutly correct because he's talking about the driver/power supply/stepper on the PRT as a total unit. The driver chip or device is all important when you're trying to get maximum speed and/or torque from a given motor. A driver/chip might be able to handle 24VDC or 48VDC or 70VDC, meaning that you would get completely different performance depending of the voltage that the driver could handle. Again, depending on the driver/chip, you might be able to wire the stepper motor as a series device, as a unipolar device or as a parallel device. Each different type of wiring will affect the performance. Personally, I believe that Ted has done a great job making the PRT model Shopbot driver/power supply/stepper motor run as fast as it does.

Now, if the driver/power supply/stepper components were changed, performance could be altered greatly - meaning that the claims made for Custom CNC, Inc. could be absolutly true. (I used the word 'could' simply because there is not enough information about their product to compare with tests that I've made using similar products.)

Earlier today I ran some torque and speed tests on an Oriental Motor's PK299-F4.5 motor, which has performance specs very similar to the motors in the Alpha. (The results from that test are posted elsewhere on this forum.) Tonight, I ran those same tests on a PK299-02 motor which is very similar to the motors used in the PRT. Using a Gecko G212 driver, a 70VDC power supply and wiring the motor as a unipolar device, and running the motor at 360 RPM, which would be similar to running the Alpha at 18-ips, the stepper finally stalled at > 45 pounds! Now, if that motor were geared down, so that the 18-ips became 6-ips, the motor would not stall until it hit more than 100 pounds! Do you see where I'm going with this? Standard off-the-shelf components, if correctly utilized would give you both Alpha speeds and PRT quality. By the way, that same PK299-02 motor with the same Gecko driver, but with the power supply voltage reduced to 25VDC stalled at 7 pounds. To me, that shows that the combination of driver/power supply/stepper motor must be considered. Add to that a reliable pulse generator that can send out pulses fast enough to drive a high performance stepper and you'd have something similar to the Custom CNC, Inc. product.

Knowing that it is possible to have Alpha speeds for a PRT still doesn't mean that replacing the controller/power supply/steppers is the right thing to do, even if the cost is reasonable. The mechanical side of the Shopbot is only part of the reason that the Shopbot has been so well accepted. You have to understand that a machine running Mach3 software will not run native Shopbot code. Every file that you now have will have to be converted to G-code. That can be done. G-code is easy to learn, but it's not generated by PartWizard (unless there's a setting that I haven't found in my copy of PartWizard). For some of us who have years of experience in computer programming, converting code is just part of everyday life. For others who are new to using computers to control machinery, the requirement to learn something very different could be a problem too big to easily overcome. Then, you have to consider what to do when something breaks. It would not be reasonable to expect the Shopbot crew to answer questions about parts and pieces that they don't sell. It wouldn't be reasonable to expect people on this forum to have intimate knowledge about other products. In short, if you change something on your machine, you'd better be confident about your own abilities to troubleshoot and repair things. (As a side note, during the last thirty-years or so when I built process control computers, I never discouraged my customers from doing whatever they wanted to do with the equipment that they bought from me; however, they were made to understand that any modifications voided my responsibility to repair their equipment. If they modified something that I'd built and then wanted me to repair it, they had to pay my normal consulting fees to study their schematics. If they didn't have schematics, I always refused to do anything. It just wasn't worth the price that they would have to pay to have me reverse engineer their modifications.)

Now to answer your question about how I feel, as an Alpha owner, knowing that the Alpha costs substanitally more than buying an Alpha frame and someone else's electronics would have cost. To me, the answer is simple: It doesn't matter to me. I'm certainly not a wealthy man, as far as money goes, but the complete package from Shopbot is superb. It has all of the individual pieces that I needed to get started and it has the Shopbot community to further assist me as my needs change. Think about buying a new car. Do you just buy the frame and then shop around for a different manufacturer's motor? Most people wouldn't mix and match automobile parts because they're buying transportation. In the same manner, buying parts and pieces for your Shopbot from various manufacturers doesn't seem reasonable unless you have needs so specialized that nothing else would work.

Greeting to all,

I have an Alpha and have been employed at a shop that was using a PRT.

I can fully appreciate the Alpha with its motor feedback system that prevents missed steps.

You have to remember that by changing the control box and software with the PRT motors, you still have a non-feedback system that has the capibility of missing steps when overtaxed.

Dan

I guess I'm a newbie here, I've only had my machine about 6 years now but I have to agree with Dave Rosenbleeth above that Shopbot has encouraged botters to enhance, improve and experiment with their Shopbot not only with the hardware but software as well. It appears by the posters in this thread that they have no idea of how many shall we say supped up and non standard Bots are out there running.

Now to get to the point. This last weekend Alan brought his Shopbot enhancement box to Doug Strickland's Shop in Ok where we put it through over 11 hours of testing, starting with what makes it tick to the final cutting of finished pieces.
All test were recorded by video and were carried out on Doug's PR model SB. These results will be compiled and posted or made available shortly. In a couple of weeks we will be carrying out the same tests on my prt. For those impatient people please be aware that Alan is in Tx, Doug is in Ok and I'm in Ks so we have 4-6 hours one way drive time between us so this is not happening overnight.

Now why the hoopla over this? I will not get into that but I met Alan 3 years ago I have found him to be a straight shooter with high integrity and the qualifications in engineering to back it up.
He is not in competition with Shopbot, he has just made a modification to his shopbot and had the foresight to realize that this could also benifit other pr and prt owers. This is not an Alpha upgrade this is for the old pr's and prt's who have been left behind and not followed Shopbot's upgrade to the Alpha's, he has filled an opening not offered by Shopbot that can give a low cost upgade to these older machines to breathe a few more years of life in the high competitive world of CNC.

Watch for test results or if any of you wish to call me I will be happy to discuss this futher.
Gary Beckwith