2007 Shopbot PRS-S 4896 Upgrade Recommendations

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acornKurt
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2007 Shopbot PRS-S 4896 Upgrade Recommendations

Post by acornKurt »

I have been reading these forum posts and looking at success stories for about 2 months now. I own a 2007 Shopbot PRS-S 48x96. I have looked thru the FAQ's and watched several of Gary's videos on YouTube. It is a hobby machine for me, been adding drag chains and upgrading this and that.

I really want to upgrade the controller to Acorn and get rid of my old Shopbot controller, mine is the one that looks like an upright Desktop Computer case.

I have stepper motors with a planetary gear box attached and the mount to the Shopbot is offset so I can't just plug and play most stepper motors. Shopbot Alpha closed loop stepper upgrade would cost me about $7000.

I have considered just doing a db25 breakout board and using my gecko G202 drivers with my current steppers as a way to get the new controller and modernize my Shopbot.

It seems my best option is to start with a closed loop stepper or servo motor that is more compatible with the Acorn Controller and then figure out how to build an adapter to mount that servo to my Shopbot and make it work. Don't know if there is a list somewhere of recommended steppers for example.

Any thoughts on how I could move forward would be greatly appreciated.
jpmsteadi
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Re: 2007 Shopbot PRS-S 4896 Upgrade Recommendations

Post by jpmsteadi »

The options are really wide open when considering the motors and drivers. Since the acorn outputs step and direction signals any device that takes those in can be used. Anything from dirt cheap amazon/ebay stepper kits to clearpath or DMM servos to other strange things.

If you are happy with the speed of your current machine you probably can reuse the same motors and possibly drivers from the current control.

As long as you don't push the machine too hard you can get the same resolution with open loop steppers as closed loop, you just can't push the machine to the very edge.
Richards
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Re: 2007 Shopbot PRS-S 4896 Upgrade Recommendations

Post by Richards »

You're looking at several problems unique to a Shopbot. You have a geared motor, possibly even the motors that had only Black/Green and Red/Blue wires exiting the motor. Those motors have high inductance, which means that they work best at low speeds. That gives you three choices: (1) Keep the motors and drivers until you can afford or need something better. (2) Replace the motors with some newer NEMA 34 motors and replace the drives with Leadshine drives. Build/buy a 3:1 or 4:1 belt-drive transmission. (3) Replace the motors with some newer NEMA 34 motors and replace the drives with Leadshine drives. Install 5:1 gearboxes from AutomationDirect (or other supplier).

If the speed/performance of your Shopbot has been satisfactory, you might start with option (1). You can easily drive Geckodrive G202 drivers with an Acorn. I've done that on my testbench. Remember that the G202 requires a +5VDC common on the G202 terminal 10. Use a DB25 break-out-board for easier wiring. That solution will give you all of the speed and performance that the original motors can produce. I replaced the original Alpha motors on my PRT with belt-drives. I tried making the belt-drive assembly from Aluminum, from Polycarbonate, and from Delrin. The Delrin was the easiest to work with. It did an excellent job. Later on, I replaces the belt-drives with 7.2:1 gear-driven Alpha motors from Shopbot. They offered an upgrade at about half the normal price. Those drives and motors worked but they worked no better in production than the belt-driven motors that they replaced.

For "snappiest" response, if you replace the motors, pick some that have 2-4mH inductance. If you use belt-drives or gearboxes, motors that produce 400-600 oz-in of holding torque will work well. (I used the Oriental Motor PK296-4.5F motors with my belt-drives. They gave excellent results. You can find similar off-brand motors for $50 or less.) A 2mH motor can use up to 45 VDC. A 4 mH motor can use up to 70VDC. Use a stepper drive that can handle the current requirements and voltage requirements of the motor. I recommend using a toroidal based power supply. That type of power supply, if it has a large filtering capacitor, can handle the current requirements of a stepper motor better than most switching type power supplies. If you decide to use a switching power supply, consider adding a large filter capacitor (10,000 uF or larger) to the output as a current reservoir.
-Mike Richards
robtown
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Re: 2007 Shopbot PRS-S 4896 Upgrade Recommendations

Post by robtown »

I can tell you from my experience (with a 2004 PRT), that simply replacing the controller and keeping your motors and those Gecko drives will result in a better performing and more stable machine. In my build I used G203's.

In my case, cut quality did improve, but not as much as I had hoped. Speed and torque are much improved.

After my Acorn build I purchased two used motors that came off a PRS and put them on my X axis, that helped a bit as well.

Buy the wireless MPG, you won't regret it.
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Re: 2007 Shopbot PRS-S 4896 Upgrade Recommendations

Post by martyscncgarage »

acornKurt wrote: Mon Apr 12, 2021 7:30 am I have been reading these forum posts and looking at success stories for about 2 months now. I own a 2007 Shopbot PRS-S 48x96. I have looked thru the FAQ's and watched several of Gary's videos on YouTube. It is a hobby machine for me, been adding drag chains and upgrading this and that.

I really want to upgrade the controller to Acorn and get rid of my old Shopbot controller, mine is the one that looks like an upright Desktop Computer case.

I have stepper motors with a planetary gear box attached and the mount to the Shopbot is offset so I can't just plug and play most stepper motors. Shopbot Alpha closed loop stepper upgrade would cost me about $7000.

I have considered just doing a db25 breakout board and using my gecko G202 drivers with my current steppers as a way to get the new controller and modernize my Shopbot.

It seems my best option is to start with a closed loop stepper or servo motor that is more compatible with the Acorn Controller and then figure out how to build an adapter to mount that servo to my Shopbot and make it work. Don't know if there is a list somewhere of recommended steppers for example.

Any thoughts on how I could move forward would be greatly appreciated.
How does your current control interface with the computer? Via a parallel port?
(I am not familiar with ShopBot)

Nothing wrong with using the Acorn DB25 to control your current motors and drives. Least expensive way to go. If the machine is performing as you expect, then that's what I would do for now, keep current motors and Gecko drives. While Gary poo-poos Geckodrive, the company does know stepper motion control. Later you can upgrade drives and motors if you like.

If you keep your current motors and drives, don't change the rapids much from where they are currently at. You might experience missed steps or at least record what the current rapids are so you can work your way down to that original number.
My .02
Marty
Reminder, for support please follow this post: viewtopic.php?f=20&t=383
We can't "SEE" what you see...
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robtown
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Re: 2007 Shopbot PRS-S 4896 Upgrade Recommendations

Post by robtown »

It's most likely USB.
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Re: 2007 Shopbot PRS-S 4896 Upgrade Recommendations

Post by Gary Campbell »

Kurt...
Like Mike says, there are a number of issues "unique" to ShopBot. I will try to list them in order of your questions.

Your motors do NOT have planetary gearboxes. They are either a straight or tapered gear that comes from the factory with 3 to 5 thousandths backlash, and get worse with time. I recommend that you follow the instructions on the attached doc and quantify your backlash. This will help you decide if you need to replace the motor/gearbox combo.

IF you do not NEED to replace them you can build a system using drives that will accommodate those old high inductance motors, even reusing your existing drives. Or you can buy one premade for $2k to $2.5K depending on which motors you have (inductance) Add ~$1600 if you need motors, planetary's and adapters. The premade closed loop systems are in the $4.5k to $5k range. Higher performing and substantially less than the factory options.

I dont understand your statement about using a DB25 BOB

You should decide if your goal is to enjoy the journey or the destination. In other words, do you want to buy a system or build one? Want to take a few months (in some cases over a year) of learning how to find components and then how to wire them? Or would you rather crank out a few more dollars and run your CNC?

Since you have a Gen1 PRS I will recommend an under 550ozin NEMA23 stepper, (open or closed loop) Those original "tall boy" gantry's cant take much torque without flexing. There are a good number of ShopBotters here, some that have purchased controllers, some that have built their own and may be willing to share their parts info. But there is no list of recommendations. Thats the "Y" part of DIY
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martyscncgarage
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Re: 2007 Shopbot PRS-S 4896 Upgrade Recommendations

Post by martyscncgarage »

robtown wrote: Mon Apr 12, 2021 11:28 am It's most likely USB.
if that's the case, then get a DB25 male breakout board plug it into Acorn's DB25 and connect the step/dir signals to it.
I would move the limit switches to the Acorn inputs directly, same with spindle on/of control.

Marty
Reminder, for support please follow this post: viewtopic.php?f=20&t=383
We can't "SEE" what you see...
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acornKurt
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Re: 2007 Shopbot PRS-S 4896 Upgrade Recommendations

Post by acornKurt »

martyscncgarage wrote: Mon Apr 12, 2021 11:25 am
How does your current control interface with the computer? ......
My current Shopbot interfaces with a USB cable. I have an ancient PC running windows XP and that has a usb hub that sends info to Shopbot controller.

An upgrade gets me a super modern computer interfacing with ethernet and I get to build a control box that can be more easily mounted to my machine.
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Re: 2007 Shopbot PRS-S 4896 Upgrade Recommendations

Post by Gary Campbell »

Kurt...
As you know, I am no longer selling retail "kit" parts to end users, but if it turns out that you need gearbox to PRS adapters Matt may be selling them retail. His email is mattdevicentis (at) gmail if you want to check. I provide them in quantity to him.
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