ron brown
03-04-2014, 09:40 PM
My ShopBot started as a cable drive. First, the cable and ball-chain encoders were replaced with gear racks and home built timing belt reduction units. Next, the screen door wheels were replaced with Bishop-Wisecarver "Dual V" bearing wheels. Some time in this process, ShopBot came out with an 'ball-screw Z'. WOW, finally a reliable machine you could spend more time cutting than working on the machine!
For those not familiar with the older ShopBot control boards, they were what I might call sensitive. And, prone to blowing drivers for any reason they might find. I know I went through several before the V4 board arrived. Mine has the Gecko 203 drivers and I do not recall any problems.
I have decided it is now time to upgrade a lot of stuff. I've bought some 1600 oz/in motors to replace the original motors. I'll probably still use a ball screw Z. I plan on replacing the UniStrut with real rails on 2" X 4" Tubing with the gear rack on the bottom. I'll also build a new gantry where I will no longer have to load from the ends or lift plywood over rails.
The Porter-Cable router gets replaced with a Columbo 3hp spindle with ER25 collets. I'm using a gas-spring and some tricks to balance the Z so the ball-screw drive won't need to work that hard.
While doing this I found out the ShopBot doesn't have the power needed for much larger steppers. First, the Gecko 203 drives will handle up to 7 Amps. So, the limiting resistors must be changed. Also, driving over 3A on the Geckos requires a heat sink on the drivers.
Then, I got to thinking about how much power I would need total ..... The toroid transformer on the boards is a bit light for what I intend to do. Fortunately, I had a 'spare' 48V 22A powersupply. And then, a 55V AC 1000VA toroid transformer showed up on eBay. I bought it. I will need to add a rectifier and capacitors to smooth the ripple but it should make an 80V 18A power supply. There will be 3 1600 oz/in 3A motors and one 428 oz/in 3A on the Z axis. I've got material to build new gearboxes but doubt I'll need them. I also 'scored' a 30:1 worm drive stepper with 8 minutes backlash for a 4th axis that has a 1.8A motor.
I did notice the V4.17 control board I have has some 5 Amp 'fuses' on the board. I'll still be way under those loads so I doubt I'll have trouble there. I am wondering if I could wire directly to the stepper drivers if that does become a problem (more power).
Eventually, this will end up a 22' X 5-1/2' X 24"Z cutting area machine with one end reserved for 'vertical' work. I'm on pier and beam so I might dig a hole and get 6 or so foot vertical work space. A 7 1/2 HP 3PH bandsaw mill will also be designed so I may do 'veneers'. It will ride on the same rails and probably use the ShopBot carriage to pull or push the bandsaw. I'm thinking an Arduino Stepper driver could be used to operate the 'Z' on the bandsaw.
Well, that is the plan ... for now, subject to change. I work for a company that has a large plasma cutter and brakes so I can build any brackets I need and can buy the steel as more than reasonable costs. I am remembering a few taps and packages of drills can eat up a few hundred dollars. But, I do plan on building everything where I can take it apart and move it.
Ron Brown
For those not familiar with the older ShopBot control boards, they were what I might call sensitive. And, prone to blowing drivers for any reason they might find. I know I went through several before the V4 board arrived. Mine has the Gecko 203 drivers and I do not recall any problems.
I have decided it is now time to upgrade a lot of stuff. I've bought some 1600 oz/in motors to replace the original motors. I'll probably still use a ball screw Z. I plan on replacing the UniStrut with real rails on 2" X 4" Tubing with the gear rack on the bottom. I'll also build a new gantry where I will no longer have to load from the ends or lift plywood over rails.
The Porter-Cable router gets replaced with a Columbo 3hp spindle with ER25 collets. I'm using a gas-spring and some tricks to balance the Z so the ball-screw drive won't need to work that hard.
While doing this I found out the ShopBot doesn't have the power needed for much larger steppers. First, the Gecko 203 drives will handle up to 7 Amps. So, the limiting resistors must be changed. Also, driving over 3A on the Geckos requires a heat sink on the drivers.
Then, I got to thinking about how much power I would need total ..... The toroid transformer on the boards is a bit light for what I intend to do. Fortunately, I had a 'spare' 48V 22A powersupply. And then, a 55V AC 1000VA toroid transformer showed up on eBay. I bought it. I will need to add a rectifier and capacitors to smooth the ripple but it should make an 80V 18A power supply. There will be 3 1600 oz/in 3A motors and one 428 oz/in 3A on the Z axis. I've got material to build new gearboxes but doubt I'll need them. I also 'scored' a 30:1 worm drive stepper with 8 minutes backlash for a 4th axis that has a 1.8A motor.
I did notice the V4.17 control board I have has some 5 Amp 'fuses' on the board. I'll still be way under those loads so I doubt I'll have trouble there. I am wondering if I could wire directly to the stepper drivers if that does become a problem (more power).
Eventually, this will end up a 22' X 5-1/2' X 24"Z cutting area machine with one end reserved for 'vertical' work. I'm on pier and beam so I might dig a hole and get 6 or so foot vertical work space. A 7 1/2 HP 3PH bandsaw mill will also be designed so I may do 'veneers'. It will ride on the same rails and probably use the ShopBot carriage to pull or push the bandsaw. I'm thinking an Arduino Stepper driver could be used to operate the 'Z' on the bandsaw.
Well, that is the plan ... for now, subject to change. I work for a company that has a large plasma cutter and brakes so I can build any brackets I need and can buy the steel as more than reasonable costs. I am remembering a few taps and packages of drills can eat up a few hundred dollars. But, I do plan on building everything where I can take it apart and move it.
Ron Brown