Centroid CNC4
So what hardware exactly should I look at to upgrade? I searched a bit but dont really know what I am looking at.
If your looking for an off the shelf system you might look at Mach Motion. I spent some time on the phone with them this week. It's not emc2 based but rather it runs Windows and Mach3. Looks very clean and priced well. It's actually very tempting. machmotion.com/cnc-products/cnc-kits/mil...achine-controls.html
I was turned on to them by a guy in Idaho that just finished a VMC using their kit. He said it works well.
To roll your own using emc2, as I understand it, and assuming you'll be reusing your steppers, you'll need three stepper drives, a power supply, stepper control, and a computer with emc2.
You can drive the stepper controllers directly from the parellel port but if you want spindle on/off, coolant on/off, indexer, and etc, you well need something that gives you some relay outputs like the Universal Stepper Controller.
I'm looking at something like this:
Gecko G203V stepper drives www.geckodrive.com/g203v-p-34.html
Universal Stepper Controller pico-systems.com/univstep.html
I may replace my steppers motors as I may want to use the cnc4 for something else. Of course the more parts I replace the more expensive it becomes. If I recycled my PC, power supply, and steppers from the cnc4 I suspect I could build it for around $700.
Either way the conversion will take time. A lot of new things to learn.
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Now I would assume if I changed the driven pulley to a larger one, to get a 2:1 ratio, that my resolution would improve as well as my torque.Provided I have the space for a larger pulley. Any negatives to changing to a 2:1 drive aside from the loss of speed?
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My machine is a little weird. Everything on it is for a Series 1 Bridgeport except for the bed which looks like one from a BOSS machine. The serial number is CNC 820 and I cant find any info on these machines. The steppers are not original but are the ones that came with the Centroid retrofit the previous owner did in the early 90's.
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Sounds Good I will have to check out that stuff.
My machine is a little weird. Everything on it is for a Series 1 Bridgeport except for the bed which looks like one from a BOSS machine. The serial number is CNC 820 and I cant find any info on these machines. The steppers are not original but are the ones that came with the Centroid retrofit the previous owner did in the early 90's.
Are your steppers the same as mine or something different? Centroid lists a bunch of options in the manual.
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You might not even lose speed. It will take less torque to move at the same speed, so depending on the motor speed/torque curve you might end up in the same place or not too far away.Provided I have the space for a larger pulley. Any negatives to changing to a 2:1 drive aside from the loss of speed?
Handy pulley-spacing and belt-length calculator:
www.hpcgears.com/calc.htm
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Naturally you won't find a lot of love for Mach here, as we have all made the choice of EMC2 and are human enough to want to defend that choice.If your looking for an off the shelf system you might look at Mach Motion. I spent some time on the phone with them this week. It's not emc2 based but rather it runs Windows and Mach3. Looks very clean and priced well. It's actually very tempting. machmotion.com/cnc-products/cnc-kits/mil...achine-controls.html
I am not sure that Mach can use the encoders. To be fair, I am not sure that EMC2 can use the encoders to any great effect. The reason comes down to the question "what should the machine do if there is a following error". If the problem is a lack of motor torque for the cut being taken, then trying to make up the difference by making extra steps, running the motor faster, will give you even less torque, making the issue worse.
I have considered the possibility of running a stepper/encoder machine in velocity mode and connecting following error to the adaptive feed pin. That might work but is untried.
Depending on the amount of auxiliary IO you might be able to omit the stepper controller. A parallel port has just about enough pins for a 4-axis mill with PWM for spindle control. It is tight for limit switches and there is no way to wire encoders with only one p-port.To roll your own using emc2, as I understand it, and assuming you'll be reusing your steppers, you'll need three stepper drives, a power supply, stepper control, and a computer with emc2.
Of the EMC2-compatible drive boards the cheapest (after a second parport) is the Mesa 7i43 at $80. It communicates via the p-port and offers 48 IO pins which can be GPIO or allocated to a range of functions such as encoder counters (4MHz), step generators (also MHz) PWM, SPI, UART...
There are compatible stepper drivers from Mesa which plug straight in, or the card can drive Gecko or other stepper drives directly. My machine uses
www.motioncontrolproducts.com/drives/msd...ping-drive.php?cat=2 wired direct to the 7i43.
The ULN2003 chip can be useful for this, if funds are tight.You can drive the stepper controllers directly from the parellel port but if you want spindle on/off, coolant on/off, indexer, and etc, you well need something that gives you some relay outputs like the Universal Stepper Controller.
I think sounds about right.If I recycled my PC, power supply, and steppers from the cnc4 I suspect I could build it for around $700.
The controller I am building now is:
Intel Atom D510 mini-ITX £60
8GB SSD drive £20
1GB ram £20
Pico-PSU £25
12V PSU £30
17" touch-screen £120
Mesa 5i23 (PCI card, 72 IO) £150
Add on 3 x Gecko G203 and that comes to £705, except with a new PC and touchscreen included to offset against the exchange rate.
Cheaper stepper drives are available.
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www.cnc4pc.com/Store/osc/product_info.ph...th=33&products_id=49
Take the LiveCD and boot it on the PC you plan to use and run the latency test.
John
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You might not even lose speed. It will take less torque to move at the same speed, so depending on the motor speed/torque curve you might end up in the same place or not too far away.
Handy pulley-spacing and belt-length calculator:
www.hpcgears.com/calc.htm
Thanks for the calculator link. The existing pulleys are 30 tooth... I assumed 60 tooth would give me the desired 2:1 ratio. I ordered a couple 60 tooth pulleys and some 720mm belts. I went cheap and had them shipped ground... so it might be a few days before I can try them out.
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Take the LiveCD and boot it on the PC you plan to use and run the latency test.
I downloaded the live cd and ran the latency test for an hour. Max jitter was 38955 and 42165. Looking at the wiki it appears to be acceptable but not ideal. Looking at the wiki there were numbers all over the board. My machine is an old P4 (Intel BF86510A). with 1 gig of ram and runs Ubuntu well enough. I've been using it for several years with my existing controller. I'm not really expecting to increase my feeds too much because my spindle can't do the rpms required. Should I expect the machine to do ok? Or should I look for something with less jitter? Any recommendations? I know several people have mentioned the Intel Atom D510 mini-ITX, how do these compare? Computers are cheap these days.
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