I started a DIY CNC project last year for basically the same reason and since then it has morphed into a 36"x30" cutting beast. I can mill aluminum, PCB's, wood, plastic. I've used it to drill the PCB's and recently had it cut the traces for some test boards. This was all DIY and mine is all aluminum. I recently upgraded my bearings, and have a new set of bearings and need some rods to take it up to a full 36"x48" cutting area.
Your most expensive part is going to be the linear slides. From experience USE GOOD SLIDES!. For what you are doing, you can eBay the a 3 or 4 axis stepper driver for under $80 shipped, with the breakout board you'll need.
For my spindle, I started with a rotozip, which lasted way longer then I thought it would, probably 400+ hours of cutting time, I have since switched to a larger variable speed router with a 1/2" spindle so it can handle the aluminum machining.
For a DIY, your lead screws can be acme screws, I get mine from www.use-enco.com, they are about the best price and you can get delrin from a local plastics place if you can find one for the nuts. I used a scrap piece of ACME rod and turned it on a lathe and cut some slots in it for a DIY ACME tap. I have both 3/8" and 1/2" tap sizes now that come in very handy.
Let me know if you need help from a guy who went through exactly what you are trying to do.
Awesome. So the linear slide would be used to move the milling tool (whether it be a dremel or something else) back and forth across the work plane?
If you could, post some pictures of your milling machine and one of it in action. I would love to see what it looks like and how it's designed...
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I will try to get some pics of it tonight when I get home. Yes, you need good quality linear slides for accurate milling. Depending on how you design it, if the milling head is going to move or if the table is going to move. I have mine setup with a fixed table and the spindle moves on three axis. For the size you want to do, the slides won't be that expensive if you ebay them, New, they are very expensive. You can use skate bearings and get by with them, that's how my machine started and I still have some slides using them and they work, but are not nearly as smooth or accurate as linear slides/bearings. You will need two rails per axis and probably 4 bearing blocks per axis. I am currently in the middle of some other big projects, A 4th of July fireworks display (controlled with a prop) and a RC Flying club that I'm building a database for and using the CNC to cut out all of the awards plaques for an upcoming show.
The CNC is pretty dirty right now, I was milling some aluminum with it recently so it has metal shavings all over the place but I suppose I can clean it up for you, maybe even post a video of it cutting a sample pcb.
Don't expect this to be a weekend project if you want to do it correctly [noparse]:)[/noparse]
Here are the pics of the machine.·· I couldn't find my 1/8" collet adapter to use the PCB engraving bit with it right now so I'll have to turn another one and then do a video of it later.
That's a pretty awesome CNC milling machine... It's almost exactly what I had in mind. I did notice that the entire top part of yours on which the X and Z axes are mounted moves to make the Y axis. Do you think that your setup for the Y axis is better than one where the stepper is on the side or back and moves the milling plane back and forth to make the Y axis?
What steppers did you use? I've been browsing for some steppers and don't know what I should be looking for when it comes to precision and quality...
Also, is that first picture the CNC part? Could you get a close-up photo if possible?
Sorry for all the questions, but I'd like to get this project going soon... I will have time over spring break to work on it, and would like to have everything planned out by then.
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The first picture is the Stepper drivers that I purchased from Kelinginc.net.· They have all kinds of good CNC stuff over there.· The drivers I purchased from them are rated at 60v and 5A running at about 50v on two of them and 30v on the other two.· I need to upgrade the second power supply to a higher voltage to match the first one.· The two X axis steppers are running at 50v with around 300 in/oz torque turning 1/2 10tpi ACME screws at a resolution of 4000 steps/inch or an accuracy of about 1/4000th of an inch.· Actual accuracy I would put closer to 1/1000th of an inch because of a small amount of backlash in the lead screws.· I'm ok with that resolution for what I'm doing. [noparse]:)[/noparse]
The reason I went with moving the Gantry over moving the work surface was because of the size of the machine.· To me it was easier to have a constant weight of the gantry being moved around vs a changing weight of a bed with whatever I was going to mill.·· I think it takes up less room this way too.· I have considered making a modification to the table to have a conveyer and rack & pinion system for doing longer boards.·
I have thought about making a smaller one just for PCB's and small engraving, but there never seems to be enough time.· A small 12"x12" I would probably go with a moving bed instead of the moving gantry.
I forget what steppers I have, but I believe they are rated at 300 in/oz for torque and are a major improvement from the original ones I started with.· With the current setup, my Z axis can lift about 80lbs at 80 inches per minute (IPM).
The highest speed I run each axis is about 60 IPM for rapids and cutting speed is around 30-40 IPM.·· I have topped the Y axis out at just over 200 IPM but there is virtually no torque at that speed.·
I have some new rotary encoders that I need to attach to the steppers this summer sometime when I get a chance that will make it a lot more accurate, but for what you are doing encoders really aren't necessary as long as you don't push the speed too high.·· With steppers, the faster you turn them, the less torque they have.· If I dropped my Z axis down to 10 IPM, I would guess the lifting capacity to be 400lbs or more.·
Oh yeah, the Y and Z axis are the ones that are mounted on the X axis.· The X axis currently has two steppers that are sync'd in the software to move each side of the gantry.· I have probably close to $1500 into this setup, but that was also a good $500 in wasted materials and the learning curve factor.·· A good chunk of that was the electronics.· The 4 stepper motors I picked up for $125 total,· the drivers and power supply were around $300 and there is probably another $100 or so in misc parts.·
The mechanical part took up probably another $500 and the rest of the expense was for parts that I either burned out or weren't strong enough or were just too cheap to begin with.
I also prefer working with aluminum over steel or wood because it doesn't rust or rot, is a lot lighter then steel and stiffer then wood and is a hell of a lot easier to machine new parts out of aluminum.
If my penny stocks I'm invested in (GOIG) ever take off like we are expecting I'll be putting up a new shop for all of my projects.·· My next CNC project is going to be a large format CNC Plasma cutter for my brother.· We plan on having a working area of 5'x12' but getting into that size poses a lot more challenges on maintaining stiffness and a heck of a lot more weight to deal with too so we need bigger steppers, supported linear bearings and a different drive system.· Screws just won't work for that distance, it has to be a rack & pinion or possibly a chain drive.
I took some more close up pics for ya to check out,· let me know what other questions you have.
On that page, there's something called an "ironless linear motor coil" that looks suspiciously like exactly what I need... Would it work if I wanted to spend $180 for the X and Y axes, and just use a stepper for the Z axis?
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If all you are going to do is a small scale PCB router and maybe some engraving, you don't need nearly the power I have in my steppers, I wanted to be able to push these with a ton of torque over a large area so I went with pretty beefy motors. The first ones I started using were from ebay at a cost of $25/4 of them and they worked ok, but I was using cheap drivers and trying to push too much weight at too high of speed and got frustrated. I didn't see the ironless linear motor coil you were talking about. What size of work are were you looking at again?
They are fairly hefty motors, and they cost me a total of $20. They include mounting holes and everything...
I am wondering whether there is an easy way to test my steppers to make sure they work properly. I did get them at a huge electronics "junkyard" so to speak, and (although I have purchased from them before with great results) I wanted to make sure they worked, and didn't have any bad coils. Is there a "simple stepper motor tester" circuit I can build to test them?
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Check the resistance of the coils. If that looks OK and they turn freely there can't be much wrong with them. If you have a scope you should be able to get a signal from them by rotating the shaft with your fingers.
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It looks OK, but the thing I am worried about is the fact that after a while, the shaft sometimes doesn't turn as easily, and gets huge torque. I noticed this on three of them so far...
I am not sure if this will be a problem though, because it does not happen often, and it does not completely jam the stepper motor, but it is why I want to get a good tester set up this evening once I'm done with more schoolwork.
If I need to get different steppers, I can just go back to the "junkyard" I got them at and get a bunch more.
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Also, my goal for accuracy is to be able to mill boards for use with a tsop package: http://weilei.ru/rys/tsop56.jpg I'm not sure if that is possible, but since this is pretty much just for PCB's (although I had to tell my dad that it can be a 3D printer in order for him to take me to get the steppers) it is my target accuracy level.
What would be needed to get this sort of accuracy? I know I would have to get really good bearings; is there anything else?
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When you spin the motor by hand, make sure none of the wires are touching.· If the correct ones touch each other, the motor acts like a shorted out generator ;-)
Chris
Vaati said...
It looks OK, but the thing I am worried about is the fact that after a while, the shaft sometimes doesn't turn as easily, and gets huge torque. I noticed this on three of them so far...
I am not sure if this will be a problem though, because it does not happen often, and it does not completely jam the stepper motor, but it is why I want to get a good tester set up this evening once I'm done with more schoolwork.
If I need to get different steppers, I can just go back to the "junkyard" I got them at and get a bunch more.
Most everything contributes in one way or another to the overall accuracy of the machine.· If the way system has slop, the resulting cut will have slop. If the lead screw is not accurate or has backlash, this too will show up in the cut.· If the spindle has runout, the cut width will be larger than the tool diameter - sometimes substantially more.· Remember, just because a machine is controlled by a computer does NOT automatically make it accurate.· The mechanics are just as important, if not more important than the controlling electronics and software.
Chris
Vaati said...
Also, my goal for accuracy is to be able to mill boards for use with a tsop package: http://weilei.ru/rys/tsop56.jpg I'm not sure if that is possible, but since this is pretty much just for PCB's (although I had to tell my dad that it can be a 3D printer in order for him to take me to get the steppers) it is my target accuracy level.
What would be needed to get this sort of accuracy? I know I would have to get really good bearings; is there anything else?
Hey--thanks for the tip on the steppers acting like shorted out generators--I think that was what was going on. At any rate, I am getting some ancient power transistors out to use the stepper motors on my basic stamp 2. I just need to find datasheets...
I always knew that the computer didn't make it accurate. The overall quality of the milling machine will influence the accuracy.
I'm on my way to making a milling machine!
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This should be an interesting project for you. I have decided to try and make a laser cutter myself to make PCB by mounting a laser cutting diode to my printer. Only problem is my new printer is in the mail at the moment and propmodule.com is currently $750 in debt so I can't buy the laser diode. [noparse]:([/noparse] oh well will just have to keep reading.
Mwahahahaha.... I have successfully rigged up a tiny circuit on a mini breadboard that utilizes 4 switches, a 5 volt regulator, and my 2.1mm to breadboard adapter, and I have made a stepper motor move! Now all I have to do is convert that circuit to the BS2...
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Could I use that chip to drive the steppers as opposed to using something like a uln2003a? Since I have the intersil chips on hand, it would be great if I could use them...
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I was finally able to spare some time for this project.
I ordered some ULN2003A darlington transistor arrays, and got my stepper motor to continuously turn using the BS2. For the connections, I just followed the diagram here:
except I only used the darlingon IC and did not include that transistor/resistor section.
The stepper motor runs fairly well; however, I noticed that I am not getting much torque when it's moving. For example, I could pinch it with my fingers very lightly and it wouldn't turn. It's a fair-sized stepper as well, rated at 6 volts 1.2 amps with 2 phases.
Is there a way I can increase the torque? I'm not familiar with steppers, and I don't have very much free time to experiment. I'm attaching a picture of the stepper and the BS2 code I was running.
Thanks.
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So are those values on the motor label the maximum voltage and current levels, or the normal levels?
I don't think I am putting that much current into my steppers, so that may be why it doesn't have very much torque.
Is there any other way to increase the torque?
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You can get higher torque by increasing the voltage and limiting the current to the stepper. I have seen 5V steppers run from as much as 36V for a brief time for the start of each step.
kwinn is quite correct. You can run these motors at much higher voltages than what the label says and it greatly increases their performance and torque. As kwinn has stated, the key is having something that limits the current. There are different ways to do this, however, so it's important to do a little homework.
One way to get the most torque is to run the motor in bipolar mode rather than unipolar mode. I think your type of motor can do that, though I'm not 100% sure. If it came with a wiring diagram, it will probably say.
I recently built a stepper motor controller using a chip, L6208. I had no idea what I was doing but just shamelessly followed the instructions in their data sheet and now I've got a bipolar stepper controller that works MUCH better than the simpler circuits of ULN2003N, etc. In fact, to test the limitations of your ULN2003N, try cranking up the speed. I'm guessing the motor probably will start freaking out before it gets up to its rated speed. Using the L6208, on the other hand, I've been able to get the motor up to the rated value. I've been using a Vexta, too.
I went with this L6208 because it happened to come in a DIP (powerdip24) version that I could solder with my limited skills. And I've not been exceeding 2 amps on the motor. I think your Vexta would be a good candidate for this chip or a chip similar to it. See the aforementioned forum link for the opinions of other forum members.
Ohhhhh, I get to contribute something to someone else again finally [noparse]:)[/noparse] .
Yes, both Kwinn and Electric Aye are correct, in fact you are going to get really poor performance and torque out of your steppers if you follow what they are rated at for voltage. I forget what my steppers are rated for on voltage, never really cared either, but one set on mine I am giving about 30 volts to and they draw about 1.5a each. The other set for my X axis pair I am pushing between 48v and 50v and the amp draw is around 2a each stepper.
I've never had trouble with the motors drawing too many amps, it's alweays been a problem on the other side, getting stepper drivers that would allow high enough amps and voltage through.
One of the biggest performance enhancers (torque and speed) that I purchased was the high voltage power supplies and high quality stepper drivers. For what you are doing, I would suggest saving the money up and going with an ebay package with either a 3 axis or 4 axis all in one unit. You can get a good deal on them for under $100 these days with a parallel port breakout board and everything.
For your lead screws, a lot of people use standard all thread rod. While this is a simple and cost effective solution, which I used to begin with, you will notice quickly that they develope backlash rather quickly and for PCB's that's a big no no.
Another thing with steppers, with high voltage and decent current, the slower they are, the more torque they have. So if you are able to bump up the voltage to 24v or more, you should get a lot of torque.
Comments
I started a DIY CNC project last year for basically the same reason and since then it has morphed into a 36"x30" cutting beast. I can mill aluminum, PCB's, wood, plastic. I've used it to drill the PCB's and recently had it cut the traces for some test boards. This was all DIY and mine is all aluminum. I recently upgraded my bearings, and have a new set of bearings and need some rods to take it up to a full 36"x48" cutting area.
Your most expensive part is going to be the linear slides. From experience USE GOOD SLIDES!. For what you are doing, you can eBay the a 3 or 4 axis stepper driver for under $80 shipped, with the breakout board you'll need.
For my spindle, I started with a rotozip, which lasted way longer then I thought it would, probably 400+ hours of cutting time, I have since switched to a larger variable speed router with a 1/2" spindle so it can handle the aluminum machining.
For a DIY, your lead screws can be acme screws, I get mine from www.use-enco.com, they are about the best price and you can get delrin from a local plastics place if you can find one for the nuts. I used a scrap piece of ACME rod and turned it on a lathe and cut some slots in it for a DIY ACME tap. I have both 3/8" and 1/2" tap sizes now that come in very handy.
Let me know if you need help from a guy who went through exactly what you are trying to do.
If you could, post some pictures of your milling machine and one of it in action. I would love to see what it looks like and how it's designed...
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The CNC is pretty dirty right now, I was milling some aluminum with it recently so it has metal shavings all over the place but I suppose I can clean it up for you, maybe even post a video of it cutting a sample pcb.
Don't expect this to be a weekend project if you want to do it correctly [noparse]:)[/noparse]
What steppers did you use? I've been browsing for some steppers and don't know what I should be looking for when it comes to precision and quality...
Also, is that first picture the CNC part? Could you get a close-up photo if possible?
Sorry for all the questions, but I'd like to get this project going soon... I will have time over spring break to work on it, and would like to have everything planned out by then.
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The reason I went with moving the Gantry over moving the work surface was because of the size of the machine.· To me it was easier to have a constant weight of the gantry being moved around vs a changing weight of a bed with whatever I was going to mill.·· I think it takes up less room this way too.· I have considered making a modification to the table to have a conveyer and rack & pinion system for doing longer boards.·
I have thought about making a smaller one just for PCB's and small engraving, but there never seems to be enough time.· A small 12"x12" I would probably go with a moving bed instead of the moving gantry.
I forget what steppers I have, but I believe they are rated at 300 in/oz for torque and are a major improvement from the original ones I started with.· With the current setup, my Z axis can lift about 80lbs at 80 inches per minute (IPM).
The highest speed I run each axis is about 60 IPM for rapids and cutting speed is around 30-40 IPM.·· I have topped the Y axis out at just over 200 IPM but there is virtually no torque at that speed.·
I have some new rotary encoders that I need to attach to the steppers this summer sometime when I get a chance that will make it a lot more accurate, but for what you are doing encoders really aren't necessary as long as you don't push the speed too high.·· With steppers, the faster you turn them, the less torque they have.· If I dropped my Z axis down to 10 IPM, I would guess the lifting capacity to be 400lbs or more.·
Oh yeah, the Y and Z axis are the ones that are mounted on the X axis.· The X axis currently has two steppers that are sync'd in the software to move each side of the gantry.· I have probably close to $1500 into this setup, but that was also a good $500 in wasted materials and the learning curve factor.·· A good chunk of that was the electronics.· The 4 stepper motors I picked up for $125 total,· the drivers and power supply were around $300 and there is probably another $100 or so in misc parts.·
The mechanical part took up probably another $500 and the rest of the expense was for parts that I either burned out or weren't strong enough or were just too cheap to begin with.
I also prefer working with aluminum over steel or wood because it doesn't rust or rot, is a lot lighter then steel and stiffer then wood and is a hell of a lot easier to machine new parts out of aluminum.
If my penny stocks I'm invested in (GOIG) ever take off like we are expecting I'll be putting up a new shop for all of my projects.·· My next CNC project is going to be a large format CNC Plasma cutter for my brother.· We plan on having a working area of 5'x12' but getting into that size poses a lot more challenges on maintaining stiffness and a heck of a lot more weight to deal with too so we need bigger steppers, supported linear bearings and a different drive system.· Screws just won't work for that distance, it has to be a rack & pinion or possibly a chain drive.
I took some more close up pics for ya to check out,· let me know what other questions you have.
I am probably not going to make mine as complex and powerful as yours, but I am concerned about the steppers. I did find a site with a bunch of steppers for low prices, but I have no clue what to get:
http://www.allelectronics.com/make-a-store/category/400600/Motors/Stepper-Motors/1.html
On that page, there's something called an "ironless linear motor coil" that looks suspiciously like exactly what I need... Would it work if I wanted to spend $180 for the X and Y axes, and just use a stepper for the Z axis?
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- 2-phase
- 6 volt
- 1.2 amp
- 1.8 degree step
- 6 wire
They are fairly hefty motors, and they cost me a total of $20.
I am wondering whether there is an easy way to test my steppers to make sure they work properly. I did get them at a huge electronics "junkyard" so to speak, and (although I have purchased from them before with great results) I wanted to make sure they worked, and didn't have any bad coils. Is there a "simple stepper motor tester" circuit I can build to test them?
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Leon Heller
Amateur radio callsign: G1HSM
I am not sure if this will be a problem though, because it does not happen often, and it does not completely jam the stepper motor, but it is why I want to get a good tester set up this evening once I'm done with more schoolwork.
If I need to get different steppers, I can just go back to the "junkyard" I got them at and get a bunch more.
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MCU Projects·- my new site where I will be posting all projects, code, etc.
Quit buying all those fixed voltage regulators, and·get an Adjustable Power Supply·for your projects!· Includes an LED testing terminal!
SD Card Adapter·- Add extra memory to your next Propeller project with ease!
What would be needed to get this sort of accuracy? I know I would have to get really good bearings; is there anything else?
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
MCU Projects·- my new site where I will be posting all projects, code, etc.
Quit buying all those fixed voltage regulators, and·get an Adjustable Power Supply·for your projects!· Includes an LED testing terminal!
SD Card Adapter·- Add extra memory to your next Propeller project with ease!
When you spin the motor by hand, make sure none of the wires are touching.· If the correct ones touch each other, the motor acts like a shorted out generator ;-)
Chris
Most everything contributes in one way or another to the overall accuracy of the machine.· If the way system has slop, the resulting cut will have slop. If the lead screw is not accurate or has backlash, this too will show up in the cut.· If the spindle has runout, the cut width will be larger than the tool diameter - sometimes substantially more.· Remember, just because a machine is controlled by a computer does NOT automatically make it accurate.· The mechanics are just as important, if not more important than the controlling electronics and software.
Chris
I always knew that the computer didn't make it accurate. The overall quality of the milling machine will influence the accuracy.
I'm on my way to making a milling machine!
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MCU Projects·- my new site where I will be posting all projects, code, etc.
Quit buying all those fixed voltage regulators, and·get an Adjustable Power Supply·for your projects!· Includes an LED testing terminal!
SD Card Adapter·- Add extra memory to your next Propeller project with ease!
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MCU Projects·- my new site where I will be posting all projects, code, etc.
Quit buying all those fixed voltage regulators, and·get an Adjustable Power Supply·for your projects!· Includes an LED testing terminal!
SD Card Adapter·- Add extra memory to your next Propeller project with ease!
http://www.intersil.com/data/fn/fn481.pdf
Could I use that chip to drive the steppers as opposed to using something like a uln2003a? Since I have the intersil chips on hand, it would be great if I could use them...
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MCU Projects·- my new site where I will be posting all projects, code, etc.
Quit buying all those fixed voltage regulators, and·get an Adjustable Power Supply·for your projects!· Includes an LED testing terminal!
SD Card Adapter·- Add extra memory to your next Propeller project with ease!
I ordered some ULN2003A darlington transistor arrays, and got my stepper motor to continuously turn using the BS2. For the connections, I just followed the diagram here:
http://www.electrical-res.com/EX/10-19-15/unipolar_stepper_big.gif
except I only used the darlingon IC and did not include that transistor/resistor section.
The stepper motor runs fairly well; however, I noticed that I am not getting much torque when it's moving. For example, I could pinch it with my fingers very lightly and it wouldn't turn. It's a fair-sized stepper as well, rated at 6 volts 1.2 amps with 2 phases.
Is there a way I can increase the torque? I'm not familiar with steppers, and I don't have very much free time to experiment. I'm attaching a picture of the stepper and the BS2 code I was running.
Thanks.
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MCU Projects·- my new site where I will be posting all projects, code, etc.
Quit buying all those fixed voltage regulators, and·get an Adjustable Power Supply·for your projects!· Includes an LED testing terminal!
SD Card Adapter·- Add extra memory to your next Propeller project with ease!
7.2W/745.699872=0.00965 Horse Power.
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Lots of propeller based products in stock at affordable prices.
propmodule.com will be closed May 1-10th. Orders made in that time will be shipped on the 11th.
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MCU Projects·- my new site where I will be posting all projects, code, etc.
Quit buying all those fixed voltage regulators, and·get an Adjustable Power Supply·for your projects!· Includes an LED testing terminal!
SD Card Adapter·- Add extra memory to your next Propeller project with ease!
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Lots of propeller based products in stock at affordable prices.
propmodule.com will be closed May 1-10th. Orders made in that time will be shipped on the 11th.
I don't think I am putting that much current into my steppers, so that may be why it doesn't have very much torque.
Is there any other way to increase the torque?
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MCU Projects·- my new site where I will be posting all projects, code, etc.
Quit buying all those fixed voltage regulators, and·get an Adjustable Power Supply·for your projects!· Includes an LED testing terminal!
SD Card Adapter·- Add extra memory to your next Propeller project with ease!
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Lots of propeller based products in stock at affordable prices.
propmodule.com will be closed May 1-10th. Orders made in that time will be shipped on the 11th.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
MCU Projects·- my new site where I will be posting all projects, code, etc.
Quit buying all those fixed voltage regulators, and·get an Adjustable Power Supply·for your projects!· Includes an LED testing terminal!
SD Card Adapter·- Add extra memory to your next Propeller project with ease!
kwinn is quite correct. You can run these motors at much higher voltages than what the label says and it greatly increases their performance and torque. As kwinn has stated, the key is having something that limits the current. There are different ways to do this, however, so it's important to do a little homework.
One way to get the most torque is to run the motor in bipolar mode rather than unipolar mode. I think your type of motor can do that, though I'm not 100% sure. If it came with a wiring diagram, it will probably say.
For a little recent discussion about stepper motor control with the Propeller, you might check out this:
http://forums.parallax.com/showthread.php?p=886539
Here is a link that helps explain the different kinds of stepper motor controllers:
dkc1.digikey.com/us/en/tod/STMicroelectronics/StepperFundamentals_NoAudio/Stepper_Fundamentals_NoAudio.swf
I recently built a stepper motor controller using a chip, L6208. I had no idea what I was doing but just shamelessly followed the instructions in their data sheet and now I've got a bipolar stepper controller that works MUCH better than the simpler circuits of ULN2003N, etc. In fact, to test the limitations of your ULN2003N, try cranking up the speed. I'm guessing the motor probably will start freaking out before it gets up to its rated speed. Using the L6208, on the other hand, I've been able to get the motor up to the rated value. I've been using a Vexta, too.
I went with this L6208 because it happened to come in a DIP (powerdip24) version that I could solder with my limited skills. And I've not been exceeding 2 amps on the motor. I think your Vexta would be a good candidate for this chip or a chip similar to it. See the aforementioned forum link for the opinions of other forum members.
The data sheets for the L6208 are here:
www.st.com/stonline/products/literature/ds/7514.pdf
www.st.com/stonline/books/pdf/docs/8607.pdf
BTW. the Propeller is able to control multiples of these L6208 chips, allowing you to operate numerous devices at once.
hope that helps,
Mark
Post Edited (ElectricAye) : 5/1/2010 2:57:41 AM GMT
Yes, both Kwinn and Electric Aye are correct, in fact you are going to get really poor performance and torque out of your steppers if you follow what they are rated at for voltage. I forget what my steppers are rated for on voltage, never really cared either, but one set on mine I am giving about 30 volts to and they draw about 1.5a each. The other set for my X axis pair I am pushing between 48v and 50v and the amp draw is around 2a each stepper.
I've never had trouble with the motors drawing too many amps, it's alweays been a problem on the other side, getting stepper drivers that would allow high enough amps and voltage through.
One of the biggest performance enhancers (torque and speed) that I purchased was the high voltage power supplies and high quality stepper drivers. For what you are doing, I would suggest saving the money up and going with an ebay package with either a 3 axis or 4 axis all in one unit. You can get a good deal on them for under $100 these days with a parallel port breakout board and everything.
For your lead screws, a lot of people use standard all thread rod. While this is a simple and cost effective solution, which I used to begin with, you will notice quickly that they develope backlash rather quickly and for PCB's that's a big no no.
Another thing with steppers, with high voltage and decent current, the slower they are, the more torque they have. So if you are able to bump up the voltage to 24v or more, you should get a lot of torque.
PM me if you have questions and don't hear back.
I will be able to work on this a lot more in June.
Thanks.
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MCU Projects·- my new site where I will be posting all projects, code, etc.
Quit buying all those fixed voltage regulators, and·get an Adjustable Power Supply·for your projects!· Includes an LED testing terminal!
SD Card Adapter·- Add extra memory to your next Propeller project with ease!