I will even go one step further, buy several G251 drives and a power supply that will output 47<>50VDC when hooked up to your local power company. And purchase motors with a rating in the ballpark of 4.5 volts.
Approximately $350 investment including some accessories, but not including motors.
I have been looking very occasionally at the reprap site, waiting for them to improve the machine "sufficiently" for me to maybe build one, but if this project takes off, I would like to build one myself.
A couple of posters have said they like the machine in post #46 and I do too, so I was wondering, does anyone know what that aluminium channel stuff is called?, so I can buy some.
With 8 cogs, shouldn't one prop be capable of controlling the machine, leaving the more complex work to be done by a PC?
does anyone know what that aluminium channel stuff is called?
I will assume that you are talking about the aluminum extrusion. If that is the case, some people call it T-Slot. The link below will take you to a T-Slot manufacturer and distributor.
Well, I certainly would not think I know enough about the subject, that's why I'm still investigating. Sure, I can buy the drives, but that would not satisfy my curiosity and desire to fully understand the issues. I can only achieve that by studying the motor and electronic interactions more. And on top of that, I expect to be offering my bench-top CNC for sale to the high-end hobby and very light commercial market in respectable quantities, so making my own drives probably makes sense.
I wasn't referring to you when I suggested buying the drives, I think your approach seems sensible enough for you.
But for those wanting to get printing/routing you can really simplify matters by using commercial drives and I suspect for little if any extra cost (for a single set).
Geckodrives are great but overkill for many applications, you can run some really big motors on them. Desktop stuff really doesn't need them.
I make my own power supplies normally, simple unregulated linear affairs. A toroidal transformer, rectifier and smoothing caps, on occasion a soft start too.
posts 110, 114, and 122 are critical information, yes?
We have a couple investigation going in parallel, yes?
Is this correct:
Power supply must be correctly sized to meet the expected load.
Correct power supply size is a function of the number and rating of motor.
Stepper motors are rated at minimum voltage, but are typically operated at 5x to 10x the rated minimum voltage.
The stepper motor current must be carefully controlled, DC can burn the motor
The prop can be made to control the motor with added custom circuitry,but off the self stepper motor driver might be an option with more consistent behavior.
We are looking at exploration of different size and capability for these printers. One route is looking at 24"x24" foot print, another is 7x7 (or does the 7x7 mean working area of the bed, and it still has the 24"x24" desktop foot print?)
There are many options for motors, the selected motors will be a major factor in the machine's final capability. NEMA 24 and NEMA 17 are discussed so far, can we determine what the influence on the max capability of the machine based on the motor spec? (For example motor with x1 ratings will be suitable for material no harder than Styrofoam or balsa wood; motor with x2 rating would be the minimum required for cutting aluminum)
Can we estimate anything about the appropriateness of a set of materials for a given size of machine? For example, if one decides one a 24"x24" machine, plastic would be too floppy for cutting, but for a 7x7 machine, plastic construction might be suitable for cutting x material?
I'm assuming that printing (plastic extrusion) would be reasonable on any machine capable of cutting? I'm still looking at the possibility of interchangeable cutting and printing heads.
Quick question: Do you think an I2C I/O expander (can maybe cycle a pin at 10 kHz) is fast enough to control a CNC machine?
There's a parallel port controller for the Zen machine that I'd like to connect to a PCA9554.
I could connect directly to Prop if I had to, but I'd like to use my PropBox PCB with TV/VGA/KB/Mouse/Network/SD and only have a limited number of pins left after all that...
(My feeling is that maybe the motors are so slow that the PCA9554 is more than fast enough, I don't have any experience.)
One more question: What do you guage the chances of using the 7"x7" Zen as a pick and place machine? I was thinking about making special trays for all the parts, so the machine would know where they are... I think the work area would be enough to 3.8"x2.5" PCB...
The idea is that I'd fill the trays with the parts by hand and then the machine would put them where they go...
@prof_braino - Yes it is critical information. Without properly sized motors, you will never push the load, and without a properly sized power supply or properly sized drivers, your motors will never reach their full potential.
I don't give advice to be a know it all. I learned a lot of hard lessons in building my CNC machines and I am just trying to teach others what I learned.
Main Lesson:
Buy good motors, a good power supply, and good drivers. That is the best advice I can give to anyone building a CNC machine.
P.S. - Think of these three purchases as an investment.
For pick and place it will certainly work but is far from optimised as it won't be very fast. I've seen a few people do this sort of thing and for small runs or for fun it can work well. This is in the context of hobby level machines. The best bet is to make nice mounts for taped components, don't try and make feeders just mount the tape flat in a holder and remove the covering film, the machine then just goes to each in turn. Some bench top machines alternatively use the head itself as an actuator to advance tape from a simple feeder.
Can we estimate anything about the appropriateness of a set of materials for a given size of machine? For example, if one decides one a 24"x24" machine, plastic would be too floppy for cutting, but for a 7x7 machine, plastic construction might be suitable for cutting x material?
I'd say aluminium is probably the material of choice in most instances, strong enough but not too tough to work with, the only reason that other materials tend to be used in these machines is for ease of machining and cost, if you only have hand tools it can be tough to work with metal. Generally smaller machines will cope better with slightly less rigid materials, and as people end up working with stock sheet thicknesses, as the machine is scaled down it will tend to become more stocky and stiff.
...critical information...properly sized motors...power supplydrivers
Main Lesson: Buy good --- Think of these three purchases as an investment.
How shall we quantify "good"? This is the absolute critical step in the research phase. Some folks are tending towards smaller cheaper, less capable equipment sized only for pick and place on a very small machine, (and maybe optimize speed); other others want to "over engineer" and explore the possibility of machine hardwe materials with possibly higher precision.
@pjv: In post #126, what kind of investigation do you have in mind? How can we contribute to this? I found my box of four (small) stepper motors (no clue about them except they are still in the box from xmas 2005) what kind of testing would contribute data points?
Since I already have motors (for free), I was thinking about getting oversize drivers so I can upgrade they motors when these prove insufficient. I like the sound of "gokodrives--overkill". Is there a particular gekodrive to recommend that we look at to start?
Among all of the bipolar stepper motors from all sources (Vexta, Minebea and random Chinese), I have had there has never seen a "bad" one so I guess they must all have been "good". Pjv is referring into is investigations in to stepper drives not stepper motors. There really is no issue, just choose the appropriate torque for your requirements or choose based on what others have proven to work. To really choose a stepper motor in a rigorous way requires quite a lot of information, a little overkill is fine and does not normally cost much on the motor side.
By thinking of the forementioned parts as investments, you will always have the ability to change your mind or design without rebuying these parts. Suppose you build a 3D printer, and over the years you have found that you rarely use this machine, and would much rather have a milling machine or router. You can easily salvage your existing parts to make that mill or router.
The Gecko G250 and G251 have mosfets rated at 7 amps, but the actual drivers are only rated for 3.5 amps. When you start talking about size NEMA 23 motors, wired in bipolar fashion, it is not uncommon to have a motor that will draw close to 3 amps of current.
"GOOD MOTORS"
First off, look at the overall appearance of the motor, pieces of junk can be seen at a glance. If it looks like junk, it is probably junk. On the outside, look for good machining, good castings, good screws, well machined shafts, etc...
Another consideration should be size. NEMA 17 motors are nice for moving light loads, but for an overall good motor, I would seriously consider NEMA 23 size. Of course there are exceptions, you can gain mechanical advantage from your motors through the use of screws (lead screws), gear trains, wedges, levers, pulleys, etc.....
All stepper motors are not created equal! Consider some of the main components, such as:
wire and insulation
bearings
magnets
shafts
I would seriously consider buying a brand name with a good reputation. Graham mentioned a few, but there are also a few others, so do your research.
As Graham said, it will affect your wallet, and some people are on a budget, but for those that can afford it, I stand by my advice.
"POWER SUPPLIES"
Power supplies are not that complicated, you can easily make one with the right parts. However, be certain that whatever power supply you use does not exceed the input voltage of the drives. If thirty people had identical power supplies, but lived in different parts of the country or world, that same power supply would most likely have thirty different output voltages. Be aware and be forewarned!
The Gecko G250 and G251 have mofsets rated at 7 amps, but the actual drivers are only rated for 3.5 amps.
From gecko's site: "The motor’s rated phase current must be between 0 Amps and 7 Amps" they also show that for 7A you don't need a current setting resistor (left open circuit), looks like they drive 7A to me. Given the machines I've seen them on with Nema 34 I feel sure they must be.
I think it is far more likely that in the future you fancy building yet another machine, you then end up buying more drivers and leave the oversized ones where they are or have to mess around swapping them. Want to upgrade? Sell the machine complete with the cheap drives. There is no right answer on this but you are buying stepper drivers not family air looms, besides you might decide to go to servos for the beast of a machine that eventually takes your fancy. Personal choice.
Of course some motors are better than others but if the spec matches what you require then everything should be fine. The Chinese no name motors work fine, I'm not running them 24/7 in production and they will probably out live me. You should choose parts that match your requirements and budget, no need to mount THK rails on your kitchen drawers even if they would last longer than stock runners
I'd agree that Nema 23 is probably about right for all but the smallest machines and even some of them, go for bipolar and make sure they are 200 step as you do get a few weird and wonderful ones. The square types are supposed to be better than the older round types but I've used both with no problems. Double ended motors are useful as you can add dampers, don't worry about hand wheels as you will probably never use them.
Sorry Bruce, mine are 201's which have a rating of 7A. I didn't notice they had started doing baby ones (assumed they were pulse multipliers or something out of the corner of my eye).
The G201's are a nice drive for larger motors, such as the NEMA 34 as you stated. In my case, I use NEMA 23, so my largest current draw was 2.86A, so I naturally opted for the G251's.
I noticed they have a 3D printer kit on their website that is cheaper than the regular 7x7 kit + 3D printer adapter kit.
Think I've decided I need a 4-channel stepper motor driver though because the "stepstruder" uses a stepper motor too.
I found a 4-channel TB6560 based driver board on Ebay for $70.
Also thinking I can do a good job with 5 Prop pins plus a PCA9554 (one for clock on each axis plus one for interrupt of the PCA9554).
Ray: Weren't you looking at a RepRap? If so, then the Prusa Mendel looks to be a much improved (and simpler) version of the Mendel. If so, then the Nema17's are fine (20oz OK but 70oz aren't much dearer). Pololu have Allegro driver pcbs $13ea using A4983 IIRC, and also Nema motors. Use a stepper for the extruder - the extruder is the main problem in the reprap project. A heated apparently helps, but that can come later.
I dragged out my stepper motors: Rapidsyn Industrial Santa Fe Springs, I could not locate a site for the company, but found a couple mentions on surplus sites.
Model 23D-6124A
Rated Voltage 24VDC
Rates Current 1.0A/0
Also has two unlabeled numbers 8009 and 504-0005
It has four wires, blue, white with blue, black, white with black.
The thing that looks odd to me is the 24VDC rating, earlier it was stated that the motors should be in the 4.5 volt range, is this a problem?
Rapidsyn are a well known brand but you might consider selling them and buying something with a lower voltage rating, at 50v you only have just over twice the rated voltage and at 80v you might struggle to find appropriate drives (only the larger geckos do 80v). Having said that they might work fine for your application but it will depend on how much effort and money it takes to work around them.
Rayman,
Hopefully we can come up with some really nice propeller based motion control code between us, using the I2C expander might prevent you from capitalising on it. My code for example which at the moment is single axis (or multiple unsynced) uses the counters to get really high performance and smooth accelerations but needs to output on pins directly. It is just something I thought you should consider. A half way house would be to use the expander for the direction pins only, they change at much lower frequencies. This is my code in action BTW:
FYI it is a Vexta Nema23 motor about 2.4v and 1A/phase, run at 26v with a 2mm lead on the screw (trapizoidal anti-backlash), no idea about the microstepping, probably 8X.
I am using a modified version of the PS-8N48, which outputs 800W 48VDC(nominal). Antek customized this power supply for me at no extra cost. The customization ensured that when I supplied local power to the power supply that it would not output more 49VDC. Basically they unwound one or two of the coils from the transformer. The Gecko G251's are rated for 50VDC, so the 49VDC output from the power supply was near but under the maximum G251 voltage specification. I doubt that you will need anywhere near 800 watts for your project, a good guide for NEMA 23 bipolar motors is approximately 100 watts per motor, but of course this all depends on the actual motor. I chose this power supply to achieve the near maximum voltage that my drive could handle and to be able to supply full power to eight motors.
A friend has an old Sorensen 80 volt 18 amps bench supply with dials for voltage and current, would this work?
It all depends on the output. First off, you must make sure that the voltage is being rectified, and outputing direct current, instead of alternating current. Providing that the output is DC voltage, you must also ensure that you can make adjustments that will allow you to calibrate the power supply voltage to under the drives specifications. Secondly, many adjustable power supplies are of the switch mode type. There are some switch mode power supplies that are suitable for stepper driving, however, most people prefer linear power supplies when it comes to driving stepper motors. You can always test and see how it performs.
I hope this was helpful information.
CORRECTION: able to supply full power to five motors
Comments
For affordable power supplies, I recommend this place:
http://www.antekinc.com/index.php
And the same goes for stepper drives!
Here is a link to a small, but powerful stepper drive
http://geckodrive.net/g251x-p-38.html?osCsid=e5d6d91dc2766d282a92c086b6801c70
I will even go one step further, buy several G251 drives and a power supply that will output 47<>50VDC when hooked up to your local power company. And purchase motors with a rating in the ballpark of 4.5 volts.
Approximately $350 investment including some accessories, but not including motors.
A couple of posters have said they like the machine in post #46 and I do too, so I was wondering, does anyone know what that aluminium channel stuff is called?, so I can buy some.
With 8 cogs, shouldn't one prop be capable of controlling the machine, leaving the more complex work to be done by a PC?
I am not sure what you mean by:
I will assume that you are talking about the aluminum extrusion. If that is the case, some people call it T-Slot. The link below will take you to a T-Slot manufacturer and distributor.
http://www.8020.net/Default.asp
Bruce
Well, I certainly would not think I know enough about the subject, that's why I'm still investigating. Sure, I can buy the drives, but that would not satisfy my curiosity and desire to fully understand the issues. I can only achieve that by studying the motor and electronic interactions more. And on top of that, I expect to be offering my bench-top CNC for sale to the high-end hobby and very light commercial market in respectable quantities, so making my own drives probably makes sense.
Lots more learning to do.
Cheers,
Peter (pjv)
I wasn't referring to you when I suggested buying the drives, I think your approach seems sensible enough for you.
But for those wanting to get printing/routing you can really simplify matters by using commercial drives and I suspect for little if any extra cost (for a single set).
Geckodrives are great but overkill for many applications, you can run some really big motors on them. Desktop stuff really doesn't need them.
I make my own power supplies normally, simple unregulated linear affairs. A toroidal transformer, rectifier and smoothing caps, on occasion a soft start too.
Graham
I think so, at least if an extensive gui is not required on the machine.
Graham
We have a couple investigation going in parallel, yes?
Is this correct:
Power supply must be correctly sized to meet the expected load.
Correct power supply size is a function of the number and rating of motor.
Stepper motors are rated at minimum voltage, but are typically operated at 5x to 10x the rated minimum voltage.
The stepper motor current must be carefully controlled, DC can burn the motor
The prop can be made to control the motor with added custom circuitry,but off the self stepper motor driver might be an option with more consistent behavior.
We are looking at exploration of different size and capability for these printers. One route is looking at 24"x24" foot print, another is 7x7 (or does the 7x7 mean working area of the bed, and it still has the 24"x24" desktop foot print?)
There are many options for motors, the selected motors will be a major factor in the machine's final capability. NEMA 24 and NEMA 17 are discussed so far, can we determine what the influence on the max capability of the machine based on the motor spec? (For example motor with x1 ratings will be suitable for material no harder than Styrofoam or balsa wood; motor with x2 rating would be the minimum required for cutting aluminum)
Can we estimate anything about the appropriateness of a set of materials for a given size of machine? For example, if one decides one a 24"x24" machine, plastic would be too floppy for cutting, but for a 7x7 machine, plastic construction might be suitable for cutting x material?
I'm assuming that printing (plastic extrusion) would be reasonable on any machine capable of cutting? I'm still looking at the possibility of interchangeable cutting and printing heads.
There's a parallel port controller for the Zen machine that I'd like to connect to a PCA9554.
I could connect directly to Prop if I had to, but I'd like to use my PropBox PCB with TV/VGA/KB/Mouse/Network/SD and only have a limited number of pins left after all that...
(My feeling is that maybe the motors are so slow that the PCA9554 is more than fast enough, I don't have any experience.)
The idea is that I'd fill the trays with the parts by hand and then the machine would put them where they go...
Yuo said
As You can see this Stepper Motor are specified to 12000 rps with Half step mode
Look at the graph again. The 12,000 is pulses per second, at 30 revs per second. However, that is probably what you meant to say.
Bruce
pps
Thanks idbruce
I don't give advice to be a know it all. I learned a lot of hard lessons in building my CNC machines and I am just trying to teach others what I learned.
Main Lesson:
P.S. - Think of these three purchases as an investment.
For pick and place it will certainly work but is far from optimised as it won't be very fast. I've seen a few people do this sort of thing and for small runs or for fun it can work well. This is in the context of hobby level machines. The best bet is to make nice mounts for taped components, don't try and make feeders just mount the tape flat in a holder and remove the covering film, the machine then just goes to each in turn. Some bench top machines alternatively use the head itself as an actuator to advance tape from a simple feeder.
https://www.manncorp.com/pick-and-place-bench-top/
Graham
I'd say aluminium is probably the material of choice in most instances, strong enough but not too tough to work with, the only reason that other materials tend to be used in these machines is for ease of machining and cost, if you only have hand tools it can be tough to work with metal. Generally smaller machines will cope better with slightly less rigid materials, and as people end up working with stock sheet thicknesses, as the machine is scaled down it will tend to become more stocky and stiff.
Graham
@pjv: In post #126, what kind of investigation do you have in mind? How can we contribute to this? I found my box of four (small) stepper motors (no clue about them except they are still in the box from xmas 2005) what kind of testing would contribute data points?
Since I already have motors (for free), I was thinking about getting oversize drivers so I can upgrade they motors when these prove insufficient. I like the sound of "gokodrives--overkill". Is there a particular gekodrive to recommend that we look at to start?
Geckodrives: http://www.geckodrive.com/
They are rated at 7A, that is a HUGE motor (they are nice but for a desktop machine you will never notice any difference outside of your wallet)
Graham
By thinking of the forementioned parts as investments, you will always have the ability to change your mind or design without rebuying these parts. Suppose you build a 3D printer, and over the years you have found that you rarely use this machine, and would much rather have a milling machine or router. You can easily salvage your existing parts to make that mill or router.
The Gecko G250 and G251 have mosfets rated at 7 amps, but the actual drivers are only rated for 3.5 amps. When you start talking about size NEMA 23 motors, wired in bipolar fashion, it is not uncommon to have a motor that will draw close to 3 amps of current.
"GOOD MOTORS"
Another consideration should be size. NEMA 17 motors are nice for moving light loads, but for an overall good motor, I would seriously consider NEMA 23 size. Of course there are exceptions, you can gain mechanical advantage from your motors through the use of screws (lead screws), gear trains, wedges, levers, pulleys, etc.....
All stepper motors are not created equal! Consider some of the main components, such as:
- wire and insulation
- bearings
- magnets
- shafts
I would seriously consider buying a brand name with a good reputation. Graham mentioned a few, but there are also a few others, so do your research.As Graham said, it will affect your wallet, and some people are on a budget, but for those that can afford it, I stand by my advice.
From gecko's site: "The motor’s rated phase current must be between 0 Amps and 7 Amps" they also show that for 7A you don't need a current setting resistor (left open circuit), looks like they drive 7A to me. Given the machines I've seen them on with Nema 34 I feel sure they must be.
I think it is far more likely that in the future you fancy building yet another machine, you then end up buying more drivers and leave the oversized ones where they are or have to mess around swapping them. Want to upgrade? Sell the machine complete with the cheap drives. There is no right answer on this but you are buying stepper drivers not family air looms, besides you might decide to go to servos for the beast of a machine that eventually takes your fancy. Personal choice.
Of course some motors are better than others but if the spec matches what you require then everything should be fine. The Chinese no name motors work fine, I'm not running them 24/7 in production and they will probably out live me. You should choose parts that match your requirements and budget, no need to mount THK rails on your kitchen drawers even if they would last longer than stock runners
I'd agree that Nema 23 is probably about right for all but the smallest machines and even some of them, go for bipolar and make sure they are 200 step as you do get a few weird and wonderful ones. The square types are supposed to be better than the older round types but I've used both with no problems. Double ended motors are useful as you can add dampers, don't worry about hand wheels as you will probably never use them.
Graham
You better visit Gecko again
And yes, I agree, get the 1.8 degree motors with 200 steps, this is absolutely critical.
I'm sorry, the mosfets are rated at 14 amps
Graham
The G201's are a nice drive for larger motors, such as the NEMA 34 as you stated. In my case, I use NEMA 23, so my largest current draw was 2.86A, so I naturally opted for the G251's.
Bruce
I noticed they have a 3D printer kit on their website that is cheaper than the regular 7x7 kit + 3D printer adapter kit.
Think I've decided I need a 4-channel stepper motor driver though because the "stepstruder" uses a stepper motor too.
I found a 4-channel TB6560 based driver board on Ebay for $70.
Also thinking I can do a good job with 5 Prop pins plus a PCA9554 (one for clock on each axis plus one for interrupt of the PCA9554).
Model 23D-6124A
Rated Voltage 24VDC
Rates Current 1.0A/0
Also has two unlabeled numbers 8009 and 504-0005
It has four wires, blue, white with blue, black, white with black.
The thing that looks odd to me is the 24VDC rating, earlier it was stated that the motors should be in the 4.5 volt range, is this a problem?
Peter (pjv)
I see this offering PS-5N50 has a single output at 50 volts and 10 amps. Is this the one you use?
A friend has an old Sorensen 80 volt 18 amps bench supply with dials for voltage and current, would this work?
Rapidsyn are a well known brand but you might consider selling them and buying something with a lower voltage rating, at 50v you only have just over twice the rated voltage and at 80v you might struggle to find appropriate drives (only the larger geckos do 80v). Having said that they might work fine for your application but it will depend on how much effort and money it takes to work around them.
Rayman,
Hopefully we can come up with some really nice propeller based motion control code between us, using the I2C expander might prevent you from capitalising on it. My code for example which at the moment is single axis (or multiple unsynced) uses the counters to get really high performance and smooth accelerations but needs to output on pins directly. It is just something I thought you should consider. A half way house would be to use the expander for the direction pins only, they change at much lower frequencies. This is my code in action BTW:
http://www.youtube.com/watch?v=bAgV2vtI468
FYI it is a Vexta Nema23 motor about 2.4v and 1A/phase, run at 26v with a 2mm lead on the screw (trapizoidal anti-backlash), no idea about the microstepping, probably 8X.
Graham
I am using a modified version of the PS-8N48, which outputs 800W 48VDC(nominal). Antek customized this power supply for me at no extra cost. The customization ensured that when I supplied local power to the power supply that it would not output more 49VDC. Basically they unwound one or two of the coils from the transformer. The Gecko G251's are rated for 50VDC, so the 49VDC output from the power supply was near but under the maximum G251 voltage specification. I doubt that you will need anywhere near 800 watts for your project, a good guide for NEMA 23 bipolar motors is approximately 100 watts per motor, but of course this all depends on the actual motor. I chose this power supply to achieve the near maximum voltage that my drive could handle and to be able to supply full power to eight motors.
It all depends on the output. First off, you must make sure that the voltage is being rectified, and outputing direct current, instead of alternating current. Providing that the output is DC voltage, you must also ensure that you can make adjustments that will allow you to calibrate the power supply voltage to under the drives specifications. Secondly, many adjustable power supplies are of the switch mode type. There are some switch mode power supplies that are suitable for stepper driving, however, most people prefer linear power supplies when it comes to driving stepper motors. You can always test and see how it performs.
I hope this was helpful information.
CORRECTION: able to supply full power to five motors
Bruce