GG1
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No problem - but from memory isn't it the shaft which is 8mm and the belt 10mm wide?
- Thread starter GG1
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you are spot on, its these little buggers l need
GG1
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When it comes to electronics I run out of road very quickly, so please correct me on this as required...
According to the motor spec the rated current is 4.0A and each phase resistance is 0.9 Ohms, therefore it will achieve peak torque at only 3.6v (at 100% duty cycle). In reality the driver will, er, drive the motor with a PWM signal at a higher voltage but lower duty cycle to send the motor the correct average quantity of pixies (in a lumpy fashion, but fast enough for it not to matter) to replicate the voltage required. I'm definitely in the verge now.
In this particular application there won't be very fast accelerations for which I think you might need the higher voltage and the power supply I suggested can put out 15 amps - 8 amps max required for this the larger of the two motors leaving plenty in the tank for the other.
This sounds like a good excuse to fire up the scope and try to understand it a bit better.
Stepper motor ratings are with the motor stationary and not turning.
As soon as it starts spinning, it generates back emf (electro motive force - the higher the motor's inductance, the higher the back emf), which means a higher voltage is needed to drive the rated current through the coils.
In electric motors, current = torque, although with steppers, torque drops of anyway. But if current drops off, torque drop-off is even worse.
For typical NEMA 23/24 motors, I'd want at least 36V, but if you want max performance 50-70VDC is acceptable with suitable drives. The main thing is the current is set correctly, and the motors aren't overheating (80degC is acceptable for most stepper motors, but only after prolonged running. If they get too hot to touch within minutes, then you have a problem)
By running only 24V, you'll greatly limit the possible acceleration, which given a plasma ideally needs to maintain reasonably constant speed around tight corners, is going to limit performance. However I do wonder if that's a deliberate choice to avoid overstressing the printed parts.
Using TB6600 drives will also limit performance, as they're pretty basic drive by modern standards.
To maximise performance for any voltage, I'd be looking at digital drives with anti-resonance (eliminates/minimises the risk of steppers stalling at the resonant point), but then you're substantially increasing the cost.
The only benefit to TB6600 drives, is they are cheap, so if you do find them lacking in performance, it's not a lot of money to have wasted.
My bigger concern given the various comments and parts mentioned, is the electrics have been selected on a pure cost basis to make the headline machine cost as low as possible, which is likely to cause some headaches later.
Things like an Arduino wouldn't be top of my list anyway, but neither would USB. USB can be problematic on machines without high voltages floating around, so it will require some very good shielding (or luck!) on a plasma to avoid issues.
Misterg
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Both of the drives linked to above aren't even real TB6600 - The TB6600 chip is good for 42V and 4.5A and up to 16X microstepping.
The cheap drives that are advertised as "TB6600" use a different chip - in at least one case the TB67S109AFTG, which is only rated at 3A. The give-away is that there is a setting for 32X microstepping on these ones. They're also really poorly made.
The ones with the real TB6600 inside seem to be billed as 'DIV 268' these days:
HY-DIV268N-5A CNC Single Axis TB6600 0.2A-5A Hybrid Stepper Motor – Makers Hut
HY-DIV268N-5A CNC Single Axis TB6600: 0.2A-5A hybrid stepper motor driver, ideal for precise control in CNC applications. Reliable, efficient, and easy to use.
makers-hut.com
It's a crude drive, but cheap.
I recently switched from the first to the second type for my little CNC machine after a couple of failures.
GG1
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Thanks for that very comprehensive reply, a lot to think about, you obviously have a lot of experience there...
I was planning on Bluetooth module rather than USB, they did mention somewhere it would be a good idea and a lot of shielding, low pass filtering etc.
This is on a shoestring from what you say sounds like could turn out to balloon as components are upgraded later on.
An additional few pounds for a higher voltage supply seems sensible then - but not sure I follow about the acceleration and tight corners - I was just thinking it's not going to be flinging round the whole mass like a 3d printer, just plodding along not too fast for the cut.
I was planning on Bluetooth module rather than USB, they did mention somewhere it would be a good idea and a lot of shielding, low pass filtering etc.
This is on a shoestring from what you say sounds like could turn out to balloon as components are upgraded later on.
An additional few pounds for a higher voltage supply seems sensible then - but not sure I follow about the acceleration and tight corners - I was just thinking it's not going to be flinging round the whole mass like a 3d printer, just plodding along not too fast for the cut.
GG1
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Thanks, and there was me thinking it was going to be simple. I'm shocked that Amazon might sell something that isn't what it says it is.Both of the drives linked to above aren't even real TB6600 - The TB6600 chip is good for 42V and 4.5A and up to 16X microstepping.
The cheap drives that are advertised as "TB6600" use a different chip - in at least one case the TB67S109AFTG, which is only rated at 3A. The give-away is that there is a setting for 32X microstepping on these ones. They're also really poorly made.
The ones with the real TB6600 inside seem to be billed as 'DIV 268' these days:
HY-DIV268N-5A CNC Single Axis TB6600 0.2A-5A Hybrid Stepper Motor – Makers Hut
HY-DIV268N-5A CNC Single Axis TB6600: 0.2A-5A hybrid stepper motor driver, ideal for precise control in CNC applications. Reliable, efficient, and easy to use.
It's a crude drive, but cheap.
I recently switched from the first to the second type for my little CNC machine after a couple of failures.
I already had a "TB660" (I'll check what it actually is in the morning) so I guess just run it until it doesn't run, if it won't harm the motor?
@Misterg you have to be wary of most stepper drives now. There are various Leadshine copies going around as well, which is why I'd only buy from a reputable source.
I was looking at some TB6600s for my current project, but the current didn't go low enough, so have ended up with some DRV8825s, but have since realised the controller only outputs differential outputs, so am currently waiting on some line receivers to arrive, so I can bodge it to get it running, then make a custom PCB to tidy it up.
@GG1 I've been involved with CNC stuff for quite a while, so have seen lots of people trying to cut costs, then it costing them more later.
I've currently got one machine that runs via USB, and it doesn't give me any problems, but my old lathe was also USB and I had to use a USB isolator to avoid issues (the bigger issue was down to it having two separate power supplies - 240V, and 415V, which I'm sure caused a ground loop), so it can work well, but it can also cause big headaches.
Plasma can be quite demanding, depending on what you're cutting. If you're cutting thin metal, then you need quite a high speed, and to maintain that speed on corners, or you risk the plasma flaming out. There's also the issue that metal can warp when cutting, which is where torch height adjustment comes in, or metal can tip up and catch the torch, which is why bigger machines will often use magnetically mounted torches so they just get knocked off.
There's also the issue given that you've upsized the design, that you'll quite quickly get fed up waiting for the gantry to move to where you need it!
I was looking at some TB6600s for my current project, but the current didn't go low enough, so have ended up with some DRV8825s, but have since realised the controller only outputs differential outputs, so am currently waiting on some line receivers to arrive, so I can bodge it to get it running, then make a custom PCB to tidy it up.
@GG1 I've been involved with CNC stuff for quite a while, so have seen lots of people trying to cut costs, then it costing them more later.
I've currently got one machine that runs via USB, and it doesn't give me any problems, but my old lathe was also USB and I had to use a USB isolator to avoid issues (the bigger issue was down to it having two separate power supplies - 240V, and 415V, which I'm sure caused a ground loop), so it can work well, but it can also cause big headaches.
Plasma can be quite demanding, depending on what you're cutting. If you're cutting thin metal, then you need quite a high speed, and to maintain that speed on corners, or you risk the plasma flaming out. There's also the issue that metal can warp when cutting, which is where torch height adjustment comes in, or metal can tip up and catch the torch, which is why bigger machines will often use magnetically mounted torches so they just get knocked off.
There's also the issue given that you've upsized the design, that you'll quite quickly get fed up waiting for the gantry to move to where you need it!
GG1
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You'd better go back and ignore everything I've said on the subject!
well it seems to have been designed by an engineer who works in the 3d printer industry who must have quite a bit of knowledge of what works and what dosent add in the fact there must be hundreds of these out there working in peoples garages and i havent seen anyone complaining they dont work so it still seems to be viable to me, but i havent bought anything but the plans yet so still time to jump ship lol
indy4x
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I'm also about to press the button on the plans for the JD Garage setup
Yes it's all designed to a budget, they have been running theirs for over a year, have cut a shed load of stuff with it and it works.
You can get better hardware and improve on what they have designed but for an occasional user it's hard to justify spending £££ if this will do the job
In my head it's a bit like the 3D printing rabbit hole, you can work with what you have and be happy or you chuck more money at it and get better steppers, drivers etc but it doesn't always make better prints or the improvements may not be worth the cost
@GG1 Sorry for the thread drift
Yes it's all designed to a budget, they have been running theirs for over a year, have cut a shed load of stuff with it and it works.
You can get better hardware and improve on what they have designed but for an occasional user it's hard to justify spending £££ if this will do the job
In my head it's a bit like the 3D printing rabbit hole, you can work with what you have and be happy or you chuck more money at it and get better steppers, drivers etc but it doesn't always make better prints or the improvements may not be worth the cost
@GG1 Sorry for the thread drift
GG1
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I think those are sensible words @indy4x x and @Baloo, it has been engineered to a budget but also has a track record of working.
I checked and the specs they suggest for the power supply which do call for 24v - maybe for price reasons or maybe because a belt drive system can only take so much acceleration anyway, or a bit of both.
It likely I've created a rod for my own back by scaling it up, the extra weight will no doubt put the drive system under greater stress but I'll find the weak points as I use it.
@Misterg was spot on with the TB660 info - I checked and the one I have and it is the 32 division knock-off with the same IC as the linked article. So it could well be a buy cheap by twice thing, however, the JD's garage bill of materials links to the same 32 division sub-$10 unit on Amazon, so go figure, as they say.
It was useful to take it apart - there was a small aluminium block stuck to the chip to bridge the heat to the main sink on the back of it - looks like it was making poor contact so I'll fix that before I put it back together and hopefully squeeze some more life out of it.
I checked and the specs they suggest for the power supply which do call for 24v - maybe for price reasons or maybe because a belt drive system can only take so much acceleration anyway, or a bit of both.
It likely I've created a rod for my own back by scaling it up, the extra weight will no doubt put the drive system under greater stress but I'll find the weak points as I use it.
@Misterg was spot on with the TB660 info - I checked and the one I have and it is the 32 division knock-off with the same IC as the linked article. So it could well be a buy cheap by twice thing, however, the JD's garage bill of materials links to the same 32 division sub-$10 unit on Amazon, so go figure, as they say.
It was useful to take it apart - there was a small aluminium block stuck to the chip to bridge the heat to the main sink on the back of it - looks like it was making poor contact so I'll fix that before I put it back together and hopefully squeeze some more life out of it.
GG1
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Yes, that is correct.
GG1
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I made the Y axis beams 2000mm, working out the X this weekend and will let you know. Will be sized to get a whole (?) half sheet of 1250x1250
