[joeybagadonuts]

jfong,

I believe the HTD5M would be more appropriate for your large motor due to the KW rating.

HTD5M 48/12 Teeth W-21mm Pitch-5mm Timing Pulley Belt set kit Reducer Ratio 4:1

JoeyB

[RCaffin]

By and large the GT2 belts will transmit quite enough power. I use them. When used on a 3D printer they are working at something lke 1% capacity. 6 mm wide belts are very easy to come by; 9 mm are harder. That said, the Chinese version of the GT2 profile is NOT the same as the original Gates design. How well they would mix - I don't know.

But the big thing about toothed belts is that the GT2 design is effectively free of backlash, while the original ones (X, L etc) are NOT. The HTD design is certainly better than the older sort-of rectangular ones, but I am not sure how good. It has rounded teeth, which is better. But the 5 mm pitch is coarser than the GT2 2 mm pitch, which makes for more 'noise' in the rotation with small pulleys.

Cheers
Roger

[joeybagadonuts]

Fellow CNCer's, "Cake-Nibbling-Customers"

Here are some belt torque rating spec's for future reference.

JoeyB

[macdowswe]

Fellow CNCer's, "Cake-Nibbling-Customers"

Here are some belt torque rating spec's for future reference.

JoeyB

Wow I wasn't aware that GT2 5mm can handle so much! Thx for the reference! ;D

[jfong]

I hear ya. He knows first hand how much damage a Lipo fire can do. He's been flying r/c since early 80's. gas now electric.

What I am saying is don't use any batteries at all and use high current power supplies for the driver.

He bought a expensive lipo charge controller after the fire. I believe he still uses the dell supplies as the power source for the charge controller.

[109jb]

I hear ya. He knows first hand how much damage a Lipo fire can do. He's been flying r/c since early 80's. gas now electric.

What I am saying is don't use any batteries at all and use high current power supplies for the driver.

He bought a expensive lipo charge controller after the fire. I believe he still uses the dell supplies as the power source for the charge controller.

Oh. Sorry I misunderstood. I actually kind of like the idea of having a battery for the reserve allowing use of a relatively small PS otherwise. Just hoping it can be done with a lead-acid battery.

[jfong]

Oh. Sorry I misunderstood. I actually kind of like the idea of having a battery for the reserve allowing use of a relatively small PS otherwise. Just hoping it can be done with a lead-acid battery.

I don't see why it wouldn't work since the peak current for these motors are 53amps. Industrial servo motors peak currents are only for a few seconds. The datasheet typical gives you time/heat duration for current peak. The Applied Motion/Copley brushless servo drives that I use, have a programmable peak current time setting. I set them around 1/2second and then it drops the current down to continuous current rating. It protects the motors from over heating if a axis stalls etc.

I'm not sure if the odrive does that but it should. Anyone know what the typical continuous current rating for this RC brushless motor is. The brushless motors I have, continuous current ratings are around 1/4 of peak value.

[macdowswe]

I don't see why it wouldn't work since the peak current for these motors are 53amps. Industrial servo motors peak currents are only for a few seconds. The datasheet typical gives you time/heat duration for current peak. The Applied Motion/Copley brushless servo drives that I use, have a programmable peak current time setting. I set them around 1/2second and then it drops the current down to continuous current rating. It protects the motors from over heating if a axis stalls etc.

I'm not sure if the odrive does that but it should. Anyone know what the typical continuous current rating for this RC brushless motor is. The brushless motors I have, continuous current ratings are around 1/4 of peak value.

Yeah it will have thermal control as part of the motor control algorithm. I think the best way would be to have a thermal model of the motor, but if that's not available, a simple time-based backoff could be implemented.

The current ratings given on these hobby motors are very ambigous. They don't state wether it is peak or continous (the way it is presented makes it seem like it is continous, but it is never explicitly stated). Also, they all have a fan on the rotor which cools the stator. But this only works when the motor is spinning, and for a CNC type of application, we may be loading it when it is not spinning (this never happens when spinning a propeller). Basically the current ratings given are very approximate.

So I think that the best way to deal with this is to bury a thermistor in the windings and maybe also add an external cooling fan. With this we can either run the thermal control with the thermistor as feedback, or we could even gather data for a thermal model for that specific motor, so that others may use this motor but without having to add the thermistor.

[macdowswe]

By the way guys, check this out! ODrive v3.1 being manufactured ;D

[RCaffin]

One of the issues I see with machine design and conversions is motor selection and power,
Agree.
The brushed DC servos on my machine are rated at about about 300 W with a 3:1 GT2 reduction onto a ~5 mm ball screw. I can't stall them.
The spindle motor is an industrial brushed DC motor RATED at about 500 W, and i have never stalled that either. Mind you, industrial DC motors are kinda rugged - I went 'oops' one time when I found it was taking ~1.5 kW for drilling titanium.

Merry Xmas
Roger

[109jb]

So the RC motors being discussed are about 1kW, but at 7000 rpm, so at 3500 rpm they are going to be 500W. Simple math tells us this. If you want to de-rate them to 500W at 3500 rpm there is nothing to say you can't. It would be easier on the motors. They are also very compact, so I would consider them a good choice.

What is the talk about belt reduction drives not being a good choice and causing lost precision, belt stretch, etc? Timing belt reductions have been used on these kind of applications for a long time and they have proven reliability and positioning precision is not an issue in a proper belt reduction system. With a 3600 rpm max at the motor, with 3mm pitch GT3 belts you could use a 15mm wide belt and it would handle about 600W of power. 15mm wide, not 55mm, and not HTD. At higher RPM you can still use the 15mm wide GT3, you just are a little limited on the small pulley diameter. GT3 belts handle more power and have a profile that is essentially zero backlash and much quieter than an HTD tooth profile. Nobody ever said anything about plastic timing belt pulleys either. Aluminum timing pulley are the norm and are readily available. The whole notion of belt stretch affecting precision to any degree is a bunch of hogwash.

[RCaffin]

So the RC motors being discussed are about 1kW
They might be 1 kW - for 10 seconds. But when you are machining for 3 hours straight, I can't help feeling that those tiny-very-low-thermal-mass RC motors might melt down. The 500 W industrial DC motor I am talking about probably weighs about 10 kg! Heating that up takes a long time.
And I agree 100% about the GT2/3 belts.

(On Z axis. Baldor DC spindle motor in background.)

Cheers
Roger

[jfong]

Websrv,

If I had the choice, I would use differential encoder outputs but those encoders do cost more. Plenty of us digital, avago, HP/Agilent single ended encoders are being used today just perfectly fine. Just as servo drivers that are only single ended encoder input such as Geckodrive and leadshine. I have about a dozen Gecko320's that's been running for years. Those companies sell thousands of them.

You don't need expensive encoders either. amt/cui encoders work well and under $25. AMS magnetic encoders are even cheaper.

You can always add external differential encoder line drivers if you require them.

The idea here is to get brushless driver/motor technology on a hobbyist budget. A single new tamagawa encoder that you propose cost more than the driver itself. Doesn't matter if you can get Tamagawa encoders and brushless servo motors for cheap. If we can't easily buy them at the same price, what's the point of even mentioning them.

[websrvr]

Websrv,

If I had the choice, I would use differential encoder outputs but those encoders do cost more. Plenty of us digital, avago, HP/Agilent single ended encoders are being used today just perfectly fine. Just as servo drivers that are only single ended encoder input such as Geckodrive and leadshine. I have about a dozen Gecko320's that's been running for years. Those companies sell thousands of them.

You don't need expensive encoders either. amt/cui encoders work well and under $25. AMS magnetic encoders are even cheaper.

You can always add external differential encoder line drivers if you require them.

The idea here is to get brushless driver/motor technology on a hobbyist budget. A single new tamagawa encoder that you propose cost more than the driver itself. Doesn't matter if you can get Tamagawa encoders and brushless servo motors for cheap. If we can't easily buy them at the same price, what's the point of even mentioning them.

A china factory is now cloning the Tamagwa 16,000RPM 2500PPR quadrature encoder for one of my works customers at a cost of $26.50/ea but come in a box of 24 so a cheap source is available if you need to make a couple dozen motors and I have the advantage of buying them in quantities of 3 or 4 on occasion so making a set of motors for a machine I'm building after the project is finished and I have the design modified or building 48 motors to sell could be something to consider if a supporting driver existed and I had the money to waste on stocking a product for sale.

Measuring cable length on my BT20 machine, the length from the X-axis motor to X-axis driver is 12M but Y-axis cable length is only 3.5M and Z-axis cable length is 6M so using differential encoders is prefered

Yes you can suggest that people could just build a board to support differential encoders and skip the encoder error detection to use with ODrive but to me that's a solution for an incorrectly designed product so I'll go that extra mile when it's done and pay to have it added it to get the flexibility in encoder support so I don't have to make a separate board which doesn't take advantage of the available encoder error detection.

No I don't think I need to reconsider anything. There are many many machines built that have used belts for reduction drives on their axes, and have done so successfully with precision that is more than adequate for the intended applications. To say otherwise totally ignores those successful applications. As a matter of fact there are machines using narrow XL belt profiles on RF-45 size machines running at +200 IPM speeds and doing so successfully, but the GT2/3 is a better choice in my opinion.


You can be damn sure thatnobody stated "emphatically" that all machines use aluminum or steel pulleys? Show me where that was said. It wasn't and any claim that it was is just BS. What was said was that aluminum was the norm and I stand by that. Sure some have used non-metal sprockets. However, by and large, the build threads on this forum show that the most commonly used are the aluminum pulleys. You can argue that all you want and you would be wrong. While speaking of non-metal pulleys, you are apparently claiming that they are so rubbery or so prone to exploding that they are not appropriate for using in a precision application. This has no basis in reality. When used appropriately they can be every bit as precise, accurate and reliable as metal. To say otherwise is wrong and totally unsubstantiated.

I have personally exploded a GT3-127T-12 GRN pulley spinning at 12,000RPM and stopping it and switched to the bullet-proof KRP pulley because I was concerned the size and weight of the aluminum pulley might distort it's shape permanently.

I'm not denying that the GT2/GT3 is a better profile over the XL and definitely quieter at low RPM over the HTD and seem suitable for spindle driving up to 2.2KW where low mass/inertia are present but it's high mass/inertia that are belt killers.

In post #98 you state that aluminum pulleys are the norm and now you state that the posts here commonly use aluminum pulleys and this may be so but it doens't make it the industry norm, just the norm here, if you really want to split hairs, this is 100% incorrect as the majority of the machines I see on a daily basis are employing composite (GRN - glass reinforced nylon or KRP - kevlar reinforced polypropylene) pulleys but in reality, direct drive is the norm and I have yet to see a composite pulley fail before it's aluminum twin when used with 4,000RPM MAX servo motors.

One of the links in his (macdowswe) post to hobby-king is for an SK3 6374-149kv, with a max voltage of 70VDC and the SK3 4250-350kv you point to has a max voltage of 19VDC, of course people overdrive these motors without thought or really understanding it's intended electrical design but I wouldn't advise or recommend it, I'd find a 24V BLDC motor and operate it at 24V.

Also, ODrive wont handle this current requirement as some other real time tests are reporting the motor is a gutless wonder if the current is restricted or limited and that it doesn't start to generate any power when the current is below 15A and this 1007W (not 1190W as advertised) is input power, since the motor is only 66% efficient output power is only 671W, 19V@53A and you think 24V@6A using ODrive to power it is going to fly?

My china clone 6364-250kv hits 6,100RPM at 24V and draws 6A (noload) and peaks at 19A and gives 310W of output, this is almost suitable if it weren't for the peak current, the required forced-air cooling and the > $80.00 price tag.

Out runner as a spindle motors is another example, I wont go into how wrong it is for the general hobbyist to make a AIO spindle from an out-runner motor without decent plans to follow or some serious knowledge in spindle loading forces and design criteria but they do it just the same.

I get a kick out of those that make a body, drop in a couple of cheap multi-purpose deep groove bearings and an ER16 or ER20 collet head and think they've got a MAC-DADDY spindle, only the smart guys will use a dual row angular contact bearing in the nose of the spindle for bi-directional thrust forces because they expect the thing to stand up to the abusive forces of cutting without eating the bearings or living more than 3 months.

I've not applied my criteria to anyone else, I simply state if you have weight to move, small skinny belts are unwise to employ and you refuse to acknowledge this making claims that the belt wont stretch or break and this is unrealistic and hilarious.

Because some yahoo has BT2-15 belts on his RF45 doesn't mean much if his acceleration/deceleration curves are so mild that the ramp-up/ramp-down speed prevent the motion from achieving >100IPM for a movement of less than 4in or ever moving faster than 200IPM.

The table travel is small, it's a dovetail machine and with the gibs tightened down it probably helps control runaway inertia by restricting movement and the table only weighs 47lbs but I couldn't call it a good quality machine that's prime for a CNC conversion without doing some serious reworking and dumping the dovetails for some unrestricted linear motion capabilities which very few do.

I've never seen an RF45 or even an RF45N2F (it has a larger table) move at more than 200IPM rapids and never cutting (a serious cut like 0.250in with a 1/2in, not a .025in pass with a 1/4in end mill) above 50IPM without noticing head deflection so it's not in my opinion a reasonable example of a real machine, it's a large toy.

Oh, again my mistake, when I say REAL machine, I am referring to a smaller version of a REAL larger machine such as a CadetMate 6030 or CadetMate 7040 where the only different is the physical size of the machine.


So despite all your bickering, your choice of a new (click to buy) BLDC motor, aluminum to make a new body, new bearings from VXB, 4150 steel for a new shaft, a new encoder from a source with an endless supply for others to buy them, a new fan, connectors and terminals of appropriate size and current rating, hardware to assemble it will cost more than I can produce a 48V or 60V 500W servo motor with a 2500PPR quadrature encoder that wont have any heat issues or require any external cooling.

Oh, I've got a novel idea, why don't you create a kit and sell it to the users here, I'm sure they would be happy to buy your parts and buy the hobbyking motor and assemble it themselves as a cheap solution.

I've ordered your 4250-350kv motor from hobbyking, when it arrives I'll connect it to my dyno and can then better comment on it but I doubt it's going to provide any eye opening results.

Now if you want to talk about spindles, your 4250-350kv wont cut it as a spindle motor if you need some serious power with RPM, with the help of a friend I've made my own 0-12,000RPM 220V 3-PH asynchronous servo spindle motor with an output rating of 3HP in a really small size (90mm x 90mm x 260mm) belt driving a BT20 ATC spindle and while cheaper than purchasing a commercial product, if you don't have access to precision lathes and mills and balancing equipment to do the work I wouldn't recommend it (you can have it balanced at a electric motor repair shop if you can do everything else) and I have yet to see a BLDC solution that can come close for the same or less money and nothing in a small size that doesn't have heat issues.

Because someone does a CNC conversion on a machine such as an RF45, it doesn't mean a whole lot when in the conversion process they plan to create limitation in movement speed to save a buck, you only see people posting about their builds if they're either doing it right or doing it cheap.

You can't have it both ways if you expect it to be duplicated by another person (because you have motors doesn't make it cheap for the next guy who doesn't) and people tend to follow the most successful build they can afford to follow, replacing the leadscrews and dovetails with linear rails and precision ground ballscrews on an RF45 is the correct way to do it but it sure isn't the cheap way to do it.

Now ODrive is being created to support single ended encoder signals and there is a difference between transistor and transmitter outputs and even with transistor outputs there are two types, NPN (most common) and PNP and they respond differently, personally I prefer a quadrature differential line transmission type but as long as a dependable source for the specified encoder (new) is provided I have no issues using it but encoder flexibility is currently limited to single ended transistor output encoders so making a decent servo motor available at a cheap price with such an encoder isn't a consideration I'd be willing to make.

Now you want to talk about flexibility and how everyone is different and can decide how they want to build things and this is false, this option is nonexistant with respect to encoders and ODrive, people are buying the board, and they can't just connect any encoder because line receivers are not employed and the device is set up and tested with the OP's encoder on hand so flexibility is limited to the type currently employed and tested so now people have no choice in the encoder they can use if they can't make or buy a board that gives them the connections for the encoder in the motors they bought or made.

You must tell them they can use any encoder they want as long as it's a single ended transistor output type.

[109jb]

I have personally exploded a GT3-127T-12 GRN pulley spinning at 12,000RPM and stopping it and switched to the bullet-proof KRP pulley because I was concerned the size and weight of the aluminum pulley might distort it's shape permanently.

Then you designed it wrong. Plain and simple. No doubt about it. No argument can be made otherwise.

I'm not denying that the GT2/GT3 is a better profile over the XL and definitely quieter at low RPM over the HTD and seem suitable for spindle driving up to 2.2KW where low mass/inertia are present but it's high mass/inertia that are belt killers.

No matter how much mass or inertia there is, if the motor cannot supply the torque to exceed the belt or the pulley capabilities then they won't break.

In post #98 you state that aluminum pulleys are the norm and now you state that the posts here commonly use aluminum pulleys and this may be so but it doens't make it the industry norm, just the norm here, if you really want to split hairs, this is 100% incorrect as the majority of the machines I see on a daily basis are employing composite (GRN - glass reinforced nylon or KRP - kevlar reinforced polypropylene) pulleys but in reality, direct drive is the norm and I have yet to see a composite pulley fail before it's aluminum twin when used with 4,000RPM MAX servo motors.

Well lets see. We are in a thread about a low cost servo drive for hobbyists using hobby motors and being discussed by hobbyists. I think most everyone would figure that the posts were in relation to hobbyists and not in relation to industry.

One of the links in his (macdowswe) post to hobby-king is for an SK3 6374-149kv, with a max voltage of 70VDC and the SK3 4250-350kv you point to has a max voltage of 19VDC, of course people overdrive these motors without thought or really understanding it's intended electrical design but I wouldn't advise or recommend it, I'd find a 24V BLDC motor and operate it at 24V.

Also, ODrive wont handle this current requirement as some other real time tests are reporting the motor is a gutless wonder if the current is restricted or limited and that it doesn't start to generate any power when the current is below 15A and this 1007W (not 1190W as advertised) is input power, since the motor is only 66% efficient output power is only 671W, 19V@53A and you think 24V@6A using ODrive to power it is going to fly?

Let me ask you what machine you think I am intending to use this on? I don't think I mentioned it, so you can't possibly look only at the motor specs and say with any intelligence whether it is or is not suitable. You can spout all the numbers you want but without knowing anything but motor parameters you are only blowing smoke.

My china clone 6364-250kv hits 6,100RPM at 24V and draws 6A (noload) and peaks at 19A and gives 310W of output, this is almost suitable if it weren't for the peak current, the required forced-air cooling and the > $80.00 price tag.

Don't really care what you think is or isn't a good value. If I want to spend my money on something that you don't think is a good value, that is my choice.

Out runner as a spindle motors is another example, I wont go into how wrong it is for the general hobbyist to make a AIO spindle from an out-runner motor without decent plans to follow or some serious knowledge in spindle loading forces and design criteria but they do it just the same.

I get a kick out of those that make a body, drop in a couple of cheap multi-purpose deep groove bearings and an ER16 or ER20 collet head and think they've got a MAC-DADDY spindle, only the smart guys will use a dual row angular contact bearing in the nose of the spindle for bi-directional thrust forces because they expect the thing to stand up to the abusive forces of cutting without eating the bearings or living more than 3 months.

Another useless diversion from the topic of this thread. Why are you discussing spindles.

I've not applied my criteria to anyone else, I simply state if you have weight to move, small skinny belts are unwise to employ and you refuse to acknowledge this making claims that the belt wont stretch or break and this is unrealistic and hilarious.

Tell you what. You tell me how much a 15 mm wide GT3 belt drive will stretch and how much it will affect precision on an unknown machine with unknown mass, unknown inertia, and unknown desired performance..

You are basically saying that belt stretch will be too much without knowing anything about the end product and applying how you want your machines to work to everyone else.

Because some yahoo has BT2-15 belts on his RF45 doesn't mean much if his acceleration/deceleration curves are so mild that the ramp-up/ramp-down speed prevent the motion from achieving >100IPM for a movement of less than 4in or ever moving faster than 200IPM.

The table travel is small, it's a dovetail machine and with the gibs tightened down it probably helps control runaway inertia by restricting movement and the table only weighs 47lbs but I couldn't call it a good quality machine that's prime for a CNC conversion without doing some serious reworking and dumping the dovetails for some unrestricted linear motion capabilities which very few do.

I've never seen an RF45 or even an RF45N2F (it has a larger table) move at more than 200IPM rapids and never cutting (a serious cut like 0.250in with a 1/2in, not a .025in pass with a 1/4in end mill) above 50IPM without noticing head deflection so it's not in my opinion a reasonable example of a real machine, it's a large toy.

Didn't you just say you just state that you don't apply your criteria to anyone else? Re-read the above snippet, particularly this part.

but I couldn't call it a good quality machine that's prime for a CNC conversion without doing some serious reworking and dumping the dovetails for some unrestricted linear motion capabilities which very few do.

and this one too

so it's not in my opinion a reasonable example of a real machine, it's a large toy.

That sure seems like applying YOUR criteria to me. Many people chose RF-45 type machines and other benchtop mills for conversion and are very happy with them FOR THEIR PURPOSES. Not for YOUR purposes.

Oh, again my mistake, when I say REAL machine, I am referring to a smaller version of a REAL larger machine such as a CadetMate 6030 or CadetMate 7040 where the only different is the physical size of the machine.

So despite all your bickering, your choice of a new (click to buy) BLDC motor, aluminum to make a new body, new bearings from VXB, 4150 steel for a new shaft, a new encoder from a source with an endless supply for others to buy them, a new fan, connectors and terminals of appropriate size and current rating, hardware to assemble it will cost more than I can produce a 48V or 60V 500W servo motor with a 2500PPR quadrature encoder that wont have any heat issues or require any external cooling.

Lets see some more application of your criteria.

First, apparently the only REAL machines are machines that match your idea of performance, that being performance equal to an industrial VMC with only smaller work envelope.

Now about the motor in question:
Aluminum to make a new body - Why? I see no reason to for MY potential application. A new body is YOUR criteria
new bearings from VXB - Why? I see no reason for new bearings until the ones it comes with start to go. YOUR criteria again.
4150 steel for a new shaft - I see no reason for a new shaft for the motor. YOUR criteria again.
a new encoder from a source with an endless supply for others to buy them - Umm what the hell is this. Any servo is going to need an encoder - Red herring
a new fan - I have a box of surplus fans that will work fine. A new fan is YOUR criteria again.
connectors and terminals of appropriate size and current rating - Once again, any motor is going to need these. Red herring

it will cost more than I can produce a 48V or 60V 500W servo motor with a 2500PPR quadrature encoder that wont have any heat issues or require any external cooling

And you are going to sell these to everyone? Your can produce it, but others can't, so this is again YOUR criteria. BTW, this is the ODrive thread, so you might want to consider a 24V motor since the ODrive has a 24V bus. Your 48V or 60V motors might under-perform

Oh, I've got a novel idea, why don't you create a kit and sell it to the users here, I'm sure they would be happy to buy your parts and buy the hobbyking motor and assemble it themselves as a cheap solution.

I've got a novel idea. If you approach is so much better why don't YOU put together a kit of your motor and sell it to everyone as the cheaper solution. When you do this then the above comment might bear some weight. Until then it is a hot air.

I've ordered your 4250-350kv motor from hobbyking, when it arrives I'll connect it to my dyno and can then better comment on it but I doubt it's going to provide any eye opening results.

Now if you want to talk about spindles, your 4250-350kv wont cut it as a spindle motor if you need some serious power with RPM, with the help of a friend I've made my own 0-12,000RPM 220V 3-PH asynchronous servo spindle motor with an output rating of 3HP in a really small size (90mm x 90mm x 260mm) belt driving a BT20 ATC spindle and while cheaper than purchasing a commercial product, if you don't have access to precision lathes and mills and balancing equipment to do the work I wouldn't recommend it (you can have it balanced at a electric motor repair shop if you can do everything else) and I have yet to see a BLDC solution that can come close for the same or less money and nothing in a small size that doesn't have heat issues.

I don't want to talk about spindles. I want to talk about servo drives in a servo drive thread, so I could care less.

Because someone does a CNC conversion on a machine such as an RF45, it doesn't mean a whole lot when in the conversion process they plan to create limitation in movement speed to save a buck, you only see people posting about their builds if they're either doing it right or doing it cheap.

You can't have it both ways if you expect it to be duplicated by another person (because you have motors doesn't make it cheap for the next guy who doesn't) and people tend to follow the most successful build they can afford to follow, replacing the leadscrews and dovetails with linear rails and precision ground ballscrews on an RF45 is the correct way to do it but it sure isn't the cheap way to do it.

More application of YOUR criteria. What you are discussing is a trade study. If a person limits performance to save money does not mean their build is invalid. Maybe to you it is, but you aren't everyone and your criteria isn't everyones.

replacing the leadscrews and dovetails with linear rails and precision ground ballscrews on an RF45 is the correct way to do it but it sure isn't the cheap way to do it.

By YOUR criteria it is the right way. Someone else may say that dovetails an rolled ballscrews are good enough for what they want to do with the mill, and that decision would be the right way to do it.

Now ODrive is being created to support single ended encoder signals and there is a difference between transistor and transmitter outputs and even with transistor outputs there are two types, NPN (most common) and PNP and they respond differently, personally I prefer a quadrature differential line transmission type but as long as a dependable source for the specified encoder (new) is provided I have no issues using it but encoder flexibility is currently limited to single ended transistor output encoders so making a decent servo motor available at a cheap price with such an encoder isn't a consideration I'd be willing to make.

Now you want to talk about flexibility and how everyone is different and can decide how they want to build things and this is false, this option is nonexistant with respect to encoders and ODrive, people are buying the board, and they can't just connect any encoder because line receivers are not employed and the device is set up and tested with the OP's encoder on hand so flexibility is limited to the type currently employed and tested so now people have no choice in the encoder they can use if they can't make or buy a board that gives them the connections for the encoder in the motors they bought or made.

You must tell them they can use any encoder they want as long as it's a single ended transistor output type.

Everyone can still decide how they want to build things, If ODrive can only use one encoder type then if I want to use ODrive I can use the one type encoder specified, or I could devise a way to use another type or I could choose to not use ODrive. Still a choice. Personally since the encoder that has been tested is a $10 piece, I have made MY decision that this isn't an issue for me. The fact that you don't like this style encoder and think there are better choices is up to you but has absolutely no effect on me.

[websrvr]

A GT3-15 belt is a 3mm pitch timining belt, following advice from someone else just like you who emphatically claimed the belt would stand up to a 3HP, 8,000RPM motor and would handle moving a 8' x 14' router gantry with a weight of 670lbs at 1000IPM was so far off the mark and the damage that was caused when the belt snapped and the gantry slammed into the front frame support was nothing shy of life threatening.

You want to claim that the belt is suitable for an application then provide the details of the application and stop making such false blanket statements and trying to discredit opposing statements based on the same lack of information you make your claims with.

Because I don't call an RF45 a quality machine prime for conversion doesn't mean that someone else has the same thoughts, I'm not telling them how to perceive the machine, I only state how I perceive that particular machine.

Now, I have no particular preference for any style of encoder and only a fool would conclude otherwise, I just know from experience that there is no such thing as a one encoder works in every application and I've seen too many issues with single ended encoders and long cables to even consider it in a design where long cables are used.

You want to accept the lack of flexibility in encoder support knock yourself out, the majority of people who will buy this product will buy it assembled and since the project creator doesn't have an available solution for use with differential encoders when long cables (>9M) are involved, it reduces the products suitability as an inexpensive solution when no option to use it with supporting encoders and long cables are involved and no, most will not design and produce a converter board just to use a differential encoder with long cables, they'll opt for a different solution.

When all is said and done, if a differential encoder is not supported I'll spend the time and make the eagle files and pay to have the support added for my own personal use and I have no issues publicly stating my intentions regarding this product and all credit for the design will be to macdowse since it's his baby and I acknowledge this.

That way if I have an application that needs or uses differential encoder, it wont be an issue and what you do has absolutely no effect on me or anyone else.

Any argumentative statement about my encoder type is nothing more than someone trying to come off as the big man on campus who is wasting their futile efforts trying to publicly discredit anything I've said which offers controversy or conjecture to statements they themselves have made.

Building and attempting to sell a BLDC servo motor when no inexpensive supporting driver is available is an exercise in foolish spending and you don't have to be a rocket scientist to figure this out.

If later I do an updated driver for myself, there's still no reason to make and sell a BLDC servo motor for public consumption since no inexpensive driver is available so making such a suggestion shows your reason for commenting is nothing more than a personal attack and less of a useful contribution.

My whole thought is that if ODrive at a cost of $50.00 to $80.00 offers flexibility in deployment, it will be seen as a suitable, viable and sought after product and making available a suitable and inexpensive supported BLDC servo motor would further increase it's value and makes sense to produce a suitable motor for general consumption but I'm not going to steal his project and build it with the flexibility I believe it should contain, it's macdowse's project, he ultimately decides what options and features the public release will contain and to think otherwise would be disrespectful.

[macdowswe]

Hey guys, the v3.1 boards have come back from the factory, check it out!


I have some more pictures here: link

[websrvr]

Hey guys, the v3.1 boards have come back from the factory, check it out!


I have some more pictures here: link

Being tied to an expensive manufacturing process and the lack of files to produce the board at other board shops makes this project look less like an open-source project.

Like many others I am interested in this project but since no one can currently produce this product at a reasonable price due to the lack of eagle files or even worst case non-modifiable gerber files we have to rely on you to make the product available at a reasonable price.

Can you please inform us when the product is available at a reasonable price and also of interest is your 3-axis and 4-axis version of this product so updates regarding their availability are of interest to many.

Depending on the results of your finished product, I may commission someone to produce a single axis version based on your code and schematic for my particular use since there doesn't seem to be anything currently available, another project here went closed source in it's final development stages and an inquiry to you in possibly producing functioning code has gone unanswered for more than a week so I'm beginning to adopt the attitude that I should not be concerned about availability for anyone else's use and unfortunately this doesn't benefit the open-source/open-hardware community.

[macdowswe]

Dear websrvr. Please stop whining about Eagle. Get a free trial of Altium and convert it yourself.
Or just use CircuitMaker instead, it's free. The design for CircuitMaker is here: https://workspace.circuitmaker.com/P...gl-2/ODrive-v3

The price I can ask for a board may never drop; if I take this project more seriously and hence do more work to cut manufacturing costs, I may also start having a non-zero margin on the boards to fund the development time. Right now my time is donation.
Or the price may drop. We will see. It depends on how much legwork people are capable of doing themselves vs how much catering I do for others.

If you want single axis, check out the VESC: VESC – Open Source ESC | Benjamin's robotics

[RCaffin]

From a technical, electronics-engineering PoV, a single-ended line driver is just as good as a differential line driver up to a point. If the distance is under a few metres, there is some screening around the cable, a 'hard' line-driver is used and the frequency is under (say) 500 kHz, then going differential brings little extra value. Many computer busses run at tens of MegaHertz like this - albeit slightly shorter. If you need to run at 100 MHz over 10 metres, then you go differential - like a twisted pair Ethernet cable.

The commercial market is a good guide for this. Huge numbers of single-ended encoders are available, and most servo-drivers can take single-ended encoder inputs. All of which means that commercial system builders around the world are happy to run single-ended.

I looked at converting my system to differential when I was rebuilding it. The cost would have been negligible for me, but it was not worth the bother. Instead I put in some optical isolation at the receiver end, and focused on getting that to run at MHz speed.

As for the belts business - we have had that argument here many times before. The older X and L types of belts may have given some problems, especially if mounted wrongly, but the modern GT2/3 belts (and variants) pump kWatts of power at high speed with no visible backlash. To be sure, if you have not used them, it might seem a big claim, but again, check the commercial marketplace for acceptance. Sales are ... huge.

Cheers
Roger