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Offline rcaffin

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Re: Only X-axis motor is working
« Reply #190 on: April 08, 2018, 02:35:51 AM »
GO FOR IT!
The microstepping thing is a non-event in practice.

Cheers
Roger
Re: Only X-axis motor is working
« Reply #191 on: April 08, 2018, 02:39:07 AM »
Hi,
by way of a reminder, say you wish your stepper motor to spin at 1200 rpm at maximum speed, that is 20 rev per second.
With microstpping fixed this would mean the driver would need to be pulsed at 20 X 2000 =40,000 or 40kHz to rotate that fast.  Mach's standard parallel port is only 25kHz.
You could of course set Machs kernel speed to 45kHz, in fact you'd have to. Upping Machs kernel speed ups the pressure on your PC to perform.

An even better way to resolve it is to use an external motion controller, but they are not free. A good modestly priced controller  in the range $100-$200.

Craig
My wife left with my best friend...
     and I miss him!

Offline rcaffin

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Re: Only X-axis motor is working
« Reply #192 on: April 08, 2018, 02:44:35 AM »
What Craig said is correct, but maybe it does not matter at this stage. If Inferno can get the machine running correctly, even if slowly, that will be a big step forward, and may be enough to justify further expense.

Cheers
Roger
Re: Only X-axis motor is working
« Reply #193 on: April 08, 2018, 02:53:39 AM »
Hi,
Roger is right, if you get these things and leave Machs kernel at its standard 25kHz then the maximum speed for the steppers would be 750 rpm and with 5mm pitch
ballscrews that works out to 3.75 m/minute, still plenty damn good!

If you get these things and put a 70V power supply on it whats the bet you will have no need to change your motors, these drivers will make them sing.  Whats more they'll keep doing it for years.

Craig
My wife left with my best friend...
     and I miss him!
Re: Only X-axis motor is working
« Reply #194 on: April 08, 2018, 01:31:35 PM »
Thanks again, guys.

I think speed won't be that much of an issue. True my ballscrews are 5mm but they will be on my mill/lathe and that would be plenty fast for that. Those would end up being direct drive with the numbers provided, though. I was intending to set up the long axis with a gear reduction but with the speed being set to what it is, I won't be doing that.

As for the steppers I have vs new ones, on the router table, I want to do the build with the new motors simply because it will be belt drive and not screw drive. The belt drive will need a little more torque than these little 1A motors can provide. It's going to be moving a 2.5 foot (almost one meter) carriage that will probably weigh 40 pounds (20K) on the X axis. I don't want to mess around there. I picked the motors I have based on specs on a machine that moves a similar sized carriage. It's just a CNC knife cutter but the dimensions are similar.

Hearing that the Gecko drives only have one setting for stepping (microstepping) is a little bothersome to me but I'm going with the voices of experience. The worst thing that could happen is I replace them with a different configuration and use them on a different project.

I don't know how much my PC would have to perform to get the kernel to run at 45mhz but it's a clean computer. The only thing it will be doing is running the Mach3 program.
I'm also not above upgrading that as well. In fact, it's part of the plan in the long term.

Keep in mind that everything is low budget to get proof of concept. Not including the CNC table itself, I'm only into this project a couple hundred dollars so far. I do have enough info on the components, now, to know it will work.

I really do wish I could put together an encoder feedback. I know it can be done but that's above my pay grade for a while. Someday, maybe.
Along with that, I eventually want to be able to do CNC threading on my lathe. For that I will need to make sure I have either a stepper driven main drive or an encoder on the main drive. That will be a different learning curve, for sure.

« Last Edit: April 08, 2018, 01:37:27 PM by Inferno »
Re: Only X-axis motor is working
« Reply #195 on: April 08, 2018, 03:01:59 PM »
Hi,

Quote
I don't know how much my PC would have to perform to get the kernel to run at 45mhz but it's a clean computer. The only thing it will be doing is running the Mach3 program.
I'm also not above upgrading that as well. In fact, it's part of the plan in the long term
Don't bother upgrading the PC, you'll likely never see the difference, get yourself an external motion controller like an ESS or 57CNC and never look back.


Quote
I really do wish I could put together an encoder feedback. I know it can be done but that's above my pay grade for a while
Correctly specified steppers, drivers and powersupply used within their ratings will NEVER lose steps and therefore encoder feedback is a complete waste of money.
My steppers came with 500 ppr encoders already fitted. Once I got them sorted and they haven't missed a step for years I took the encoders off.

The companies who push these hybrid stepper servos are playing on your fears. If a standard stepper is going to lose steps because its overloaded then a feedback stepper of the same
size is also overloaded and will lose steps, the feedback may mean it tries to catch up, but it will fail....its plain overloaded and feedback wont save it, it'll fault 'following error'. Don't waste your
money on these things, learn whats required to have ordinary steppers perform as designed and the limits within which they'll work.

If you want more performance than that go to AC servos, genuine AC servos....not those really expensive Clearpath things....there again another company playing on your fears to print money.

Craig
My wife left with my best friend...
     and I miss him!

Offline rcaffin

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Re: Only X-axis motor is working
« Reply #196 on: April 08, 2018, 05:17:33 PM »
I think you underestimate what a belt drive onto a ball screw can do. Do not EVER let any part of your body get in the path of an axis movement. These machines can crush skin and bone without raising a sweat.
I agree with Craig about the rest.

Cheers
Roger
Re: Only X-axis motor is working
« Reply #197 on: April 08, 2018, 06:07:59 PM »
I think you underestimate what a belt drive onto a ball screw can do. Do not EVER let any part of your body get in the path of an axis movement. These machines can crush skin and bone without raising a sweat.
I agree with Craig about the rest.

Cheers
Roger

I hope I didn't give the impression of ignorance on the strength of belt drives and such. I'm intimately aware of what kind of power I'm looking at.
I've been very lucky in life that my hard learned lessons haven't separated me from my body parts, not that it didn't come close a few times.

I was thinking direct drive with the ballscrew for a couple reasons. Reason one being that one ballscrew is already set up as a direct drive.
I suppose if I had an issue with the axis being too slow (unlikely on the lathe) then I could gear it up instead of down.
Re: Only X-axis motor is working
« Reply #198 on: April 08, 2018, 06:26:50 PM »
Hi,
all my ballscrews are direct drive. I use those el-cheapo aluminum couplers with a spiral slot in them. They flex a bit
and result in 'lost motion' which is not desirable but what has happened is on the odd occassion where I've crashed
the coupler shears off rather than wrecking the gearbox/stepper/ballscrew. Something like a mechanical fuse.


Craig
My wife left with my best friend...
     and I miss him!
Re: Only X-axis motor is working
« Reply #199 on: April 08, 2018, 07:26:27 PM »
Hi,
all my ballscrews are direct drive. I use those el-cheapo aluminum couplers with a spiral slot in them. They flex a bit
and result in 'lost motion' which is not desirable but what has happened is on the odd occassion where I've crashed
the coupler shears off rather than wrecking the gearbox/stepper/ballscrew. Something like a mechanical fuse.


Craig
I was thinking of using those but maybe something a little beefier than the cheap Chinese ones. I know there are a few styles of the cheap ones though so who knows.
I don't need to buy a new ballscrew every time I make a programming mistake.

Maybe a coupler system like this will work