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Author Topic: Glitch on X movements  (Read 1944 times)

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Re: Glitch on X movements
« Reply #10 on: January 16, 2022, 04:17:58 PM »
Ok I'm winging this from memory and I'll double check the numbers next chance I have.
I'm using clearpath servos. And they are set up via the clearpath software Auto tune. From memory I think I did de-rate them to about 75% max torque as part of that setup. These servos have a peak torque rating of about 7.75Nm. Can move axis at max 7000mm/s with acceleration at 10000 something's.
Like you say, it's scarry and clunky.

In Mach I limited the max travel speed to 5000mm/s (will have to check on that, may even be 3000mm/s) and acceleration to 1000 something's.
Basically I set it up so I could visibly see the deceleration and acceleration when moving back and forth at max speed. This was also well below the clunkiness of fast acceleration. All Axis are set with the same numbers, X axis being the lightest at maybe 45kg including the 30kg vice.
The Auto tune was run with the vice in place as well.

I like your PCBs. Very tidy.
Will see what I can find out about adding resistors
Re: Glitch on X movements
« Reply #11 on: January 16, 2022, 05:55:11 PM »
Hi,

Quote
first about accl deccl , the first improve its to add external resistor this improve a lot but and its long story between me and craig

Can't with Clearpath servos, there is no place to hook up a braking resistor....I can do so if I want or need with my Delta servos because they have a separate drive
but Clearpaths do not have a separate drive.

As it turns out I only use 60% of the acceleration that my servos could provide, and that's only its rated acceleration, its overload is 500% more than that! Despite my machine weighing over 800kg
it still lurches around, not uncontrollably, but it does move so so winding up the acceleration only makes that worse.

Quote
In Mach I limited the max travel speed to 5000mm/s (will have to check on that, may even be 3000mm/s) and acceleration to 1000 something's.

Did I read that right.....5000mm/s ........or is it supposed to be 5000mm/min?. 5000mm/s is 18km/hr!!!!

Craig
'I enjoy sex at 73.....I live at 71 so its not too far to walk.'
Re: Glitch on X movements
« Reply #12 on: January 16, 2022, 07:08:35 PM »
Lol. mm/minute not mm/s
Re: Glitch on X movements
« Reply #13 on: January 18, 2022, 04:56:19 PM »
Checked over the numbers this morning and you were right Craig. Turns out I had an extra zero on both max velocity and acceleration on the X axis. giving them a speed of 50000 and acceleration of 10000. Run the same drill hole program and it run sweet.
Re: Glitch on X movements
« Reply #14 on: January 20, 2022, 01:33:16 AM »
I've been reading stuff about the HLFB on this thread- https://www.machsupport.com/forum/index.php?topic=37464.20
I think I have mine wired in series to one input. Will definitely have to take a look at this.
Re: Glitch on X movements
« Reply #15 on: January 20, 2022, 02:11:23 AM »
Hi,
if I'm not mistaken the HLFB output is an opto-transistor. Given that the base is purely optical there is no DC ground reference
so you can indeed wire them in series.

Phototransistors saturate in a broadly similar manner to a regular BJTs but tend to have higher saturation voltages, say 0.8 V or so compared
to 0.2V-0.3V for a small signal BJT. Thus if you had three in series all saturated then the voltage would be 2.4V. If you have a 5V BoB then you are in
no-mans land. If you have a 12V or better still a 24V BoB then 2.4V should still be comfortably below the low level threshold.

What sort of motion controller or BoB are you using? Is there any need to economize on inputs? Do you not have enough spare inputs to have one HLFB per
input?

I use an ESS and I made my own BoB. I elected to have ports 2&3 of the ESS as input dominated, ie pins 2-9 of each port as inputs in addition to
the regular inputs 10,11,12,13, and 15. Port 1 has pins 2-9 as outputs and are used for Step/Dir

Port 1
Outputs 1, 2-9, 14, 16, 17 =12 outputs
Inputs 10, 11, 12, 13, 15 =5 inputs.

Port 2
Outputs 1, 14, 16, 17 =4 outputs
Inputs 2-9, 10, 11, 12, 13, 15 =13 inputs

Port 3
Outputs 1, 14, 16, 17 = 4 outputs
Inputs 2-9, 10, 11, 12, 13, 15 =13 inputs

Total
Outputs =12 + 4 + 4 = 20
Inputs = 5 + 13 + 13 = 31

I have used them this way:

Port 1
10 outputs = Step/Dir for up to 5 servos
1 output = Enable, applied to all installed servos in common
1 output = Reset, applied to all installed servos in common
5 inputs = one alarm per servo

Port 2
10 inputs(
X++, X--, X home,
Y++, Y--, Y home,
Z++, Z--, Z home,
Probe.)
3 inputs (Spare)
3 outputs(
Spindle On/Off
Spindle PWM
Coolant Pump)
1 output(spare)

Port 3
5 inputs(
Incremental/Velocity jog
2 inputs, X/Y/Z axis select
2 inputs MPG A/B inputs)
8 inputs (spare)
4 outputs (spare)

Outputs 15 committed, 5 spare
Inputs  20 committed, 11 spare

So as you can see I have used inputs where I need to without trying to economize at the expense of function, and yet still have a healthy margin
of spare IO.

Craig
'I enjoy sex at 73.....I live at 71 so its not too far to walk.'
Re: Glitch on X movements
« Reply #16 on: January 20, 2022, 03:35:39 AM »
They are indeed wired in series. Had no idea what I was doing when I wired all this up and was just following what other people had done. And I'm pretty sure there is no software to support the HLFB anyway. It's currently just an input that does nothing. Once again, at the time had no idea what it was for or meant to do.

I'm running the ESS with a C25 BoB, 5v. I think it would be beneficial to run a 12v or 24v system to mitigate signal interference. I think the clearpath servos support that so would be just a case of upgrading the BoB. I've attached the pin layout. I do have 2 spare inputs which I'll use to change HLFB.

Would you like to share a picture of your BoB? Do you sell them?

Was just online looking at the C52 for the third port expansion. Would cost to get it from the states and add a whole other level of ugly to the control panel. The MB3 looks like a clean option.
Re: Glitch on X movements
« Reply #17 on: January 20, 2022, 04:38:00 AM »
Hi,
Quote
I'm running the ESS with a C25 BoB, 5v. I think it would be beneficial to run a 12v or 24v system to mitigate signal interference.

No, if you choose the impedance levels correctly then the noise performance is IDENTICAL between 5, 12, 24V systems....it all comes down
to Signal-to-Noise Ratio....not voltage level.

My mini-mill which I operated for seven years had a 5V BoB and 5v signaling. My new build mill, in service for about six months now, uses Delta
servos, which use 24V signaling as is common with industrial gear, thus I made my BoB 24V also, excepting the Step/Dir outputs which are
5V differential for higher signal speeds. My choice to use 24V signaling is not about noise performance, its about having a clear and consistent
design throughout supported by a wide range of suitable electronic and electromechanical parts.

I looked at the MB3, its a well thought out design and a quality build and deserves its high reputation. If using the MB3 you are perforce limited
to the design choices CNCRoom have made. When I designed my BoB I could have exactly what I wanted and absolutely nothing I didn't.....no
compromises. My own BoB has been working great....but like all designs it can be improved.

I have found that I can make a better PWM circuit than my existing circuit. When I get around to making the new circuit it will be within 1% of
linear with duty cycle whereas my current circuit is linear within  7.5%.

About a fortnight ago I discovered that the circuit (2 dual channel OP-amps per axis) I used for generating the differential Step/Dir signals
while fine with my Delta servos is just a little to noisy for Step/Dir of my Allen Bradley servo used for my heavy duty spindle motor.
I have redesigned the BoB so that the differential Step/Dir signals are generated by a new generation line driver IC.....with considerably better
characteristics than my previous home-brew attempt. The ICs are $11.00NZD each, I require three of them, which is a little more than I like
paying for analogue ICs, but they look the part. I ordered them 10 days ago and they turned up yesterday from the UK, freight free.

My mill is working perfectly well with my existing BoB....so I'm in no great hurry to build another....but will get around to it in the next few weeks.
I want to be able to use my Allen Bradley servo spindle motor in Step/Dir position mode so that I can use it for rigid tapping. I've used it for rigid tapping
on my mini-mill a dozen or so times over the previous two years since I built the spindle. I have only just started to make the changes necessary
to have the same functionality with my new mill which lead to the discovery of the noise shortcoming of my first BoB design.

Quote
Would you like to share a picture of your BoB? Do you sell them?

I'll take some photos of them, they are split into two boards. Given that I have design improvements to make to both of them...no I haven't sold any,
but may do. They are hand-made and hand soldered which makes them a labor of love rather than a profit making exercise. I could post
the design files if you wish to make your own, although it might pay to wait until I have the GenII boards made, tested and in service before
copying what I have done!.

Quote
Would cost to get it from the states and add a whole other level of ugly to the control panel.

My ESS, BoBs and power supplies are screwed  to a plastic chopping board, they are about the right size and cheap source of plastic. So when I say
that my control system is 'breadboarded'....I bloody well mean it. I have another breadboard that has the single board PC and its power supply,
yet another breadboard that has the three Delta servo drives, the AC distribution buses and  EMI filter and yet another breadboard for the VFD and
Allen Bradley servo drive for both spindles. You might laugh, and to be fair its pretty untidy......but better than my mini mill. When I built that
I just nailed the various boards and things to a piece of MDF, promising to go back and do it properly later. Seven years later and its still the same. There
is nothing more permanent than a temporary solution.

Craig
'I enjoy sex at 73.....I live at 71 so its not too far to walk.'
Re: Glitch on X movements
« Reply #18 on: January 20, 2022, 02:26:31 PM »
I have to be honest, most electronics, circuitry is well beyond my current level. I dabble in it when the project requires it but it's all very much trial and error and smoke.

My mill is working ok as is but I'm not sure I'll ever be content with it. There is always things I'd like to improve on. The spindle is one of them. It's only a matter of time before the retro fit bearings give up and I wont be replacing them, it will be a whole new spindle design. I'd love to machine up a new spindle cartridge but I'm afraid my little lathe is just not up to the task.
Spindle motor and drive are on that list as well so will need the ESS third port at that point for the encoder on the spindle. Rigid tapping would be a nice option to have.
Re: Glitch on X movements
« Reply #19 on: January 20, 2022, 04:50:30 PM »
Hi,

Quote
I'd love to machine up a new spindle cartridge but I'm afraid my little lathe is just not up to the task.

You might surprise yourself too.

I have a 750W 24000 rpm asynchronous spindle, and I use it extensively and have done so for seven years. It spins too fast with way to little torque to be
a serious contender in steel and stainless......so I made my own spindle. I was lucky enough to find here in New Zealand a second hand 1.8kW Allen Bradley AC servo
and drive for $900NZD including shipping ($650USD). I still had to buy and/or make the cables, another $250NZD and buy the setup and tuning software for another $200NZD.
I still had a good torque dense motor for a spindle at reasonable price.

Like you I thought I would be unable to make a creditable spindle housing, my machining skills just aren't up to that standard. The problem was however that the cost
of a precision spindle or getting one made was just beyond my means. By this time I had already bought a 'You Beauty' Rego-Fix cyclindrical tool holder ($450NZD) and
a set of P4 matched angular contact bearings, seals from the UK,....so I had all these parts on hand and yet could not use them. In the end I decided 'to hell with it' I'll make
my own and see how it goes....and thats what I did. The design was very straight forward as I needed to consider very carefully how I was going to do it to maximise
my chance of success WITHOUT sending it out for cylindrical grinding....and costing a fortune. While my attempt was far from perfect it works a treat. I don't have the bearings
as well aligned as I would like and they run hotter than I would expect so instead of getting thousands of hours use I suspect I'll get hundreds....but still I'm very happy with
my effort. Most importantly I have been able to utilise all the parts I invested in and have got the functionality that I wanted. I've had about 200 hours use with it, my highspeed
spindle has seen thousands in the same time but when I need low speed-high torque, I NEED it.

Craig
'I enjoy sex at 73.....I live at 71 so its not too far to walk.'