Actual limit on encoder frequency

[kreutz]

Hi,
Attached is a block-diagram showing the overall components of the system and how they are connected as well as the schematic for the X-axis servo. Both are more or less reflecting the current state of system and IS work in progress. The complete schematic is now over 20 pages...

/Henrik.

Good Work!!

Best regards,

Kreutz.

[H.O]

Todor,
The HP-UHU logic supply is 15VDC, I didn't find a suitable 15VDC DIN-rail mount supply so I went for a 24V supply and a 7815 for each drive - seems to work fine. (I wish the logic supply would've been 24V since that is more "standard" but this is fine too)

The limits aren't included in the block-diagram yet.... They are all wired in series with the E-stop, the power-supply is turned off and the bleeder resistor discharges the caps. With no load on the powersupply it discharges from 130 to <20V in ~1s. Mach3 is informed about the Limit-condition via the C11 breakoutboard and on the control-panel there's a pushbutton that bypasses the switches so the system can be enabled again. It also, via the PLC, signals a limit-override to Mach3 so recovery is possible.

The plan is to automatcailly set the jog-rate in Mach3 to a very low value when the Limit-override button is pressed, this will hopefully prevent damaging the machine when jogging off the limit. Not that I will ever hit a limit... ;-/

Thanks!
/Henrik.

[contactirfu]

HI Henrik - read your posts on the Mach yahoo forum - interesting talk on the Estop being handled by the drives and you writing a macro to see that mach recovers and re-homing is not necessary - with so many thing goin on within you - I wonder why there is no thread yet - are you documenting it on ur web site ?

havent seen ur website since long - wait I will take a look - hmm its almost same - if I did not notice any

hope ur build will complete soon and you will be able to share your work - its so interesting and at the same time feels way overhead for me.

My best to you -

RGDS
Irfan

[H.O]

Hi Irfan,
Thanks! The build is very slow going at the moment due to a few other things getting in the way and the fact that it's freakin' winter here.

I haven't updated the web-site in well over a year now but will do that shortly, I also plan on a thread here but I want to get a little bit further so it doesn't end up like my spindle thread... :-( (That project isn't dead yet by the way...)

Regarding the encoder thing there still quite a bit of researching/experimenting to be done as I see a few problems sneaking up that needs to be sorted out for this to work to I want it to. It is easy to read and write the part-coordinate DROs in Mach3, it is also easy to read the machine coordinate DROs but AFAIK there's no easy way to WRITE to the machine coordinate DROs which I would like to do for this to work properly.

/Henrik.

[rokag3]

hello henrik,
Are you trying to make a double closed loop ?
mixing linear encoder and rotary encoder

[H.O]

Hi,
No, not at all, Mach3 is completely open loop - always been.
What I've done is split the rotary encoder on the motor between the HP-UHU drive and the Smoothstepper. The Smoothstepper counts the pulses from the encoders and display the position in a set of DROs on the Mach3 screen.

If the servos are tuned tight (which they should be) they WILL fault if an E-stop condition occurs while the machine is moving at high speed. When that happens the position is lost since the drives no longer controls the motors and they coast to a stop. The true position is still known though because the Smoothstepper keeps counting the pulses so IT knows where the machine is even if it's moved manually or whatever.

The idea is that when I take Mach3 out of E-stop it will let me update the position with the data from the encoder DRO so I don't have to re-home the machine.

The problem, as I said earlier, is that it is not allowed to write to the machine position DROs in Mach3. You can write to the local coordinate system DROs (G54, G55 etc) but that means that I'll have to rezero/set the encoder DRO each time a new fixture offset is in use. This will take some investigation/experimenting to come up with a suitable solution (if there is one).

I want to make it as transparent as possible. I don't want to switch screens and press 10 different buttons to "sync up" I wan't it to be semi-automatic. When I hit Reset to take Mach3 out of E-stop it looks at the machine cooridinares and compares with the encoder DROs - if they don't match it'll give me an option to home the machine (as must be done on power up) or to resync. Well, that's the vision....we'll see how it goes.

/Henrik.

[contactirfu]

bump bump - whats happening Henrik

[H.O]

Hi Irfan!
Well, work on the knee mill conversion continues...slowly. I've started a thread about the project so please come and join me there!

And to tie into the subject a bit I've had absolutely no problems with the Renco encoders during the months that I've run with them on the bench. Hopefully I'll be able to testrun them on the actual machine in a not too distant future.

/Henrik.