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Messages - bigandy

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1
SmoothStepper USB / Re: SmoothStepper plugin noise filtering.
« on: June 09, 2009, 01:37:05 PM »
I know the stepper drives have optical isolation already, it is just the inputs to the SS that are not isolated at present.

My machine is very much "lashed together" electrically at present.  I am intending to construct a little portable trolley type enclosure for it, so I'll tidy up all the wiring, and replace the input signal wires with shielded cables when I do that.

For now though, I am getting results just using the noise filtering options available.

cheers
Andy

2
SmoothStepper USB / Re: SmoothStepper plugin noise filtering.
« on: June 09, 2009, 01:00:36 PM »
That's correct Jeff, the limit switches are fed straight into the SS (all on Port 2).  I'm using a really basic breakout board that I cobbled together from a small sheet of veroboard (stripboard).  I'm still at the experimenting stage, so I may get around to pruchasing a better breakout board in the near future.

Does opto isolation have any effects on reducing the noise seen?

Cheers
Andy

3
General Mach Discussion / Re: Feed rate strangeness.
« on: June 08, 2009, 05:04:04 PM »
Ah I see, I'll give the 027 version a shot tomorrow.  Thanks for the info re. the SmoothStepper versioning too.  I've just had a peek at their website, and I'm still on the "me" revision of the plugin, so I've downloaded the "ogb" version, and I'll try that tomorrow :)

Cheers
Andy

4
SmoothStepper USB / Re: SmoothStepper plugin noise filtering.
« on: June 08, 2009, 02:28:35 PM »
I did notice that the Estop was being triggered especially when powering up the stepper motor drives, and also when I started an axis moving.  Once the axis was moving (when the noise filtering value was around 10µs) it would carry on fine, but then trigger the Estop when it changed direction.

Thinking about it, I haven't used shielded cable for the limit switches, so I'll have to change that when I get a moment.

Cheers
Andy

5
General Mach Discussion / Feed rate strangeness.
« on: June 08, 2009, 02:16:01 PM »
Hi folks.

I've just been testing out my limit switches on a small 3 Axis mill, and I have encountered a bit of a strange one.  I have slowed down the feed rate using the little + and - signs in the feedrate box on the main screen.  This works great, and has the mill moving at a snails pace, so I don't damage anything if the limit swtich fails in some way.

However, I have noticed that if I hit a limit switch (thus triggering an Estop) and the reset that condition by clicking the reset button on the PC (i'm manually winding the axis off the limit switch), the feedrate goes back up to 100%.  The strange thing is that the display in the feedrate panel still shows the much reduced rate.

If I change the feedrate slightly (say reduce it by a couple of percent), it then starts behaving as expected, with the axes moving very slowly.

Has anyone encoutered this before?  Anyne got any ideas why it may be happening?

I'm using the R3.042.020 lockdown release.  I am driving my mill through a SmoothStepper USB device (which I suspect may be the problem here).

Cheers
Andy

6
SmoothStepper USB / SmoothStepper plugin noise filtering.
« on: June 08, 2009, 01:55:28 PM »
Afternoon all.

Just a quick query about the noise filtering in the SmoothStepper plugin control menu.  I have connected up all my limit switches today (6 in total) and I have found that my system has become unusable.  Everytime the reset button is pressed in Mach 3, it would immediately trip out again.  On the odd occasion where it didn't trip out, I could jog an axis for a fraction of second, before it tripped out.

I have tried a few things like tidying the cabling up, and re-routing a few wires, but the problem does seem to be down to noise getting onto the limit switch lines.  Some switches are worse than others (I've tried enabling them each indiviually) but they all seem to suffer.

I have also tried the noise filtering in the SmoothStepper plugin control menu.  This seems to have had a good effect.  I tried setting the noise filtering on the "Limits" to 5µs and this didn't really help.  Increasing it to 10µs made things better, and as I incremented it upwards, things got better and better.  I have been tinkering for about an hour now, with it set to 50µs, and have not had one noise problem.

Can anyone tell me if they have had to use this noise filtering, and if so, how much?  Also, are there any negatives of using it at all?  I'm a bit wary of just masking the problem here, but despite re-routing wires, I cannot seem to eliminate it.

Cheers
Andy


7
SmoothStepper USB / Re: Smoothstepper + steping motor drivers M542
« on: February 02, 2009, 10:47:31 AM »
I am using the MDS542 drives on my machine, driven from a smoothstepper.  I have it setup so that the signal line from the SmoothStepper (i.e. the pulse and direction signals to the drive) are wired into the + lines on the MDS542 drive, and the -side is wired to the 0v signals from the Smoothstepper.

This seems to work great for me :)

Cheers
Andy

8
General Mach Discussion / Re: Limit switch location on axis?
« on: January 15, 2009, 06:30:54 AM »
Good stuff re the softlimits.  I've got an afternoon/evening of testing and work scheduled for Sunday so, fingers crossed, I'll be able to get the limit switches and limits nailed :)

Regarding the drives I am using, they are MDS542 stepper drivers from Motion Control Products Ltd.  (see here: http://www.motioncontrolproducts.co.uk/product_info.php?cPath=26&products_id=3 ).  They actually support up to 128 microstepping, but as you say, anything over ten is pretty pointless in this application.  Being pointless didn't stop me from making a c*ck up though! :) :)

Cheers
Andy

9
General Mach Discussion / Re: Limit switch location on axis?
« on: January 14, 2009, 06:17:41 PM »
Cheers for the input guys, much appreciated!  I'm going to redesign my breakout board to feed a disable signal (5v) into the stepper drives on either an E stop or a Limit switch event, and this should stop the drives/motors in the quickest fashion.  I just need to do some more testing to determine the best position for the switches to ensure I don't get any crashes.  Hopefully it won't eat into my available travel though (Only got 9"x9"x4"!). :)

I've just spent a couple of hours wondering why my sums for the "Steps per" in Mach 3 were miles out, only to find I had got a dip switchin the wrong position, resulting in 64 Microsteps, instead of only 10!  Doh!

I like the sound of these Soft limits too.  I hope they work with the Smoothstepper driver I am using :)

Cheers
Andy

10
General Mach Discussion / Limit switch location on axis?
« on: January 12, 2009, 09:29:26 AM »
Afternoon all.

Please forgive the rather obvious question (it's not for me though, otherwise I wouldn't be asking!).  I am nearly ready to run my 3 axis router, and I just need to mount the axis limit switches to the machine now.  However, I am not sure of the best place to locate them, in terms of the axis total movement.

For example, my X axis can move a total of 12".  If it travels any more than that limit, the carriage will hit the machine frame, and something has to give (either the leadscrew nut, the motor coupling or the machine frame!).  Although that is my ultimate machine limit, is it good practice to mount the limit switches at (say) 90" of the axis total travel?

I'm thinking that perhaps it is, that way there will be time for Mach3 to detect the limit switch trigger, and stop the axis moving (allowing a bit for deceleration too).  The only thing I am wondering, is the amount of room required for this, which will determin where to mount the limit switches.  Are there any guidelines for this sort of thing anywhere?

Any opinions would be much appreciated!

Cheers
Andy

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