Messages

621

General Mach Discussion / Re: g540 spindle speed sensor help

« on: April 29, 2010, 06:57:49 PM »

I see Peter is right, I should have spent a bit longer looking at the data sheet and kept all the time units consisatnt.

500Hz = 500 cycles/second so 500 cycles/second * 60 seconds = 30,000 cycles / min (or 30K RPM).

Good catch Peter!

622

General Mach Discussion / Re: g540 spindle speed sensor help

« on: April 29, 2010, 12:05:21 PM »

You have the right idea, but the response frequency is too low on that one:

Response frequency *2 50 Hz min. (Average: 500 Hz)

It won't work much past 500 RPM...

623

General Mach Discussion / Re: g540 spindle speed sensor help

« on: April 29, 2010, 11:12:12 AM »

You need a sensor with an 'NPN' type output. Connect the sensor's power supply DC Common to the G540 DC Common and the sensors output to the G540's input. The sensors output will pull the G540's input to DC Common.

624

General Mach Discussion / Re: Problem homing when Autozero is disabled.

« on: April 28, 2010, 07:38:25 PM »

Hmmm...homing mid program while it is not a typical operation should not cause problems I think. Currently though, if you try to reference all axis with 'Auto Zero' off it will do silly things. See my post above about using the G28.1 command for the MDI line, generally I would suggest waiting until motion stops before commanding a new motion.

625

General Mach Discussion / Re: Problem homing when Autozero is disabled.

« on: April 28, 2010, 07:03:21 PM »

Are you stopping mid program or at the end of a program? I've not had a problem homing at all with 'Auto Zero' turned on, just with it turned off.

626

General Mach Discussion / Re: Problem homing when Autozero is disabled.

« on: April 28, 2010, 04:40:08 PM »

Hi Hood I have confirmed that the problem occurs with the SmoothStepper and not the LPT driver. The situation is complicated as the 'Verify' button also does strange things. I've been talking to Greg about the problem, though we have not found the cause on Greg's suggestion I tried a G28.1 with each axis individually which will home that one axis properly no matter that the 'Auto Zero' mode.

So it looks like a work around at this time is to first keep 'Auto Zero' turned on, reference all, turn 'Auto Zero' off and then us the MDI input to run a G28.1 on each axis. (i.e. G28.1 Z0, wait until it is done then G28.1 Y0, etc). I'll try and remember to update this thread when a solution is found.

627

SmoothStepper USB / Re: Whats the current developement state of the SS?

« on: April 25, 2010, 01:01:19 PM »

But remember, even VMC's with ground ball screws and all the rest also use backlash comp.  It matters for best results.

I suspect this has more to do with marketing than performance. Open loop backlash comp will always have serious drawbacks, no matter what type of machine your trying to use it on. Ask any machinist about watching the table jump on a manual mill as all of the backlash in one axis is suddenly taken up by the cutting forces as your feeding the opposite axis. The same things happens on our CNC machines, so without knowing exactly where the table is there is no way you can accurately compensate for backlash. One benefit of having relatively poor performance lead screws is that the increased friction helps to prevent the table from being pushed around.

Now, if you have glass scales or other form of auxiliary encoders on your table there are some high $$$ motion control cards that can make use of them for closed loop backlash compensation. But then you in a completely different price range, at 10x to 20x the cost of the SmoothStepper just for the motion control card.

Don't get me wrong, I would love to see backlash comp for the SS. My main interest to is to see if there would be any improvement to the circuit boards I make.

628

General Mach Discussion / Re: Machine not backing off switch when homing

« on: April 09, 2010, 12:17:41 PM »

If you have an oscilloscope, or access to one, take a look at the signals your home switches are putting out. I suspect you'll see a lot of noise and one version of Mach's driver just happens to ignore just enough of it to work. The thing about making things noise tolerant is that what might work well in your case will not work for many other folks. If you can provide a cleaner home switch signal to mach you may have better luck. (Try a 0.1uF cap across the switch.)

629

SmoothStepper USB / Re: smooth stepper works differently in different computers?

« on: April 07, 2010, 03:30:52 PM »

Are you saying that the SS does not show up in Device manager when it is hooked up? If so what is the status of the three LEDs on the SS?

630

SmoothStepper USB / Re: smooth stepper works differently in different computers?

« on: April 07, 2010, 01:10:08 PM »

I would not say that the cable is 'known good' as it could be just marginally working on the laptop.  Checking with another good quality cable is cheap and easy to do. The symptoms you are describing sound like a bad USB cable. Also, make sure you have all the right drivers for your  PCs hardware.