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Messages - SimonD

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General Mach Discussion / Re: Getting Outputs to work?
« on: August 11, 2007, 06:43:23 AM »
Thanks to everyone for their suggestions. All is working now.

I think it must have been a bad connection somewhere. I took the PC apart, removed the LPT card, put everything back together after swearing at it all and it seems to be working now! I have a healthy 5v coming out of the pins when activated by MACH3.

Thanks again

General Mach Discussion / Re: Getting Outputs to work?
« on: August 10, 2007, 06:33:40 PM »
Thanks for the reply.

I had no idea what an "open collector port" was so I had a bit of a read on the net (I'm slightly more enlightened now)

I have 2 ports on the PC and have tested both, neither of them give out any voltage on the pins themselves with nothing connected even when MACH3 says that is it.
I will try and get a parallel printer and see if it works ok.

I should try pin 8 & 9, I have not tried those ones, I was hoping to save them for a 4th axis.

The port pin test program would be handy to try please.


General Mach Discussion / Getting Outputs to work?
« on: August 10, 2007, 12:46:48 PM »

I have 3 axis with enable, limits and home switches all working fine.
I am trying to get a couple of relays to work but have run into problems...

I have set the Output#1 & Output#2 pins to 16 & 17 respectively and have set the flood and mist commands to point to one of these each and removed the "disable" checkbox.
The lights on the diagnostic screen flash as expected when the buttons are toggled on.

The problem seems to be that I am not getting any volts out of either pin. I have checked with a multimeter on both pins and neither of them are giving out any voltage and appear to be permanently connected to ground?

Has anyone got any ideas as to what might be going wrong please?


General Mach Discussion / Re: limit switches and cable sheilding
« on: August 03, 2007, 06:09:25 PM »
I am using 2 core and shield for the limits. Grounded at the controller end only.

After reading through the forum one suggestion was to connect a 0.1 microfarad capacitor across the switch.

The only capacitors I have to hand are 1 microfarad and so tonight I tried it...
I attached a 1 microfarad capacitor across each of the two switches on the longer run and it seems to have cured the problem.
The machine ran a long test program without failing which was encouraging.
I will do some more testing tomorrow and see if I can just connect the capacitor at the controller end of the cable, that way I will only need 1 capacitor per axis.

Is a 1 microfarad capacitor too big? What effect will it have?

General Mach Discussion / Re: limit switches and cable sheilding
« on: August 03, 2007, 01:55:35 PM »
I am suffering with Limit Switches triggering at the moment albeit only occasionally now.

My machine currently has 2 axis running, with 2 limit switches on each axis, wired in series to individual inputs.
Both the motor cables and the limit cables are shielded. One cable works fine (1.5m) , the other seems to pick up interference, it is almost as though it is a "tuned length" (2m)
The cables are wired so the shield is connected only at the controller end. If I switch the cables around then it trips amost immediately.

I have tried debounce up to 2000 and it seems to improve the situation slightly.

General Mach Discussion / Re: Stepper Torque
« on: May 24, 2007, 01:11:15 PM »

I used...
Practical Efficiency 0.9
Torque 0.83
Ratio 2.5
Pitch 0.005
Gravity 9.81

(0.9 x 0.83 x 2.5 x 2 x PI)/(0.005 * 9.81) = 239.2 Kg

However the efficiency is wrong. it should be...
0.943 Theoretical efficiency * 0.9 Practical Efficiency => 0.85 according to the SKF Ballscrew Manual.

This is for the load acting directly on the leadscrew.

The reason for the losses as you said is the friction in the slideway, not getting the maximum out of the stepper etc etc.

Once I have a more reliable setup I will do a test again. I am using a trapezoidal thread though so will get significantly more losses than a ballscrew. My stepper is "pulsing" at the moment! I think it may be down to the power supply shutting itself down. It does about a full turn of the leadscrew then pauses for a second then does another full turn etc. It is not consistent though, sometimes it runs fine.


General Mach Discussion / Re: Stepper Torque
« on: May 23, 2007, 06:11:24 PM »
I've fixed the problem.  I stripped it all down and started again...

It does help if you read the multimeter correctly! I had set the current way too low!
Oh well you live and learn...


General Mach Discussion / Re: Stepper Torque
« on: May 23, 2007, 02:23:56 PM »

If my sums are correct...

Assuming that the motors give the the same force in both direction. If the motors can only just lift the head then that is 32kg for the head and 32kg force from the leadscrew. Obviously the ratio is more in favour of the leadscrew otherwise it would not actually be able to lift it due to frictional losses.

I calculated that theoretically your stepper/drive train should be able to lift a 240kg mass in an ideal world. Clearly something is amiss.

Eitherway, I would be more than happy with 32kg from my motor! that would take some force to stop the slide. I am getting nowhere near that!


General Mach Discussion / Re: Stepper Torque
« on: May 22, 2007, 04:06:22 PM »
Sorry, forot to say...
The machine is a small bench-top mill.

Competitions / Re: ******Guess and win a G100 Grex******
« on: May 22, 2007, 03:49:05 PM »

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