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Messages - jimpinder

481
General Mach Discussion / Re: (2) controllers - setup questions
« on: June 25, 2008, 12:52:09 PM »
What you seem to be saying is that you are having Mach 3 running a mill on port 1. What you want to do is run another set of kit on port 2, using a different GCode program.

I do not see how you can run multiple versions of mach 3 simultaneously on the same machine.

Mach 3 uses a great deal of the computers processing to generate the various pulses, in strcit time, required for moving the steppers/servos.

What exactly are you asking.

482
General Mach Discussion / Re: Backlash
« on: June 25, 2008, 12:28:52 PM »
It doesn't matter - does it

Backlash is that number of pulses the computer puts out, where the axis does not move. As long as the computer calculates the number of pulses correctly, including that required by backlash, then it will arrive at the right point. If you are saying that the computer moves your axis back by 1 mm before adding the backlash - how can it ??? The computer puts out the pulses, and the axis does not move until the basklash is taken up, the gears are bedded in and got their shoulders to the table ready to shove the other way.

Mach 3 deals with backlash in a funny way, and it is a little bit disconcerting. The axis appears to move, the backlash then is applied (usually at a different frequency so you hear it) then the movement continues - three distinct sounds. You can adjust the speed of your backlash if you wish (on the backlash page).

Are you saying by this that your backlash is incorrect becaue in my experience, although the way backlash is applied is a bit odd, it is still accurate.


483
Your calculations for your motor steps per unit are way out.

Modern drives use microsteps (my Geckos have 10 - yours may be different - they may be switchable - if they are try 1/8th as a compromise). Modern motors are normally 1.8 degree motors so in themselves require 200 steps per rotation. So combined with the drivers they require 2000 steps per rotation - NOT 32.

If you then attach this motor to a leadscrew on a lathe or mill, the leadscrew will require a number of turns to move one inch - mine is ten, so I needs 20,000 steps. I also have a gear down system so my actual steps per unit is  60,000.

Set your steps per unit at what you calculate it will be on the mill you are building - or pretend - about 20,000 which isn't far off. The fill in your speed per axis at about 10 ins per minute, and set your acceleration at one.

See what the results are then.


484
General Mach Discussion / Re: Tangental control can it be better???
« on: June 25, 2008, 11:16:46 AM »
If your code is all little straight lines, then - yes - I think if you then precalculated the tangent of the line and put that in as an A command on the line, then you can do away with tangential control and just use the CV.

Now its not going to be completely accurate, so you might be able to even use two adjacent lines and calculate an A angle to suit the mid point between the two, but, what the hell, we are only talking about the small bit of time when the machine is moving from one line to another, and the cutter (if thats what it is) is going to be on the right line for the new line anyway, so it might take up a slightly wrong angle in the first place, but this is only going to get better.

485
General Mach Discussion / Re: Macro
« on: June 25, 2008, 07:51:19 AM »
Got a quick half hour before lunch -

All three Macros in the one file. You will have to split them and post them in your Macro folder under M3, M4 and M5

Rather than using the original M3 DoSpin etc, I just got the macro to turn on Output 1,2 or 3 as required.

Now this works on my office computer - I haven't had it up and running on my workshop machine attaced to the  lathe or mill.

It turns the Outputs on and off - allocate the outputs to which ever pins you are using.

The delay time is in Milliseconds and can be altered to suit.

486
General Mach Discussion / Re: Macro
« on: June 25, 2008, 06:35:12 AM »
That was quick - I took my post back and added a bit - but you had replied anyway.

I think I would utilise the output# pins. If you look on Config/Ports and Pins/Output Pins - you can see that there are quite a few designated. So pick 3, one for forward, one backward, and one for motor on. You can then allocate these to whichever pins you want.

The program would then be:

Switch on direction relay pin
Delay
Switch on Drive relay pin
End

- and -

Switch off Drive Relay pin
Delay
Switch off pin
End

I don't know whether you have a list of the Vis Basic commands for use with Mach 3 but they are on the forum. I don't know the syntax off by heart so I will have to look them up.

You could put this post on the Vis Basic and the Brains forum - you might have a lot more people familiar with the syntax - particularly with Brains ( I have never done any - and they might be much simpler).

There are two Brains video tutorials you can watch, and one on scripting if you have never done any.

I get back to you when I have had a look - my wife says I've got to tidy the "shed" today. >:(



487
General Mach Discussion / Re: Macro
« on: June 25, 2008, 06:14:25 AM »
It is fairly simple to write,
At the moment the M3 and M4 put out seperate signals on seperate pins any how, so all that would be required is the addition of another signal to turn on the drive after the delay -  but  - it might be easier just writing a script using the output# pins to do the switching.

1. How are you going to control your contactors - are you using outputs through the LPT1 socket to drive intermediate relays to close the   contactors - or can you drive these contactors directly.
2. What is the timing on the delay - are we looking at the time for a relay to close or longer.


488
Everybody seems obsessed with circles.

Now are you cutting a circle using G2 or G3 command or have you got a cad and cam program that make your cicle up from lots and lots of little lines.

G2 and G3 are catered for on Mach, and smoothly alter the acceleration and decelation of the axis is sequence.

With lots and little straight lines, Mach has to stop after each line, calculate the next line and carry on.

You can smooth this out by selecting CV mode in config, but cutting the circle in G2 or G3 is preferable.

489
When you say 1.5 rotations - rotations of what? the motors themselves, your lead screw or what.

To get some idea of the frequency of this, what is your number of steps per  unit set at.

Does this occur on all axis simultaneously.

I have a similar little stutter in my system and little while ago - and I traced this to my 5 volt supply system - the voltage regulator was on the points of giving up - it did give up - so that was how I traced it.

490
General Mach Discussion / Re: Tangental control can it be better???
« on: June 24, 2008, 12:32:19 PM »
I was hoping you wouldn't ask me that, because I have to use my brain, and lay back in my chair, drink my second can of beer and think:

Calculation of tangent is easy, and requires one calculation per line - tan@= x/y or whatever - and you look up in tables, arrive at @ and can set the A axis at the right angle. A little bit more in it, depending on + or - but essentially a one off operation per line.

CV is much more complicated - since, depending on the setting when CV is to start, and depending on the acceleration settings for your axis, then (because this is in the slowing area of one line, and the acceleration of another) :-
1. You have to calculate where the XY poisiton of the old line would be, in line with the deceleration rates set.
2. You have to calculate where the XY of the new line would be in relation to the acceleration rates set and the times of the introduction of the CV.
3. Combine the two into a new XY position.
4. Save the where are we now position and then calculate the speeds necessary to move the axis to the new position.
5. Implement those speeds.
6. Do this again immediately because the situation is always changing.

What you are then asking is do another calculation of new x - old x, new y - old y, =  x(t) and  y(t). Then do the tan@ -= x(t)/y(t) again and then ook up a new tangent angle for the A axis.

I suppose it can be done - but whether it will be inside the parameters of our bog standard P.C. to do it in the near future, or whether you will have to add Smmooth Steppers amd an add on maths cards in the computer, I wouldn't like to say.