Messages

21

General Mach Discussion / Re: Losing steps

« on: June 17, 2009, 02:37:13 PM »

If it is a simple job, swap the drivers - i.e. run the Y on the X driver card and vica versa.

If the trouble transfers to the X axis, this would indicate some problem om that card, which as Ray said, could be replaced (and I would not dispute using Gecko). If the fault does not transfer itself, then it might be a problem with the motor.

How many steps per inch are you using ? Is there any stiffness or wear on the axis that the slower speed has difficulty in overcoming.

22

General Mach Discussion / Re: Slave ax less Master ax. Help to move it correctly

« on: June 12, 2009, 02:39:04 AM »

Greg - I didn't realise a slaved axis just took over all the data from the master - I thought it just moved the same distance in the same time - pity.

Inna - I think I would post this on the brains page, and see if someone could write a brain to repeat the X axis commands to the A axis at a slower speed.If the ratio is constant it should be now problem. I dont know anything about brains.

23

General Mach Discussion / Re: Is this backlash or missed steps????

« on: June 12, 2009, 02:34:22 AM »

Ray - I didn't mean to argue - the way I saw it, the 0.2 is the pitch per tooth - thats how these  read in my catalogues. A 40 tooth gear revolving once would give 8 units of movement.

Perhaps mgandy02 can photo the set up and show us. Tell us what the movement is on this rack. i.e. how far does the table travel for one revolution on movement of the final drive.

24

General Mach Discussion / Re: Gecko 201 Dir pulse and step pluse?

« on: June 10, 2009, 04:14:43 AM »

I use three (3) with acceptable results. I use Gecko drives which say 2 but it is better to have a longer pulse than is needed. Unless you are talking super fast speeds, there is enough tinme for any length up to 5.

Bear in mind, if you change this figure for one axis, then all will change, so this should suit your slowest drive.

25

General Mach Discussion / Re: Is this backlash or missed steps????

« on: June 10, 2009, 04:07:11 AM »

I am a bit at odds with Ray - this might be because we see your set up differently.

I see it as the motor drives the gearing. (why you didn't use simple numbers for this I don't know - I use 3 to 1 timing belts) the gearing drives a 40 tooth pinion which sits on a rack of 0.2 pitch. You do not say whether this is mm or inches, but it does not matter.

With this set up, every turn of the 40 tooth gear means 8 units of movement.

Both axis -  200 (motor steps per rev) x 10 (microsteps - 10 for gecko - alter this to whatever you are using) = 2000.
Pinion on rack - divide by 8 = 250 steps per unit.
Multiply this by 4.875 for X axis = 1218.75 steps per unit.
Multiply this by 5.143 for Y axis = 1285.75 steps per unit.

This needs amending for the microstep function - may be to 8 or 16 whichever your drives use but I think it is accurate.You will notice, of course, that the steps per unit are not whole numbers, and this is becasue of your odd gearing, It doesn't make much difference in the scheme of things, becasue Mach calculates to 12 places of decimal - but for working these things out a simple 5 to 1 would have been easier, or even a 4 to 1 to offset the pinion. Are these numbers anywhere near what you have been using.

26

General Mach Discussion / Re: Slave ax less Master ax. Help to move it correctly

« on: June 10, 2009, 03:34:00 AM »

You seem to be saying that you want both these axis to move together, but A to move more slowly that X.

I would try a clever trick - which may work - alter your steps per mm or inch (whichever you use). If say your A axis requires 100 steps per unit, then alter the steps per unit on the motor settings to 90. This means that the computer will only deliver 90% of the pulses to the A axis, meaning it will travel a shorter distance.

You can then make one slave the other and both will move in the correct relationship.

27

General Mach Discussion / Re: microsteps

« on: June 10, 2009, 03:26:54 AM »

You have arrived at the correct answer by a long route.

Calculating steps per unit is easy - your motors need 200 steps per rev, and therefore your 5mm pitch leadscrew gives you 1mm movement for every 40 steps (1/5 of a rev).

Your drives add micropulses to give smoother operation, and as Hood said, and good number to try is eight which seems to  give good performance.

If you used 8 then your pulses per mm would be 40 x 8 = 320 - and this is the figure you would put in the motor settings.
You appear to have stumbled upon 16, which is obvoiusly 40 x 16 = 640 steps - which is clearly what the drivers are set to.

It doesn't honestly matter. If you run with that and performance is satisfactory, then use it. Ray mentions rapid speeds - i.e. the speed you want your machine to traverse on a non-cutting move. Yes if your computer and drives will run at that speed so be it. If you find you set your rapid speed, and the axis starts missing or stopping (it stops moving and there is a big whine from the motors) then you may have to alter the DIP switches to the 1/8 setting, and alter your steps per mm to 320. The effect will be the same, it is just that the electronics will not have to operate as fast to give you the actual speed on your table.

28

General Mach Discussion / Re: motors no go in mach 3...

« on: June 10, 2009, 03:09:49 AM »

I am not sure exactly where you are.

I take it Mach is installed in a computer, and works without any machine being connected to it. You can run programs etc and watch the software "cutting" your pattern. I take it the drivers are properly installed. If you are not at this point, then this should be your first proirity. Disregard any router, and get the Mach software running. Fill in the port and pins details (and activate them) as though you had a machine connected. If you can calculate your steps per unit for your new router motors, enter that. In other words do everything just as though your router was connected.

You do not say what connection there is to your router elctronics from your computer. I use the printer port, many now use a smooth stepper etc. If you are using the printer port, it is a simple matter to connect the cable, and test the various pins with a multi meter to see if signals are being sent. I must admit is you are not seeing anything on the diagnostics page, then you must probably have some settings incorrect - like enabling each axis, or entering the prot number as well as the pin.

You do not say what your drivers are (gecko etc? ) or what your motors are (200 step steppers ?) Are you using a breakout board ?


If you can set out where you are a bit more clearly, we will be able to help you with the problem.

 

29

General Mach Discussion / Re: Is this backlash or missed steps????

« on: June 09, 2009, 03:29:15 AM »

Backlash does not repeat - by that I mean that doing it 10 times or 100 times makes no difference, the backlash is always the same.

It is the amount the axis "dwells" at either end of a move, as it changes direction. If you set off from zero, and move 1 inch, that will be accurate (if you moved to zero in the same direction. If you now move back to zero, the axis will now come up short, becasue of the backlash the axis had, whilst reversing.

However, if you now move again to the 1 position, this will be accurate again (because the axis did not start from zero, and backlash could be taken up before the axis moved) - so backlash only counts once, at either end of the cut.

You cannot be loosing steps, becasue you say that one of your axis moves too far. This must then be steps per unit.
You must CALCULATE the number of steps per unit - not measure.
If your motors are steppers, they need 200 pulses per rev.If your drivers have microsteps, then your must multiply by that - e.g. Gecko is 10 - i,e, 2000 steps. Your gearing, through the timing pulleys, must be taken into account - I have 3 to 1 on my lathe - i.e. 6000, so you come to the final drive.

I do not understand what your final drive is, on an 8' x 4' gantry, but this is simple enough - how far does it move for one turn of the drive spindle from your last timing pulley. From that you must work out the number of pulses per inch - or per mm.

Be careful with your final drive, is it imperial or metric - a lot of stuff these days comes in either, and is wrongly marketed as being imperial when it is metric and vica versa.The conversion is 25.4mm to one inch - and the .4 makes all the difference

You say your carriage moves exactly one inch, when you move it one inch. Make sure you are taking any backlash out by - moving right - stop - set up measuring device - move right again - stop - measure. If this is exact, then move back one step and see how much short this is on the return. That is your backlash.
You can enter this in the backlash table under Config and turn on the backlash compensation.

The only other thing we have had on these pages is that some of the electronics (breakout boards particularly) which inverted signals, were sometimes prone to miss the first pulses, which means that things came up short, bu I wouldn't bother with that till you have checked everyting else.

Sorry I have gone on a bit, you probably know most of this anyway.

30

General Mach Discussion / Re: Gecko 201 Dir pulse and step pluse?

« on: June 09, 2009, 02:50:02 AM »

Robbi - Which number are you talking about

Are you talking about steps per unit, are you talking about speed, pulse length or what.
Are you talking about a +5v or 0v signal to the Gecko - Gecko requires a 0v signal.
Remember Gecko's are set to 10 micropulses, so if your have set the steps per unit for your motors at 200 pulses, then you will have to change it to 2000 to allow for the micropulses.

We cannot advise you until we know what it is you want.