Messages

41

General Mach Discussion / Mach 3 and Burny 3

« on: March 06, 2010, 02:06:36 PM »

Hi,

Ive just been offered the box that goes under a burny 3 controller with the servo drive cards in and all the buttons on the front, i presume it has input and ouput cards as well, my question is can mach interface with this using step / direction or does it work on a bus or some needlessly complicated system like that? It would be ideal if i could connect to it since i dont really want the burny 3 but the servo drives would be nice.

Thanks for any help

Matt

42

General Mach Discussion / Re: Encoders, steppers and mach

« on: March 03, 2010, 02:40:33 PM »

Thanks for the input,

I bought a g100 a while back with the aim of trying to do some of this stuff but have found it to be worthless, everytime i touched a home switch it would reset all axes to zero so ive given up on that. So what would anyone recommend?? I had a quick look at the kflop and galil but not knowing what i need i cat really judge them. I need to be able to drive 3 4.2A steppers, take encoder feedback from them and maybe drive some ordinary dc motors on the motorised z posts i have. Can any of these units do this? i think it would be easier to have a controller and separate drives since most of the integrated packages are only good for sort of 3.5A. What will it cost me??

Another question i have is how much should a decent 400w servo and gearhead cost me? Whats the difference between ac dc brushed and brushless?

Thanks again

43

General Mach Discussion / Encoders, steppers and mach

« on: March 03, 2010, 08:46:44 AM »

Hi,

Im currently upgrading my gantry with an old esab bridge, this uses frction drive which im  a bit worried about but assured it will be fine, the servo system that would have been on this table would have had encoders turned by a gear rack on the rails, so if there was wheel slip i think it should have compensated for it?? So with my stepper system can i do this? am i right in saying mach would support encoders and would correct the position of the gantry according to the encoders rather than by the number of steps???

Not really on mach but the other question i have is about the steppers themselves, they are rated to take 90vdc, am i right in saying when you rectify an ac voltage it is reduced? Also can i over supply my steppers with voltage by a little and still not kill them? Im just wondering if i can rectify the 110vac in the shop and run the motors from it to save having a transformer?

Any help would be great

matt

44

General Mach Discussion / Re: Plasma Application, Mach3 torch height control.

« on: February 13, 2010, 03:08:35 PM »

Im interested that others are looking down the route of using a plc, i looked at this, in simple terms this is what other thc systems use, an external processor to do the thinking and tell mach what to do. The reason i decided against it, and i got as far as buying the plc, is that i found mach would do all this for me if i used a brain. Critics of the system say brains are slow, thats maybe true but i still think they are fast enough for this application, more of a limitation is there is no ability to make a p i  d loop, also you have to get an analogue value into mach. I was/am using a pokeys to do this, the analogue input is less than great, the value wanders quite alot when the voltage is constant. I was planning on using a g100 for this instead but after spending ages changing my machine over i had huge problems with the g100 so had to abandon it. Maybe i should revisit this, maybe through using buttons in mach i could enable/ disable the plc with connections and raise and lower the target voltage in the same way, i just dont really like the two screens and input buttons etc, its just ugly.

As far as interfacing with the plc goes using the voltage divider there should never be voltage spikes formt he plasma cutter larger than the maximum voltage of the transformer unless they are noise, so if you can fire into free air and not cause a problem with over voltage to the plc surely voltage spikes will simply give an erronious reading??

45

General Mach Discussion / Re: Homing, machine co ordinates and touch off

« on: January 31, 2010, 02:16:10 PM »

Ive been trying the G31 all afternoon, still no luck.

I have substituted G31 instead of G28.1, put in a value of 50mm so the torch has loads of slack to go down and touch the switch, then reset the dro to zero, then lift the torch by the switch offset, then reset the dro to zero, then raise to the peirce height. so goes a bit like this

G31 Z50

G92 Z0.0

G00 Z10.7

G92 Z0.0

G00 Z5.00

I figure that should work? But it doesnt, the torch comes down, the switch trips, the dro resets, then it goes wrong, if my torch offset value is posative then the torch goes up until it hits the z axis limit switch somewhere around +60mm, if it is negative then it reduces this movement but reagrdless of where it stops the torch going up when the next G92 is issued it adds a value into the dro, then my G00 Z5.00 simply goes up 5mm after this, usually ending up somewhere around 35mm.

Surely when the offset is put into the dro at the G92 making it greater than 5 the G00 Z5.00 should make the axis go down not up any more since im in absolute distance mode?

Where is this offset coming from? At the last G92 the dro just wont zero?

Any help would be greatly apreciated, im getting to the point im going to take the g100 out and throw it as far as possible

matt

46

General Mach Discussion / Re: Homing, machine co ordinates and touch off

« on: January 30, 2010, 04:46:26 PM »

Not sure, i will try it and let you know, will try to see if the other home switches do the same or if its just the z

Thanks for the help

Matt

47

General Mach Discussion / Re: Homing, machine co ordinates and touch off

« on: January 30, 2010, 04:24:45 PM »

That would suck if it was since i just spent ages fitting the g100!!

48

General Mach Discussion / Re: Homing, machine co ordinates and touch off

« on: January 30, 2010, 04:18:59 PM »

I think ive attached the xml, i am also running a G100 motion controller.

Thanks again

49

General Mach Discussion / Re: Homing, machine co ordinates and touch off

« on: January 30, 2010, 03:51:10 PM »

The other axes do not move, they are just zeroed as the z axis is zeroed, the code looks like this:

N0080 G00 Z25.0000
N0090 X95.5000 Y22.7500
N0100 Z5.0000
N0110 G28.1 Z3.00
N0120 G92 Z0.0
N0130 G00 Z0.0520
N0140 G92 Z0.0
N0150 G00 Z5.0000
N0160 M03
N0170 G01 Z1.5000 F1000


Im not great with g code but when the z switch contacts the machine co ordinates for all axes are zeroed

Thanks for the help

50

General Mach Discussion / Homing, machine co ordinates and touch off

« on: January 30, 2010, 03:14:44 PM »

Hi,

Ive been looking further into my touch off problem on my plasma, it appears that when my z axis home switch is tripped the machine co ordinates on all axes are zeroed. I understand the z machine cordinates should be zeroed but why the x y and a axes? Is there a setting that would change this? Ive ruled out mechanical problems by disconnecting all the home switches except the z.

Any ideas??

Matt