Messages

1

General Mach Discussion / Reading a pwm signal into Mach 3

« on: August 31, 2015, 04:26:32 PM »

Hi,

I have an application where a want to control 4 servo motors using Mach and make their speed relative to another control system which puts out a Pwm signal, is it possible to read this into Mach? I think I can handle a script to make it adjust feedrate if I can get it into a variable.

Any ideas?.

Thanks

Matt

2

General Mach Discussion / Plasma accel values, position accuracy and cut speed, servo tuning

« on: January 31, 2013, 04:42:39 PM »

Hi,

Im looking to get the views of plasma users on my set up/ tuning.

I have an old boc falcon which i have fitted up for cnc with mach, i have two 250w dc servos on the x and one on the y, whale drives from cncdrives.com driven with rack and pinion.

For anyone who is no familiar with the machinery it looks a bit like this

http://fplreflib.findlay.co.uk/articles/22842%5CESAB_refurbished_cutting_machine_main.jpg

My plasma is a hypertherm max 100

I have been asked to do a job in 3mm steel with loads of 3mm holes and slots and i told the guy im not sure but i wanted to try so i found at 1000-1500mm/min i could operate reasonably well at the proper cut speed 2000mm/min or higher the cut was hopeless, most lines look like saw teeth.

Really what im after knowing is do i have a problem i need to find or am i tryin to achieve something thats impossible? After trying some parts in steel i tried some on paper with a pen, with my aceel valu at around 15-20milli gee's the paths were pretty straight but at the 40-50milligees that people say you need for plasma the machine just resonates back and forth whilst cutting these small parts, but at the 15-20 value when trying to achieve 4m/min the machine never gets up to full speed when cutting the perimeter of a 50mm square, but the corners are perfectly square, is that a problem? When running these parts if i get the error viewer up for the x and y axis i never see more than what equates to 0.3mm error even under the highest acceloration so i was kind of thinking my motion looked good in terms of position error and the trouble was caused by mechanical resonance in the frame.

Where would a proffesional go in trying to improve this?

Matt

3

General Mach Discussion / Re: Simple code for simple shapes

« on: December 22, 2012, 01:19:10 PM »

Ok, what im imagining is i set the computer up to run mach on startup, mach is all the computer does as far as he is concerned, it would be great id the wizard could be put into a tab in the main screen set, (maybe if you give me some pointers i could do this as i plan to make him a screenset and cut down on stuff that he wont use and will confuse) , go to the wizard, type in relevant criteria, ie shape size and feed rate, press generate code and return to program run, jog to the 0,0 position, bottom left of a square i presume? press a button to run your script to check the extents of the part on the material and check for nozzle clearance, return to 0,0 light the torch, preheat the metal, pierce by turning the knob on top of the torch, when a hole is made press the cycle start and watch mach guide the torch around your shape, make minor adjustments to feed rate using an external fro knob, complete the part and shut the torch off.

My only question is over lead ins, if they are possible then great, if not thats fine

matt

4

General Mach Discussion / Re: Simple code for simple shapes

« on: December 22, 2012, 01:47:54 AM »

Looks good!

I suppose the z axis stuff either needs removing or it could jus be ignored couldnt it? No motor connected, no pins assigned, no numbers put into the wizard?

It looks as though there is no lead in so he could just position the torch where he wants the shape, 0 x and y, light the torch, wait for the desired preheat time then press cycle start?

Maybe i will hook him up a push button for cycle start and a knob for fro, then he can drive just like the magnet machine.

Thanks

matt

5

General Mach Discussion / Simple code for simple shapes

« on: December 20, 2012, 02:49:26 PM »

Hi,

Im a mach user of several years and i love it, i had a friend call me today and ask if i could help him, he has a gas profile burner which copies a part and woul like to convert it to cnc. He makes really simple geometirc shapes, circles from 2 inch plate to turn into bearing housings squares rectangles etc and its really important that i can get him the ability to generate code for tese simple shapes easily, i mean really easy, hes not fussed by work offsets, he knows his nozzle has a set kerf and is happy to add it to the size of shape, he needs no z axis at all, no gas on and off, he literally needs something that will run along a path when he presses the cycle start button, what is the best way to do this? I looked at wizards, very close but most of them seem to be aimed at milling operations, is it something i could develop easily myself?

Thanks alot

matt

6

General Mach Discussion / Re: Acceloration, cv settings and cut speed

« on: April 30, 2011, 11:59:39 AM »

An interesting thought, i will take a look, surely there must be some cv settings that can help with that?

On the subject of cv settings what should i be using for plasma?

Matt

7

General Mach Discussion / Re: Acceloration, cv settings and cut speed

« on: April 30, 2011, 08:32:07 AM »

I tried a few tests this morning,

I attached a pen tot he torch and drew some shapes with the machine, a 100mm square with a 50mm circle inside at 1200mm/min and 2000mm/min, the shapes were closer than i could measure to the right size so im having trouble understanding how it could be a problem with my servo tuning, is there any better way to show the problems? My only guess is to increase the feed rate to try to force some backlash or something although 1200 to 2000mm/min is the sort of speed i would typically aim to cut at.

Thanks

Matt

8

General Mach Discussion / Re: Acceloration, cv settings and cut speed

« on: April 30, 2011, 01:34:03 AM »

Thanks for the reply,

So maybe i need to learn more about servo tuning, is there anywhere good to start? or do you have any good pointers and ways to test if im getting good results? I have whale3 drives from cnc drives.com and used their servo config software which showed me i had a following error of only a few steps which is fractions of a mm.

Thanks again

Matt

9

General Mach Discussion / Acceloration, cv settings and cut speed

« on: April 29, 2011, 09:11:18 AM »

Hi,

Ive recently built my second plasma table using servos, my first was using steppers. I have been having trouble reaching the recomended cut speeds in the book for the plasma but have found that when i decrease the acceloration value i can achieve much higher speeds, using the servo configuartor sofware i have i have tuned the servo drives so that the following error is pretty small so i think that is ok but if i reduce the acceloration enough to get the correct cut speeds my accuracy is hopeless, i never encountered this problem with the steppers, is it likely a cv problem or a servo problem, im sure the first response will be asking for more detail about the machine but i thought i should ask a general question and hope for some advice.

Thanks alot

Matt
 

10

General Mach Discussion / Spindle speed

« on: March 25, 2011, 02:32:25 PM »

Hi,

Im looking to try to use the pid loop available for spindle speed to do other things, im feeding in a pulse on the spindle index pin which is being recognised, is there a dro number for where the resulting spindle speed is displayed that i can pick up in a brain? Is it possible to pick up the outputs of the pid loop in a brain aswell?? I want to use the pid loop to control the z axis position, if i were to select the step/dir control in the spindle setup and then configure it to my z axis outputs which are also used byt he g code im sure it would cause problems wouldnt it??

Sorry if i m being a bit vague!

Matt