Messages

21

General Mach Discussion / Re: Position Errors Only on Diagonal Moves

« on: January 14, 2015, 11:52:54 AM »

Terry,

It cuts absolutely PERFECT squares, EXACTLY on-dimension, and EXACTLY square, as long as they are aligned to the X/Y axes.  So, yes, the bed is square.  Yes, the DRO values are correct.

Regards,
Ray L.

22

General Mach Discussion / Re: Position Errors Only on Diagonal Moves

« on: January 14, 2015, 11:43:25 AM »

Terry,

No math.  Draw a square, CAM the square.  The problem is NOT the g-code.  It has been verified by hand, and by simulation.  The square is a perfect 1.25" x 1.25" square in all cases.  It has been verified correct 12-ways from Sunday, and hand-generated code gets the same result.

Regards,
Ray L.

23

General Mach Discussion / Re: G=code question

« on: January 14, 2015, 10:52:49 AM »

G0/G1/G2/G3 always use fixture coordinates, not machine coordinates, unless preceded by G53.

Regards,
Ray L

24

General Mach Discussion / Re: Position Errors Only on Diagonal Moves

« on: January 14, 2015, 10:51:23 AM »

Tweakie,

All code is generated either by CAM, or hand.  No Mach3 scaling or rotation is in effect.  It appears to me like Mach3 is giving incorrect move commands only for coordinated moves..  I can't think of anything in the hardware that coudl behave this way.  Yet behavior is identical with several different Mach3 versions.  Very odd....

Regards,
Ray L.

25

General Mach Discussion / Position Errors Only on Diagonal Moves

« on: January 14, 2015, 12:55:08 AM »

Someone I know is having a strange problem that really has me stumped.  The machine is a bed mill, with AC servos.  It will do unlimited, perfect, single-axis moves, cutting exactly to correct dimension every time.  But when cutting a square, rotated 45 degrees so diagonals drawn between opposite corners would be parallel to the X and Y axes, the square becomes a rectangle, with on pair of sides about 0.04" too close, and the other pair of sides about 0.040" too far apart.  There is NEVER any position loss.  It returns to exactly X0, Y0 perfectly, every time.  A square cut so the sides are parallel to X/Y will come out exactly on dimension every time.  Steps per is set correctly, and confirmed by measurement.  Backlash is well under 0.001" on all axes.

As I said, I am stumped.  We've tried it running with a UC100 motion controller, and with the PP, and results are exactly the same.  Reducing velocity and acceleration, even dramatically, makes no difference whatsoever.  Running exactly stop makes no difference.  DROs always show the "correct" position (i.e. - where the machine should be, as opposed to where it actually is).  We've tried several different versions of Mach3 from 3.043.066 down to somewhere in the 050s, and get the same result with all of them.

Any ideas or suggestions?

Regards,
Ray L.

26

General Mach Discussion / Re: Need a 7th Axis.

« on: January 12, 2015, 08:28:48 PM »

If it's one position, doing one rev each time, then all you need is a motor and a cam-operated micro-switch....

Regards,
Ray L.

27

General Mach Discussion / Re: Need a 7th Axis.

« on: January 12, 2015, 06:25:15 PM »

Russ, thanks a lot. That sounds exactly what,s needed, but i have had trouble finding a Parker OEM 10, if you have a link that will be appreciated.

I actually do like the Geneva plan from Ray, only thing i`m not getting is how to short the contacts breifly ? is that with a timer ?
Would it be possible to do it with a mach3 brain ? can you change a pin from high to low from a brain ?

The other thing with the Geneva thats getting me going, is i should be able to mount 4 cut off discs, driven off a central motor, and rotate them one at a time to do the cut off opp.
4 times the wheel life. those discs are only 0.030" thick.

I was considering going with Kflop for the 8 axis, but you guys have again showed me how knowledgeable you are and will find a solution to any issue.
Thanks again.

A Geneva can be easily controlled by a brain or a macro.  The output only needs to be active long enough to ensure the Geneva motor has turned far enough that the microswitch comes off the cam and closes, and it will power the motor from there, until it again hits the cam, which will stop the motor, leaving the wheel correctly positioned, and locked in that position, and ready to start the next move.  For something that only needs a small number of fixed positions (up to about 16 or so), a Geneva is FAR simpler, and FAR cheaper. than driving it with a stepper or servo.  All you need is a $30 DC gearmotor, and perhaps a relay.  No motor drivers, no software, no complexity whatsoever, and it's dead reliable, and very rugged.

Regards,
Ray L.

28

General Mach Discussion / Re: Need a 7th Axis.

« on: January 12, 2015, 11:05:03 AM »

cheers for that. I hadn`t seen them before.
I`d still need to control the motor position tho as it could stop mid cycle.
There could be as much as a minute or 2 between weld cycles while the rest of the machine does its thing. sorry I should have mentioned that.

All you need to control a Geneva is a microswitch driven by a cam on the motor shaft that is open when the motor is in the "stopped" position.  Use a relay to short the contacts on the switch briefly, long enough to get the motor started and move the cam off the microswitch so the microswitch is closed and providing power to the motor, then open the relay.  When the motor has rotated about one turn, the cam should open the microswitch, stopping the motor.  That's the nice thing about a Geneva - it requires absolutely no precision control whatsoever to give very consistent, repeatable position.

Regards,
Ray L.

29

General Mach Discussion / Re: Hood's 12 tool tool changer

« on: January 06, 2015, 05:23:55 PM »

Hood,

VERY cool, but looks like you've got a pretty massive coolant leak!  :-)

Regards,
Ray L.

30

General Mach Discussion / Re: Ethernet Communication From CB?

« on: December 19, 2014, 01:19:36 PM »

Terry,

No point.  GetPortByte would read a single register within the Ethernet chip - useless.  The protocol is handled in large part by the Ethernet drivers in Windows.  My macro needs to communicate with those drivers, not with the chip itself.  It would be like trying to do 3D graphics by reading/writing directly to registers in the Graphics controller.

Regards,
Ray L.