Messages

1

General Mach Discussion / Axis Calibration - Set Steps per Unit on Slaved Axis

« on: August 10, 2010, 03:30:00 PM »

I'm trying to determine how to calibrate my slaved A axis in Mach 3.

I have a CNC Router, 48 x 48" bed, Mach 3, Gecko G540.

The Y axis has two identical motors running identical screws (as close as I can determine), one on each side of the bed. 

When I ran a 10 minute long carving program recently, the A axis ended up not in the same place as it started as measured from fixed points (ended closer to zero). Consequently, the carving is drooping slightly as it is being made. 

The A axis is slaved to the Y axis in Mach 3. 

I have tried a variety of motor tuning methods (manual and the auto version on the Settings page) with no luck.  The steps per setting is Y=4004 and A=3996.  The calculated value should be 4000.

There is no “clunking” like the sound of losing steps during the run from any of the motors. 

The motor is running 155F typically (IR thermometer) and is quiet, at rest.  The couplings are tight.  With the system off, the motor turns easily and both sides of the gantry roll freely.

I have attached digital calipers to both ends of the ganty and using the "set steps per unit" button determined that a one inch move is slightly different at either end.  My goal is to get them to move the same distance, perhaps not exactly one inch.  I have tried the A axis button but it doesn't really apply in this situation, I think.

Am I missing something here or is this about as good as it will get?     Thanks!

Bill

2

VB and the development of wizards / Re: Digital Z Axis Control Questions

« on: January 09, 2010, 05:06:24 PM »

Hi sunmix,

The home position switch would activate when the quill retracts to the top position.

The "bottom of stroke" limit switch is adjustable to set the right depth of hole (these are blind holes being drilled, not just drilled through).  I would want the pneumatic cylinder to reverse direction once the bottom of the hole has been reached.

The events in the cycle are:

- Move the drilling head into XY position
- Activate the pneumatic cylinder to drive the quill/rotating drill bit into the material
- Once the appropriate depth has been reached, reverse the pneumatic cylinder to lift the quill/rotating drill bit out of the material
- When the quill reaches the top/home position limit switch, move the drilling head into the new XY position.
- Start above cycle all over again
- Once last hole is drilled, move to the safe XY home position

Hopefully, that makes sense.  Cheers!

Bill

3

VB and the development of wizards / Re: Digital Z Axis Control Questions

« on: January 07, 2010, 09:09:38 AM »

Thanks sunmix for the response.  I'll try to describe it better.

The machine is built around a small drill press head.  I have a limit switch that activates when the quill is in the fully up position.  This is "home", which indicates it is safe to move in the X or Y direction since the drill bit is retracted from the material.

I have another limit switch that activates when the quill is in the bottom position.  This switch activates at the bottom of the drilling cycle.  It indicates the drill has reached the depth that it should in the cycle and that the quill should be retracted.

Let me know if that makes a little more sense.  Cheers!

Bill

4

VB and the development of wizards / Digital Z Axis Control Questions

« on: January 05, 2010, 05:01:38 PM »

Thanks for all of great topics and answers on VB and control tactics. 

My situation is close to the question posed in http://www.machsupport.com/forum/index.php/topic,3879.0.html . 

I'm building a machine to drill a particular bolt pattern, repeatedly.  Mach3 R3.042.020, G540 controls.

My X and Y axes are steppers and I'm using a pneumatic cylinder to drive the drill (Z) into the material. 

I have a "home/retracted" position limit switch for the Z and a "hole depth" input limit switch for the bottom of the Z stroke.

My question is how to control it.  I read through the use of 2.5D to control the solenoid valve for the pneumatics.  I would like to use the two inputs I have to know when it is safe to move the drilling head to the next location.  I don't think I can depend on the G4 Px to pause to wait for the drill to retract.

I have limited VB experience but it would seem that writing an Mcode macro is probably the "right" way to get this operation automated.

If you have a suggestion as to how to best approach this, I would appreciate it.  Thank you.

Bill

5

G-Code, CAD, and CAM discussions / Re: Slow step in G19 G2 move

« on: October 06, 2008, 11:32:01 AM »

Chip,
I'm just running a Demo version, R2.63.  I noticed a warning in the Status line regarding the Radius being different at the end of the arc than at the beginning but I can't recreate that either.  I pulled the numbers from AutoCAD so I thought they were good.  I will redraw and see if I get anything different.  Thanks for your thoughts on this.
Bill W

6

G-Code, CAD, and CAM discussions / Slow step in G19 G2 move

« on: October 06, 2008, 12:12:32 AM »

I am writing the code below for a CNC router and am working in a test environment (not on the machine yet).  When I step thru the code, Mach3 hangs up on the G19 G2 move.  It takes a minute or more to move thru that line and then moves on thru the rest of the program as normal.  I imagined it was a problem moving from - to + but that didn't make sense since the G19 G3 move works normally.  Mach3 displays the correct toolpath but runs that one step very slowly.  The program will be fitted out with an M98/M99 subroutine so I've declared some variables.  What am I doing that is causing this?     Thanks.
Bill W
........
G17 G20 G40 G49 G54 G80 G94

G0 X0 Y0 Z0
G1 F25

#1 = 0.0805
#2 = 0.161

G0 X0.0805 Y0.1532 Z-0.08

G1 Y-0.041
G19 G2 Y-0.4252 Z0.1 J0 K0.5
#1 = [#1+#2]
G1 X#1
G19 G3 Y-0.041 Z-0.080 J0.3842 K0.32

G0 M2