Messages

61

General Mach Discussion / Re: Mach3Turn Offsets?

« on: January 29, 2011, 08:48:24 PM »

Hi Hood,

Attached is a diagram showing examples of how the tools move from one position to the next when called from the Tool Table.

The other drawback is that CSS was also affected because Mach3 thinks that the new Position of the tool is at a much larger diameter, so the spindle rotates at minimum speed.  That is, it appears to behave like the job is larger in diameter by a factor of the tool offset distance.

Its been quite a while since I witnessed all this so my recollection is sketchy.  I think I recall seeing the X DRO indicating the larger diameter. I suspect that this is because Mach3 thinks that the job is bigger in diameter that it really is when a tool with an X position greater than the Master Tool.

Regards

Chrisjh

62

General Mach Discussion / Re: Mach3Turn Offsets?

« on: January 29, 2011, 06:30:42 PM »

Hi Hood,
I took your experienced advice ages ago and setup using one tool post only.  In my case, I selected the front tool post option, so tools that cut from the rear side have negative values of X whilst tools that cut on the operator side operate in positive values of X.

Using the Tool Table and calling individual tools works fine with Mach3. However it was not suitable for my gang setup (and I suspect most gang tool setups).  The problem I had in the gang setup was, when a tool whose centreline was located, say, 100mm from the Master Tool position was selected, the cross slide would try to travel to a position beyond the X+ limits before returning to the correct position.
 
I proved that Mach 3 Tool Table calls worked OK with a tool whose centreline displacement from the Master Tool was 40mm.  When this tool was called from the Tool Table, the initial travel from the Master Tool Position was towards the operator (positive X direction), then return to the correct position 40mm (in a negative X direction away from the operator) from the Master Tool position.  The first movement stopped just short of the X+ Limit Switch.  Any other tools greater than 40mm from the Master Tool simply tripped the limit switch on the first, unnecessary excursion.

I suspect that double movement I was witnessing has something to do with the maths algorithm within Mach3.  Because I couldn’t do anything about the algorithm, I had to seek an alternative solution.
The total Cross Slide travel between limit switches in my setup is approximately175mm so I have work within these limits.

You are correct in that there are many ways to skin a cat.  This Mach3 journey, for me, has been long and rewarding.  Still learning and trying pass on my experience in this fascinating hobby.

Leeway,
 
It was one of your YouTube videos that got me started down the gang tool setup path.  I thank you for these videos. Love the Pink Panther!! (Still in my favourites).

Here is one for you.  http://www.youtube.com/watch?v=gsw5JtYMGSI&feature=mfu_in_order&list=UL

Regards
Chrisjh

63

General Mach Discussion / Re: Mach3Turn Offsets?

« on: January 28, 2011, 10:17:01 PM »

Hi All,

I have been following this thread for a few day now.  I gave up using Tool Tables for Gang Tooling in CNC lathes controlled by Mach3.  I now use G52 Offsets for all tools in the Gang setup.

Here is my experience and solution to the problem. 

http://www.cjh.com.au/Gang%20Tool%20Block%20Offsets%20for%20CNC%20Lathes%20under%20Mach3%20Control.pdf

Regards

Chrisjh

64

General Mach Discussion / Re: PWM Spindle Control using Mach3 - How I did it

« on: January 13, 2011, 01:58:59 AM »

Hi,

My understanding is that Kernel Speed is not important when using a Smoothstepper as the step and direction pulses are generated by the Smoothstepper, not the controlling computer.

To answer your question, my Kernel Speed is set to 45000.  I use a 1.6GHz Centrino Dell Laptop.

Regards

Chrisjh

65

General Mach Discussion / Re: PWM Spindle Control using Mach3 - How I did it

« on: January 12, 2011, 07:03:41 AM »

Hi Peter,

The input to T1 on the PWM Converter is channelled through an Opto Isolated C23 Breakout board.  The Output to the VFD is as recommended by Danfoss documentation.  The PWM converter is powered by a 12VDC supply which is used only for the PWM Converter and a workspace illumination lamp.  All power supplies (5VDC, 12VDC and 42VDC) are all securely grounded to the chassis on the -ve side. 

I am a firm believer in having all supplies grounded to the chassis on the negative side as it make things safe and easy to troubleshoot.  I believe that isolated, floating power supplies introduce problems that are difficult to faultfind when things go wrong.  I have a Syil CNC Mill that has multiple isolated supplied with at least 2 separate grounds.  It is a right menace to faultfind and is downright dangerous to work on because of isolated, non common grounds.  It was because of this poor design that I deliberately designed my lathe to make it safe and easy to work on.

Regards

Chrisjh

66

G-Code, CAD, and CAM discussions / Re: G41 Offset being ignored

« on: October 10, 2010, 07:07:19 AM »

Hi Graham,

I have been giving this problem some further thought.

I recently had a similar problem when I tried to use a G68 to rotate the toolpath so a job could fit in my vice jaw limits.  Long story short, but I rewrote the code with the dxf file rotated and, did not use any G68 rotation commands.  The result is shown in the successful toolpath in the previous post.

So I thought, "What if i get rid of subroutines?"

The result was a successful toolpath as shown in the image attached.  The program is useless for my purpose but proves the point.

So it appears that Mach3 does not like the combination of G41 Offsets with Subroutines or G68 rotational commands.

Fot the job in hand, I guess I have no choice but to abandon my attempts to use G41 offsets and go back to my old proven, long winded, methods of using toolpaths generated with Bobcad.  So a few more hours rewriting 4 new programs doing battle with Bobcad.

Regards

Chrisjh

67

G-Code, CAD, and CAM discussions / Re: G41 Offset being ignored

« on: October 09, 2010, 08:25:52 PM »

Thanks Graeme,

Very efficient and compact code!!   However I still have a problem with wild arcs in both your and my programs.  See Attached Toolpath images.

The crazy thing is that I have a program that works using a "P" rather than a "D" offset.  See example of the Toolpath image and program attached.

I prefer not to use Tool Tables (and any data therein) for 2 reasons:
 
1.   I am a learner and my mill does not use a tool changer (yet) and I use gang tooling on my lathe, and

2.   I found that using tool table data on my lathe caused excursions beyond the limits of my cross slide travel so I settled on temporary G52 offsets for each tool in the gang. (Works great)

As a result, all of the data in my tool tables is set to 0.  I will use tool tables when I have access to a tool changer.

Whilst fiddling yesterday, I actually saw a correct Toolpath using a "P" offset on the simulation screen in my office.  So I closed the file and rushed out to my shed to test the code on the mill computer, only to see the wild arcs again.  I went back inside to recheck but the Toolpath had reverted to "wild arcs".  So I now suspect that Mach3 has some form of "intermittency".

68

G-Code, CAD, and CAM discussions / G41 Offset being ignored

« on: October 08, 2010, 09:10:19 PM »

The G Code in the attachment below ignores my G41 Offset Lines.

What am I doing wrong?

There is a reason I am using the subroutine.  I have 3 other similar programs with multiple identical holes and using subroutines is the most compact and efficient way.

If I can get this simple one hole version going, I can then fix all programs and learn by my mistakes.

Regards

Chrisjh

69

G-Code, CAD, and CAM discussions / Re: Cutter Offset Learning Problem

« on: September 28, 2010, 09:45:37 PM »

Hi Gerry,

You hit the nail on the head!!

I removed the G68 Line and the problem went away.  It was because the G68 command put the program into a cartesian quadrant where G02 and G03 arcs go in the opposite direction.

I'll try to reverse the offending G02 and G03 commands and see what happens.

Plan B is to completely rewrite the code with the original dxf rotated 90 degrees.  The reason I needed to use the G68 was because after I wrote the code, I found that the 100mm material would not fit into the 90mm limit of my vice jaws but the 80mm dimension would.  So I tried to be clever but my cleverness backfired!!

Thanks for your help.  Much appreciated.

Regards

Chrisjh

70

G-Code, CAD, and CAM discussions / Cutter Offset Learning Problem

« on: September 27, 2010, 10:23:09 PM »

Hi,

I am trying for the first time, to program my mill using cutter compensation but with no success.

Wizard generated code for circular items (both internal and external) work fine with "Px" cutter offsets.

When I add a "P6" to my own programs with G41 offsets, I get large 360 degree arcs at the 0.2mm radii on the corners.

Attached are 2 files. The first one results in correct toolpath (without cutter compensation) and the second file with added "P6" to the G41 lines results in the circular arcs at the 0.2mm radius corners.

What am I doing wrong?

I am using Version R3.042.040.

Regards

Chrisjh