Messages

1

G-Code, CAD, and CAM discussions / Re: G12 Trouble...

« on: October 01, 2013, 06:38:44 AM »

Thank you for giving it a try.

The little code segment I posted is enough to cause the behavior - no other G codes.

So given that this is very uncommon, if not unique to my setup, what could be causing it?  It does not appear to be an issue with the CNC machine itself, so it must be the computer setup, no?  This is a licensed copy of Mach3 installed on a machine with nothing but XP on it.  It certainly does not seem to have any trouble keeping up.  I am at a loss.

I did find a partial solution - I reduced the precision from .0001 to .001 and I was able to bore all the holes I needed.  I thought it was a real solution until I jogged to a new location and it cut only the short line.

Is there some Mach3 configuration that would affect precision or otherwise affect how G12 is executed?

Thanks so much for your help

Bart

2

G-Code, CAD, and CAM discussions / Re: G12 Trouble...

« on: September 30, 2013, 10:05:13 AM »

I am glad to learn the H parameter is not needed - not sure why I had it there.

Removing it does not fix the problem.

I understand that G12 does not cut a pocket, I just want it to describe a circle and it does not always do that.

The new code:

Code: [Select]

g0 x.8622 y.8207
g12 i.078125 f10
g0 x.8624 y.8207
g12 i.078125 f10
behaves exactly as the old code did, which is to say, it does not describe a circle @ (.8622, .8207) but it does at (.8624, .8207).

Bart

3

G-Code, CAD, and CAM discussions / G12 Trouble...

« on: September 30, 2013, 07:30:58 AM »

Hello - I am struggling to make a small circle using G12. 

The code:

Code: [Select]

g0 x.8622 y.8207
g12 h.125 i.078125 f10

makes a line, not a circle -  3/16" line along X only.  It is not only that it cuts only a line, but in the toolpath display, only a line is shown.  The Y axis simply does not get moved.

I have restarted the computer, and it is highly repeatable for me.

The code

Code: [Select]

g0 x.8624 y.8207
g12 h.125 i.078125 f10

creates a circle, as expected.  Note the only change is to shift the X axis by .0002"  It also works to move the Y axis by .0002".  It appears this problem shows up in very specific x,y positions.  Unfortunately, this snippet is part of a larger program which triggers this behavior in about 40% of the holes.

I found a couple previous threads:
http://www.machsupport.com/forum/index.php/topic,23272.0.html has no resolution. 

http://www.machsupport.com/forum/index.php/topic,9850.0.html solves his problem with scaling - I am not sure how I would use scaling in my program, but I could imagine that tweaking the scaling would change the x,y positions enough to avoid the issue.

I am attaching a photo of Mach3 running the combined code:

Code: [Select]

g0 x.8622 y.8207
g12 h.125 i.078125 f10
g0 x.8624 y.8207
g12 h.125 i.078125 f10

As you can (hoipefully) see, the toolpath display has a large circle with a highlighted line running from the center of the circle to the right edge.

In the next photo, the only change is that I commented out the second G0 line.  There is no circle, just a short line (and it is all very small).  The toolpath displays are accurate in terms of what my machine actually does, but not in terms of what the GCode seems to be asking for.

Any thoughts as to a) why this is happening or b) how I can avoid it?

Thanks!

Bart

4

General Mach Discussion / Re: Mach3's DRO pauses intermittently

« on: September 28, 2013, 10:09:15 AM »

Right - I should have included the gcode, sorry about that - here it is.

As you can see, I use a subroutine for the actual drill/bore, and the main code does the translation - so it still does not make sense to me that different holes would come out differently - but there is much I do not know!

Code: [Select]

f30 (feed rate)
g20 (inches)
g0 x0 y0 z.25 (zero)
m98 p1234 (call subroutine)
m30 (exit)

o1234 (subroutine 1234 - do most moves on y axis for speed)
g0 x00.8622 y00.8208
m98 p2345
g0 x00.9060 y12.2972
m98 p2345
g0 x00.8748 y23.8758
m98 p2345
g0 x00.8959 y35.4391
m98 p2345
(many more moves trimmed out)
g0 x0 y0
m99

(do the counter bore and drill)
(assume that we are in the right x,y spot, and clear on z)
(assume z=0 is the top of the board)
(feed z to the depth of the counter bore, make a circular pocket at the right diameter)
(feed z to the depth of the drill, make a circular pocket at the right diameter)
(retract z to positive to be clear)
o2345
g1 z-.5 (feed to 1/2" deep counterbore)
g12 h.125 i.078125 f10 (assume 1/4" endmill, this makes a 3/8"+ counterbore)
g1 z-.875 (feed to 7/8" deep drill - assuming 1" material, this prevents hitting the steel below the table)
g12 i.015625 f10 (assume 1/4" endmill - this is a 1/4"+ drill)
g0 z.25 (1/4" above board)
m99



Thanks,

Bart

5

General Mach Discussion / Mach3's DRO pauses intermittently

« on: September 27, 2013, 02:56:46 PM »

Hello - I am relatively new to the world of Mach3 and CNC machines.  I have an older 3-axis router which I am trying to make usable.  I am running Mach3.

I am in the process of making a new table to mount to the existing subtable - a 'simple' matter of drilling a set of holes with counter bores.  I am using G12 to make the counter bores and drill the holes with a 1/4" cutter.

The trouble is that some holes are not coming out round, they are simply 1/4" wide grooves, there is no activity on the Y axis at all.  It was suggested that this was likely to be a problem with the machine getting hung up, so I disassembled the X and Y axis, cleaned them, lubed them, and they both glide nicely when not attached to the screws.  I find no points of hesitation.  I have turned the acceleration down to 1 to further limit the effect of mass/stiff glides.  The screws are acme with Kerk anti-backlash nuts, all clean, lubed, and in apparently good shape.  I have the speed set at 40 because the motors stall at 80.  The feed rate in my drilling program is 30.

There are three things I do not understand:
1) For those holes that are mis-cut, the DRO does not show the Y axis moving - if it was just the steppers missing steps, shouldn't the DRO on the Mach3 screen show the numbers on the Y axis changing, like it does for the X axis?  Why does it not?  On good holes, both axis are shown changing by the DRO.  There is a (related?) issue that occassionally in a traverse the movement will pause, then start again in half a secod or so - and again the DRO also pauses.

2) Not all the holes are misshapen - but it is consistent as to which are.  In particular, the first one is each time (which is nice for testing).

3) I made a test pattern of 25 counterbores (using the same G12 line as for the table) and every one of them is perfect - even when I put it in the same spot on the table.  The only difference is that the test pattern is being cut on the surface of the table, rather than into the table, so the Z axis is in a different spot.

I am not sure where to go next. 

I just ran the driver test - it says I could be running at 65k without trouble.  I am running at 25k.  Nothing else is installed on this machine and it is not networked.  It connects via parallel cable to a Xylotex driver. 

I had some trouble with noise in the control lines which are all shielded cable but do run together with the spindle power.  I am not sure if noise would show up as a pause in the DRO - it seems like it would be more likely to be just skipped steps.

The same holds for trouble with the Xylotex - would those problems show up on the DRO?  There is no feedback, these are very basic steppers.

Any thoughts would be most welcome!

Thanks

Bart

6

General Mach Discussion / G12 not moving Y axis, sometimes.

« on: May 26, 2013, 12:10:33 PM »

Hello - I recently got a cnc with Mach3 and I have been slowly getting to know it and how to use it.  The table that came with the machine was done, so I want to make a new table.  I wrote a little gcode program to drill and counterbore for the socket cap screws that hold the table to the base using a 1/4" end mill.  There are about 30 holes in the table.

Most of the holes are fine - their counterbore is round, and the socket cap screws fit with a little slop, as planned.

But a few of them do not have round counterbores - the tool enters the workpiece, moves in the positive x direction, moves back to the center, drills, and returns.  The Y axis is never engaged.  I have tried it with the spindle on and off, with a workpiece and without, it always does the same thing.  One of the holes is the very first so I thought it might be softlimits, but another hole is out in the middle of the field.  I also suspected the machine itself, but it is incredibly consistent - always the same holes, always the same way, I never see the y-axis steppers move at all, and the x only goes and comes back. I am using Mach3 R3.043.066, appropriately licensed to me.


The code is very simple, here is an excerpt:
...
g0 x.8622 y.8208
m98 p2345
g0 x.9060 y12.2972
m98 p2345
...

o2345
g1 z-.5
g12 i.078125 f10
g1 z-.875
g12 i.015625 f10
g0 z.25
m99

As you can see, it moves around to all the locations of the screws (which are not at all regular) and at each location calls the subroutine o2345 which uses g12 to cut two circular pockets - one counterbore, .5" deep, a little over 3/8" in diameter, the other 7/8" deep, a little over 1/4" in diameter.


Thank you for any thoughts you might have!

Bart