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Messages - alenz

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81
General Mach Discussion / Re: I need help to make this subrutine run.
« on: December 06, 2010, 10:45:14 PM »
It’s all in the way G2 and G3 are implemented. For example in G90 (Abs) mode your line
g2 x0 y1.0215 i0 j-1.0215 z-.170
tells Mach to draw a clockwise arc starting at the current position, (the last position before this line which in this case is X0, Y1.0215) and ending at the position specified in this G2 line, (which is also X0, Y1.0215). The I value is the X distance from the starting point to the arc center, (X0 + 0 = 0) and the J is the Y distance from the starting point to the arc center, (Y1.0215 – 1.0215 = 0) thus the arc center based on the STARTING point is X0, Y0.  Since the starting and end points are the same, obviously they will both have the same radius and everything is fine.

Now look at the same case but with G91 (Inc) active. Now the absolute values in line
g2 x0 y1.0215 i0 j-1.0215 z-.170
are redefined as the previous value shifted by the amount specified in this line i.e., the new X is the old X(0) + 0 = 0, the new Y is the old Y(1.0215) + 1.0215  = 2.0430 and the new Z is the old Z(0) -.170 = -.170.  Thus in absolute mode the line now means
g2 x0 y2.043 i0 j-1.0215 z-.170.
The start point is still X0, Y1.0215 (from the preceding lines) but now the end point has changed to X0, Y2.0430 thus the error message that the start and end radius doesn’t agree. The I and J modes are handled differently. They aren’t affected by G90 or G91. Their mode is set independently in Config / General Config and will normally be set to Inc. That’s why just changing the Y1.0215 to Y0 fixes the problem in that line.  It no longer changes the end point, still retains the same radius but allows the Z to increment as intended.

HTH,
Al

82
General Mach Discussion / Re: I need help to make this subrutine run.
« on: December 06, 2010, 02:04:39 AM »
As a follow up to the previous post, the G91 is actually in line 17, not 18. Also the use of a variable is only one of several ways to increment Z in the loop. Another would be to simply revise line 18 from
g2 x0 y1.0215 i0 j-1.0215 z-.170
To
 g2 x0 y0 i0 j-1.0215 z-.170
This will correct the cause of the error, i.e., the Y is being shifted due to being in incremental mode. The I and J are always incremental, so aren’t affected, thus by making Y = 0 only the Z is changed which I think is what  we want.  I just happened to have been using the variable method recently and it came to mind first.

Al

83
General Mach Discussion / Re: I need help to make this subrutine run.
« on: December 06, 2010, 12:10:37 AM »
Captain, If you delete the G91 from line 18 it will run but I doubt that will give the result that you want. I’m going to guess that you probably want the Z to feed continuously for all four passes in the sub. If so you might want to use a variable to increment the feed for each loop.

Something like this:

%
(Shock Spacer)
g17 g20 g90
g0 x0 y0 z.250
m3 s1600
g1z-.625 f6
g1 y.190 (Shock shaft diameter)
g3 x0 y .190 i0 j-.190
g0 y0 z.250
g0 y1.0215 (Shock piston diameter)
g1 z0
M98 P006 L4 #1 = 0
g90
g0 z.250
m30
%

O006 (sub)
(g91)
#1=[#1-0.170]
g2 x0 y1.0215 i0 j-1.0215 z#1
M99
%

Hope this helps,
Al

84
General Mach Discussion / Re: Tool offset On/Off not working.
« on: November 14, 2010, 02:26:36 AM »
Are you pressing the "ENTER" key after entering the "1"?
Al

85
Glad, I’ll try to help as best I can.

>Coming from you it is all sounds easy and very optimistic. I started believing that 4th axis is not a big deal  .
No big deal getting it installed and set up but depending on what you want to do with it, the sky is the limit so far as complexity goes.

> My first challenge will be to rewire Sherline stepper from 6 wires to 4 (Xylotex board).
Sounds like you have good input and a handle on that part.

> Second, is to properly setup table in Mach3.
The Sherline stepper is 1.8 deg/step or 200 steps/rev (360/1.8) and the rotary table has a 72:1 gear ratio or 5 deg/step (360/72). So for single stepping that would be 200/5 = 40 steps/deg. Multiply the 40 times the micro stepping jumper setting on the Xylotex board, e.g. if it’s set to 8 then 40 X 8 = 320 steps per deg for the Mach3 entry. The velocity and accel numerical values will likely be drastically different from your X, Y and Z due to the deg/min units.  Presumably your linear axes are already set-up so here is what I would do. Open the spreadsheet at this link:
http://www.machsupport.com/forum/index.php/topic,16315.0.html
Enter the input data for both linear and rotary axes. Enter your known reliable max rapid velocity for a linear axis and read the corresponding stepper RPM. Then enter that RPM in the rotary column and read the result steps per degree for the Mach3 velocity entry. That way you are comparing apples to apples (RPM). The accel will need to be changed in the same proportion as the velocity.

>Last but not list, to produce a G-code to engrave patterns on a flat surface using Y, Z and A axis.
>The idea is to install RT flat on an X/Y table perpendicular to Z. Attach lathe type of tool bit on Z axis pointing >down perpendicular to X/Y.  Z axis will go up and down driving tool bit into the engraved part installed in RT >regulating engraving depth. Spindle will not rotate. Y axis will move in longitudinal direction fore. and aft. from >outside toward center of the engraved part. So, when all three axis moving simultaneously: A rotates clockwise >holding eng. part, Z drives non rotating tool in and out of the eng. part, and Y moving RT (eng. part) fore or aft.
>I hope my explanation makes some sense.
You may have lost me here. Sounds like your rotary table is going to be mounted flat on the X-Y table with it’s rotational axis vertical, i.e. parallel with the mill Z-axis. If so, then the rotary is now the C-axis (following accepted convention; A-axis is parallel with the mill X-axis).  On the other hand if this is so, i.e., you are engraving a flat pattern on a flat surface, then why use the rotary? Wouldn’t the X, Y and Z do the same thing? And BTW converting Gcode X values to equivalent C values is not a trivial exercise. Been there, but sometimes it’s worth it. I would suggest that you invest in a 90 deg mount for the rotary and mount it on the X-Y table with it’s axis parallel with the mill X-axis and practice some cylindrical engraving first. Configure as X, Z, A. Lots of free wrapping software to convert Y values to A and I think you will find it quicker to get a feel for the rotary.
Hope this helps
Al


86
Fastest1,
Wrapping feature… Hmmm..  I don’t know anything about it. Time to start reading. I was trying to avoid manual code writing as much as possible hoping that ArtCam will take care of code generating for all 4 axis, but I never thought it is going to be easy to setup and run. Getting table two days from today and will start experimenting.

Glad.
Glad,

The choice of wrapping software vs. manual code etc. all depends on what you are intending to do with the rotary. If for example you intend to engrave on a cylinder then you definitely need ‘wrapping’ software. However if you are just indexing, for say cutting a gear, then manually entering the code is very straight forward and hardly worth the fuss of a dedicated app.  Since you intend to use axes Y, Z and A then that would seem to eliminate engraving on a cylinder, (since that would only cut a single varying depth groove) so I assume the latter. (Engraving on a cylinder is normally axes X, Z and A, i.e. Y is converted to A.)

Just to make sure we are on the same page, the RT A axis is parallel with X, B is parallel with Y and C is parallel with Z.

And as others have suggested, do make a separate profile for each setup. I have for instance ‘Sherline-A’ and ‘Sherline-C’.

Regardless, not to worry, once you get your hands on the hardware it will all come together. This group will get you over any rough spots.

As a fellow Sherline (and Horological) hobbyist I predict that you will find this to be the most bang for the buck of any Sherline accessory.  Also I give you less than six months before you miss the fun of using all four axes and invest in a fourth driver. For example, by using the RT in the C-axis you can use an ordinary end mill to cut a gear! Lotsa fun!

Al

87
General Mach Discussion / Re: Scaling problem need help
« on: October 25, 2010, 08:40:36 PM »
Romano,
From Mach3’s main menu select ‘Config’, then ‘Motor Tuning’. A ‘Motor Tuning and Setup’ window will open. Select the axis that you want to set, then enter the ‘Steps Per’ value in the lower left box. Then hit ‘Save Axis Settings’ and OK. That should do it.
Rich thanks.
al

88
General Mach Discussion / Re: Scaling problem need help
« on: October 25, 2010, 05:33:10 PM »
Hood, I wonder if this little spreadsheet might help folks setting up their machine for the first time?
If so where would be a good place to post it?
Thanks,
Al

89
Durl
Try changing offsets. Add a G55 (Offset #2) just ahead of the pause (M00 ?) line. Then reset the Z-DRO. The file will now run at the new Z-offset. At the appropriate place near the file end enter a G54 to return to offset #1 and return to your original Z for the next run.
Note, this will offset the entire file in the Z, i.e., outline cuts will cut deeper into your spoilboard, etc. Not sure if that is what you were asking.
HTH
 Al

90
General Mach Discussion / Re: Trouble cutting accurate parts
« on: September 11, 2010, 09:37:35 PM »
Woody, Hood will be able to answer your question definitely, however in the meanwhile you might like to play with a little excel sheet that shows the relationship between various parameters. Note in particular that it is possible to specify distances that require fractional steps :).
Al

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