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Help with 4th axis
« on: August 05, 2010, 03:59:41 PM »
 OK I am very limited in my knowledge here so bear with me. I just setup a Sherline rotary table on my Taig mill with my G540 controller. I have it setup right and it works fine the trouble I am having is understanding how to use it. I downloaded CNCWraper and tried some simple text on a bar of aluminum but it wants to put the 0 position in the middle of the part. Not just the center of the A axis but in the center of the X axis as well? Where do I set the cutter as the home position? I am not sure what I am doing wrong or right for that matter. Is there somewhere I can find the dummies guide to using a rotary axis? Also I do not wright G-code, I rely on cam programs. I have Dolphin CAD/CAM and Lazy Cam.  ???
"Gravity, its not just a good idea its the law"
Re: Help with 4th axis
« Reply #1 on: August 06, 2010, 07:46:04 AM »
No One??
"Gravity, its not just a good idea its the law"
Re: Help with 4th axis
« Reply #2 on: August 06, 2010, 08:07:26 AM »
Hi Astro,

I do not use CNC wrapper but I set the cutter to the same real work position as the origin used in the CAM
For me, I set Z0 the centre of rotation of the A axis origin and end of the bar as by X. (Y is centre line of the bar.)

If Im just using the A axis as an indexer, then I set Z0 to the top face of my trunnion (which is 25mm above the rotary table axis)

ATB
Derek.
You can "chop it off" but can't "chop it on"
Re: Help with 4th axis
« Reply #3 on: August 06, 2010, 10:09:56 AM »
Thanks for your response. Why can't you set Z0 as the surface of the bar? I am so used to the surface of my work piece being Z0 I have a hard time with it being the center of rotation. That means that if you are using a 1" round bar you would start with the cutter in the Z +.5 position?
"Gravity, its not just a good idea its the law"
Re: Help with 4th axis
« Reply #4 on: August 06, 2010, 12:46:40 PM »
Thanks for your response. Why can't you set Z0 as the surface of the bar? I am so used to the surface of my work piece being Z0 I have a hard time with it being the center of rotation. That means that if you are using a 1" round bar you would start with the cutter in the Z +.5 position?

Hi Astro,

You can set the suface of the bar a Z0. It depends on whet you are trying to achieve.
For surface engraving (which I have not done) it may be best to set Z0 as the top surface of the bar.
If you are machining a component in 3D then Z0 set at the centre of rotation works for me.

The important thing is to know where the origin is in your CAM and set the tool in the real work to match.
I'm sure some CNC Wraper guys will be along to help soon

ATB
Derek
You can "chop it off" but can't "chop it on"

Offline Tweakie.CNC

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Re: Help with 4th axis
« Reply #5 on: August 06, 2010, 01:09:08 PM »
Just something to think about.......

Angular mode is the most common and also the most useful way in which a rotary axis is used but there are alternatives to this,

When engraving on the surface of a cylinder, for example, it is convenient to have the rotary axis set for (linear) movement in mm but as this will vary, depending on the diameter of the work, there is a trick to getting it just right. One method for finding the ‘Steps Per’ is to calculate how many steps are necessary for the axis to complete one revolution and divide this figure by pi. In my case this is 200 (steps) x 8 (micro steps) x 60 (reduction ratio 60:1) / 3.142 (pi) = 30553.787 steps per to enter in Mach. Now this figure represents a linear movement of 1mm around the circumference of a 1mm diameter cylinder. In order that this can be used for any diameter of cylinder another calculation has to be performed and that is 1 divided by the diameter of the work (1/diameter). The result of this calculation is then entered into the rotary axis scale DRO within Mach. (My version of Mach did not have an A axis scale DRO (like the X,Y &Z axis have) so this had to be added using Screen4 (For reference the A axis scale DRO is OEM Code 62 and it’s associated LED is OEM Code 44).

As an example, to engrave on the surface of an 80mm diameter cylinder it is 1 / 80 = 0.0125 so 0.0125 is entered in the A axis scale DRO now a GCode command of G0 A10 will rotate the axis so that the surface of the 80mm diameter work rotates 10mm. Using this method means that simple, conventional, engraving programs and existing GCode programs can be used for engraving onto curved surfaces.

Although perhaps not quite as accurate as when the axis has been set up for angular movement in the first place - entering pi / 360 or 0.00873 into the A axis scale DRO will allow the axis to then operate in degrees ie. G0 A10 will rotate the axis 10 degrees.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: Help with 4th axis
« Reply #6 on: August 06, 2010, 01:30:21 PM »
Thanks Tweakie, I am starting to wrap my head around this. For now I am going to stick with Angular mode in inches as I have it working well in that mode. What I want to start doing is just engraving cylinders for now to learn the way it works and then move on to cams and gears. I may have more dumb questions I am a slow learner.
"Gravity, its not just a good idea its the law"

Offline Greolt

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Re: Help with 4th axis
« Reply #7 on: August 06, 2010, 08:02:30 PM »

I downloaded CNCWraper and tried some simple text on a bar of aluminum but it wants to put the 0 position in the middle of the part.

Not just the center of the A axis but in the center of the X axis as well?


This is not something that CNCWrapper is doing.  It is the result of where you set your origins in the CAM that produced the original toolpath.

CNCWrapper when converting code, or "wrapping" it, does only two things.

First it changes the designated axis definition.  Example, I set it to change X to A.

Second it scales all the positions for that axis to read in angle rather than linear units.  It arrives at this scale value using the diameter/radius value that you enter. This is the ONLY thing the diameter/radius setting is used for, to establish the scale factor.

The important thing relating to your query, is that CNCWrapper DOES NOT alter the Z axis position values.


In the CNCWrapper help files it does recommend using the centre of rotation as the Z axis zero.  And for most jobs I agree with this recommendation.  

However if you choose to use the surface of your existing cylinder as Z axis zero, that is fine.

So as far as wrapping with CNCWrapper is concerned, where the origins are set is something to be established in your CAM program.

HTH

Greg
Re: Help with 4th axis
« Reply #8 on: August 07, 2010, 04:47:23 PM »
Thanks for the reply, I figured out what you were are talking about about it was the the way I had set zero in the cam  I now have that straight. Thanks!!

"Gravity, its not just a good idea its the law"
Re: Help with 4th axis
« Reply #9 on: August 07, 2010, 04:54:33 PM »
I thought things were all fine until I made a few test cuts today. For some reason when running a program with the A axis the Z looses steps gradually through the program, it just cuts deeper and deeper the longer it runs. When I go back to just using X,Y,and Z everything runs great just like it did before I added the A axis. Also the A axis never misses a step I'm stumped???????
"Gravity, its not just a good idea its the law"