Newbie- MadCAM and 4 axis cylinder/rotary

[etzz]

Hello,

I recently purchased madcam, and have been investigating its capabilities. I have a Taig mill with 4th axis rotary table. In evaluating the software, it appeared to me cylinder machining would be the most challenging. Normal 3D operations are very quick to implement in Madcam. So I decided to practice creating some toolpaths on a cylinder to see what could be done.

Here are my observations/questions. Note that some operations of this type of machining is probably more suitable for a lathe. So some questions may be a bit silly.

My model part looks like this:


1) MadCAm does 4 and 5 axis "indexed" machining. That means cutting 3D toolpaths on a part that is rotated around. From what I could figure out, Madcam can move in very minute increments (say degrees of revolution on a rotary axis) by advancing the rhino cplane to whatever angle is desired. Or you can set the cutting cplane normal to any surface. This is for creating the toolpaths.

2) One thing I noticed about Madcam is that the roughing toolpaths can not be limited in degrees, but only by surface curves. Surface curves that remain in a small area (say for a pocket) present no problem. If you have surface curves that go all the way around this can be troublesome. The pic below shows some cylinder tool paths. Note the middle roughing toolpath. To provide a better cutting toolpath, I would like to increment the cylinder by say 10 degrees, make some cuts, and then continue another 10 degrees, etc. Madcam always tries to rough the whole surface. This makes it harder to "approximate" a continuous contour by reducing the increment between 3D cutting operation.




3) It appears that I can only create square bar stock. The ability to create cylindrical stock would really help. Can you define cylinder stock? The 3D operation on a cylinder represented by barstock creates unnecessary toolpaths in free space. Not really a problem for me, it just means the cuts take a bit longer.

4) For engraving text, I projected text on a cylinder as shown below. This will be cut with 3D operations, but will "approximate" continuous contouring if the text is small. I read somewhere that you can trick the cnc machine by moving the y axis to the rotary axis by editing the post process, but this is beyond me at this point.



So are my assumptions for these operations above correct? I have only been using the software a couple of days, so there may be different ways to do things. Seems like a couple of good additions would be: A) Part stock that can be defined by shapes other than rectangle (define from surface or solid). B) 4th axis machining that can have degrees of motion "clipping planes". This could be used to approximate continuous contouring.

The software seems excellent and easy to use for 2.5D and 3D machining, but the above case is what I am wondering how the veterans would go about implementation.

Thanks for any info,
Eric

[etzz]

I find out a bit more info by experimenting.

A slightly more efficient way to rough the cylinder (cutouts) is to use bounding curves for the machining (region curves). You can add, for example, six individual region curves all the way around, and then let Madcam machine each region in succession.

This is to minimize wasted cutting in free space (due to Madcam trying to rough a bar shape when using an unbounded roughing pass). A single yellow region curve is shown below which bounds a single 3d roughing operation below.



A good feature to add would be the ability to define cylinder shape stock, or define stock shape from model.

While I am requesting things, part tabs would be nice too. For 2.5D contouring of thin sheet, I think the best way to currently handle this is to trim out segments in your contour (Rhino 3D trim). This is pretty easy. But if you are contouring at multiple Z depths, it becomes more complicated to implement.

Regards,
Eric

[etzz]

This is useful info if you want to engrave text on a cylinder.

Rotational machining on a cylinder using 3D operations like engraving text is called "Y axis wrapping". I tested a real nice freeware application for doing this that has been discussed in other threads on this site.


The program is called WRAPPER which can be found here:
http://www.vectric.com/forum/viewtopic.php?t=2920

This is a very nice application that a fellow wrote to take an XY file which you created in MADCAM or any other CAM software, and wrap the Y axis around a cylinder. I tried it last night and it works great. you can even wrap around and around continuously, but I did not try that. Another user had some pics of that type of operation

On MACH3, you will have to enable the radius speed compensation (ie enter the radius of you cylinder stock into mach3). Otherwise, your A axis will turn very slow, as the feedrates are interpreted as degrees per second (for example 10 degrees per second).

Another option in MACH3 is you use the "formulas" function for your Y axis control. With that you could project 2D text onto a cylinder and machine it in MACH3, but that is pretty much already handled by MADCAM/RHINO directly.

Regards,
Eric