Virtual slicing with the rotary axis

General MeshCAM Questions

Virtual slicing with the rotary axis

Postby ArchieF » Sun Apr 24, 2011 2:33 pm

In this thread viewtopic.php?f=3&t=1377 jeffD mentioned the following :
My work around is to take a real thin slice out out of the stl. Unroll it with Rhino to flat and use the rotary as a linear. Numbers all have to match up and you do have to lie to the mill some.

Not easy the first time, and I don't know how to take a slice = to finishing step over out of an stl model. All my models might be mixes of meshes and nurbs... slicing nurbs is easy, well sort of ;)


Would the following idea create a toolpath with similar quality ?

1. open your model in 4 axis mode
2. define i.e. a 36 side job type
3. now define a very small region along the x-axis from the left to the right and start calculation

Attached you will find a screenshot of the region definition and a screenshot looking in x-direction and showing one of the 36 virtual slices.

Richard
Attachments
CarmenAnim.gif
Toolpath animation
CarmenAnim.gif (764.81 KiB) Viewed 8020 times
CarmenRegionToolpath.PNG
Toolpath at 0 degrees
CarmenRegionToolpath.PNG (129.37 KiB) Viewed 8027 times
CarmenRegion.PNG
The small region I defined
CarmenRegion.PNG (59.21 KiB) Viewed 8027 times
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Re: Virtual slicing with the rotary axis

Postby jeffD » Sun Apr 24, 2011 6:01 pm

Richard,

I just don't know.

I did try using the 4 axis mode with lots of small rotary increments a few years ago. Too many g-code files to stick together and I was NOT happy with the results VS time involved. I went back to my old tried and true methods quite quickly. Not quite brain dead easy but the fingers still remember which keys to press and I know where my brain will screw up :mrgreen:

Try your ideas and mill the part. Simulations might be neat but simulating even in wax is real. Looking at your screen shots and my first reaction is that you are making things far more complex and slow than required.

jeffD
I have no financial interests in MeshCam. Nothing I say here has had any approval from MC. Any errors or omissions are mine alone. Use at your own risk.
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Re: Virtual slicing with the rotary axis

Postby ArchieF » Sun Apr 24, 2011 6:21 pm

Jeff,

I know the time is the most important thing if you want to achieve a perfect surface.
A lot of small g-code parts need a lot of time to handle so it will perhaps make less sense to mill it in this way. :)

It was just an idea and a continous rotation will always give a better result. Sometimes I'm gonna try it and see what the result will be.

Thanks

-Richard
AMD Athlon II X2 215 Processor 2.7 GHz

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Re: Virtual slicing with the rotary axis

Postby jeffD » Mon Apr 25, 2011 5:07 pm

Richard,

Time does matter, my solution was to lock the mill in the dungeon and run a wire to a LED next to my computer. Light goes out and I go down to see the results. No way am I going to stand there and watch :-)

MC does not do continous 4 axis (yet) I do a fair bit of 4 axis stuff with my rather crude hack and work around. Geometry does get distorted and often the 3D model has to be distorted to compensate. It is fun and fills my needs but is not perfect. Not quite good for feeble hearted anal perfectionists but good enough for me. HeHe... a bit of 5 axis stuff worked but I lost brain cells in the process :-)

jeffD
I have no financial interests in MeshCam. Nothing I say here has had any approval from MC. Any errors or omissions are mine alone. Use at your own risk.
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Re: Virtual slicing with the rotary axis

Postby ArchieF » Mon Apr 25, 2011 5:54 pm

Jeff,

that's a nice idea with the LED. But you obviously have a lot of confidence to your g-code. A crash coz of a wrong G0 instead of a G1 or a broken tool might happen very fast :)

In dungeons sometimes strange things gonna happen :D


Do you verify your code with a backplotter ? I'm searching for a backplotter especially showing the 4th axis in a solid mode.

Do you know of such a backplotter in a lower range of price ?

Richard
AMD Athlon II X2 215 Processor 2.7 GHz

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Don't waste water - dilute it !
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Re: Virtual slicing with the rotary axis

Postby jeffD » Mon Apr 25, 2011 6:39 pm

Richard,

No backplotter. I just run the sucker. MC does not let me down with bad g-code, it might crash generating code but even I can see that something is very wrong. Backplotters cost $$, if the damned computer will lie to me once I see no reason to trust it a second time to check for errors. Screen stuff and finished pieces are often quite different.

Besides I use MC in ways Robert never imagined. I know nothing about MC internals but am good at knowing what I want it to spit out, (and I am good at breaking MC for my wicked ways :-)

I also keep my messing with the g-code to a minimum. I muck about with post files too much but when they are stable I don't worry any more.

I use little tool bits so a crash only costs a bit, no holes in the table yet. :)

jeffD
I have no financial interests in MeshCam. Nothing I say here has had any approval from MC. Any errors or omissions are mine alone. Use at your own risk.
jeffD
 
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