Thanks for the help, but new question

Topics related to wrapped rotary machining in Aspire or VCarve Pro
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MikeSibley
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Thanks for the help, but new question

Post by MikeSibley »

Has anyone tried to carve any design into a square versus round workpiece? My thoughts are that if I carve a three sided piece such as a corbel that is lets say, 3 inches square, do I have to start with a much larger piece and unwrap the piece and insert the design? Maybe I am thinking about trying to get too much out of the 4th axis.

To simplify, can the 4th axis work on a generally square 3D model?

Thanks,

Mike

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Re: Thanks for the help, but new question

Post by 4DThinker »

Yes, and possibly no. I've done several similar projects for my students. The wrapping capability though keeps the bit centered on the blank axis and turns the wood to position the bit for cuts on that axis. When I need to carve on a face or cut mortises I mix some regular 3 axis post processor files with the wrap XtoA (or YtoA) post processor files. You can cut a square from a cylinder, and even twist the square if you want. You just can't make mortises wider than the bit diameter, and certainly not off center using the wrapping post processor.

I simply use the controller software to turn the blank 90, 180, 270 degrees before running XYZ axis files on each face. Gcode is typcially G0A90, G0A180, and G0A270. For anything with more or less sides than 4 you can do the math to figure out the angles for each face.

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TReischl
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Re: Thanks for the help, but new question

Post by TReischl »

Most corbels I have seen are not rotary axis work. They are indexed type work. Whether or not a rotary axis is used to index the piece as mentioned in the above reply is up to the programmer and the capability of the control.

One thing to keep in mind when using a rotary axis to index the work. . . the holding power when cutting off axis is completely dependent on the power of the stepper/servo motor. It is quite easy to overcome the motor when the machine starts cutting away from the centerline.

A lot of folks think that indexers are rotary axis, they are not. An indexer is equipped with locks that engage when the index is complete to prevent the problem mentioned above. Of course, a powerful motor can accomplish the same thing.
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MikeSibley
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Re: Thanks for the help, but new question

Post by MikeSibley »

Thanks guys! I'm stil playing with my rotary axis. I have an AVID pro NEMA 34 so I might just play with it. I just figured it would be more accurate trying this on the 4th axis than trying to cut three sides and re-reference the workpiece and keep it aligned accurately.

My project is to repair an antique wall clock whose glue joint came apart and fell off the wall breaking the case and really messing up the decorative corbel piece on the bottom. It is not large, about 2.5 inches square. Repairing the broken piece was not possible due to the damage. I've still got a lot to learn about the 4th axis especially on indexing in Mach 4.

One of the shortcomings on all of this is the lack of detail on these subjects. I know that a whole lot of people will not be interested in that, but I've always been one of those types from a kid when I would take things apart to figure out how it worked.

Mike

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Re: Thanks for the help, but new question

Post by mtylerfl »

Hi Mike,

Do you have some photos you can post? Seeing exactly what you are wanting to duplicate for the repair will be helpful all around.
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Re: Thanks for the help, but new question

Post by Leo »

TReischl wrote:
Mon Oct 11, 2021 1:46 am
A lot of folks think that indexers are rotary axis, they are not. An indexer is equipped with locks that engage when the index is complete to prevent the problem mentioned above.
AGREED - a rotary axis is NOT an indexer.

It CAN be used that way, but it most likely does not have a lock on the rotation like an industrial machine has.

You CAN do index work, but try to stay as close to the axis centerline as possible. The further away from centerline the more torque is applied and can overcome the holding power of the stepper motor - even on NEMA 34.
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