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.

4D

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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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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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Re: Thanks for the help, but new question

Post by sobfu »

I recently tried to use the 4th axis for indexing on a piece of 80 mm square pine but it didn't end well. As Leo suggested there was too much torque away from the center line and the piece moved. It was a bit of fun trying though but I ended up cutting the piece flat and just rotated the piece with stop blocks as guides. I did need to allow plenty of waste either side of the carve so I could cut it off on the drop saw at 90 degrees. .
4th axis attempt.png

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Re: Thanks for the help, but new question

Post by IslaWW »

Yes its tough, but can be done. Here is a testing video from 7-8 years ago that was part of my rotary axis "mythbusters" machine. Test is not for quality, but to see how aggressively one could plunge and cut close to 4" off center as a comparison to some OEM 4th axes. As you can see (about 5 minutes in) fast plunges straight into material with a 3/8 compression bit doesnt seem to phase the rotary. As per my usual, all toolpaths generated with VCarve Pro.

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Re: Thanks for the help, but new question

Post by MikeSibley »

mtylerfl wrote:
Tue Oct 12, 2021 1:21 pm
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.
I'm sorry guys, I have been out of pocket. My company decided to make changes in its structure and eliminated my entire group, so I was tied up trying to change insurance, etc. Don't worry, I just transitioned to retirement so all is good, just came about 8-months earlier than I planned.

I didn't mean to leave you guys hanging, especially when you are trying to help me!! I just got my 4th axis for my Avid pro (NEMA 34) machine this year and due to all the "stuff" happening, I haven't had time to play with it and learn. My wife had asked me if I could make some corbels to decorate/support some shelves that she wanted to display some of her "trinkets" on and I thought, what the heck, maybe the 4th axis could do that without me having to cut a three sided project.

I know that if the bit is out some distance from the centerline of the machine, torque is higher and subject to excessive pressure on the machine. But, just thinking, a significant reduction in cut depth would reduce those pressures (just physics) at the expense of machine time. Since I am learning, maybe some trial and error via the school of hard knocks is preferred.

But, as I am new to this, I purchased a textbook to learn how the machine interface and G code works. I'm about 3/4 through the textbook (textbooks are not really good and easy reading!) and am beginning to understand what you guys are discussing about inserting the g-code for the rotary axis.

I'm thinking about doing something like the following photo, but maybe not as elaborate. There are websites that have corbels in 3-D STL files. I'm thinking about using a softer wood (just to test) and play with it.

I appreciate you guys very much. I am again sorry for the delay, but I'm about back at the stage of getting used to my new machine capabilities.

Mike
corbel.jpeg

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Re: Thanks for the help, but new question

Post by pviljoen »

I am in the same boat learning about Corbels. A major thing I have learned so far is to think outside the box and cut the corbel at an angle, meaning that the flat back can be up to 45deg to the center line. That way you minimize the stresses on the outer parameter.
Once you start setting up you model, move it so that the center-line is just behind the thinnest piece, and in the middle of the thickest piece.
Yes it does add some trimming and cleaning up after the fact but allows you minimize the off-center stresses.
This also allows you minimize deadwood/lost wood or wood that is going to be cut away anyhow. You will just have to play with the drawing to find the correct way to laminate the wood so that the majority is inside the corbel model and minimal is lost.

The next problem I am having is how to set up a virtual rod around the center of the model, so that the rotary does not cut all the way through. Maybe this is a question for the developers to add a function whether the rotary add this center rod automatically for you when you set up a project. I know there are some software out there that does it.

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Re: Thanks for the help, but new question

Post by Rcnewcomb »

Maybe this is a question for the developers to add a function whether the rotary add this center rod automatically for you when you set up a project.
Can you explain further what you mean by this?

Perhaps a screen shot or diagram would help me understand. Vectric products definitely are aware of a centerline -- in fact, they will not cut below the centerline.
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Re: Thanks for the help, but new question

Post by MikeSibley »

4DThinker wrote:
Mon Oct 11, 2021 12:46 am
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.

4D
Thanks! So, I purchased a book on G-Code programming and am learning between all the other things that I have to accomplish in retirement! Do you design the model in Aspire and then insert the rotational commands, or would you do an individual design for one side then rotate and load another file? I guess my question is whether you do four individual sides and rotate between each side or do you incorporate into one model file? Maybe I am overthinking this.

I guess I could take a square piece of stock, and experiment.

I sincerely appreciate all of everyone's help.

Mike

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Re: Thanks for the help, but new question

Post by pviljoen »

Rcnewcomb wrote:
Tue Jan 25, 2022 9:30 pm
Maybe this is a question for the developers to add a function whether the rotary add this center rod automatically for you when you set up a project.
Can you explain further what you mean by this?

Perhaps a screen shot or diagram would help me understand. Vectric products definitely are aware of a centerline -- in fact, they will not cut below the centerline.
Think of a dowel going through the center line of the cut, not necessary the model. This will serve as an extension to the piece holding the model in place and also eliminate the router bolt from pushing into the left over pieces in the ends of the rotary cut. This dowel should be able to be set by the programmer/designer,(size and angle). The dowel then becomes the piece that prevent to cut from going all the way to zero.

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Re: Thanks for the help, but new question

Post by 4DThinker »

MikeSibley wrote:
Sat Feb 05, 2022 4:52 pm
Thanks! So, I purchased a book on G-Code programming and am learning between all the other things that I have to accomplish in retirement! Do you design the model in Aspire and then insert the rotational commands, or would you do an individual design for one side then rotate and load another file? I guess my question is whether you do four individual sides and rotate between each side or do you incorporate into one model file? Maybe I am overthinking this.
Mike
When I've cut 3 or 4 sided projects on the rotary axis I make individual files for each side. You could optionally put each on a different layer. Each toolpath is save separately. a GCode command issued in my control software rotates the a axis before loading and running successive file. How much torque is applied when cutting away from the centerline depends on how aggressive the cuts and plunge moves are. Ramp plunge moves. Slow down feed speed. Experiment on scrap wood until you're happy with your results.
4D

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Re: Thanks for the help, but new question

Post by MikeSibley »

Thanks everyone for helping me learn!

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