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4th axis

Re: 4th axis

Postby Awesomeness » Fri Apr 08, 2011 4:37 am

On the other hand, if you want a rotary axis that can do huge, heavy material, you may have to stand it up so that the weight is downward on a rotary "lazy suzan". That would require redesigning everything, including the machine.
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Re: 4th axis

Postby Kevin » Fri Apr 08, 2011 1:22 pm

A friend of mine moved back home in the Norman Oklahoma area and started a little machine shop on the side. His neighbors built themselves a CNC in polar coordinates to machine full size human sculptures from foam. They make fiberglass sculptures for outdoor display. The work stands on a rotary axis lazy suzan. A vertical rail supports a trolley for the dremel they use as a spindle. Drawer slides allow an in and out axis. I'm pretty sure it's still 3 axis. They make arms and legs separate often so they can do undercuts and other complex shapes with the limited axes.
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Re: 4th axis

Postby servant74 » Wed Jun 01, 2011 12:34 am

One idea for another gantry mounted too... a rotatable saw, like a panel saw. For a full size (4x8 or larger) it would be nice to do this. Especially since saw blades have a narrower kerf than most typical router bits.

Also if the tools were quickly (and quick release for power, possible positioning motors, etc as required) would make it easy to change kinds of tools/routers/etc.
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Re: 4th axis

Postby Ronan » Fri Apr 19, 2013 6:42 am

I have been thinking about how to make a BYCNC setup into a machine using a 4th axis for some time and I think it would be as easy as setting up the table properly the first time. This should not take any greater adjustments than extending the Z-axis drive and the table itself. The ideas I have for updating my table, are as follows:

Extend the Z-axis for the router so that you can travel beyond the surface of the table that you are doing parallel cuts upon. This will extend the overall height, but only enough to get the appropriate depth of cuts in the material you are turning. I am thinking I will invest in a longer screw for the z-axis and just cut myself some duplicate parts, just a bit longer, to facilitate the added depth.

The second part of this process is to build the table top in a fashion that not only offers the rigidity that you need while cutting flat stock on the table top, but a method by which the center can be removed, either by slide mechanisms or leafing, so that you can reveal the under portion of the table. Because the design currently does not require any mechanical parts to run under the table top, and also due to the majority of the burden being on the outside edges of the table top the center should be able to be removed without creating undue stress on the structure while giving you a space to mount a rotating piece of material.

Finally, I am imagining that there is a second NEMA 34 powering a rotational mount, so that you can mount material in the middle of the table and pin it in place, like a lathe mount. One side will be fixed in place, which is the corresponding end to the motor. I also see this system working with the same #25 roller chain and sprocket system of the other axis points. The far end for fastening the material would include a lazy susan type rotational bearing system fixed to a screw type device so you can adjust the length of the mount accepting diverse height of material.

If this method works out I will definitely share it and link it up, it will be a bit of time before I can get everything prototype d but this idea, I think would be the most cost effective and easiest if you want to convert an existing setup to accept a rotational 4th axis. All the parts that you would need to order in addition to your existing setup would be a longer drive system for the Z-axis, which may just be a longer screw, an additional motor and drive components, and a way to allow for the smooth turning of the material.

Converting the table should not be too difficult, however, I realize that when you compromise a solid flat surface for something that is modular you may run into a problem with tool resolution due to flex at the joints. I am not sure how to overcome this and allow for many uses of the same cnc for different applications, but, once you have something that is perfect, the soul of a hacker is to make it better....its just the way of life for our kind.

Hope this sparks some ideas in your brains!
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Re: 4th axis

Postby benjamin.willhoite » Sat Feb 14, 2015 5:14 pm

Hey Everybody, I am not trying to spam the board, but I am catching up on the forums and I intend to read them from start to finish in certain areas. I can say that right now there is a pile of 4th/A axis kits available on eBay from China with varying levels of quality, shipping methods, and shipping costs. I know that at the time these posts were written those parts were not available. I am not certain, but I think there may be one on the website bycnc website now.

I hope that this subject can be reopened and discussed a little more, or somebody can point me to the current discussion.
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Re: 4th axis

Postby Awesomeness » Mon Feb 16, 2015 11:27 pm

Patrick sells one now. It looks to be one of the same Chinese variety, originally designed fro a small metal mill, but I suppose at least it's "hand picked" and somewhat vetted by Patrick.
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