Hi all,
I am going to attempt to make a 5 axis router table. I have the bulk of the design done and am just missing a few of the finer details and feel that I'm close to the point where I can order some material. My goal is to have a 4' x 3' x 12" cutting area. The material for construction will be aluminum. I am planning on using stepper motors and acme screws for my power transfer. I need to double check my calcs for my acme screws, but so far I have 1"-10 for the X and Y axes and I think 3/4" for the Z axis. The estimated weight (minus the base) is about 150 lbs.
For those that have the software, or desire to look at it, here is a link to a step file for download (let me know if the link doesn't work): https://app.box.com/s/6b5fycwxox7mqudn05urpm0k5op533d9
The first picture is of the overall design. Currently, I don't have a base modeled in. I will either be purchasing a table from my work, or order one from online. The four uprights in the corners will be attached to the top of the table and will also house the acme drive screw and the motor for the X axis. The part of the base that has the grid in it will be made out of cement for the self leveling and rigidity. The grid will be for a vacuum system.
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The second picture is of the gantry. I went with the split design like this in attempt to make it so that the forces that would be applied to it would be more uniform instead of having a large moment about where the next component interacts.This will ride on a piece of angle and roller bearings on both sides.
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The next pictures is of the Y axis. The large hole in the middle is where the acme nut will go for the acme screw. I don't have this modeled in yet. I'm not really sure what to do about that. I know that brass is a self lubricating material and would work well for a nut, but it is also pretty expensive. I only plan on cutting wood, so a wet lube on a steel nut wouldn't work very well. Would a dry lube work well? What about a plastic nut? I plan on making my own acme nut.
In the second and third pictures, I have bearings on the top and bottom outsides. These will slide on angle pieces on the gantry. I have it designed so that the plates holding everything together have slotted holes for any alignment issues. The Z axis tube will also slide on bearings thru the center of this pieces as well.
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The next set of pictures is the Z axis with A and B axis (I believe that's what the additional axes are called). There will be a steel rod connected to the motor thru a coupler which then rotates the parts. I have it so that router will be in line with the axis of rotation. This will help more in attempting to write the code for cutting. The large slot in the vertical tube is clearance for the cross acme screw. In the second picture, it's a little hard to see, but there are two small holes where the top motor is. The hole placement isn't finalized, but those will be for constant force springs (similar to a contractors tape measure) to help raise the Z axis up so there is less strain on the Z axis motor. (I have most of the components in the pictures set to transparent so that you can see the internal components).
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My main concern with the design is how much flex that it will have. All of the box tubing (with the exception of the 4 corners) are 2" x 3" x 1/8" 6063-T5 aluminum. Most of the plates are 1/4" 6061-T6 aluminum, and the angle pieces are 1/8" 6063 or 6061 aluminum. I have tried doing some FEA thru SolidWorks, but I am new to that part of SolidWorks, so I am not sure how accurate it is. With just the Z, A, and B axes isolated, a 20 lbf on the tip of the router, it will deflect about .014". When I try to add the next component to the FEA study, it errors out. Does the .014" sound accurate? I have read that 20 lbf is on the upper end of the forces that I would see when cutting wood. I'm assuming that the .014" would be acceptable for a roughing pass and that when I do the finishing passes, the force and ultimately, the deflection, would be much less. My gut tells me that I need more bracing on the gantry to try to limit flex, but I'm not sure how much is needed.
Any feedback is welcome.
Thanks,