[jimluu]

Hi. I've been on this forum for a while. I've been planning my cnc router machine for years. I've got 6' long THK rails for th x-axis, 44" thk rails for the y- axis and 15" rails for the z axis. I've got nice ballscrews driving each direction. I've got 3 gecko vampire drives. I've bought bobcad 22, mach3. What an idiot I am. I have all these top of the line equipment, but have been searching for months for someone in my area (Colorado Springs) to build a metal table, but can't find anyone. I contacted 8020 and gave them the dimension, they want around $3k. Now I'm thinking about building out of wood unless some brilliant member could help me with some ideas. If you live in my area and can help, please let me know. I'd hate to have to get rid of all my rails. Took forever to hunt them down on ebay.

I might try something out of wood or synthetic wood. Any help appreciated.

[gerryv]

Boggie on down to the closest community college or high school that has a welding & machine shop (and preferably a large flat fabrication table) with a plan in pocket, the money needed to pay for the materials and a promise of lots of pizza, etc. Their budgets are short and they're running out of projects right about now. They also get discounts on metal & supplies but you'd need to pay up front as they can't afford to risk getting stuck with anything.

[slickrick]

That's a good idea.

I would definitely stress the importance of the squareness and plumbness with the table to the students, and probably explain why it needs to be so exact.

Welding is an art form and can take yrs to learn to do well.
It is not that difficult to run a weld a little too long and get the whole thing out of whack, especially when your starting out with welding. And when your trying to concentrate on making a nice weld, you can sometimes forget about the fit up.

[donnelson]

i have a bunch of bosch type 80 20 what size do youn want

[jimluu]

Thanks donnelson. I just sent you a PM.

[DavidD]

I'd go inquire at the following two welding forums and see if someone is in your area and would make you a table. I'd suspect though that the general opinion would be to buy a decent mig welder (they will have recommendations) and make it yourself. Steel is going to be much more rigid than wood.

Give them an idea of how big, what specifically you think you want it made out of (size of material), etc. I'm pretty sure a couple of the members are into CNC work themselves. I know some do for plasma cutting tables.

I know zip about CNC but aren't you going to shim the rails off the table to get them exactly in the same plane anyway? I could make a heck of a table out of some heavy wall square tubing for under $500 in material.

If you make it yourself (my recommendation) be sure to tack weld the whole thing up before really welding on it. Then move your welds around as you really weld it up. I'm a hobbiest woodworker/welder getting into metalworking and it was easy to ramp up my welding skills to make something like a table.

http://www.shopfloortalk.com/forums/index.php?

http://www.hobartwelders.com/weldtalk/

[HuFlungDung]

If you wanted a metal table, you could perhaps construct one out of aluminum plate and bar. My idea is first get a piece of 1/2" aluminum plate sawn out for the base size. Then, build your own T-slot system by sandwiching bar stock on top of this base. For example use a 1/2 x 2" risers with a 1/2 x 3" header on top. The header overhangs the riser to create the T slot.

The basic mode of construction would be drilling and tapping a bunch of holes through this. If you do this from below, then you could hide the evidence of construction A skim cut would clean up the top.

Perhaps in this day and age of magic epoxy compounds, you could use more epoxy and fewer screws to join it all together in a rigid mass.

If you bypass the welding, you'll make decent use of the stock flatness of the material, which is often not all that bad.

[mxtras]

I concur with Mr. Flung. You do not need to weld things together. In fact, you will likely have a flatter, straighter frame if it is bolted - unless the frame is to be machined after welding.

Scott

[andy_ck87028]

That's a good idea.

I would definitely stress the importance of the squareness and plumbness with the table to the students, and probably explain why it needs to be so exact.

Welding is an art form and can take yrs to learn to do well.
It is not that difficult to run a weld a little too long and get the whole thing out of whack, especially when your starting out with welding. And when your trying to concentrate on making a nice weld, you can sometimes forget about the fit up.

I used a different approach. I am not an expert welder and I know that all sorts of distortion has crept into my frame. However, I don't care and that is because I have introduced positioning adjustments into my rails.

Once positioned, they can be locked in and if required, an epoxy backfill in the spaces created by adjustment.

I reckon that perfection can be achieved by working around the limitations of your production method.

Andy

[mhasting2004]

I'll second what Andy has said as this is a similar approach I've been taking with my build.

http://www.cnczone.com/forums/showth...t=53824&page=2

While I did get some welding done for the threaded rod studs and the "N" leg pairs they are not critical allignment parts. Its early days in my build but so far Im really happy how the gantry moves (smooth as silk) and I have high confidence in my gravity leveled epoxy shim.

It all comes back to how good is good enough. If you intend to machine steel to high tolerance then my method would probably be far from good enough. Timber and foam to 0.1mm should be fine... I hope.

Good luck with the build.

Cheers

Mark

[ahren]

I would suggest this:

http://www.buyrack.com/fastrak_workbench.asp

I've thought about making a router based on one of these for a while. Maybe it's time for me to get going....

Ahren
www.cncrouterparts.com

[jimluu]

Thanks for all your great help and suggestions. I'm leaning towards picking up some 8020 garage items when they go on sale to use for the crucial parts, then use wood to build the not so crucial parts.

I do have another question. At some point I'd like to pick up a power supply. I'm leaning towards the 48v switching power supply from kelinginc. Perhaps I'll use 2. One for the x axis (very large screw) and one for the y and z axis. The alternative is to buy one of those things with huge transformers. Some how the power supplies with the exposed transformers seem real intimidating. Does anyone have experience with this type of power supply? How easy is it to implement? Is it better than 2 smaller switching power supplies?