Moving table router design questions

[montanamac]

I am a newbee to CNC. I am a self taught hobby machinest with some cad skills. I have been lurking for a while and now have semi firm plans to make a moving table router with the Z axis stationary. My plan is to construct the frame from 1 inch square tube using ball bearings for rolling gliders on the tubing. For the Z axis I am looking for a good price on Ebay for a set of Linear rails and bearings.
My main question at this point regarding the moving table ... is it manditory (or recommended) that the X and Y movements have bearings top, side and bottom on the tubing runners or is top and side enough.
I have attached a couple of drawings showing some thoughts of the machine design along with the "glider" details.
Any thoughts or suggestions would be appreciated!
Also ... hope this is the correct place to submit this sort of post ... please correct me if it is out of place

Mac
Corvallis, Montana

[vladdy]

For a router support on axis [axes?] is required..plasma or torch type table additional upward support isn't needed...
I'm about half way through building another plasma /oxy table, and I used cheap chinese bearings for side to side [4 brgs] and support on bottom [2 brg], with no regard for any upward pull...after all if the cutter pulls the arm up, then it's way too low on the table..
for any significant load, which is pretty well any 'contact' type of cutting, support in all directions is required..
Last table had linear bushings with acme thread and rudimentry zero backlash nuts, the one before had actual THK rails and 'store bought' ballscrews..
for the intended purpose of this one [flat steel cutting for brackets, braces, etc.) a final cut tolerance of +/_ 0.005 is more than enough...if it turns out that tight..
So far X/Y movement with 50 lbs pressure applied is around 3 thou..on the torch carriage..don't have the screws tied in as of yet...
maybe tomorrow...

enjoy..

[herschmidt]

vladdy:

I'm building a plasma table too, do you have nay pictures of it?

what kind of motors are you using and what is the torque of them?

Thanks. Hernan

[vladdy]

no pictures as of yet, could take a few tomorrow..
got most of the x and y axis bearing carriers done, on to the screws and mounts now...

[Chad_Clark]

Originally Posted by montanamac I am a newbee to CNC. I am a self taught hobby machinest with some cad skills. I have been lurking for a while and now have semi firm plans to make a moving table router with the Z axis stationary. My plan is to construct the frame from 1 inch square tube using ball bearings for rolling gliders on the tubing. For the Z axis I am looking for a good price on Ebay for a set of Linear rails and bearings. My main question at this point regarding the moving table ... is it manditory (or recommended) that the X and Y movements have bearings top, side and bottom on the tubing runners or is top and side enough. I have attached a couple of drawings showing some thoughts of the machine design along with the "glider" details. Any thoughts or suggestions would be appreciated! Also ... hope this is the correct place to submit this sort of post ... please correct me if it is out of place Mac Corvallis, Montana

It would honestly depend on the material you plan on cutting and if you are going to be using a plasma/oxy head on this machine or a Router head. It would also depend on the speeds you plan on running this machine at. If you are using a plasma/oxy head and running low speeds or a router head and only cutting wood or plasitic than what you plan on doing is fine. If you are running a router head and going to try cutting metal and other dense materials or cutting at faster speeds it would be suggested to go with the top bearings also. I hope this helps. Also have you given any thought into a CAD/CAM for programming this machine? Is it going to be run on g-code? Just some other questions I was curious about.

[montanamac]

This project is to gain some knowledge about CNC prior to a CNC conversion of my milling machine. I will be using a router head and most likely cutting wood, plastic and possibly aluminum with this router setup.

I currently use Design Cad for drawings which has the ability to export in several formats including DXF. I have been reading about Mach3 for CAM operations and conversion to G code. With the little knowledge I have, this program seems to have the features I need. What suggestions do you have for someone with limited bucks?


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[montanamac]

Here is a sketch of my idea for X and Y carriage travel dollies.

Any feedback would be appreciated



Also ... how can I post pictures directly to a post such as this?

Mac

[Chad_Clark]

The top side will be enough. Mach 3 is an excellant program also. Not very expensive and easy to learn and use. When you do go cnc I would suggest a non-expensive CAM system too. Just a CAM also, no need to learn CAD over again and what you have will work fine. May I suggest looking into Dolphin CAD/CAM when the time comes. The website is www.cadcamconsultants.net. If there is anything else I can assist with, please let me know.

[ger21]

If LazyCAM (included with Mach3) can't quite do what you need, take a good look at SheetCAM. www.sheetcam.com

It should work fine with DesignCAD and the price can't be beat.

[montanamac]

I have been thinking of different ways to build an inexpensive trolly system and this is my latest design.

This design uses cheap skate board bearings running on 1/2" angle iron welded to 1" square tube (the frame). The side limiting bearings are tucked under the angle iron preventing the table from moving upward if lifted.

The top bearing will track on top of the angle iron (might need to be milled flat ... we will see) and the side limiting bearings will track directly on the 1" square tube. My cad drawings show the distance from bottom to working surface to be right at 6".

Any thoughts ?

Mac