Need suggestions on a 9'x5.5' setup -screws and slides

[turbotoys]

I have been doing research for a few months here and my plan is too build a nice fairly accurate router table for doing wood/plasma/ and some light aluminum work. The questions i have is with the slides and the ball screws...

I am looking for an accurate slide for the x-axis on my table - 9' to be exact. I started looking at nook industries and was looking at the .75" or 1" pre-drilled linear shaft assemblies - the tech guy i got on the phone said that for a few more dollars the PROFILE RAIL LINEAR GUIDE RUNNER is a better choice. anyone with any input on this would be great - im trying to make this on a low budget but still staying at a fairly good accuracy. Any pros or cons on either?

next question i have is the ball screws - i plan on driving it from both sides so i will need 2 ball screws - i was thinking of using 0631-0200 XPR but im thinking deflection will be an issue. so I thought maybe something around 1000-0250xpr will work better but the tech guy said that is only good for up too roughly 80" - what are you guys using on the bigger machines? any input would be greatly appreciated .....

[High Seas]

BIG SIZE + Low Budget + reasonable precision + light tool loads = Garage Door Rail (It is Screws and Slides in one piece)

Just a consideration for you, the Screw driven Garage door Rails combine the screw and track in a single piece. You could get and try out for a very cheap price at garage sales/the Sally's/Op Shops etc. I've noted by push and pull they can be reasonable in terms of repeatability. An added feature -- the screw is supported in the track inside a nylon tube. You'd need to keep the weights down on the gantry or stiffen the setup with some other bits. I've been considering such a design and build -- but this season is soon coming to a close for me and it'll have to wait for next trip.

May seem off the wall - but you asked for ideas. (PUN INTENDED )
Jim

[ahren]

I would say that for a machine that large, rack and pinion might be a better choice to keep your costs down. By pre-loading the pinion gear into the rack, you can eliminate most of the backlash in the system and maintain accuracy. If you wanted to go high-end, a setup this large would probably do best to spin the nut on a stationary ball screw. THK, IKO, and other ballscrew manufacturers sell spinning nut options. Pricey and a little complicated to implement, but worth the reduction in inertia and risk of whip.

[solodex2151]

Originally Posted by ahren I would say that for a machine that large, rack and pinion might be a better choice to keep your costs down. By pre-loading the pinion gear into the rack, you can eliminate most of the backlash in the system and maintain accuracy. If you wanted to go high-end, a setup this large would probably do best to spin the nut on a stationary ball screw. THK, IKO, and other ballscrew manufacturers sell spinning nut options. Pricey and a little complicated to implement, but worth the reduction in inertia and risk of whip.

I second this opinion. I don't personally like ballscrews over 4 feet. Rack and pinion is the industry standard for this length although I have seen some belt driven setups.

Is 9' by 5x5' going to be your cutting area or the total length of the router?

[turbotoys]

9'x5.5' is the total length x width- i started looking at the costs and i didnt mind paying $3000 for some ball screws but for what i needed it would have been around $6000 so i purchased some rack from mcmaster carr - i would have to say it was a lot cheaper -LOL but now how the heck do you mount the stuff ? it is like 1/2" x 1/2" I wanted to bolt it but i guess i didnt realize how small 1/2" was when i ordered it ... so im gonna have to weld it - how in the heck do you keep it straight and then also how do you manage to get 0 backlash from the pinion? i have looked all over on this site for pictures of how people are mounting this stuff and i cant find any....

[marchantdice]

Rack and pinion? has its place.
Ballscrews over 4', if you select a large diameter this is not an issue, I think your real issue is cost?
We just completed a job for a company in China for 10' x 30' ballscrews and there very stiff.

Our cost for 1" or 1 1/4" diameter, preloaded class 5 with double nuts to suit this machine envelope: budget price £1400 $2800usd including delivery.

Marchantdice
www.worldofcnc

[solodex2151]

Check out this picture: http://www.torchmate.com/industrial/TK510xmotor.jpg The torchmate systems use 80/20 to keep the racks straight. There are several other pictures.

[Switcher]

I would use rack & pinion, with the teeth on the rack facing down.

.

[GaryCorlew]

You may want to check out this site
http://www.mechmate.com

[Gerald_D]

Easiest way to mount rack is with double-sided tape. I am dead serious about this. It does work well.

http://solutions.3m.com/wps/portal/3M/en_US/VHB/Tapes/

In the MechMate drawings I tell the guys to put one screw at each end of the rack, but that is belt & braces. The tape manages quite happily by itself.

[TSJ]

I will be using a rack and pinion system on a router 10' X 5', the 5' gantry will be with a 1.5" ball screw. For the X axis I have purchased 2 six foot and 2 four foot pieces of 1/2" 20 pitch gear rack that will be welded to some 1/2" X 2" flat bar. I will cut a slot in the flat bar about every 3 - 4 inches for mounting to the bottom of a 2"X6" channel that forms the side of the table. If I were really a good machinist I could drill holes but a slot will give me more freedom to make the gear and the rack have less backlash. The cold rolled bar does not have a good flat 1/2" edge so I plan to mill it square before welding. I will take a grinder and cut a small "V" (1/4" long 1/8" deep) in the edge on the top and bottom about 3"-4" apart for fill welding. Next clamp the two pieces of bar stock together with a 6' and 4' piece of rack on one side and a 4' and 6' piece on the other. This way each rack piece will mesh the teeth aligning all the teeth in the gear rack pieces. With the pieces well clamped it will be fill welded in the small "V"s with a mig welder. When it is complete there will be a piece about 2.5" wide and 0.5" thick, hopefully still straight, but if not that is why the slots and not holes for mounting.

Just some thoughts, I have the pieces, now I need the time to get going...