Idea for CNCRouterParts covered Y axis

[ben_jackson]

I am designing a router with a flat table and a gantry. The table needs to double as a work surface and tablesaw outfeed and so on. Also, I don't want any obstructions for loading sheets onto it. I had already planned to turn the cold rolled steel plates vertical and place the R&P drive underneath. My first drawing shows the top edge of the steel plate basically flush with the table top (it sticks up 0.5 and there's a 0.75" top).

Some comments about keeping the rails clean got me thinking about how the rails could be covered by the table instead. So I swapped out my straight 3030 with a 1545+1530 "L" shape, shown below. It provides the right geometry for the steel plate and the R&P drive. The rightmost edge of the spindle reach is about the edge of the 1545.

As shown, the top carriage is exactly flush with the bottom of the table. However, if my part models are accurate you can get a little less than 0.1" clearance just by moving the steel plate down (slightly compromising rack engagement) and/or about 1/8" clearance by milling down the top of the carriage. The underside of the wooden top could also be thinned.

Thoughts?

[lunchtrayrider]

i wouldn't want to rely on that kind of bolt connection along the side rails.

i sketched this up quick to show.

run a 1545 across the end, and then butt a 3030 for the side rail into it. the steel plate for the rail can also reinforce this connection. it should also use way less 8020.

edit: view is from underside. large flat piece being table.

[ben_jackson]

My original flat table is just like that (but with 3030 on the end). I considered your arrangement but I think I'd also add a 1515 to support the edge of the table (so, same profile I made with 1545+1530 but with 3030+1515). In that variation I also have to make the 5 inner stretchers and other end plate into 1545.

Is that bolted connection really any different than the regular bolted steel plate? There shouldn't be any twisting force, just vertical load from plate to 1530 and 1530 to 1545, which are essentially identical connections here. I'd probably use a few extra BHCS to Tnut connections to secure the 1545 to the 1530 so they don't slip around while the steel plate is adjusted.

(and in case it wasn't obvious I'd be using bolts in both tslots, I only drew one bolt for the whole rail as an example ;-)

[lunchtrayrider]

i just can't imagine bolting the side of a 1530 to a 1545 and ever being happy with the result.

[jsheerin]

That general idea would probably help, but I do get dust build up on vertical rail surfaces as well. So I imagine the top of the rail would be good, but the bottom bearing would be the one you'd have to worry about. Maybe if you added an enclosure to keep dust from falling on the top side of the bottom carriage and then added wipers on the bottom carriage that would be a more complete solution.

[lunchtrayrider]

yea i was thinking about your design some more. on mine the dust builds up and then needs to be wiped off with my finger. (dust that floats in the air and gets everywhere) you'll want to be able to touch all sides of the rail with your finger to wipe it once a day.

[ben_jackson]

My other tricky idea for protecting the edge of the rail was to mount tape measures on both ends of the rail and secure the tapes to the top carriage. As the gantry moved back and forth it would pull out the tapes to cover the rails on both sides. I've seen a similar system used to protect rails which was just a loop of material that returned under the table.

I like the overlapping table solution more for my purposes because now the front edge of the top is nice and clean for 'table' use with less risk of damaging the rails or having the rails damage a workpiece.

I will be using dust collection and I won't put the whole unit in a muffler box (like lunchtrayrider did) so perhaps eliminating the direct bit-to-rail path is sufficient to solve most of the problems. Keeping ambient dust down will be done with a good filter on the DC and possibly a standalone filter (currently I use a 20" box fan with a couple of 20x20" furnace filters bungied to it).