Here are some pics on the 4x8 project

[wcarrothers]

Be nice.. Everything support wise is not inplace but figured I'd post some pics of the build up so far.

Z is pretty much done except for motor mount.

Y is getting there but will not have my full length rod support brackets till monday I think...

X has the trollies done for riding on the square steel but still lots left to do and figure out..

b.

[Guldberg]

Looking good, where did you buy all the stuff, ebay?

[wcarrothers]

I got the 3/4" plate that I made the ends from ebay allong with most of the other stuff. The cast pieces I'm using to mount the wheels to the b-line I found at home depot and milled to the shape I wanted..

Parts were milled on my mill which was convered to CNC with Jeff's plans. So that made making the parts SOOOO much easier..

Ball screws and other bits from MCmasterCar The Vgroove bearings from National precision bearings.

Hopefully I'll have something moving around the gantry by this weekend/or next I think..

b.

[project5k]

Looks to me like your off to a great start.. there is one thing that i cant tell from the pics tho.. it looks like your angle iron is in a horoxontal pointing position.. im just currious how you mounted it... im planning a similar angle iron set up, and hadnt considered doing it sideways.. what do you see as the pros and cons of this configuration?

[wcarrothers]

actually that is thinwalled box tube or what ever you call it. I think it's 1 1/2 or 1 1/4" square tube. Anything larger then that and the edges are not sharp enough for the v grove bearings to ride. It is welded to Bline channel strut. Although at it's size you have to be carefull to make your weld beed small else you will have to grind alot away so the bearings don't bump the welds. Seems like it will be a good way to do it and rides very smooth. Perhaps the poor mans linear runner or something.

[wcarrothers]

One thing I do wish I would not have cut the rods for the Z to length just yet. I later saw pics of some one who made his motor mount sit out on a bracket clamped to the rods that extended through the other end clamped piece. Would have made for a perfectly aligned motor mount really if the same program used to cut the end plate was used to cut the motor mount plate.. Anyway guess I didn't look around the net to find that idea early enough..

Hopefully this weekend I will perhaps get the Z motor mounted (and maybe run it up and down for fun) and perhaps also get the Y motor mounted. Bummer my rod support bracket will not be here till monday. But managed to get what is at least a 4' section of DSCR support bracket with 1" rods and another DSRC platform off ebay for pretty cheep..

With out support for the rods I'd say this design would have to much twisting flex in the middle. As it is now it does not have much if any up and down flex due to weight in the middle. But should work great with the support bracket once that is in..

b.

[txcowdog]

Can you tell me where the thread is on Jeff's mill conversion that you used?

Thanks.

[wcarrothers]

The mill conversion I used are the plans from www.homecnc.info
Jeff Davis is the name of the guy who wrote them up/sells the plans.. Well worth getting the plans for the conversion although you could dream it up on your own I suppose. Haveing the parts list is priceless to prevent buying things you don't need for doing your mill conversion..

Since my mill was a geared head mill my Z is different (hangs off to the side of the mill head rather then being burried in the middle) Also I used gas pipe turned in my lathe along with some creative welding to make the center spiner shaft of my Z axis (plan calls for it being made from aluminum but I had no success turning aluminum in my lathe as I'm new at turning metal and was not so good at it to start out.) But now I'm pretty good..

One key thing I found for turning ends of your ball screws is spin up the ball screw in your lath and take the initial amount off with a angle grinder rather then using turning tools...

[project5k]

ahhh ok i get it, using the box would be stronger and easier to keep straight over a distance than angle... and by welding it into the channel you have to parts working together to generate a straight line... good thinking.. its better than what i was gonna do... let me just pose this question for your consideration... if i were to go with a larger box tubing, where im going to make my own rollers, wouldnt you think that it would be more stable than using something smaller? i can make my rollers any shape i want on the lathe....

[wcarrothers]

It can be good thinking BUT... Because the box is thin walled you have to controll your self while welding NOT to over heat the piece. Taking small 1" every 12" or so weld beeds. Also clamping the piece to a longer 2x2 box tube isn't a bad idea.

Over heat it and it will bend (ask me about the first one I made) I SOOOOO knew better but the speed of my welder and wanting to get it done got the best of me as I watched it twist up as it cooled...

Good thing was the box tube was only like 20 bucks a section....

Answer: Yes a bigger box (like 2x2 by 3/16 thick (which is what I'm making my frame out of) would be stronger. But if using groved bearings the edge of that rolled square tube isn't sharp enough for it to ride on and maintain lateral stability. If you were going to do separate bearings in a holder that could ride on either side lower then the round part of the cold bent steel square then that might be better.

I thought about making my own rollers and insert bearings into the hub pressed fit or something. But these bearings off the shelf and are dual row supported so they are for the most part overkill but have no lateral play and roll very nice. I got 4 extra incase I wanted to mount 2 horizontal to ride the tip of the box but don't think I will need them to make things more stable then they already will be.

b.

[wcarrothers]

What I thought about was doing larger square tube and then welding angle iron to that to get the sharp edge back to.. Although I cam to the conclusion that would add weight and welding one thing to another like that would result in a less then even surface.

as it is I'm pretty sure the size i"m using will support the weight. I might have to put a support mid way down the length (10' total length) but I hope to have a section of at least 4.5' open from the side of the machine so I can slide a 4x8 sheet of plywood or what ever in from the side incase I need to rip it or something (plan on mounting a 7-1/4" circular saw to my gantry at some point for that.)

With out an opening like that I think the use of the machine at least for me would be limited a bit.. Would like to be able to slide work pieces in from the front or side if I can.. If I have to I'll weld a larger square tube to the base of my bracket to make it stronger rather then making the box the bearings ride on larger.

b.

[project5k]

mounting a circle saw to is is somehting that i hadnt considered.. but i also have a big cabinet table saw.. so i really dont think i would personally gain much from it..

im just sitting here trying to think up how im gonna get the angle or box tubing straight and then hold it there while i either weld it or bolt it down or whatever it ends up taking... i guess i could rig up something with a string so that i could pull it really tight, that might help me see any sag or twist...

i ahve noticed that some people are using pipe, and or things like EMT rather than spending all the big $$ on the ground rails.. i have to wonder about the longevity of each idea...

The only other idea that ive seen that i think might work would be to use the angle iron up on one side, have the rollers run along this edge, but bolt the angle to the top of the table frame, this would allow you to wallow out the holes a bit, and correct it for straightness by either moveing the rail in or out, or adding small shims under it to raise it a bit if you needed to...