Alternative to round pipe.

[thkoutsidthebox]

As mentioned in Post number 65, thanks to ger and everyone's ideas in this thread, I am ready to start building this weekend if anyones interested.

http://www.cnczone.com/forums/showthread.php?t=35211

[the__extreme]

Guess its time I add a few more cents to the mix...

I played around with this idea before. I was also looking for something simple and effective, preferably cheap. Anyone ever used CR tube for their bearings? As you can see from the last front view, I haven't drawn it correctly since the horizontal bearing is interfering with the wood, but you get the idea

So a brief description:

The side with the single tube is the table, and with two tubes is the Gantry (or mobile component). With regard to the gantry tubes, the top one would be anchored to the gantry and the bottom temporarily free floating. Once the top bearings are resting on the rail, the bottom can be snugged upwards to meet the rail. Then the bottom could be pulled tight to the gantry side.
On the opposite side of the gantry, the tubes would be mounted on a horizontal adjuster block similar to Joe's and Steve's and Andy's and .... machine, so all the bearings could be snugged to the gantry.

It also eliminates the need for eccentric collars, and requires only surface drilling. The only problem, which I've addressed by adding a third bearing in the middle, is that every 12" or so there would be a hold drilled in the rail to mount it to the table. I suppose you could also use to 2 bearings on each end, instead of one, with a space between them so they miss the hole entirely.

Any thoughts?

- Shawn

[Oldmanandhistoy]

Originally Posted by the__extreme Guess its time I add a few more cents to the mix...

I very much like your design; it simplifies things with the rails in comparison to ger21’s rails in that they are ready made. The system may have more rigidity using square tube as opposed to angle as the bolt length would be reduce and you would have a cantilever fixing.

I haven’t studied Joes design but in both yours and ger21’s design I wonder how you would make adjustments if the Y axis was not running square with the X axis?

John

[ger21]

Originally Posted by Oldmanandhistoy I haven’t studied Joes design but in both yours and ger21’s design I wonder how you would make adjustments if the Y axis was not running square with the X axis? John

That would depend on how the gantry is mounted to the sides, or may be leadscrew related. I would ue 2 leadscrews to keep the gantry square.

[Oldmanandhistoy]

Originally Posted by ger21 That would depend on how the gantry is mounted to the sides, or may be leadscrew related. I would ue 2 leadscrews to keep the gantry square.

I am thinking of builders who will be using one lead screw in the centre.

John

[ger21]

Imo, one lead screw in the center will always be a problem on small low budget machines. Even if you can get it square, there's a very good chance you'll get some flexing at when cutting at the ends. The only way to really square a single screw gantry is to shim it to get the mounting points square.

[greybeard]

Originally Posted by the__extreme Guess its time I add a few more cents to the mix... ... The only problem, which I've addressed by adding a third bearing in the middle, is that every 12" or so there would be a hold drilled in the rail to mount it to the table. I suppose you could also use to 2 bearings on each end, instead of one, with a space between them so they miss the hole entirely. Any thoughts? - Shawn

Drill table tube fixing holes only through from the table side.(De-burring might be a problem).
Slide a nut down the table tube on the end of a telescopic magnetic holder. When it appears opposite the hole a drop of superglue(or epoxy) through the hole onto the face of the nut, then temporary bolt to pull the nut into place, etc....

John

[mike hide]

Originally Posted by ger21 The problem with that is the bearings are still loaded axially, and they can't handle much preload that way. That's one of the main things I'm trying to avoid.

Actually finished my modified Joe' 2006 see pictures using the concept suggested earlier .I did double up on the bearings

[joecnc2006]

Mike, it looks very good, are you going to make a build log, other in the cnc model 2006 theads will be interested in it. also a possible upgrade people can make.

Joe

[mike hide]

First thanks for the kind words .As you can see the Y and Z axis are pretty faithful to your design and for all the info you have provided to me and the group as a whole I am deeply gratfull.

I am aware of several people trying to improve on the double pipe design but it seemed to me that most ended up with ever increasing complexity. My main objection was with the pipe design basically it was one round surface running on another resulting in point contact, high local loading to the point of wearing flats on the pipes.

Initially I used single bearings per axel and later pairs per axel fter Ger suggested at some point . This concept does not alleviate the bearing axial loads but it does produce line contact which in turn should reduce the local bearing loads .

The other aspect is it is a concept that can be reproduced using regular woodworking tools and no CNC availability. with the pipe design there are no forstner bits that are the odd diameter of the pipes so one has to resort to getting the closest bit and then using a rotating sleeve sander or simply having a vee notch to hold the pipes. As far as costs go I got 40 feet of angle iron at the local steel company for half the price of the pipes.

I did keep pretty good records of the lower section construction and if there is any interest will be more than happy to show pictures and commentary. regards . if someone can give me directions on how to present it .

[Kipper]

I had a play with this yesterday and may build a 6'x3' router table with it. The bottom bearing set isn't going to stay there (it's for the side) the lower will have an eccentric pre loading arrangement on it when finished. 50mm and 40mm tubing used and 35x15mm bearings on the 200mm carriage twin lead screws are to be used.... I must call it "Rail 'O' Skate" (Patent) :lol: No drawings are available as I haven't drawn any and will just "wingit" Special tools used are a drill and hacksaw and maybe I'll use a file later

[Oldmanandhistoy]

Originally Posted by Kipper I had a play with this yesterday and may build a 6'x3' router table with it. The bottom bearing set isn't going to stay there (it's for the side) the lower will have an eccentric pre loading arrangement on it when finished. 50mm and 40mm tubing used and 35x15mm bearings on the 200mm carriage twin lead screws are to be used.... I must call it "Rail 'O' Skate" (Patent) :lol: No drawings are available as I haven't drawn any and will just "wingit" Special tools used are a drill and hacksaw and maybe I'll use a file later

Hi Kipper,

Nice to see another local on here. It would be interesting to know how many people from the UK use this site.

Do you have another picture from a different angle; cant quite see what is going on?

I have very recently changed my X axis from round tube to square. I would like to take this opportunity to thank the_extreme for his post #86 which I have very nearly copied to the letter and have to say I am very impressed with the improvement. When I get my didgi camera back (gone on holiday with my sister) I will take some pictures if anyone is interested. Basically I have used 25mm square ERW for all the construction. The rails have been drilled every 125mm on one side with an 8mm and through the other side with a 6mm hole. This is for fixing the rail to the side of my machine and allows #8 dome head screws to be used which gives me some adjustment to the rails for straightness. I have used twin bearings horizontally spaced to avoid the rail fixing holes and the vertical bearings are spaced away from the tube by only the width of a washer. I have used 4 bolts through the bearing carrier tubes (two top and two bottom) to fix it to my gantry sides which allows adjustment for levelling the gantry. The only thing I would like to solve is a method of adjusting the carriages to be able to square the gantry to the X axis which I think I may have a fix for. I hope all that makes sense but if anyone needs more or would like to see some pictures please let me know.

All in all I have to say this method is a VAST improvement over round rails (I have used them on my last two machine builds).

John