Homemade Linear Design, Feedback.

[sol]

Well actually...
I think it is a good idea in that it is adjustable, solid, self contained and not dependent on whatever it is connected to for its stability.
The drawback I see is that the top bearing needs to be adjustable as well, or the side bearings have to be able to be dropped to accommodate larger pipe. Of course this could be accomplished simply by adding shims (washers) to the side bearing's mounting/axle bolts.

Another plus for your design is that it allows the side bearings to be slid out far enough so that they could completely clear the track if/when total axis removal is necessary.

One of the features you wanted was perpendicular hole drilling which, though it may not appear so, is there in my units that Torsten linked to (post #2). I came up with that design for the same reasons you listed, but its strong point (very adaptable) is also its week point (lots of slop ‘till finally mounted to its supporting axis). I have found it extremely difficult to create a bearing truck that rides perfectly straight since the slightest misalignment of ANY of the bearings will pull it off course; on test-runs the assembly spirals down the track/pipe. Again that is why I settled for a decidedly basic unit with adjustment in virtually every dimension.

Your idea if carefully built resolves this but of course requires more metal and time to fabricate. For a turnkey unit which is already trued and that could be easily installed I think that yours is good solution.

Build ‘em! Don't let us dampen your enthusiasm!

[Hobbiest]

I think its a good idea Bean. Does seem like a lot of work though. While I would not consider myself to be a lazy person, I do believe in economy of motion, and energy, especially when it is my own! To repeat Sol, do it! If you have the machinery, and the time, try it out! Some of my best designs have always been the ones people tried to lead me away from, in fact, all of my hot rods have been "that'll never work" projects. It sure surprises the heck out of people when you finally show up, revving that obnoxious engine!

Cheers

[ynneb]

Yes Mr bean I also think it is a good idea, it is a nice looking setup and would be very strong too. I say go for it. Make up a set and take some pictures of the results. Give us some firsthand feedback of how they perform. If they are easy to build and cheap then you will have others who will follow you.
I hope you dont feel my earlier contribution was distracting to your great thread.

Oh and nice drawings too, I wish I could draw like you.

[coolman]

The design uses belts. Belts are probably cheaper than acme screws/ball scews and accomodates long axis (e.g. 6+ feet). The question is how accurate can belts be? I understand there will be some flex in the belts, correct? Are there belts that reduce or even eleminate the flex? How about overlapping a second belt over the first one to create a 2-ply affect. Will this work?

[jeffserv]

OK, I saw a man build a unit with Pipe for the rod, and then use skate bearings for the rollers. Then used pipe flanges on the end to support each end with an elbow on each end. This was low cost and for wood carvings and engraving gave good results... would be accurate to within .015" when all dial in I suppose. If you are not trying to machine down to a micron you could look into this idea. If longer runs use heavy sch. 80 pipe instead of sch 40.

I loved the idea for it's simplicity.

[Mcgyver]

the need for accuracy with the belts is eliminated if its a linear encoder closed loop system, but still I wonder if stretching would be a problem.

is your idea to go with welded fabrication, lost foam casting (i really like the build your idea cast approach) or bolt together?

also, those renderings look good - what cad app did you use?

[ger21]

Originally Posted by coolman The design uses belts. Belts are probably cheaper than acme screws/ball scews and accomodates long axis (e.g. 6+ feet). The question is how accurate can belts be? I understand there will be some flex in the belts, correct? Are there belts that reduce or even eleminate the flex? How about overlapping a second belt over the first one to create a 2-ply affect. Will this work?

Good quality belts may not be cheaper than decent acme, depending on size. GT2 runs about $30 meter. go to http://www.sdp-si.com to read all you'd ever want to know about belts. The majority of stretching will occur very quickly after installation. After that, good quality belts shouldn't really stretch much at all.

[ynneb]

but still I wonder if stretching would be a problem.

I run my machine over 4 Metres with steel impregnated belts. It seems fine.
I guess it depends on what you are cutting and how accurate you need your items to be. I have had no accuracy issues with the things that I cut. But I guess if want to start machining high precision components other systems would be much better.
All I know is if I cut a square out of timber, 2m x 2m and measure it afterwards it is just that. No micrometer stuff, just a tape measure.

[lerman]

Originally Posted by ynneb I run my machine over 4 Metres with steel impregnated belts. It seems fine. I guess it depends on what you are cutting and how accurate you need your items to be. I have had no accuracy issues with the things that I cut. But I guess if want to start machining high precision components other systems would be much better. All I know is if I cut a square out of timber, 2m x 2m and measure it afterwards it is just that. No micrometer stuff, just a tape measure.

Hey Benny,

Could you send me a sample 2m x2m square so I could check it to see if the diagonals are equal using my three meter micrometer? :-)

Ken

[ynneb]

Lol @ lerman... good one

I suppose we could call a tape measure, a "macrometer"

[mdreitzusa]

Mr. bean
the design looks great.i saw a website with an engraving machine made from savaged printer part that was belt briven.and it could carve a photo the size of a postage stamp.go for it
if bill gates had listened to his freinds we wouldn't be talking rite now.