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noid
09-22-2004, 04:59 PM
I'm new to the site but not new to cnc. I'm working on my own design for a cnc router based on existing mass produced machine ideas. I have noticed that the standard slide systems ie. rails (thk,round bars etc.) are expensive and hard to modify if need be. My design for the rails should be cheaper and easy to adapt to any length for a reasonable price. This is still in the design stage but my research tells me that I can manufacture my design cheaper.
I'm planning to use a precision ground shaft machined with a flat running the entire length and a suitable square bar drilled to match.
My question is has anyone tried this idea and has it worked? :wave: :wave:

DDM
09-22-2004, 05:15 PM
so your idea is basically a supported thompson rail with and open pillow block correct? it would probably work but percision ground shaft isn't the cheapest to begin with and you'd probably want to harden it someway if it isn't already. If you could elaborate I'd be more than happy to help.

Carl

noid
09-22-2004, 05:24 PM
Yes a supported thompson rail with the open blocks. I find a that in canada with the shipping and such the rails themselves are the expensive touch. Precision ground shafting is about 2.50/ foot this means of course a 10' bar costs 25.00 heat treating is about 1.00/pound so I can produce 2 5' rails for about 32.50. Now this is only a ballpark price so far but it blows the 125.00 usd/36inch length figure out of the water.

jcc3inc
09-23-2004, 10:19 AM
Dear Sir:

When I built my 3 axis table I too worked toward an economical approach. I used cold drawn flats for the ways and used standard bearings with eccentrics on the carriages. Cold drawn flats are dimensionally quite good and the cost is right. If you would email me, I will sent back photos of my ways etc. My drive is rack and pinion.

Regards,
Jack C. jccinc at owc.net

HuFlungDung
09-23-2004, 10:59 AM
Yes a supported thompson rail with the open blocks. I find a that in canada with the shipping and such the rails themselves are the expensive touch. Precision ground shafting is about 2.50/ foot this means of course a 10' bar costs 25.00 heat treating is about 1.00/pound so I can produce 2 5' rails for about 32.50. Now this is only a ballpark price so far but it blows the 125.00 usd/36inch length figure out of the water.

I'll be interested to hear how the shafts turn out after hardening. Doubtlessly, they will use induction hardening methods, but I wonder how much warpage will occur, because they have to use a water quench (I believe) in order to harden precision shafting (typically grade C1045).

ESjaavik
09-23-2004, 12:28 PM
With precision hardened bar I believe the method is to put in hardening first, then precision.

Graham S
09-23-2004, 02:53 PM
try ebay

DDM
09-23-2004, 11:33 PM
maybe the key is to find some sort of happy medium in material. I'm not much in to different metals and alloys (wish I was, would appreciate any links) but couldn't you use some kind of chrome plated rod that was machinable, do your flat and drill your holes, countersink for the screw head and go right into the base of the rail through your square stock and do away with the heat treating. This wouldn't be as good as a thompson supported rail but it wouldn't come with the price tag either.

The other thing is don't worry about using a hardened material and incorperate a lubrication system into the pillow blocks. It wouldn't be that hard if you had the time to work it out.

The other question I have is where you can get square or rectangular solid stock that has pretty tight tolerances and is out of a good quality alloy that would be sutible for a linear rail for a bushing to ride on?

Carl

Graham S
09-24-2004, 06:40 AM
I think it all depends on what you are trying to do, for a lot of hobby machines they don't see that much work and if a rail is really cheap and it wears then you replace it, same with nuts etc. It is a different way of thinking about it expensize linear rail lifetimes are rated in 10's of Km but half the time we don't need that. Main thing I suppose is to have something that is flat/straight enough.

If you look for example at CNC plasma cutter kits they use cold rolled bar as the rail, why? Because it the accuracy matches the cutting process and when they wear you replace them for peanuts (not with peanuts, that doesn't work).

So in this case if the blocks were delrin the need for hardening would seem to be less and again they could be replaced if needs be.

Why not make a test pair for the z-axis

BigDaddyG
09-24-2004, 07:17 AM
Some alturnatives to the standard Thompson type rails:

You may want to look into Igus Dry lin rail systems, far cheaper than the thompson and actually superior in quality. I have been using them now for years, and have many in production as well as some home shop use. (www.igus.com if your interested, I have written about these many times)

Another one, is Pacific Bearing. They make a square bearing and rail that also works great. I have many machines out there still in production after many years.

If I had to suggest one over the other, I would go with Igus. They actually fasten right to Aluminum Extrusion, have tremendous loads and capacity's and are very cheap. I have been using the DryLin W Guide System on a series of Custom Lathes (3-axis cnc with 2" Dia. capacity) and these babys work great. I hope this helps.
Good Luck,
Glen

Moondog
09-24-2004, 09:24 AM
Hey BigDaddy... I am just setting up my Igus system for my build. I would like to talk to you about how you set up the paralel and tolerances etc if you wouldn't mind...

you can email me at frans@cfbs.com.au

cheers

Graham S
09-24-2004, 06:46 PM
Glen, have you ever posted any info on these lathes, they sound sweet!

uscra112
09-29-2004, 09:42 AM
In answer to the original question - yes Prazi (Germany) still use a round bar with a flat on it for small lathes. This was a common construction for watchmaker's lathes going way back into the misty deeps of time.

Not really very good, IMHO. The asymmetry of the cross-section will tend to make the bar warp during heat treat. And it would also warp during grinding if ground from a heat-treated bar, as the internal stress is relieved asymmetrically.

Stick to the commercial way bar designs - they have MANY years of experience behind them! I speak as one who has been around way-grinding in the machine tool industry for a good many years.

noid
09-29-2004, 09:49 AM
You're absolutly right just finished one bar and the darn thing is like a snake. I machined the flat on it and whaamo right off the mill she was bent. SOOO I think I might try another method to produce cheaper rails. I've hear of cold formed flat bar and bearings being used and this may be another alternative. I'll keep everyone posted.

Fred in NC
03-03-2005, 11:12 PM
Glen, have you posted a pic of a machine that uses the Igus rails? I looked at the site and looks good. I need it for the y axis (gantry) and I am planning to use an 80/20 crossbar as a base. Thanks !

mikeschn
07-20-2005, 02:00 PM
I know it's been a while since you've written this, but I was hoping you had some photos of the machine you built with the Igus W rails...

Thanks,

Mike...


Some alturnatives to the standard Thompson type rails:

You may want to look into Igus Dry lin rail systems, far cheaper than the thompson and actually superior in quality. I have been using them now for years, and have many in production as well as some home shop use. (www.igus.com if your interested, I have written about these many times)

Another one, is Pacific Bearing. They make a square bearing and rail that also works great. I have many machines out there still in production after many years.

If I had to suggest one over the other, I would go with Igus. They actually fasten right to Aluminum Extrusion, have tremendous loads and capacity's and are very cheap. I have been using the DryLin W Guide System on a series of Custom Lathes (3-axis cnc with 2" Dia. capacity) and these babys work great. I hope this helps.
Good Luck,
Glen

yukonho
07-20-2005, 11:31 PM
I am just about to begin construction on my IGUS equiped router.
I found out the other day that the guy I was going to get to CNC the parts for me is on vacation until August 3....
The good news is that the design is finalised, finally. I will probably abandon using IGUS slides on the Z, but I am sure they will be perfect for the x and y.
I will be sure to do a build thread when the time comes. In the meantime, I am going to work on the control panel.
This machine will be swank and I am excited to get it finished up.
Colin