Dirt cheap Polyester PETP rods for Z axis???

[andy_ck87028]

Hi all

Is there an engineer in the house who could confirm the suitability of this product as a dirt cheap alternative to hardened steel?

(http://www.smallparts.com.au/cgi-bin...earches=0=post)

Tensile strength is quoted as 90Mpa and hardness at 96 Rockwell M. Assumedly the Bearing Grade TX is the better suited material and still dirt cheap.

I am not an engineer but if it is sufficently stiff, hard and strong than all I would need would be linear bearings, mounting blocks and a lathe to machine it down to 16mm.

If a suitable alternative, it would answer many peole's needs to build within a tight budget.

Would there be wear issues of having a metal bearing and a plastic rod?

Am I onto something good here?

Andy

[High Seas]

I took a quick look at www.mcmaster.com searched "PET (Polyester) Rods" and I probably not use it. I note it has a higher Rockwell than you stated 117, but its ease of scratching might be the big drawback. Chips and all ya know.
What about ripping into old printers/scanners/copiers for hardened rod and FREE price.
Jim

[greybeard]

Sorry Andy, but as a typical tight budget wannabee, $7 Australian for 4 inches of plastic rod which I then need to turn to size, is a non-starter compared with picking up a scrap printer.
Especially as, by definition, a wannabee, I wouldn't be able to access a lathe to turn it down anyway.

John

[fyffe555]

Key thing here is the tensile strength. 90Mpa sounds like a lot but its not. Assuming that's ultimate strength then Steel compares at ~ 650Mpa - 2000Mpa depending on alloy, Aluminium is about 200Mpa.

Steel used for linear rails would be as much as 20 times tensile strength of similar sized PETP and roughly the same in Youngs modulus too, that means that any deflection you can calculate for a Steel rail could be roughly assumed to be 20 times greater with PETP.

[andy_ck87028]

Aaahhh the voices of knowledge and reality bring me back to ground

High Seas suggestion is good. Ironically, I have managed to get some rod (from a scanner) but am finding accessible bearings to be of a different size I was thinking it might be easier to retrofit rod to available bearings as I certainly can't retrofit bearings to available rod.

Thanks guys, I'll put that idea to bed.

Andy

[High Seas]

rat the bearings from the scanner light mount. Take a quick peak at a pic in my gallery - I think there's a photo there of 2 mounts from printers to do the same job. If not I'll try and locate and load.
Jim

[andy_ck87028]

Jim

Have found .. thanks.

I've found 10mm bearings in UK which I'm about to purchase.

My wife is going over to see her sister so I have capitalized and bought like crazy. So far she is coming back with 3 nema 34 steppers; 4 16mm bearings (bad purchase but you can't unbid with Ebay); 4 10 mm bearings and 4 10mm rod supports.

I'm not popular

Andy