Lead Screws and Smooth Rods- best bang for buck?

Hi Everyone,
I was wondering what the current best advice was for buying smooth rods and z lead screws. I am looking at putting together a TK-0, so I am looking to spend in the $800 regime and they suggest stainless steel for both but I wasn't sure if it was necessary.

For the smooth rods they suggest SSFHR10-500.0 by Mitsumi which are these polished 10mm diameter by 500mm 304 stainless steel which seem very nice but they are $34 a piece so if you need to get 6 of them that is close to $200 for just smooth rods! Do people think that it is really worth that or are there cheaper options that would give a similar performance? It seems like most of the newer designs are going toward 10mm rods but would a different company or different material work just as well?

I have a similar question about the lead screws. I can purchase stainless 18-3 rods for pretty cheap on mcmaster but some people recommend acme rods. Are the acme leadscrews that much better? I believe I received a quote that was about $30 each but I did see this website that was selling a pair for $28:
[techpaladin.com]
They almost certainly are not stainless steel though.

What US companies have people found good deals with? Despite the glitz associated with stainless, are there options from a materials perspective that would be just as good and perhaps be cheaper? What do the most seasoned builders tend to use?
Here I am defining good for the smooth rods as something that won't pit using linear bearings, resist rusting, be very smooth and straight
For the threaded rods I want something that will minimize binding, be straight, and be rust resistant (using oil is fine too)
Are there other considerations I should have?

Thanks!

On my phone, so forgive crappy answer.

Get trapezoidal leadscrews. Avoid ACME. Investigate difference. If cost is a factor, get M8 fine pitch rods to start.

Not sure about x-ends for tk-0. Maybe jebba can speak to types of rods and nuts supported.

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- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

IGUS has great super-precision aluminum rods, for about $15 per 500mm or so. You have to ask for a quote. They have 10,12,16,20mm etc. AWM10 would be the 10mm I think.

Great plastic bearings also. The J plastic is the long wear version. I think they are like $7 each in low quantity.
look up dry-lin RJMP-01-10 for a 10mm version.

VXB also has rod and bearings in different diameters.

akhlut Wrote:
-------------------------------------------------------
> On my phone, so forgive crappy answer.
>
> Get trapezoidal leadscrews. Avoid ACME.
> Investigate difference. If cost is a factor, get
> M8 fine pitch rods to start.
>
> Not sure about x-ends for tk-0. Maybe jebba can
> speak to types of rods and nuts supported.

For all intents and purposes, they are the same.
Please see Ref.

Either can be used without issues.

But do consider the costs... m8 threads are MUCH cheaper.

Ref: [books.google.ca]

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Custom all metal CoreXY
- Duet 2 Wifi w/ PanelDue 7i
- 330mm x 360mm x 500mm
- 750w Silicon heater

Custom Mendel90
(Backup printer - Old reliable!) - Sold

I just bought M8 rods on McMasterCarr and was super pleased with the cost when I build my Prusa.

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Ryan
Quality Engineer & Hobbyist
thingsandtrains.blogspot.com

I hadn't considered plastic bushings and aluminum shafts. How do they move compared to lm8uu?

banthafodder- which rods did you buy in particular from mcmaster? Were they ground stainless smooth rods because I saw that they ran about $30 for 500mm, or something cheaper?

akhlut- where did you get those trapezoidal leads screws and are they just cheaper or do they work better? What material did you go with and do you have a link? I was seeing that carbon steel is a common choice.

Thanks for the advice everyone!

Edited 1 time(s). Last edit at 03/03/2013 08:52PM by ambiguousphoton.

[www.roton.com]

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--------------------------------------------------------
Custom all metal CoreXY
- Duet 2 Wifi w/ PanelDue 7i
- 330mm x 360mm x 500mm
- 750w Silicon heater

Custom Mendel90
(Backup printer - Old reliable!) - Sold

I brought a pair of 500mm long 12mm stainless steel rods off ebay for about £7 each. They aren't precision ground, but seem perfectly straight and are bang on 12mm. I stuck them both in a drill, spun them round and polished them to a shiny finish with some brasso. So far they have worked perfectly. I have also done the same with 8mm rods but I didn't polish them and they seem to be fine too.

Thank you Mogal for illustrating what I was attempting to say.

ACME is standard.
Trapezoidal is metric.

Do not buy standard screws - get metric!

But Roton is a good supplier, as well as misumi. Misumi will step the ends for you where roton won't (unless you buy in bulk). But you should be able to have plain roton or misumi screws stepped at a local machine shop.

Now after looking at the most recent BOM it looks like they have moved away from 3/8 - 12 ACME rods to M6. So if you want to stick to the most recent BOM go that route.

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- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

ACME is trapezoidal. In fact, it is the first trapezoidal profile. The difference is that metric trapezoidal uses a 30 degree included angle, vs the 29 degree included angle of the imperial trapezoidal, or "ACME", so metric is ~%3 more efficient.

We are using M6 threaded rods for the Z on the TK-0 now. This is "final". It is nice too, because they aren't very expensive. Josef Prusa pushes for these (M5s, at least) and here is a nice doc explaining more about the ACME vs. metric issue:

[www.evernote.com]

The fancy Misumi smooth rods are overkill, but we wanted them spec'd within a certain tolerance, and most smooth rods are not. But when you are building a lot of these, just getting ones you know are all perfect from the get-go saves a lot of hassle. You can save a lot of money there by going with lower cost smooth rods though.

We are using the Igus bearings, not metal ones. This is primarily to make the machine quieter. Plus we have used similar ones (in pillow block form) on the AO-100/101 and they work quite nicely. We have nice pile of Misumi metal LM10UUs here though, as that is what we were initially going to use...

[www.igus.com]

304 stainless steel for smooth rods is not overkill but even a bad choice if using ball linear bearings., as this type of steel is not hard enough. For Igus bushings it will be ok but not needed.

You need either a high chrome/vanadium rod or a 100C6 high carbon + chrome(european spec) hardened and grounded one. Dont know what is available in USA, but this kind of rod is very easily found here in grounded form at a very low cost. They will last forever. Here they are commonly available in 2 quality, and the fine one will be much finer than any stainless rod for 1/10 price.

The important point is that if you put linear bearing on them, hardness must be at least 54 HrC preferably 58-62 HrC. 304L is an austenitic stainless which is a lot softer. Igus famous aluminium rods are probably harder.

BTW a harder rod will also induce less vibrations and noise.

For the screws, metric trapezoidal is indeed the best but AFAIK dimension under Z10 are not easily available. Z10 is available in 1 or 2 entries, but anything under will be normal Triangular (M6 or M8). And I would argue that NPT is a better profile

If you use plastic bushings, you can get the IGUS, or print some:

[reprap-fab.org]

[www.youtube.com]

[www.thingiverse.com]

The video has 10mm, but I also made 8mm.

Don't use aluminum shaft! You can buy ground steel shaft cheap from McMaster - $30 for 12 feet.

[www.mcmaster.com]

Don't buy stainless. All machines are steel - lathes and mills. They are not stainless.

I am building a TAZ:

[www.matter-replicator.com]

And these are the rods I am using:

Line Product Ordered Shipped Balance Price Total
1 6112K47 Hardened Precision Metric Steel Shaft, 10 mm Diameter, 500 mm Length 6
Each
6 0 14.63
Each
87.78
Merchandise 87.78
Shipping 5.97
Total $93.75

Payment Received 6/26/13 (93.75)

Edited 1 time(s). Last edit at 06/26/2013 01:09PM by rsilvers.

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[www.matter-replicator.com]

Quote
konwiddak
...I stuck them both in a drill, spun them round and polished them to a shiny finish with some brasso...

Brasso is likely to be incompatible with linear bearings, such as LM8UUs and is definetely incompatible with non-petrolem based lubricants. Brasso is petrolem-based and over time will degrade the bearing's polymer inner sleeve into mush. Same is true for petroleum based lubricants. Depending on the chemical composition of Brasso and/or the various petroleum-based lubricants this can take days, weeks, or months.

Quote
nitewing76

Quote
konwiddak
...I stuck them both in a drill, spun them round and polished them to a shiny finish with some brasso...

Brasso is likely to be incompatible with linear bearings, such as LM8UUs and is definetely incompatible with non-petrolem based lubricants. Brasso is petrolem-based and over time will degrade the bearing's polymer inner sleeve into mush. Same is true for petroleum based lubricants. Depending on the chemical composition of Brasso and/or the various petroleum-based lubricants this can take days, weeks, or months.

He used the brasso to clean/polish the rod, not to lubricate it. If he cleaned the rod properly after polishing it, there should be no incompatabilities with bearings or bushings.