Smooth Rods - O1 Tool Steel, Stainless, Delrin, PTFE

Looking at building a RepRap, specifically a Prusa I3 Single Plate Einstein Variant as listed on Reprap.org

Anyway, I have been perusing the forums and notice alot of people talking about having to grease their rods for rust, etc.

So I checked into Stainless Steel in 5/16" (which is slightly smaller 0.3125" vs 0.314961" for 8mm smooth rod) since I am in the US.

I have found 304SS for about the same price as O1 Tool Steel ones and 316 SS Rods for about $3 more for a 36" length.

I was researching and then discovered that the same supplier has Delrin and PTFE rods in 5/16", and they actually are cheaper than either stainless or O1 Tool Steel

Has anyone tried to use Delrin or PTFE for the Y and Z Axis smooth rods?

Plastic Info: Online Metals Plastic Info

316 SS rods: 316 SS Rods

Delrin: Delrin Rods

SpeedyMetals also has the Stainless Steel Rods for about the same price.


Any thoughts?

Is there an advantage of using the O1 Tool Steel that people link on Mcmaster Carr vs Stainless?

With 316 SS, it will never rust, ever.

Hello mattmc, welcome to the forum!

Plastic rods will not be as stiff as steel rods. There would be a loss of accuracy due to the plastic rods flexing as the machine operates. Sticking to steel would be much better.

O1 is delivered in an unhardened state, so it may not be any harder than 316, or wear any better either. If anyone knows anything about the mechanical properties of O1 vs 316 I'd also be interested. The few samples I've seen, I found the tool steel had be ground to a more accurate dimension than the stainless rods. That is nice and helps reduce slop in the linear bearings, but I don't know if that is always the case.

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Yvan

Singularity Machine

Thanks for the reponse!

That makes sense.

I can tell your from experience 316 SS is much harder than mild steel. I have never messed with O1 Steel, but 316SS is pretty difficult to cut, drill and tap compared to mild steel. I am sure the 316 SS rod would be the same.

Think I will stick with 316 SS.

Yes, I've noticed any type of inox alloy is tough to work with. I think toughness is not the same as hard wearing though. Some metals flake off quickly under point loads like a ball bearing. I wonder how annealed tool steel compares to 304/316 for example.

Those two are not often interchanged or compared, so haven't run across a good comparison yet.

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Yvan

Singularity Machine

Yvan is right about the difference between the machinability and surface hardness of metals. From my experience and from what I have heard from others on the forum, precision chrome plated steel rods are the only type of linear rails that can effectively be used long term with linear bearings. Both mild steel and SS are not hard enough and wear as a result of the repeated point loads of the linear bearings. Unfortunately Chrome Plated rods are quite expensive compared to SS rods and are honestly a bit overkill considering that 3d printers are not high-force machines.

Ultimately, I think as the RepRap community begins to explore harder and more wear resistant plastics like Nylon, Polycarbonate, PET, etc... people will move toward printed bushings on cheap SS rods. Printed bushings are also MUCH quieter than linear bearings.

Eric

Eric,

Yes, I see a bunch of posts from people saying they are switching to a polymer bearing.

Just came across this: Igus polymer bearing

But at $5 a piece they are pretty pricey compared to LM8UUs.

I figured I would start with the LM8UU and then may try to print a bearing like the polymer bearing when I get good enough.

I would rather have rods that won't rust and bearings that wear out, then rusty rods that last forever, but that stick with whatever bearing is used.

Yeah, IGUS bearings are very expensive, but your alternative approach seems like a good way to go.

Ok, if you are looking at printing IGUS style linear bearings then you can check out this thing. This IGUS imitation is well designed and prints quite well. Just make sure that you have a well calibrated printer with a hot end that doesn't clog easily as there will be about half a hundred retractions per layer!

Good luck!

Eric

For the metal properties
Chrome is harder than stainless and stainless is harder than untreated tool steel.

A chromium rod has a surface hardness around 65 HRC
A 304/316 stainless rod has a surface hardness around 40 HRC
Non heat treated tool steel has a surface hardness around 30 HRC
Heat treated 01 tool steel at best has a hardness around 60 HRC

It looks like heat treated tool steel may be the way to go.

I wonder, are HSS drill bits made from heat treated tool steel?

Eric

HSS is a subgroup of tool steel, which seems to be a rather broad term covering a range of steel alloys. Just read that it has good wear resistance, but I assume that is once hardened -and- tempered. That might distort long rods? Either way, it would be awkward to harden them without some kind of good set up. You have to hit just the right temp and so forth.

I O1 steel pdf

I'm going to have to try a nylon versions of those IGUS bushings. I tested nylon in my home made hot en and it works, just need to get it to stick better to the build surface.

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Yvan

Singularity Machine

Couldn't get the pdf link to work, but found it online (I think)

[www.cintool.com]

Thanks for the info.


Jim

High Speed Steel is essentially tool steel with tungsten in it.
The tungsten allows the steel to get hotter without losing its tempering which keeps blade edges sharper. This allows drill bits and saw blades to be run at a higher speed (getting hotter with friction) than with plain tool steel and stay sharp. Thus the name high speed steel.

Rod made of tool steel that has been heat treated properly will work well for a glide rod. Trying to heat treat it yourself is difficult and expensive. You can buy a lot of chromium rod for the cost to properly heat treat a tool steel rod yourself.