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Posted · Ultimaker - Black Edition

I think you might run into trouble with the exactness of the rod positioning if you weaken their mechanical support (meaning the mounting of the bearings). The standard solution with the bearings firmly in place inside the precision-cut frame walls is probably hard to match with printed parts that are somehow attached to the frame.

But please prove me wrong! I'd love to have a solution with the stock rods.

I know a Swiss metal trader (metall-laden.ch) who does have stainless steel rods with 5mm,8mm and more diameters. But I don't think these are precision "shaft" rods. I'll have to check though; will visit them when I have time.

 

It works. I designed a nice adapter which relocates one bearing by something like 16-18mm. On second try I managed to print it in exactly the right size for the bearing. I just printed the first backlash test piece with direct drive on both axis. I have now a resdiual backlash of incredible 50um on each axis. I'm actually very happy that I got rid of the short belts. Quality is greatly improved! :smile: :smile:

 

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Posted · Ultimaker - Black Edition

Nice to hear :)

I guess I'll try a rod from Misumi - they have awesome prices. Being able to use the standard rods could however be a useful alternative for anyone who doesn't have access to longer rods.

Can you make a picture of your solution? Or maybe even share the design? ;)

 

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Posted · Ultimaker - Black Edition

This is a quick picture of the adaptor itself including the bearing and two M3 hex nuts.

Bearing adapter

I may put the design onto Youmagine but for that I'll have to shoot some pictures of the piece actually mounted.

EDIT: You will also need http://www.thingiverse.com/thing:54075 for fixation of the rod...

And as it is: just five minutes after having implemented this work-around I got an offering for longer rods with a straightness of 0.02-0.04mm... :wacko:

 

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Posted · Ultimaker - Black Edition

lol :D

It's always the same...

AAAAH now I get it... You use this part for the side opposing the motor!? So that the rod will protrude on the other side and you can fix the coupling. Jeez that took long :)

I just wondered what difference that part would make if you still occupy the hole where the bearing sat originally... ^^

I think this solution is great - no need for a longer rod, no need to go searching or get some rod that's probably more of banana than the original one...

By the way, I rolled my rods on the table yesterday (does that sound a little odd? o.O) and thought they weren't perfectly straight. But honestly - it could just as well be the table. Are the specifications for the original rods known? Like is there a BOM available for the public?

 

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Posted · Ultimaker - Black Edition
[...]

By the way, I rolled my rods on the table yesterday (does that sound a little odd? o.O) and thought they weren't perfectly straight. But honestly - it could just as well be the table. Are the specifications for the original rods known? Like is there a BOM available for the public?

 

I did the same with the original rods and for one the straightness could be better... There is a BOM but it says nothing about detailed specs.

 

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Posted · Ultimaker - Black Edition

I just received an offer from Hertsch company for rods:

8 pcs, 400mm long (I don't have the exact needed length yet - so this is an estimate for generating the offer)

price: CHF 12.50 per piece

If I take 20, it's CHF 8.85 per piece.

Material specs: 1.1213, inductive hardened 62 HRC, tolerance h6/h7 (yeah, nice... two tolerances)

I don't really know what to do with these tolerances, they're just gibberish to me :(

Misumi:

"SFU8-400" would be their part number for:

precision linear rod, 8mm diameter, h5 tolerance, 1.3505(100Cr6), no surface treatment.

Price: EUR 10.28 per piece

Available surface treatment: hard chrome coating, hardness HV750~, 5 microns minimum thickness

(this increases cost to EUR 12.13)

More alternatives:

tolerance g6 (cheaper)

tolerance f8 (cheaper)

material 1.4125 (X105CrMo17) (EUR 14.56 per piece) -> is that molybdenum steel? That is pretty awesome steel, no?

Can anyone translate that to me, please? :)

/edit:

By the way, I'd like to help myself: I bought that german book called "Technisches Zeichnen by Hoischen / Hesser, edition 33" which I believe could be called the "bible" for technical drawing.

I'm sure everything is described in there, but it has 500 pages and I have no clue where to look. I have no mechanical education so most of the terms and abbreviations used are unknown to me.

If anyone knows that book, I'd be very happy if you could point me to where I need to look :)

/edit:

From what I think I can read from these values myself:

1. Hertsch will be a little cheaper, but the difference will not matter at all - I want the better quality. So ignore the prices for now. I think the prices are definetly not cheap, but way lower than I expected them to be and well within the limits I'm willing to pay.

2. h5 is superior to h6/h7, no? Does that say anything about the straightness or just diameter tolerance?

3. It was already mentioned that hardness is not much of an issue, so I guess from that point of view, all three materials mentioned are way above the minimum (Misumi is in the HRC 60 range if I read the datasheet correctly).

For now I'd be tempted to just get the CrMo rods from Misumi. They're the most expensive, but I guess they will outlive me and my great-grandchildren will still proudly own them as a family heirloom...

 

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Posted · Ultimaker - Black Edition

I'm not sure how you're accessing the MISUMI website. There are probably many ways in.

I went to their site and punched in the part number you supplied. There is a row of tabs on that page. The 'Catalog' tab takes you right to a PDF of the actual corresponding printed catalog.

http://us.misumi-ec.com/vona2/detail/110300000120/?HissuCode=SFU8-%5B20-800%2F1%5D&PNSearch=SFU8-400&CategorySpec=00000028943%3A%3A400#

I tool an image of it, but it is a JPG which the forum doesn't like. You can view it in my gallery:

http://umforum.ultimaker.com/index.php?/gallery/image/3087-misumi-shafting/

There is a tolerance chart over to the right. The tolerances you have mentioned only relate to diameter. Any of these shafts will be very straight. on the left of that catalog page, there is a link to Pg.97 that should explain that as well.

 

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Posted · Ultimaker - Black Edition

As you mentioned about hardness, not too critical for the 8mm shafts. For the 6mm shaft though, you'd want hardened shafts to act as the inner bearing race there.

The g6 shafts will always be a bit under the nominal diameter and are generally for use in commercial bearings, couplings, hubs etc. At its maximum material condition (MMC) the h5 is exactly the nominal diameter which - depending on the components you're mounting, can complicate the fits. On the ball bearings, for instance if the shafting came out on the high side you would have a size on size fit. A little polishing or heating/cooling would ease the fits.

So, h5 is a tighter tolerance, but might be a bit more trouble to fit. I would personally go with the h5 unless cost prohibitive.

You'll be further ahead to buy the shafting in longer pieces and cut them to length yourself.

 

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Posted · Ultimaker - Black Edition

One more thing there Jonny. The part prefix for Misumi is critical.

The SFU you mentioned implies 52100 bearing steel and an h5 tolerance. Specify SFJ for 52100 and g6.

SSFU would be 440C (stainless) with h5 tol. Specify SSFJ for 440C and g6.

I would be tempted to stick with the stainless. As long as your printer is in normal service the bearing steel will be lubricated and not rust. If it sits for an extended period it could become an issue...

 

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Posted · Ultimaker - Black Edition

This is a quick picture of the adaptor itself including the bearing and two M3 hex nuts.

 

I may put the design onto Youmagine but for that I'll have to shoot some pictures of the piece actually mounted.

...

 

It's up on Youmagine: https://www.youmagine.com/designs/bearing-adapter-for-direct-drive-um-original

 

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Posted · Ultimaker - Black Edition

Thanks for looking into this mastory.

I guess there are some differences between the USA and Europe pages.

The part numbers are hopefully the same, but they seem to give different names to the steel sorts.

SFU: "bearing steel" is just called "1.3505/100Cr6"

SSFU: "440C stainless steel" is called "1.4125/X105CrMo17"

I suppose that's the (stupid) ISO system that gives unrecognisable numbers to all steel sorts instead of just stating (the heck) what kind of steel it is. But anyways - I guess we're talking about the same thing in the end.

You wrote "h6" on several occasions above. I suppose you meant g6?

The comparison (on Misumi) is h5 vs g6. h6 is never mentioned there.

g6 makes the shaft a bit cheaper. Even with the stainless steel it's "just" around 11 Euros per piece.

So, I guess the ideal choice would be:

- Tolerance g6

- Stainless steel so you never have to worry about (eg in the corners where you can't reach the shafts)

- no hardening

One more thing to consider:

While I'm at it, should I switch out all the rods, or wouldn't that have much of an impact on precision?

This would cost quite something, probably around 100 Euros for 4 8mm rods and 4 6mm rods. I guess the thick z-rods can be left as they are.

Consider that I need my Ultimaker to get me very precise results - as precise as possible. I'm willing to pay much more than 100 Euros if it helps.

I know that in the end, the plastic itself doesn't allow for tolerances below 0.1mm, but I need the machine to add as little as possible to that.

And even one more thing:

Would it make sense to replace the bronze bushings with those that have these black spots (I don't know how that's called in english...). Are these just for use without oil (which is unnecessary here - I can put on as much oil as I want) or do they improve the gliding ability compared to the standard bushings?

 

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Posted · Ultimaker - Black Edition

Yes, h6 was a typo. I went back and edited it. I deal with a bit of the ISO steel classifying. It sucks. With the SAE system there are some number codes to relegate to memory, but the majority of common alloys are easy to recognize. If you go looking for a cross reference, you will find that there are often no exact direct equivalents (metallurgically), although there is always something appropriate in either system.

The plugs in the bearing you are referring to are called graphite in English. The advantage there would be negligible. I am not sure if the graphite plugged bearings are sintered (porous) or not. The porous bearings (standard) retain the oil to improve lubrication.

There are alot of bearing compounds that could be tried for the plane bearings. Possibly UM had tried some of them before going with the tried and true sintered bronze. Ceramic, rulon or a host of other plastics... The bronze works well. Unless there is a problem, I would stick with bronze. If you were to change the bearing, consider how the shaft selection might be affected.

 

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Posted · Ultimaker - Black Edition

Sorry to switch directions on you Jonny...

Looking at it again, the f8 shafting should be more than accurate enough, and you bearings will fit much easier.

For an 8mm shaft:

g6 = -.005/-.014 -.0002"/.0006"

h5 = -.000/-.006 -0/.0002"

f8 = -.013/-.035 -.0005"/.0013"

For a point of reference, common paper is around .1mm or .004"

 

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Posted · Ultimaker - Black Edition

I ordered one of these rods from Mc Master http://www.mcmaster.com/#6112k15/=qkuc17.

I tried rolling the rod on a mirror, quartzite kitchen counter, and a glass table. The rod had a noticeable wobble. I found gaps between the rod and surface of about 0.1 mm in some regions along the rod. Basically, the rod doesn't seem to live up to their specs.

The rod appeared the same on all the surfaces. I also compared the quartzite countertop to a 12" ruler from a Starret combination square and couldn't see any gap between the two.

They are sending another rod, so hopefully it will be better, or at least I can scavenge a straight section from each rod.

 

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Posted · Ultimaker - Black Edition

Thanks for the info.

I guess I won't change any of the bearings - the Ultimaker stuff seems very appropriate.

Atm I fancy LTBC coated shafts (black matte chrome finish) from Misumi. I know, that's a friggin waste of money, but it would look gorgeous!!

If I switch to tolerance f8, then the material and coating choices change (C45E as suggested earlier). So I suppose that's a completely different product. Also, the price is about 3 to 4 times lower for f8 compared to h5 / g6.

In fact, only the g6 shafts can be ordered with LTBC. h5 is the same material, but can only be hard chrome coated.

I suppose I will try out g6 with LTBC. We'll see if it's worth the money (even if only for the style factor...).

A full set of shafts should top out at about 150 EUR. That's definetly too much to make it a "standard recommendation". So, considering I have two Ultimakers anyways, I'll just order one set of the expensive ones, and one set of the f8 stuff (which will come out somewhere at 50 Euros or maybe less).

Then I can compare directly.

I received news from Hertsch.ch. They can't make any statements concerning the straightness of the rods - apparently no one wants to do that... Also, they can't chamfer the shafts which is one thing that I want. I cut myself while installing the rods for the first time. Not Ian's kind of bloodbath, but it still hurt :)

Why would I care if there is a difference of 0.001mm in diameter??? I only care if there is a wobble of 0.1mm or even more because that's something which will introduce a measurable error in the print result.

As for a reference surface: We don't have a stone kitchen counter anymore, and my dad would kill me if I used a mirror. Guess I'll just have to use my brand new work bench desk top...

But honestly, if a "precision linear shaft - straigt" from a professional supplier like Misumi is not good enough - then what is?

/edit:

Orders are out - I expect it'll take until the end of february for everything to arrive...

 

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Posted · Ultimaker - Black Edition

A little update here:

The shafts from Misumi arrived. BOY ARE THEY AWESOME!!!

The LTBC coating is some kind of dark grey / anthracite, and very matte (but perfectly polished which sounds kinda strange...). Almost looks like plastic.

The shafts are perfectly straight: I put two of them together, held them towards a light and turned them. Not even a slight bit of light passes by between the shafts... Also, the bronze bushings and linear bearings fit ridiculously well - there's almost no play at all, but they still move fine.

Made in Japan - that's quality to be proud of, period.

I guess that was money well spent ^^

Technically, I could have left the LTBC away, but it's going to look gorgeous :)

It's probably going to take a while until I can start building the UM black edition because I'm still busy designing my test adapter for work which has #1 priority...

(Just hope I'll be able to finish it before the launch of TES online o.O)

 

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Posted · Ultimaker - Black Edition

Good to hear about the shafts. I think I will have to order a pair from somewhere besides McMaster. Their shafts do not seem up to spec.

 

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Posted · Ultimaker - Black Edition

Good to hear about the shafts. I think I will have to order a pair from somewhere besides McMaster. Their shafts do not seem up to spec.

 

Misumi does deliver world wide, if you can make an account from your company (they don't allow private accounts... :( )

Sad to hear about McMaster, their specs seemed pretty good.. One of the few to specify straightness (if Misumi does specify straightness, then I just can't read their specs well enough...)

 

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Posted · Ultimaker - Black Edition

Seems like the black coating is only available in g6 tolerance. Would it be noticeably better to get the bearing steel with the normal chrome plating in h5 tolerance? h5 is slightly more precise, but my instinct is that the rest of the machine isn't precise enough for the difference to matter. Also noticing that the g6 or h5 bearing steel with chrome plating is about half the price of stainless, though I am a little worries about the chrome flaking.

BTW, Was RSFJ8 the part number you ordered?

 

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Posted · Ultimaker - Black Edition

Misumi specifies g6 as the preferred choice for their linear bearings - also, the g6 shafts fit my linear bearings - as well as the original bronze bushings - perfectly.

I don't know about the chrome plating coming off. I hope it won't...

Usually I'd recommend getting standard shafts without coating. I ordered LTBC just for the looks ("Black" edition...). I even replaced all the shafts instead of just the ones that need to be longer.

I ordered RSFJ8, yes.

By the way, something I noticed too late:

I measured my shafts by hand and specified some of them too long. That's no problem for the 8mm shafts, but the 6mm carriage shafts must not be too long or they will bend the carriage! It's better to order them 1mm shorter than necessary. I believe that even my original shafts (UM drawings say 267mm length) are a bit too long and therefore make the printhead carriage a bit harder to move around than it should be...

I hope I'll find the time to advance some more with the improved z-stage over easter. At the moment there's just too many other things to do :(

 

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Posted · Ultimaker - Black Edition

I was thinking that the chrome coating would protect the bearing steel from rust and it is cheaper then going to stainless steel.

 

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Posted · Ultimaker - Black Edition

If the chrome plating was done well, it shouldn't be coming off. With the quality I have come to expect from Misumi, I don't have much doubt.

Chrome plating can serve at least 2 different purposes, not generally both at the same time. It is most often the cosmetic high gloss type. In the case of linear shafting or other industrial uses, it is for hardness and wear resistance. I has a hardness that surpasses most heat treated steels, but can be plated of softer metals yeilding a very hard surface and ductile core. When used for wear purposes, it has a 'satin' finish .

 

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Posted · Ultimaker - Black Edition

I was thinking that the chrome coating would protect the bearing steel from rust and it is cheaper then going to stainless steel.

 

Also a good purpose for chrome plating

 

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Posted · Ultimaker - Black Edition

Found a picture I made of the LTBC finish:

Misumi LTBC shaft

The flash / room light may have over-exaggerated the glossiness of the shaft. But it's somewhat accurate.

No progress yet, but I promise I will try to do as much as possible over the next week - I'm going to have the next week off.

 

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