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I'm new to Utilimaker. My engineering students are just finishing building the unit. I am not an engineer.

I was thinking about the accuracy of the print head positioning. I see several blocks sliding over metal rods. I got to wondering if a small amount of stiction between the sliding parts could cause tiny variations in the acceleration / deceleration of the printer head, leading to very small variations in the final resting position and hence, cumulative inaccuracies.

There are some new, high-tech lubricants out there which may leave no residue to accumulate, to grab dust particles and actually do more harm than good.

:?:

I wonder if I am thinking in the right direction, has anyone else thought about this or experimented with additional lubrication of the moving parts?

Alan

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This won't affect the print quality at all as the steppers motors always move a certain amount of steps. If it is not well lubrificated the motors will use a bit more current but they will give the same precision.

Think of it like this: you can climb the stairs for 10 steps and then do the same thing carrying a shopping bag. In both cases you made 10 steps. Of course there's a limit: you can't climb the stairs with a bag which weights 1000kgs and for the same reason the motors may not be able to move correctly if there is not enought lubrification, but that's unlikely to happen and in any case you'll notice that easily as you would see the object built completely wrong.

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My machine needs lubrication right now. I don't have quality problems, but when I try to move the printer head faster then 150mm/s it starts to miss steps. Other then that it runs fine. Lubrication should also protect your machine from wear, so it's always a good idea to keep it lubricated.

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Been wondering about this myself, anyone play foosball? Foosball is the table game with the little men that hit the hard ball that is the size of a ping pong ball. The little men are on metal bars that you slide back and forth while rotating the bar to hit the ball. When you play foosball seriously you want the bars to move as freely as possible and you can really feel it when the bars are slow. You never want to lubricate them with any kind of grease. You want them as clean as they can get. A tee shirt can clean them pretty well. Once they are really clean you can use some silicon to make the bars feel like they are practically floating. Grease does make it feel good for the first couple minutes after that it just feels gunked up. Sticky and slow.

Getting back to Ultimaker, I kind of think the bag of groceries analogy is realistic. Still, I think grease can only attract dirt and add more binding than it reduces.

Just my two cents, anyone with other ideas?

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I used some "universal machine oil" on my rods yesterday, it moves a lot smoother now. It is a bit tricky to apply, as it can drip to your wooden parts.

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There are two types of bearings used by the Ultimaker. Linear ball-bearing and bush bearing (the ones on the X/Y rods where the belt pulleys are).

As far as I know are the bush bearing self-lubricating and the linear ball-bearing are pre-lubricated. So, the only thing I have to lubricate is the M8 Z thread.

Or are there some positive experience with putting silicon on the rods?

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Well, I feel like a fool. I bought a one pound can of the same green grease that came with my Ultimaker. I have applied it to the rotating rods (with the sintered brass bushings) and on the Acme thread Z axis.

I have not printed in a few months, now I find that I can barely move the X and Y axis by hand. Touching the rods, the grease has become a sticky coating.

I'm going to clean it off and put some dripless oil on it.

I think it may have reacted with the oil in the sintered brass, because it has not done this on the Z axis threaded rod nor on the linear bearings, which I had very lightly greased.

 

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I'm using a full synthetic sewing machine/tool oil now call "liquid bearings". It only takes a drop on each rod, no sense in overdoing it and lubricating your print surface. A drop of oil makes a world of difference in the ease of moving the printhead around.

I was using regular sewing machine oil previously, but it doesn't seem to last as long.

 

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Grease is a definite disaster, light oil is pretty good (much better than dry) but as mentioned needs to be

re-oiled reguarly.

I dont know exactly what the slider sleeves in the XY blocks are made of, but for it to work it needs to be

sintered phosphor bronze (which is highly porous, like a sponge). These then need to be impregnated in oil

preferable under pressure.

http://www.use-enco.com/1/1/86630-sae-841-oil-impregnated-bronze-round-rods.html

People used to just drop them in a bucket of oil for a week and call it done, but

that will never force the oil into the structure very deep so they stop working quickly. The whole idea of

self lubricating phosphor bronze is that its sponge structure is filled with oil, which slowly leaches out over

months and years keeping it running well.

Many people dont really understand how it works, and just buy a bar of "stuff that looks like bronze" and lathe

sleeves out of it. Of course it doesnt work very well at all....it has to be sintered phosphor bronze which has been

properly oil impregnated. The phosphor helps a bit, because its so soft and has some self lubricating properties. Which

is much better than just steel on steel, but not really good enough for constant high speed friction.

http://www.bearingbush.com/sintered.html

Possibly a good thing is to try properly engineered dry lubrication bushes, like these. They will only work with low loads.

http://www.igus.eu/wpck/default.aspx?Pagename=RJUM_01_ES&C=DE&L=en

At the moment I am still just using light oil every 20hours of printing, and it works very well. But its not really a great

solution.

 

Either that or put linear ball bearing races in everything. But honestly the loads probably dont warrant it and

might even result in more play - given the pretty wide tolerances on the standard steel axes.

C.

 

 

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I'm also using sewingmachine oil. It works fine but it 'evaporates' very quickly.. I thought it would stay much longer regarding the high boilingpoint of oils. Maybe it has a large portion of solvents.

 

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Graphite is just about the worst possible thing you can do, its electrically conductive....

The fans will blow it around and the electronics fan will (at some point), suck it into the electronics main board area.

The point about the oil imprgnated bushing is that it does not require anything else to be applied.

 

 

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Graphite is just about the worst possible thing you can do, its electrically conductive....

The fans will blow it around and the electronics fan will (at some point), suck it into the electronics main board area.

The point about the oil imprgnated bushing is that it does not require anything else to be applied.

 

 

What about something less electrically conductive like Molybdenum Disulfide then?

 

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Well its probably "ok", but its certainly not classed as an insulator either...

However the issue with all these things is "what do you DO with it".

If you suspend it in grease, its just moly grease. Which due to the soap suspension gives you the same

problems as all other greases which is to say massive friction drag.

Or you can "apply" it as powder...which will then be very effectivley wiped off by the runner blocks. I couldnt

say how many hours it would take it wipe it all off or at least wipe the stuck bits all down to the ends of the rods..where

they dont do anything useful.

The best things to do, are either apply something like moly as a baked on coating to the rods (expensive), which

keeps it where you want it. Or you can just buy the dry-lube bushes I already posted a link for.

You dont have to get THOSE ones, its just an example of the kind of things you can get off the shelf.

But its a very good idea to get the lubricant as part of whatever bit is moving, because otherwise it just gets

wiped off.

So if you run plain steel rods, with dry-lube purpose make bushes it will probably work very well.

Lubrication is an extremely complex science, and there are so many coatings and so on available that the best

is to find a supplier of dry-lube bushes and telephone them and explain the exact application you need.

The speeds, loads, duty cycle, mating material, surface finish are all critical bits of info to make a good system.

If that all sounds like a pain in the arse, then just go old-school and buy some properly oil impregnated

phosphor bronze bushes and be done with it. I cannot comment on what the UMaker has because its

only "semi-open source". So I dont know what materials specs or suppliers they use for any of this stuff.

 

Perhaps the standard ones ARE as above...who knows.

Regards

C.

 

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I want to reactivate this old thread, because of snowygrouch's answers. I read them the first time.

 

This bearing from the link is a linear one. So it's actually for linear motion without an inner rotating axle like our outer 8mm UM ones, right?

 

Just an idea / question:

 

Is there any special reason why we don't use bearings like the flat ones for the frame? Two for each slider block. One on the left side and one on the right side. Ball bearings can handle the linear motion (or not?) and are made for radial forces and an rotating axle.

 

I just done a quick research, and found things like these: http://www.kugellager-express.de/Miniatur-Kugellager-/Miniatur-Kugellager-CMR-----Hybrid-/Keramik---Hybrid---Miniatur-Kugellager---C-MR128---8x12x3-5-mm.html (ceramic) or http://www.kugellager-express.de/Miniatur-Kugellager-/Miniatur-Kugellager-SSMR-----Edelstahl-/Edelstahl---Miniatur-Kugellager---SS-MR128---8x12x3-5-mm.html (stainless steel).

 

I'm sorry if someone else had already explained the reason - but I didn't find it.

 

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I think the ball bearings would perform very poorly in linear motion. It would probably be better to put them on the outside of a thinner linear bearing... but regardless, I think this is a fairly well solved problem with the current solution.

 

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in my local town... you can buy a small bottle of sewingmachine oil for 1 euro :-)

I like putting a little drip on all my axis once a week.. The maschine runs like hot sexy butter with zero problems..

And for about 5 cents of sewingmachine oil, a great smoth operator ;-)

Ian :-)

 

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I think the ball bearings would perform very poorly in linear motion. It would probably be better to put them on the outside of a thinner linear bearing... but regardless, I think this is a fairly well solved problem with the current solution.

 

Ok, sounds logic. And of course the bush bearings work well. But I think they will have the biggest abrasion of all bearings too. Anyway, that's are all just thoughts about possibilities.

 

I like snowygrouch's explanation about the sinter bearings. Some months ago I revised the gear from my scooter. It also has a big sinter bearing inside. I read about it in the repair manual and they written that you have to use a special sinter oil to insert the axle after working. Just for safety.

 

Shortly: this oil was very expensive and really difficult to purchase in small bottles. I got it from a friend who repairs record players. Maybe I try this one.

 

I don't think, that the original bush bearings are sintered ones!?

 

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And what would happen if instead of sewing machine oil, I used a little (in liquid form) WD40?

 

I know it lubricates much, I even do tests on small engines. But we must not drowned WD40. We must put a few drops ...

 

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When I was reassembling the whole XY part, because I wanted to change all the pullies, I was playing with the brass bushings by moving it over the rod by hand. First I cleaned it with a dry cloth and they bushing slided very easilly over the rod. Then I applied some machine oil and.. it felt like it behaved like a Newtonian liquid. The faster I moved the bushing over the rod, the more friction it gave. Imagine with print speeds up to 200 mm/sec (travel) this generates a lot of friction. Then I cleaned the rod and applied some WD40. The effect was still present but much less. And the best lubrication that I got was by spraying some WD40 on a cloth and swiped the rods slightly with it.

So.. yeah, you could do some test for yourself, maybe I'm wrong. But because of the effect that I noticed, I'm hardly using any lubricant than just a superthin film of WD40 (actually it's Silicone72 from Kontact Chemie but it's almost the same stuff).

 

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Oldish thread, apologies for reviving, but I couldn't find anything more recent.

For the X and Y axis rods -

I was wondering if a dry lubricant (Molybedenum disulphide based) may be a good alternative to sewing machine oil? (Reasoning being that any oil is eventually going to attract dust and other detritus = a nice grinding paste)

There's several Gun based formulations I've come across, one I've used with success on my target rifles is this stuff:

http://www.hoppes.com/gun-oils/dri-lube

so long as you're prepared to polish it after application (Bit like applying car polish in that respect)

Has anyone tried any dry lubes ? Results ?

Incidentally... I'd advise against using WD40 as a lubricant - it isn't - once the carriers evaporate you're left with a nasty sticky goo. :smile:

 

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