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aaronalai

Why doesn't the UM2 ship with Loctite or similar product applied?

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After reading the forums for a couple of weeks, I was wondering why Loctite isn't being used in assembly. It seems like the bolts and set screws, especially the set screws, are susceptible to vibrations during shipping. I understand Loctite can negatively interact with plastic, but it seems like the places where it could be used would be very helpful.

 

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I've also seen screws that had some kind of pre-applied, hardened Loctite on them. These would probably also be more expensive than standard screws though...

I generally use only Torx screws. Almost impossible to mess up the screwheads.

But UM uses stainless steel hex screws which are also very good quality. Not the crappy stuff you usually get...

Usually, I buy my own screws at a Swiss quality hardware store and replace the original stuff (mostly for computer stuff), except for the Ultimaker which is probably the very first time :)

 

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It seems several manufacturers have these...like Nyloks "Nylok Blue Patch" or KerbKonus "TufLok The Blue Patch".

Example here:

http://www.klee.dk/wp-content/kleekat/catalog/pdf/kkv60.pdf

No price though.

I've also been wondering why Ultimaker did not choose torx heads.

Because the hex heads wears out after a while, like in the UM Original since the short belts needs to be stretched by untightening the motors, stretching the belt by putting force on the motor and then re-tightening the screws.

For me, the only benefit of using hex screw heads is that with the right screwdriver, you can actually access the screws from an angle, which is a benefit when accessing some hard-to-get-to screws in corners and such...

 

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An alternative to loctite might be to use coated screws such as nylon or other coatings. There are companies that manufactures and sell such screws but I'm not sure what they cost...

 

They are really expensive. We looked into that when we noticed there where problems with the pulleys going lose. But price wise it's not feasible.

I think they are using torque wrenches now to assemble the machines, as tests show that properly screwed down pulleys hold as well as the ones with loctite. And we're looking into slightly different pulleys that have less problems with vibrations.

 

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In professional assembling one usually avoids using loctite due to the time it takes to apply it. It means additional assembly time which results in a higher price of the product.

 

I agree, but I've seen people simply just dip the bolt into blue loctite and then insert; you don't need much. The extra step adds a few seconds which at most would accumulate to a couple of minutes of additional built time in an ideal situation. I thinks it's kind of a grey area as to whether or not it is financially worth it in the long run to deal with the few who have problems as a function of loose bolts and set screws or to add a few extra minutes to each build.

 

They are really expensive. We looked into that when we noticed there where problems with the pulleys going lose. But price wise it's not feasible.

I think they are using torque wrenches now to assemble the machines, as tests show that properly screwed down pulleys hold as well as the ones with loctite. And we're looking into slightly different pulleys that have less problems with vibrations.

 

Great to hear; will you keep us posted on this? I think something to address the loose bolts and set screws would prevent a lot of minor issues. Also could you potentially provide the torque settings for maintenance?

 

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Is there a recommended torque for those of tinkering with UM2
at home?

 

If you need a tool regularly so it's okay. But even if one wishes to perform work technically correct, it is also good. The normal user will have this additional investment safe maturely to consider, I think.

In our company we use Loctite mainly for the assembly of very large bearing blocks for heavy rotating knife slices, and of course in machine areas with a lot of vibration. The additional cost is very low, and the price is negligible, as it can go even life-threatening for the machine user in a faulty installation. A loose pulley on the 3D printer is, however, in any event, harmless and for the user at most an annoying matter.

Our machines also go on a world tour, just like that of Ultimaker. Only we clearly have the larger machines. :smile: Like all, of course, we also have to be very careful that we ship fundamentally functioning machines. Reversals are very uncomfortable for all involved, but you can not completely avoid it.

But back to Topic:

Not everyone is a mechanic and has a torque wrench in his range. The designer next door, or closing time hobbyist so uses an expensive part probably only one to three times a year. For Professional it is of course fine, but obsolete for private people.

The pulleys are currently used but actually quite adequate, better and more expensive is certainly feasible, but is it still useful?

Why need to use a torque wrench, but if it goes well with some fine-feeling? The little key that came with the UM, should be enough really. When the tool begins to easily bend then I stop to turn. A pulley does not cost very much if he actually needs to be replaced. The part is still sitting in the same position, and a sensitive linear bearing can not reach that position.

Much more than a failed print it will not be well in the end.

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I agree, but I've seen people simply just dip the bolt into blue loctite and then insert; you don't need much. The extra step adds a few seconds which at most would accumulate to a couple of minutes of additional built time in an ideal situation. I thinks it's kind of a grey area as to whether or not it is financially worth it in the long run to deal with the few who have problems as a function of loose bolts and set screws or to add a few extra minutes to each build.

[...]

 

I agree with you. It's a trade-off between assembly costs and service costs. Another reason to apply it could be safety (some parts don't do any good if they get loose...).

 

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...

Also could you potentially provide the torque settings for maintenance?

 

Dito. Would be a very useful information I think.

I've got a torque screwdriver but not much experience with mechanical assembly (I'm an electronics guy...). I've picked up a lot of knowledge on my apprenticeship at Esec (today Besi Switzerland) where there are more highly skilled people per square meter than I've ever seen before, but scarcely had to actually do assemblies myself.

I screwed in my UM pulley setscrews really tight, very close to ripping them apart. I guess that's too much but I don't have that "fine feeling" of an experienced (and maybe simply "trained") assembly guy.

There's another problem with Loctite: The usual stuff (242 as well as 243 I believe) simply doesn't work with stainless steel (according to the datasheet it should reach 25% strength after a considerable amount of time). It won't harden even after 12 hours of curing time because it just doesn't cure around passive materials such as stainless steel.

I'm also not sure whether it's a good idea to combine Aluminum with stainless steel and whatever other kind of steel the rods are made of: That could lead to some electrochemical corrosion effects..

Of course there are special threadlockers for exactly that purpose. But where would a layperson find this, and what does it cost? Probably not feasible...

So, one more reason to just use the right amount of torque (be it with a torque tool or fine feeling) instead of a threadlocker.

 

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I have only used LocTite on the pulleys mounted directly on the stepper motors on my UM 1 build. So far nothing has come loose in about one year.

I had thought about LocTite on the screws for the pulleys on the XY gantry, but decided against it because of the difficulty of dis-assembly. Instead I made black edding marks on pulleys and on all axes. This way one can see if anything has loosened.

A trick to loosen inbus bolts that have been treated with loctite: I take a fine soldering iron and heat the inbus screw, this softens the loctite sufficiently to be able to loosen the bolt without messing up the screwhead.

30 years of model helicopter flying have taught me to be very careful with LocTite. The stuff is absolutely necessary in certain cases but can amount to a giant headache when you have to take things apart.

 

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Great to hear; will you keep us posted on this? I think something to address the loose bolts and set screws would prevent a lot of minor issues. Also could you potentially provide the torque settings for maintenance?

 

I'll try. I'm mostly concerning myself with software. So everything I say about the production is 2nd handed information. The new pulleys could be a few months off, it's not a component we switch out easy, as the whole machine depends on it.

I do not know what amount of torque they use.

Dipping bolts in loctite is easy, dipping the setscrews however, is a different task. As you suddenly have to put in loctite and insert the setscrew while the pulley is already in the machine, which is significant more difficult.

 

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There's another problem with Loctite: The usual stuff (242 as well as 243 I believe) simply doesn't work with stainless steel (according to the datasheet it should reach 25% strength after a considerable amount of time). It won't harden even after 12 hours of curing time because it just doesn't cure around passive materials such as stainless steel.

 

 

Dipping bolts in loctite is easy, dipping the setscrews however, is a different task. As you suddenly have to put in loctite and insert the setscrew while the pulley is already in the machine, which is significant more difficult.

 

Very good points, it looks like the torque wrench is the way to go; it's nice to know the UM team has something up their sleeve.

 

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When I was taking things apart I noticed that the machine uses the same sort of nut traps-in-sheet-material as on the OG Ultimaker, Cupcake, etc. This design coupled with the type of material seems like it is prone to compressing somewhat over time. I suspect that even if all the screws had originally been installed in the outer case with threadlocker and a torque driver, they would still loosen up somewhat due to the material compression. Granted, they wouldn't fall out, but they wouldn't be tight and the rigidity of the machine would be compromised regardless.

Of course, this wouldn't explain what some have reported seeing on their pulleys.

 

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