Should I print bushings or buy bearings?

Just getting the last few pieces together for my big smartrap order. I just got a recommendation to print bushings instead of buying the bearings because the bushings are super cheap and are supposedly quieter.

Is it worth it to buy the bearings? I intend to print a lot of things. Probably almost daily.

How fast will bushings wear out? Do they work as well as bearings?

With a little lubrication the only noise I hear is the singing of the stepper motors (here is an example of singing smartrap)

I am at present experimenting with Delrin bushes.
The first tests seem to be very good. I tried some brass bushes and found that I had jamming issues, don't know why.

The Delrin has a proper bearing surface, is easy to machine and the price of the material is not too much.

So far I have used all metal linear bearings and although they are designed for the job, I also find that they are noisy and do wear out after a few hundred hours of printing.
Maybe my information will be too late for your build, but I am making the bushes the same size as the linear bearings so they will be a direct replacement.
I didn't intend to mass produce these, just for my own use, but if they work out good I may make more in the future if there is some interest in them.

I am also making and using Delrin Z nuts on the last few machines I have built, with excellent results.

Edited 1 time(s). Last edit at 10/13/2014 11:21PM by regpye.

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[regpye.com.au]
"Experience is the mother of all knowledge." --Leonardo da Vinci

Sorry reg you just caught me a few minutes too late. I just ordered steppers, ramps, and the linear rods and I decided to go with bearings. I ordered 12 lm8uu's and 10lm6uu's so I'm set for a while.

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knife-edge
Sorry reg you just caught me a few minutes too late. I just ordered steppers, ramps, and the linear rods and I decided to go with bearings. I ordered 12 lm8uu's and 10lm6uu's so I'm set for a while.

No problem, they will last quiet a while.
I will have fully tested the Delrin ones before yours wear out, so if mine are any good you can always change over to them when needed.
In the meantime, I will build another machine (if I can find somewhere to put it ha..ha..) and give the Delrin bushes a real good test.

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[regpye.com.au]
"Experience is the mother of all knowledge." --Leonardo da Vinci

Hi,

fun to see my video here
I don't know if you see in this video that it isn't really a Smartrap it's her daughter
The Gastrap is a mix of Smartrap, Regpye mod and a little bit of my madness It was full printed on the Smartrap (also bushings ) because I have some meters of stainless steel smooth rod in 10 mm and I wanted to try
More pictures of this "thing" here (clic on picture for next )

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gaston
Hi,

fun to see my video here
I don't know if you see in this video that it isn't really a Smartrap it's her daughter
The Gastrap is a mix of Smartrap, Regpye mod and a little bit of my madness It was full printed on the Smartrap (also bushings ) because I have some meters of stainless steel smooth rod in 10 mm and I wanted to try
More pictures of this "thing" here (clic on picture for next )

Hey!, Looks pretty good.
You have a lot of work there, well done.

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[regpye.com.au]
"Experience is the mother of all knowledge." --Leonardo da Vinci

Update on the Delrin bushes.
Strange that this happened, but after talking about this issue on this thread, one of my printers developed a big problem with the linear bearings on the Y axis.
It started making a horrible grinding type of noise as it moved back and forth. (sounded like the balls were grabbing on the shaft)
It seemed to be printing OK, so I left it to do a print that took about 1 hour. When I gave the part a check, I found that the Y had been skipping steps and the part was printed in steps and stairs.
I tried to move the Y axis by hand and it was pretty tight and grabbing along the rods.
Checked to rods and they appeared to be OK.
\So here was my opportunity to tryout the Delrin bushes that I had made and waiting for a new build. Instead I took this machine apart and fitted to new bushes.
I found I had to open the size up a little, exactly 8mm was too tight to use, so I went to 8.1mm.
I slipped the bushes in place where the linear bearings had been, and re-assembled the printer.
I gave it a test piece to print and I couldn't believe how quiet the Y axis is now.Parts printed out perfect, so now I may even change the linear bearings for Delrin bushes for the rest of the axis

The Delrin is not an expensive plastic, but it has the properties needed for this job. Problem is that you need a lathe to make them.

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[regpye.com.au]
"Experience is the mother of all knowledge." --Leonardo da Vinci

Just a thought, Delrin is sold in long square bars so in theory you could make your bushings long and rectangular. That way you could even drill small holes through the square bar to mount it to the smartrap. Might make mounting a bit more secure than the cable tie option and it would look more streamlined.

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mikefiatx19
Just a thought, Delrin is sold in long square bars so in theory you could make your bushings long and rectangular. That way you could even drill small holes through the square bar to mount it to the smartrap. Might make mounting a bit more secure than the cable tie option and it would look more streamlined.

Delrin is available in several shapes. If you can't find the shape and size you want, maybe you can get a piece cut from a thick sheet like I did. I needed some square in an odd size, and my supplier was kind enough to cut a strip for me, and then didn't even charge me for it. I think he knows I will be back to buy more because he told me that I will love machining this material, and he was right.
It is a dream to machine, probably the very best for machining of all the materials. The price is not too bad either, at least in Australia.
I just finished machining a batch of Z nuts with a flange today, and two sets of bushes to replace my linear bearings that are too noisy.

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[regpye.com.au]
"Experience is the mother of all knowledge." --Leonardo da Vinci

Update on the Delrin bushes.
I made a few sets of standard size Delrin bushes that would replace the normal 8mm linear bearings.
What I found was that it is hard to line them both up and it causes some drag. I think the problem was not the bush, but the printed mount that the bush is pressed into.
I tried for a while and they did work a bit looser, but I was not real happy with the setup.
I decided to make a double bush so that it is like two bushes end to end. This took care of the alignment problem and they work extra well.
These double bushes have a groove in the middle to allow the bushes to be retained in place, and it also allows the bushes to be cut at this point so you can make single bushes from a double.
I have tried them on a machine now and am so happy with them I decided to get a batch made rather than spend hours making my own. I will have them in about 2-3 weeks time.
The machine is much quieter than before and also seems much smoother too. No more grabbing and high noise levels, and no more damaged rods after a few months of work.
I guess this is why Ultimaker use bushes instead of linear bearings.

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[regpye.com.au]
"Experience is the mother of all knowledge." --Leonardo da Vinci

I believe Ultimaker have to use bushes because linear bearings don't like rotation and Ultimakers use the same shaft for both.

Bearings should not damage rods in months. They last for years of continuous use for me. The rods need to be hardened steel and h6 tolerance though.

The problem with bushings is they need some clearance giving some slop and that only increases as they wear. I have only had them last for days

Linear ball bearings have pre-load, so there is no slop until they wear out. The downside is more friction and noise. If they run out of oil they seize but a few drops of oil on the rods generally fixes them.

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[www.hydraraptor.blogspot.com]

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nophead
I believe Ultimaker have to use bushes because linear bearings don't like rotation and Ultimakers use the same shaft for both.

Bearings should not damage rods in months. They last for years of continuous use for me. The rods need to be hardened steel and h6 tolerance though.

The problem with bushings is they need some clearance giving some slop and that only increases as they wear. I have only had them last for days

Linear ball bearings have pre-load, so there is no slop until they wear out. The downside is more friction and noise. If they run out of oil they seize but a few drops of oil on the rods generally fixes them.

Is there some special oil to use, because I have tried sewing machine oil and loaded the linear bearing before assembly, and I have also tried lithium grease.
The rods were RF hardened 316 stainless steel ground to size.
But I still had grabbing issues and a lot of noise after about 20 hours of use. Eventually they were too bad to use. These rods had not worn, but the bearings had certainly worn. Maybe a different oil is required??
The bushes seem to be working fine and are not noisy at all. Time will tell if they are better or not for this purpose, I have a machine running round the clock to test them.

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[regpye.com.au]
"Experience is the mother of all knowledge." --Leonardo da Vinci

personnaly i had a very short and quiet bad experience with brushing.. as with the smartrap, X and Y axis rods are in porte a faux.. we need some balls (no joke here to take the forces along the axis.

I understand well it works when you have only sliding forces .. like on I3 x axis .

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smartfriendz
personnaly i had a very short and quiet bad experience with brushing.. as with the smartrap, X and Y axis rods are in porte a faux.. we need some balls (no joke here to take the forces along the axis.

I understand well it works when you have only sliding forces .. like on I3 x axis .

What were the bushings made of Serge? I had very bad experience with bronze bushings and didn't think I would use any bushing again after that, but these bushing I am now using I have made myself and they are working fine. The material is very important I think, and also the actual design of them.
Until I have put a few hundred hours work through the test machine, I am not going to say yeah or nay on bushings. The tests will convince me of whether they are better or not.
So far the machine has only done around 45 hours continuous use, and is still printing now ( more printer parts ha..ha..)

Edited 1 time(s). Last edit at 10/29/2014 04:47AM by regpye.

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[regpye.com.au]
"Experience is the mother of all knowledge." --Leonardo da Vinci

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Is there some special oil to use, because I have tried sewing machine oil and loaded the linear bearing before assembly, and I have also tried lithium grease.

Car engine oil works for me. Lithium grease gums them up completely.

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The rods were RF hardened 316 stainless steel ground to size.

Were they h6 tolerance? It is +0 to -9um, very high precision.

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[www.hydraraptor.blogspot.com]

Would delrin tubes work? I've found Mcmasterr-Carr carry's them for imperial rod here: [www.mcmaster.com]. Do you put notches in the inner diameter of your bushings such as in IGUS bearings?

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runninfarmer
Would delrin tubes work? I've found Mcmasterr-Carr carry's them for imperial rod here: [www.mcmaster.com]. Do you put notches in the inner diameter of your bushings such as in IGUS bearings?

The size of bush is important to match the rod exactly, so maybe tubes ready made may not fit well enough.
I was going to broach some recesses into the bushes, but after trying decided that it wasn't necessary.
Printer has now done almost 70 hours no stop printing, except for changing filaments, still going good, no issues.
It is 0430am here, and I am up changing the parts to print, the machine is going round the clock to do this test.
It is producing some of the best prints I have ever done. Maybe because I am using Bowden as well and the head is very light weight.

Edited 1 time(s). Last edit at 10/29/2014 02:15PM by regpye.

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[regpye.com.au]
"Experience is the mother of all knowledge." --Leonardo da Vinci

Thanks for info, I'm looking forward to seeing some pics. I went ahead and ordered a 5/8" OD, 3/8" ID delrin tube to try on some 3/8" aluminum rod I picked up at the local hardware store. Once I get those going I'll report my results. The less machining required, the better, so I'm hoping they will work well.

Hm my take on this:

LM8UU make noise
the grease on the rods is not all that desktop friendly

So Delrin sounds good to me.

It seems to be an issue when the rods are not 100% parallel, then the LM8UU start to lock and scratch the rods, I gooled and found a few other printers with damaged rods some blamed it on bad Chinese bearings (though that was not all that convincing) And one person measured the distance beween the rods at both ends and found 0.5 mm difference. I can't find the webpage right now, but if i find it back i sure will post the link.

With that in mind i think Delrin is an excellent solution, the Delrin bearings will probably cos the same as LM8UU, but they probably won't damage the rods. So that saves some money... And it will reduce noise.
So i'm the first in line to order these.. :-)

Yes they are lower friction, quieter and won't wear the rods, but will they stay tight for any length of time? My experience with Igus plastic bearings is they were great for a few builds but after that the carriage started racking.

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[www.hydraraptor.blogspot.com]

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nophead
Yes they are lower friction, quieter and won't wear the rods, but will they stay tight for any length of time? My experience with Igus plastic bearings is they were great for a few builds but after that the carriage started racking.

My test machine has now been running for 115 hours non stop and doesn't seem to have any issues yet. Very quiet, smooth running, prints are very good.
Will keep printing more printer parts as long as I can to give this a real good test.
I would say the five full i3 machine sets, five extruder sets with extra mounting brackets and five gear sets for extruders, several large ornaments and several spare parts is a little more than a few builds, and I haven't finished yet.
Making sure the rods are lined up and parallel is pretty important, but that is so with linear bearing setup too
These are not Igus plastic bearings, they are custom made Delrin bushes, double length.
So far I am very happy with them.

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[regpye.com.au]
"Experience is the mother of all knowledge." --Leonardo da Vinci

I received my delrin tube and seems to fit the rod fairly well. I noticed, like you said reg, that two single bushings have to be exactly lined up or you do get binding. I should have made them a double. I think I can make them work though.

Yup I printed a new bearing plate andy bearings lined up so terribly. It took two hours worth of filing to fix it.

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knife-edge
Yup I printed a new bearing plate and bearings lined up so terribly. It took two hours worth of filing to fix it.

I made the bushes so that the two are joined together and that eliminated the alignment problem.


The ID opened to 8.3mm and when the rods are adjusted the small gap is taken up so there is no play what so ever. It also stops any binding. There is no need to have the ID the same as the rod, if it is the same the rod will not move within the bush.


The bed axis I am still using singles (double cut in half at the groove joint) and made some printed mounts for them to replace the ones that came with the normal printed parts set.
I made them a bit strong, because I wanted to print a hole for the zip tie to go under the bush and not come through the bottom of the mount. It makes for a very neat assembly.

Bush Mount

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[regpye.com.au]
"Experience is the mother of all knowledge." --Leonardo da Vinci

Coming up to 500 hours printing now and still going great.
Have lots of parts printed, several more machines to put together now and a lot of Christmas presents printed.
I can't see any wear in the bushes so far, so I will continue printing some more and see how long it can go before failure.

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[regpye.com.au]
"Experience is the mother of all knowledge." --Leonardo da Vinci

If i wanted to order some how much do you think a full set for the 6mm rods would cost?