PLA/Brass Bushings

Hello Everyone,

I'm currently attempting to build a Prusa, but have kind of hit a standstill, as the bushings for my bottom plate have somewhat made it angled, and therefore unable to fully slide in either direction. The board becomes caught in the washers from the structural part of the Prusa, not to mention it is not straight...

Does this mean that I will somehow, have to re-aquired PLA bushings or somehow make brass/metal bushings, in order to make it properly, or should i proceed, even though it is not fully centered?

Also, I am still trying to calibrate the smooth rods so that they are exactly parallel with one another, I think you can use a hairdryer/heatgun to heat the smooth rods and sequentially slide the PLA bushings down in order to make a good fit, is this right?

any help would be appreciated!!

Thanks!
Schulz

Hi,

taking into account my limited knowlage of the pursa, from whatr i have been told the best way to make the bushing slide on the smooth rod is to run then up and downt he threaded rod a little so it "files" them to the right size.

If you have a spare bushing or tow you could give it a try.

Otherwise you might want to try and get along to the melbourne CCHS meeting tomorrow night as we will be starting to build a couple of pursa's then and maybe a few minds is better than one.

regards

Peter

Hi,

I don't think I would be able to make it tomorrow (school), but as far as I understand, these meetings run once a week right? I would love to come next week... Do you know who runs them, and if it costs anything? Would be awesome to meet some fellow rep-rappers!

I also managed to get some Aluminium tubing (8mm int. diameter), which fits perfectly over the smooth steel rods. The only problem is gluing that to my bottom plate, I think I will use some flat Lego parts to make an mini (flat) elevated platform, which the board can be glued to.

Has anyone else ever used bushings that are not PLA?

Thanks!
Schulz

Hi Schulz,

People have used bushing not made of PLA with mixed results. It all depends on the materials.

Brass apparently works well. Dunno if anyone has tried Aluminium.

As for CCHS/HackMelbourne (see http://www.hackmelbourne.org/ for details).... It's a group of its own. They do ask that people join if they attend a few times ($50 a year), but if you're just turning up to 'see what it's all about' then it's free.

You need to follow the details on their webpage to contact them about the location (it's in a personal garage at the moment - a proper public location is in the works).

HI..

As I have a working Prusa and have used the PLA bushing when I first built I found that they worn out very quick, so quick I just printed a new set before the ones in the printer failed.

I now use LM8UU liner bearing I got from china. I use a 3 bearing X carriage desiged by Greg Frost, and LM8UU bearing holder for Y axis I downloaded and printed from thingverse. As for Z I use felt bushings desgined from Prusa hinself.

Hope that helps
Auzze

Auzze Wrote:
> As I have a working Prusa and have used the PLA
> bushing when I first built I found that they worn
> out very quick, so quick I just printed a new set
> before the ones in the printer failed.

Ack, so Scorpias reservations about the longevity of brushings turned out to be somewhat prescient, huh?

Roughly how many hours of printing would you say they lasted? Do you think ABS would fare any better?

HI..

About 10 hours before they ststed to show problems in the prints.
Abs would wear faster, plus they would break when you tried to snap them on
.

Auzze

Myndale Wrote:
-------------------------------------------------------
> Auzze Wrote:
> > As I have a working Prusa and have used the PLA
> > bushing when I first built I found that they
> worn
> > out very quick, so quick I just printed a new
> set
> > before the ones in the printer failed.
>
> Ack, so Scorpias reservations about the longevity
> of brushings turned out to be somewhat prescient,
> huh?
>
> Roughly how many hours of printing would you say
> they lasted? Do you think ABS would fare any
> better?

Thanks for the heads-up Auzze.

One of the main problems I see with things like the Wiki is that people experience gamblers syndrome...they only report their successes. Where RepRap really benefits the most IMO is when people report their failures, it saves the rest of us from wasting our time making the same mistakes. I remember reading an anecdotal story somewhere about Edison stating that the X-hundred failures he had while trying to discover an appropriate compounds for light-bulb filaments were actually X-hundred successful experiments to determine compounds that weren't suitable. It's a good attitude to have in experimental technologies like RepRap.

Did you use any lubrication? What type of smooth rods did you use and how smooth are they?

I too have my reservations about the life, but I would have thought Josef would have rejected them if they only lasted a few hours for him.

This is the first post I have seen anywhere where somebody has said how long they last but there must be many hundreds of people using them.

---

[www.hydraraptor.blogspot.com]

yes i must say that 10 hours seems like a really small amount of time to start seeing failures.

but i still maintain that for long term reliability i cant see how they would be better than a bearing setup. they are cheaper for sure but better?

I am currently printing 3 sets of prusa parts on my wolfstrap. We have decided to use the lm8uu bearings on the bed but the other axis's we havnt got to yet. I guess we will see once we get there.

Hey..

I brought in some ground M8 rods from the UK and used both silicone spray and PTFE grease on the rods but PLS bushing worn down very quickly. I also think that it was because of the weigt on the Y carrige, I was running 3 peices of 6mm MDF, 2mm Alum and 4mm Glass.

Now I run LM8UU on the X and Y axis and felt on Z axis and now use 2mm Alum for the frog and bed with 3mm glass.

Since doing this my prints have imporved so more plus now changing to Alum pullies I now have round holes.
It does cost extra to do these mods it's worth it in th end..

Latez
Auzze

Edited 2 time(s). Last edit at 06/29/2011 01:15AM by Auzze.

Right, awesome, thanks for all the tips guys!

Auzze, how many teeth are in your Aluminium pullies? I might as well get some now, and save myself the hassle...

Thanks to everyone!

Schulz

Hey

I used this trader on ebay, [cgi.ebay.com]

Super fast service.

Auzze

schulz Wrote:
-------------------------------------------------------
> Right, awesome, thanks for all the tips guys!
>
> Auzze, how many teeth are in your Aluminium
> pullies? I might as well get some now, and save
> myself the hassle...
>
> Thanks to everyone!
>
> Schulz

Cheers thanks Auzze,

Ordered the pullies and the linear bearings, should be good!

Thanks,
Schulz