My extruder mount is rocking!

A forum dedicated to the stock LulzBot TAZ 3D Printer
billyd
Posts: 234
Joined: Thu Mar 12, 2015 11:06 pm

My extruder mount is rocking!

Post by billyd » Mon Mar 16, 2015 4:47 pm

And not in a good way. It has a fair amount of play between the bearings and the x axis rods. Is this normal?

When I hold the extruder in my hand when facing the front of the printer I can rotate the extruder assembly right and left maybe 1 or 2 degrees. The play is coming from the bearings whose ID is larger than the x axis rods diameter. I realize there needs to be a slight difference, but I think it is too large.

Is this "normal" for the Taz 5?

discojon
Posts: 432
Joined: Sat Mar 07, 2015 1:54 pm

Re: My extruder mount is rocking!

Post by discojon » Mon Mar 16, 2015 4:54 pm

I have the same thing on my Taz 5. I also get some movement of the extruder from flex in the printed toolhead mount.
TAZ 5, Open rails X,Y,Z. Marlin 1.1 RC2. Mangrove dual fan, reinforced extruder mount

billyd
Posts: 234
Joined: Thu Mar 12, 2015 11:06 pm

Re: My extruder mount is rocking!

Post by billyd » Mon Mar 16, 2015 5:12 pm

Did they source the wrong size x-axis rods? I think this is something that needs to be fixed. It could be a small part of why my prints, while very good, are not perfect. I think removing play in the print head can only help in any case.

wantmys2000
Posts: 83
Joined: Fri Mar 06, 2015 11:01 am

Re: My extruder mount is rocking!

Post by wantmys2000 » Tue Mar 17, 2015 6:24 am

No, everything is 10mm. The IGUS bearings they chose though are meant for a compression fit sleeve. The printed bearing holders on the TAZ just can't put the proper compression on them so they are oversized. In some cases this can be improved by putting a slight twist on the Y-axis bearings, and squeezing the top and bottom bearings on the x-axis closer together.

A few of us have given up on the IGUS bearings and upgraded to hardened linear rods with linear ball bearings and are very happy with the results. There are a few posts on it in the forums, viewtopic.php?f=36&t=88&start=40 has some misumi part #s in it.

Thanks!
Steven
Last edited by wantmys2000 on Tue Mar 17, 2015 10:44 am, edited 2 times in total.

billyd
Posts: 234
Joined: Thu Mar 12, 2015 11:06 pm

Re: My extruder mount is rocking!

Post by billyd » Tue Mar 17, 2015 10:18 am

So this is a known issue. Ok thanks. Irritating.

wantmys2000
Posts: 83
Joined: Fri Mar 06, 2015 11:01 am

Re: My extruder mount is rocking!

Post by wantmys2000 » Tue Mar 17, 2015 10:43 am

I am not sure if it would be classified as an issue. More as a design decision to keep costs in line with their target, lower maintenance (IGUS is self lubricating), sound level (bearings can be louder), etc. Good hardened linear rods for X & Y plus bearings can run $125. I believe all versions of the TAZ have been built using these IGUS bushings.

The nice part is the rest of the machine is so well engineered that it only takes an hour or two to swap it all out for those of us that want perfection in our prints.

Thanks!
Steven

billyd
Posts: 234
Joined: Thu Mar 12, 2015 11:06 pm

Re: My extruder mount is rocking!

Post by billyd » Tue Mar 17, 2015 11:33 am

wantmys2000 wrote:I am not sure if it would be classified as an issue. More as a design decision to keep costs in line with their target, lower maintenance (IGUS is self lubricating), sound level (bearings can be louder), etc. Good hardened linear rods for X & Y plus bearings can run $125. I believe all versions of the TAZ have been built using these IGUS bushings.

The nice part is the rest of the machine is so well engineered that it only takes an hour or two to swap it all out for those of us that want perfection in our prints.

Thanks!
Steven

Sorry to disagree but this is why the Taz can't print well at high speeds. My R2 can print twice as fast and get better quality than the Taz. Part of it is the smaller build volume which allows for lighter and more rigid moving parts. But a big part is the play in the Taz system. They need to bump the price up and get rid of the slop. There are things you skimp on, and this is not one of them.

wantmys2000
Posts: 83
Joined: Fri Mar 06, 2015 11:01 am

Re: My extruder mount is rocking!

Post by wantmys2000 » Tue Mar 17, 2015 12:23 pm

If I remember correctly the R2 uses bronze bushings that need to be lubricated over time and add mass to the toolhead. The R2 is a bowden setup so it can tolerate the extra mass. The TAZ being a direct drive needs to keep the mass as low as possible.

I agree that there is too much slop in the stock TAZ, but it seems like most people are able to tune that slop out. I was not able to, hence the upgrade to bearings. Saying that, my prints looked ok at 100mm/sec stock, but I wanted higher accelerations for sharper ABS corners. After the upgrade I can run 100mm/sec, 1700 mm/sec/sec acceleration at 0.14mm layer heights and get stellar prints.

I find each printer in this price range has its pros and cons. You have to choose the one that best fits your requirements and make it work for you.

So far I am impressed with the quality of the TAZ and how easy it has been to tighten it up in the few places it was not perfect for my needs. There are faster, more accurate, more turn key printers out there, but none of them have the open source hardware approach, build volume, ease of modifications, toolhead options, active community, and support team that backs up the TAZ.

All this is my opinion which is worth what you paid for it. :-)

Take care,
Steven

billyd
Posts: 234
Joined: Thu Mar 12, 2015 11:06 pm

Re: My extruder mount is rocking!

Post by billyd » Tue Mar 17, 2015 6:00 pm

Sorry I didn't mean to give the impression that I didn't like the Taz. I do very much. Like the old phrase, if I didn't care I wouldn't say anything.

I did get some help from the help desk and I spread and tightened the bearing holders, that removed a lot of the slop, but there's still about 1mm movement at the nozzle due to slop in the bearings. IMO you don't want any. As in zero.

Anyway I am a perfectionist in some respects, and I can't stand a mechanism that isn't functioning the way it should. If we remove all the slop (or as much as possible) we should be able to approach the accelerations of the R2, and maintain quality. The only thing I don't like about the Taz is the stock accelerations are slug-like, so for small details and models it is excruciating to watch.

I will be upgrading my printer with better bearings (tighter tolerance) and harder x axis shafts. But I wanted to bug Lulzbot techs about this because they SHOULD be doing this already. I spend over 2g's for this printer. I expect good quality and speed. Not one or the other. Especially since it is clearly attainable with the design. Heck the frame is a brick S house. So we are 90% of the way there already. Spend another $200 and make this thing properly stock.

ps The r2's extruder is very similar to the Taz. The only difference is the stepper is directly connected to the hob but in both cases the stepper is mounted on the moving mass. I've never lubricate the bushings on the R2. But the Taz's print head weighs a ton, making it even more imperative to remove all slop. I will admit I have added a lot of upgrades to the R2 to get it where it is, so perhaps it is not a super fair comparison. But even the stock R2 has no issues with play at the nozzle.

discojon
Posts: 432
Joined: Sat Mar 07, 2015 1:54 pm

Re: My extruder mount is rocking!

Post by discojon » Tue Mar 17, 2015 8:14 pm

Video I just shot of my 2 week old Taz 5

TAZ 5, Open rails X,Y,Z. Marlin 1.1 RC2. Mangrove dual fan, reinforced extruder mount

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