PLA Gears VS ABS Gears

I've noticed that PLA gears hold up better than ABS Gears (unless you hit their low Glass Transition Temp).

I posted a short video where I tried to destroy both, PLA won easily. I printed the ABS gears at 50% fill and the PLA gears at only a 25% fill, and it was no contest. PLA does seam to have a minor "wear in" for the first 50 hours of printing, but after that, they are practically perfect. I've only had one PLA gear go bad, and that is because I heated up the whole machine to 45°C in a heat chamber while printing. It took abou 20 hours, but the stepper motors heat plus the residual heat from the extruder finally won out and warped the set screw/ nut area till the gear started slipping.

ABS gears work well, but do seam to wear out (after a LOT of print time).

I struggle to see any advantage in using ABS over PLA. The only thing ABS has is higher temperature range but that's about it. PLA smells nice when it's cooking, has a harder surface and is significantly easier to print with - I just clean the bed off with a razor blade and print the next job often not even letting it cool down if it pops off the glass OK. I must be wrong as so many people seem to only ever use ABS but I'm buggered if I can see the reason why you would bother with it.

---

_________________________________________________________________________________________

Richmond, New Zealand
Thingiverse ~ YouTube

Abs has a couple of advantages, no need for a fan on the Hotend, better temperature tolerance, less prone to cracking if you insert a fastener that's too large or over tightened.
PLA is harder, but it's more brittle.

I print predominantly in PLA, but I actually prefer ABS for most structural parts, the bulk of my printer is ABS parts, the gears on the extruder being the exception, they are PLA.

Sorry to revive this old topic, I just wanted to add the fact that I noticed PLA has less friction when you rub it against eachother and I have the 'feeling' that the gears move more smoothly over eachother.

I can imagine an extruder that is above the hotend to have gears out of ABS, but when using a Bowden (as in my case) you would be crazy to use ABS after you've felt how the PLA gears work together

- Marinus

I have not seen any real issues in using pla, except if the motor becomes hot and the shaft heats up enough to soften the pla.

The main reason that I use mainly ABS is because it can go to higher temperature before getting soft. I once printed a GPS mount that worked fine through the winter and spring but did not survived being inside the hot car during the summer.

To minimize warping when printing larg parts with ABS, I run my printers inside a box that goes up to 40C. I don't think PLA would survive under that condition so I printed all the plastic parts in ABS.

a little off topic, but brnrd got me thinking....

anyone know how well printed acrylic fairs outside in the sun/ or in the car?

A cars interior can easily reach 130ºF or more.
I've measured temps a lot higher than 130ºF in my car.

I doubt also that the same acrylic resin is used by all the filament extruders.
You will have to conduct your own test to determine if your acrylic resin will perform as you expect/need.
Additives, and fillers can be compounded with the acrylic to extend the service temperature range.

Glass-transition temp of acrylic:
Range: 105°C to 110°C, (221ºF to 230ºF).
Average: 107°C, (226ºF).

Maximum Service Temperature (air), 65.0 - 180 °C, (149 - 356 °F).
Average value: 98.9 °C

Edited 1 time(s). Last edit at 01/07/2014 02:44AM by A2.

ive made gears in pla, abs, nylon, and polycarb. the polycarb is probably the best because of its impact resistance, however it needs to be printed fairly hot to get proper layer adhesion. nylon is also good as its very slippery, however it need to be dried first in the oven. pla gears are nice if your extruder is away from any heat source, however since i live in arizona, i refuse to print any parts in pla that are not models because after spending a little time in my hot truck they tend to warp severly. now as for abs, its not as hard as pla, but if you acetone smooth the surface of the gears they become much stronger and smoother, infact ive been running the same gear set for about a year, i have had to replace the extruder body twice already though. so anyways, pla is good for making gears if they dont get hot, and pla allows for sharper tooth profiles than abs. just my two cents.

I don't find PLA particularly useful for real world objects as it appears to be to brittle.

e.g. I printed a set of replacement feet for my step ladder, but PLA would have broken almost immediately when I use it on a concrete surface.

I can see the advantages of PLA for things like cogs, but other printer parts like brackets seem to be better in ABS as long as its thick enough.

Strange, most people say that PLA is brittle, but in my experience, PLA (from plastic2print) was rather sturdy and held up against shock loads. Even tried to destroy parts with a hammer, but only succeeded after several heavy blows. The only downside I have experienced so far is worse temperature performance.

i have had a much similar experience to uGen, but i will say that PLA part for me liked to break with little notice.

---

[mike-mack.blogspot.com]

Sounds like all PLA is not created equal ;-)

I would not like to use mine for anything that needed to be shock load resistant.

I have had a couple of people that use a standard non-Bowden extruder that have warped one of the PLA gears with the extruder directly over the hot end. In both cases, they lived in hot climates and printed in a non air conditioned environment. ABS works fine, but they wear out and develop slop in the gears sooner (which you can readjust when you catch it).

I have used PLA parts for lathe fixtures and other high impact stuff, with good results, but the parts have to be thick. I made two of these Hobbed Bolt Fixture when I first started making my own hobbed bolts. I printed 2 because I was sure I would destroy the first one on the first day. The machined hobbed bolts would get stuck in the bearings and I would pound the daylights out of them with a 3 lb hammer and never even cracked the first fixture. I never used the second part. ABS would have warped and vibrated quite badly under the force of the lathe and would have made bad bolts.

On the other hand, I printed a tri-blade boomerang from Thingiverse (no longer listed) and it was a thin wall PLA part that shattered the first flight when it hit a brick wall.

The PLA I used both times were from Ultimachine and was the Natureworks PLA 4043D.

I still use PLA gears for all of my shop machines and am quite happy with the results, but I can see why someone would use ABS.

@ jamesdanielv: It would depend on the grade of Acrylic. Tail lights are made out of Acrylic, but headlights are made out of Polycarbonate. The Polycarbonate always crazes after 5 to 7 years but the automotive grade Acrylic is always like new.

@Ohmarinus : the PLA we use has a lower coefficient of friction and is much smoother than ABS, maybe it's because of ABS's rubber component (the "B" in ABS). It's why lots of people used to make their smooth rod bushings out of PLA.

A couple of years ago, I found out the hard way not to leave PLA show parts on the car seat in the summer.

I took several videos of PLA parts warping on my Jeep's dashboard this summer. When the temp outside was 90°F (32°C) and the driver's side door window cracked 1 inch (25mm). Once the sun hit the dash board, the temp would rise to over 55° and the PLA would start to warp like a stick of chewing gum. I need to edit the videos and I will post them on youtube.

I also put a built up I2 frame on the sunny driver's seat on the same day, and although it didn't look warped, every nut was not even finger tightened anymore and the smooth rods for the Z axis slid right out and dropped to the ground.

Quote
Beekeeper
@Ohmarinus : the PLA we use has a lower coefficient of friction and is much smoother than ABS, maybe it's because of ABS's rubber component (the "B" in ABS). It's why lots of people used to make their smooth rod bushings out of PLA.

Ah yes, I was looking for good experiences with PLA bushings, however, I haven't found the most excited topics about it. I still wonder if it's a good idea.

My current bushings are working really well, (metal lined with PTFE) but I notice they are prone to getting 'stuck' on certain parts of the shaft, they don't really get stuck, but they move less well over some areas somehow. I am keeping the rods lubricated with PTFE lubricant and the rods are hardchromed steel, the hardest one I could get so it's not the rods.

I think LM8UU ball bearings will wear pretty quick on hardchrome rods, so I might try out PLA bushings, and a new X-carriage, and then will make the bushings so that they can be attached with tie-rips, the heavy duty thick variant tie-rip to make sure they don't start to loosen up over time.

Besides gears, what are some of the experiences here of people with PLA bushings in combination with Hard Chromed rods? (8mm)

Maybe PLA's impact resistance and overall mechanical strength also depends on layer adhesion. For example, I have printed with PC that broke and shattered rather easily because the layers were not adhering properly. Layer adhesion is best at around 210°C for PLA in my experience while anything under 200°C delaminated too quickly to be usable in mechanical applications.
If the high temperature PLA (there are several different products out there) is in any way as good as promised by the manufacturers and vendors, we might be able to combine the best properties of both materials with little to no trade-off. Alternatively, I am keen to try the Colorfabb XT material, which is some kind of Co-Polyester. They didn't disclose which Co-Polyester it is exactly, but the material properties sound interesting and close enough to PLA without the temperature penalty...

@Ohmarinus: I have had bad experiences with PTFE dry lubricant. Silicon lube seems to work extremely well for plastic bushings, though. So maybe it is the PTFE accumulating on the rods in several places?
That being said, PLA bushings are supposed to wear out after a week or something. I have never tried them because of this. The LM8UU won't wear because of the hard-chromed shafts as far as I know. They are indeed intended to run on such shafts. It's just that a lot of people seem to run the linear ball bearings on un-hardened stainless steel so that they wear grooves into their shafts. Never really understood why they don't go for slightly more expensive linear rails that won't wear down. An alternative to the ball bearings are bronze bushings. They run extremely well on chromed shafts - almost without friction. And although they are usually intended to be pressed into some bore with a specific tolerance so that they assume their final internal diameter to fit the shaft perfectly, the play in the bushings is so minuscule when not pressed in that it shouldn't matter at all. Just make sure only to apply a VERY light coating of oil onto the shaft. Oiling the bushings will cause them to run worse (maybe because of the surface tension?) and they already come loaded with oil. Indeed, sintered bronze bushings are intended to be maintenance-free (or very low maintenance) because of this. Slap them in and go, more or less.

Edited 1 time(s). Last edit at 01/08/2014 07:04AM by uGen.

Aha, I didn't know PLA bushings only last a week!!

Time to look into these Bronze bushings then. I have found a few sellers, but they are all outside EU and the shipping cost is simply too high for me


I have found some nice versions though in the US:

Sintered bronze (is this self-lubricating too?)
[sdp-si.com]

Longer version sintered bronze
[sdp-si.com]

Press-fit sleeve bushings
[sdp-si.com]

Any recommendations?

Edited 1 time(s). Last edit at 01/08/2014 12:20PM by Ohmarinus.

That's strange. I have found several suppliers in the EU and UK:

bearingboys in the UK, even offering machinable stock in case you need something custom.

Metallbau Pietrzak in Germany. Got some from this one, rather decent, free shipping for some parts.

Caspar Gleitlager, also in Germany. They are listing the tolerances of their bearings, which is rather helpful in my opinion.

Last but not least, RC model shops might have some bronze bushings.

Edited 2 time(s). Last edit at 01/08/2014 12:06PM by uGen.

Found a seller in the Netherlands, I don't know if this is what I need.
I think I emailed them and they advised me to go for the PTFE lined bushings because they were specifically designed for chromed hardened rods:

[www.thn.nl]

However, the Reprap community tells me the bronze bushings are better?

Edited 1 time(s). Last edit at 01/08/2014 12:22PM by Ohmarinus.

No, I just said that I have tried bronze bushings and found them to slide very well. Someone I work with prefers them over PTFE lined ones because he also had problems with the PTFE bushings.
You might try to remove all lubricants from the shafts first. As far as I know, most bushings are designed to be used with no or minimal lubrication, so adding some might lead to worse performance. Fit and finish might play a big role in plastic bearing performance, too. My DIY bearings also react a little sensitively when I overtighten them by just a little bit, so solid bronze bushings might indeed alleviate this specific problem alltogether.

Ah yes, I have been creating numerous test objects for making the perfect push-fit, this is not the problem, however, I have read that PTFE lubricant would help with the bushings. It works very well for a while, but after hours of use the sliding becomes less good.

I will try and see what happens when I remove the lubricant from the shafts!

Also I have 12 backup bushings, but these are collared bushings and they tend to be less in-line with the rods because the print surface isn't flat everywhere, while the inside push-fit surface is optimal because I printed all the holes where the bushings should go in in a vertical way so the hole-sizes are very consistent where the surfaces on the outside are less straight.

The machine hasn't encountered much trouble yet though, so I will just let it run out of lubricant and see if the sliding improves. Meanwhile I can look for a reasonably priced bronze bushing.

What did you think of the links I placed? I think this one is the most promising since it's also self-aligning:
[sdp-si.com]

I've sent the Dutch company an email if they have advice for me, I'll keep you posted. They have very reasonable prices (around 1,20 euro per bushing) so if the bushings work well for me, I might take the small step to becoming a small reseller for bronze bushings.

Edited 1 time(s). Last edit at 01/08/2014 04:22PM by Ohmarinus.

pla bushings should last a lot longer than a week! keep in mind the person that says they only last that long has never used them. nothing personal, lets get some data before we all jump on this one!

Edited 1 time(s). Last edit at 01/08/2014 05:20PM by jamesdanielv.

Yep, jamesdanielv is right - I have never used them because of what I have read. Now, you have piqued my interest. So, how long do they really last in your experience?

@Ohmarinus: OK, maybe PTFE really helps with certain designs. It's just that it caused me more trouble than anything else. Maybe if you have small cavities in your bushings to act as a lubricant reservoir, PTFE lube works well. My DIY bearings however have a plain surface, so build-up of PTFE dust eventually led to higher friction as I adjusted my bearings to be as tight as possible.
Well, the THN bushings look like any other bronze bushings to me. For me, they all look alike anyway But if you have made good experiences with this company, I guess giving them a try should be ok if the price doesn't exceed 1 or 1.50€ per piece as bronze bushings usually are dirt cheap. I also would loved to have ordered something from SDP-SI, but supposedly even Americans sometimes have trouble getting parts from them because they are usually supplying to companies etc. Don't know if you will have any luck with them. To be honest, it is a little bit excessive to import some bushings over the ocean when you can get them local. The self-aligning feature might be interesting when pressed into metal parts, but we can also self-align with printed parts or with something like this

Been using PLA bearings for almost a year - still not worn.

---

_______________________________________
Waitaki 3D Printer

How Do your PLA bushings look on the inside?
Just straight ribs (like IGUS bushings) or something fancy?
I constructed several types, but did not test them yet.

Keep in mind that the finish on the rod will have a big impact on how long a bushing lasts.

I've seen many commonly available 304(inox) rods that had a rather rough surface. They were ground, but not polished.

---

Yvan

Singularity Machine

I haven't seen the fact yet, that PLA is biodegradable, that should be a benefit in some applications (?)

---

3D Printing Blog: [www.absplastic.eu] - The Future, The Possibilities

@Ramon88: Biodegradability of PLA is an overhyped property. Yes, PLA is biodegradable, but not in a scale that is in any way noticeable for the end user. To biodegrade this plastic, you usually need big industrial composting facilities with a controlled environment etc.

@waitaki: Wow, that's far more than I have ever expected! Can you elaborate a little bit on which rods and lubricants you use, how often you print and if there is any noticeable slop anywhere? Don't get me wrong, but I would love to know specifics in order to put everything a little more in perspective.

when i had my prusa i2 i had then 8mm igus bearings, and they were great on the z axis, but they just had a lot friction on the x and y axis, those actually did wear slightly, which is wierd because they were supposed to be the "marathon runners" or something in their class. anyways continue the discussion.