Best Adhesion?

[djprinter]

Glass bed with hairspray, auqanet extra super hold to be exact.

[Todd-67]

I use glass with Kapton tape. I don't use rafts unless I am doing something really tall with a small contact patch. I have issues getting stuff off the plate. The first layer height, width and speed are where I would look. I also use brims to get the extruder flowing before it starts to print the part. I almost exclusively print with ABS.

[curious aardvark]

why ?
Given the alternatives around these days, why use abs - genuinely interested.

[Alibert]

Because:

1) ABS has a higher glass point and heat deflection temperature than regular PLA
2) Is less brittle than regular PLA
3) ABS can be smoothed safely with acetone (a substance your body produces itself, relatively harmless), also makes it 100% water-tight
4) Costs less than half of what the 'performance' PLA variants that try to come close to ABS as to 1) and 2) cost... ?
5) Prints with very fine detail and without any stringing. PLA and PETG tend to string more or need much more precise calibration to prevent it.

As to point 1) and 2), even ABS does not cut it for a lot of my applications. Hence now printing a lot with polycarbonate and now exploring PEI filaments....

As has been remarked before, there are a lot of applications in which any PLA or PETG simply does not meet the specs.

[Todd-67]

Because:

1) ABS has a higher glass point and heat deflection temperature than regular PLA
2) Is less brittle than regular PLA
3) ABS can be smoothed safely with acetone (a substance your body produces itself, relatively harmless), also makes it 100% water-tight
4) Costs less than half of what the 'performance' PLA variants that try to come close to ABS as to 1) and 2) cost... ?
5) Prints with very fine detail and without any stringing. PLA and PETG tend to string more or need much more precise calibration to prevent it.

As to point 1) and 2), even ABS does not cut it for a lot of my applications. Hence now printing a lot with polycarbonate and now exploring PEI filaments....

As has been remarked before, there are a lot of applications in which any PLA or PETG simply does not meet the specs.

LOL Well that covers it..... Almost everything that I print is a functional prototype or going into a production environment. I have to post process and paint a good deal of parts. I need them durable as well. Snap fits and other fine features wont cut it in PLA and yes there is the cost. I have gotten to the point where I buy natural ABS for dirt cheap and it prints flawlessly. The stuff doesn't degrade in moist environments.

I think that people lean on PLA because it's easy not because it's a better material.

[Alibert]

Also:

6) ABS can be etched to enhance adhesion when (vapor deposition) galvanizing or painting. This etching process makes the surface micro-porous, hence the better physical adhesion.

I think that people lean on PLA because it's easy not because it's a better material.

Mostly because you really need an enclosed (and preferably heated) printer if you want to print bigger parts. A lot of printers do not have that. You can still print with ABS, but only smaller parts to prevent warping and cracking. Also the smell when printing is nicer and it is touted as being biodegradable.

I am now adding a regualed ceramic heater to a second printer. With that I can heat up the interior to a consistent value (using 50 to 60 C at the moment, will gradually increase to 70-80 C in the near future). When the ambient temperature approaches the glass transition temperature, you negate virtually all warping with any polymer. I might write a post on that topic when I have more time....

[Todd-67]

I agree with you. I have all my vents taped off and pump a lot of heat into the bed to get the temps up. a regulated heater is a better option. You do need to stay on the cool side of the glass transition temp though. otherwise you may get some sag in the prints. I thought Stratasys has a patent on the heated chamber which is why the market stays clear of that feature.

Interesting to see someone talk about glass transition temps in the printing world. Obviously you have had some education on the subject. I attended Akron U for their plastics program. Usually we only worry about those things in failure mode analysis and when specifying materials based on application. I would welcome you to write a post up on it if you have the time.

[Alibert]

I am a chemical engineer by profession, so not that afraid of polymer properties...

Just a quick post:

Some time ago I stumbled on this post: https://groups.google.com/forum/m/#!...ot/4evJNxIPY2E

I have looked up typical glass transition temperatures and linear expansion coefficients and set up a graph plotting chamber temps versus estimated stress for a number of polymers. Assuming an ambient of 30 C for PLA, that means that one has no problems with a stress of around 100. The PETG almost superimposes the PLA which explains the 'low-warp'. Extrapolated to ABS, it means that 65 C would bring it to the same stress level as PLA, thus virtually warp-free. I still need to verify that assumption.

Also, polycarbonate (PC) requires a lot of adhesion to the build plate to overcome the stresses and not warp. So far I am having good success with PEI and parts with dimensions up to 100-120mm.


stress_Tg.jpg

[curious aardvark]

I know all that. But when i wa susing abs, the abs parts I made were always inferior to the pla parts. Maybe I was using crap abs or i just use great pla, I don't know.
But between the smell of hot abs, acetone and the sheer hassle of printing it, not too mention it never performed as well as pla - I'll never go back to abs.

Your body also makes small amounts of formaldehyde - but you don't want to ingest it.
Over exposure to acetone can lead to anosmia, among other things. It's not healthy stuff.

Hell our bodies make minute amounts of lots of really toxic chemicals - does not been long term exposure to larger amounts is good for you.

[Alibert]

I think you just didn't have the right settings for ABS. My experience is just the other way around, PLA parts are vastly inferior to ABS parts once you put in the effort to get ABS printing right. Even dirt cheap ABS (once dried correctly) outperforms PLA on all those aspects listed above.

As to acetone, the MAC value is still in the region of 800 ppm I think, which is orders of magnitude larger than non-body common substances. MAC is the maximum allowable concentration you can be exposed to for 40 hours per week during a whole life time without adverse effects. It is the by product of burning fat and is much more abundant in the body than the minute traces of formaldehyde.

A famous saying is that the toxicity is in the dose. 200 grams of common kitchen salt is also lethal. Breathing 100% oxygen is also lethal. Too much ethanol is also lethal. On the other hand the total absence of a lot of substances is also lethal (think iron, zinc, magnesium, etc). I did not say that you should liberally start drinking acetone, just that is a lot less harmful than the solvents you need to smooth PLA (which is actually possible).

I know you are a strong advocate of the premise that anything can be done with PLA, but for many people this is simply not the case.