Maximum Print Size

Hi, I'm new to 3D printing. I'm looking to purchase, build or modify an existing design to allow me to print an item approximately 450mm x 300mm x 100mm. Can someone help? I can't afford to spend 10s of thousands on a commercial size unit.

Thanks,
Trish

Divide into smaller parts and then glue/bolt/snap them together. From my experiments superglue bonds appear to be as strong, if not stronger than PLA.

With a single large print if something goes wrong then you are out a lot of time and money. These printers still have a significant learning curve and trial and error period.

Andy

Alternatively, if you need the part in ABS, applying a little bit of acetone onto the contact surface and pressing both parts together works extremely well. You will have to let it set for some hours to achieve maximum strength. If you have to bridge small gaps in the contact surface, a 50/50 acetone & ABS slurry might be better as it already contains a little bit of structural material.

Printing big is always troublesome without heated chamber, but if you need that large a build volume, the Mendel90 design might be one of the better ones.

Agreed regarding ABS but I think the time required to purge the acetone is a bit longer than a few hours for most items. I'd give it at least a full day to offgas. And as with all carcinogenic and/or poisonous solvents, do so in a ventilated area...

Acetone is widely used as nail polish remover so I'm sure you can safely say that it's not a carcinogen.

A single part of that size in ABS will warp depending on the shape unless it's printed inside a hot chamber. It probably will even need a chamber that would be too hot for most repraps that use printed plastic parts. But it might work with PLA which doesn't warp as much.

brnrd Wrote:
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> Acetone is widely used as nail polish remover so
> I'm sure you can safely say that it's not a
> carcinogen.
>

Asbestos was never thought to be a carcinogen! Mercury wasn't thought to be poisonous either.

+1 on konwiddak's post.

Acetone is now known to be a low level carcinogen. Most current nail polish removers are labeled as 'Acetone free". Most likely that means they use a chemical similar to acetone, which is not yet known to be a carcinogen.

In any event, always use acetone in a ventilated space. Wear gloves if you expect significant skin contact. Dispose of acetone soaked rags, cloth, or cotton balls in outside garbage cans - putting them in the inside trash just creates a source of acetone vapors that will sit around for hours outgassing and letting you breathe the fumes in.

All that said, it is still a low level carcinogen, so you shouldn't treat it like nuclear materials or strong acid/base. But do exercise some caution.

To konwiddak's list of things we learned were dangerous, I'd add lead. Rich Roman citizens would get lead plumbing to their houses. Their kids grew up stupid and didn't contribute to the empire like their parents did. Gibbon notes the trend when he comments that many of the leading citizens of Rome in the later days of the empire were foreigners, and few native sons did anything of significance. Further, the emperor had to be native, and the later emperors were a pretty sorry lot overall. A similar phenomena occurred during the industrial revolution. And finally I have heard of tribes of Native Americans that settled in areas where the drinking water was contaminated with lead - typically the tribes died out or moved away.

FYI, lead in drinking water stresses the kidneys, sometimes causing kidney failure, and in children, hinders brain development. If you're an adult, your brain is now safe from lead, but your kidneys are still vulnerable. All in all, it's a bad thing, and the human cost of learning this was huge.

Sorry for the off-topic ramble. Take home message - be careful with acetone.

Regards,
aeronaut

In terms of building a printer, I'd strongly consider the Mendel90 for large sizes. Nop Head's design is such that you can specify the x, y, and z dimensions, and the design parameters will adjust the size of things to make it work. Expanding the Y direction is particularly easy - it's just the length of the base board, 2 carriage support rods, and the belt length that have to change (as well as the bed length and associated parts, of course).

That said, printing on larger scales will likely involve problems like warping, and will likely require an enclosure. Additionally, getting larger parts, particularly a bed heater, may be problematic. It's a tricky problem, and one I don't envy you.

I suspect the best bet is to make a few smaller parts that you can connect together with screws, glue, etc. There are several good ways to connect parts together that are pretty rigid (although almost never as rigid as the a solid piece).

Good luck with it.

Regards,
aeronaut

@aeronaut - What's the basis for your statements that acetone is a low-level carcinogen? Source please. If this is true, then we would be in deep trouble since acetone is a natural metabolism product of living things including humans.

brnrd,

Thanks for making me check on this. My P-Chem teacher in grad school told us all that acetone was a low level carcinogen, but when he was a grad student, he greased huge vacuum pumps with some sort of grease, and washed his hands off with acetone afterwards, and he's still (at that time) kickin'.

A quick check of Wikipedia reveals that acetone is not considered a carcinogen, but is a low level toxin. "Acetone has been studied extensively and is generally recognized to have low acute and chronic toxicity if ingested and/or inhaled." - Wikipedia page on acetone.

So not carcinogenic, but not perfectly safe.

Finally, because something is produced in humans doesn't make it safe. There's a reaction that happens in the eyeballs that produces trace amounts of formaldehyde, but that doesn't make it safe to drink or eat. (Formaldehyde, for any readers out there who aren't up on chemistry, is embalming fluid.) The trace amounts produced are metabolized, but larger amounts are not safe. This reaction is driven by methanol, which is why drinking methanol (wood alcohol) leads to blindness - you end up producing lots of embalming fluid in your retinas, all the cells die, and you can't see anymore.

Bottom line, I withdraw my statement about acetone being a carcinogen, but still urge anyone working with it to exercise caution.

Regards,
aeronaut