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Metal build bed

Posted by Kyle Corbitt 
Metal build bed
May 01, 2007 09:46PM
Hey, I know there has been a bit of discussion on the material for the bed of the extruder (right now the instructions have it as 12mm MDF) but is there a reason it couldn't be built out of, say, 4mm aluminum? I found some speculation in a previous thread (a quick skim didn't turn it up for me again) that rapidly cooling the models (an aluminum bed could act as a heat sink) may lead to sturdier layers and less curling at the edges. In addition, I have access to a waterjet cutting facility (actually the headquarters of FLOW, the biggest waterjet company in the world smiling smiley) where I could get the metal cut for free, and I can probably get the raw stock free from them as well. Is there a reason this is a bad idea?

Aluminum has a density of about 2700kg/m^3, while MDF has a density of about 800kg/m^3. This makes aluminum 3-4 times as heavy. Will this strain upset the stepper motors or any of the other components? If I use thinner aluminum, will it bend and skew the printing? Is this all just a poor idea and I should stick with the default material of MDF (incidentally, the waterjet can cut that too, as long as getting wet won't harm the wood)?

Feedback is appreciated. I'd love to experiment, but unfortunately being a student I don't have very much disposable income. I'd like to get a workable solution for this the first time.

PS how do you make the links show up in brackets, showing only the domain like is common in posts here? edit: I figured it out, never mind. Durn these intelligent systems! smiling smiley

Edited 1 time(s). Last edit at 05/01/2007 11:15PM by Kyle Corbitt.

Re: Metal build bed
May 01, 2007 10:17PM
I could be off base, but I think the idea was to design it around the fewest resources possible.

Might I recommend something? Take a scrap of your aluminum, just a scrap, melt some of your choice plastic on it, and see how easy it comes off. If it's stuck for good, using aluminum is probably contraindicated. If it pops right off, you probably have a winner.

As for warping, I doubt that's an issue with the weights and dimensions involved, but if you feel it is a significant risk, you can always add a couple ledgers to the plate, or bend the plate at a right angle on both sides. This would reduce warping along those dimensions. Making the aluminum into a box lid would go further. A diagonal, or two, would be even better, but should probably be made from the same material.
Re: Metal build bed
May 01, 2007 10:41PM
Roach_S Wrote:
> I could be off base, but I think the idea was to
> design it around the fewest resources possible.

Right. I'm certainly not suggesting the project adopt aluminum as the material for its build bed, nothing of the sort! But another core principle of it is that people can innovate and do what they want with it, that's why it's called open-source engineering. So I was asking the community at large if they had any opinion on this particular tweak I'm considering making to my own personal RepRap. And certainly if I end up doing it I'll report back to the community on how it worked out, so others will be able to benefit from my experiment.

I'll see if I can obtain some aluminum large enough to use for this and of a workable thickness and test it like you recommended. Are there any cheap household objects that people know are made of HDPE (that's the prospective material of choice right now, correct?) I could melt down to test without actually going out and buying a significant supply?

Re: Metal build bed
May 02, 2007 02:14AM
Plastic Milk jug.. got milk?
Re: Metal build bed
May 02, 2007 09:28AM
also, most cutting boards are made out of HDPE... but ask your mom first =)

in a few weeks i should also have 5lb coils of HDPE for sale somewhere in the range of $20 /ea
Re: Metal build bed
May 02, 2007 10:01AM
Good, so you're going to start distributing HDPE filament, then?
Re: Metal build bed
May 02, 2007 12:19PM
ya, it makes alot of sense... theres basically no place online that has ecommerce setup to buy it... you either have to call or email someone to get it. human interaction is soooo pre-2000
Re: Metal build bed
May 02, 2007 12:29PM
My suspicion is that once 3 mm HDPE filament becomes a stock item places like New Image will set up e-commerce sites. They stand to make a lot of money eventually.
Re: Metal build bed
May 02, 2007 01:08PM
yup... but who would you rather support? reprap or new images?

...dont answer that winking smiley
Re: Metal build bed
May 02, 2007 01:18PM
Good man. You've stopping to think. LOL!

I've got a good working relationship with Jim at New Image, for now at least. I'm not sure whether or for how long he's going to want to continue retailing filament, though. smileys with beer

Mind, I think that what you're setting up is good, though, and it's good of you to take on the job. Newbies to RepRap need one stop shopping if this technology is to take off in this very critical time for technology adoption. You're making that possible, but aside from filament your sales outlet won't be particularly good for the sorts of things that I need to continue my own work.

Come Mendel, and that could very well change since I understand that Mendel will be using some of the technology I'm working with now. That's a few years down the way, though, and who knows, I may have shifted over to newer still technology by that happy day. smiling smiley

Edited 3 time(s). Last edit at 05/02/2007 01:31PM by Forrest Higgs.
Re: Metal build bed
May 02, 2007 01:34PM
You can get HDPE filament via e-commerce here in the UK but it costs
Re: Metal build bed
May 02, 2007 01:41PM
If you buy it from a retail outlet here in the US that's about what it will cost you here. The trick is to figure out who actually is making the stuff and buy it from them. That was my contribution the the RepRap project.

We're a little different than the average customer for plastic welding rod, though. One of our 3D printers uses a LOT more filament than your average plastics welding operation does, so that makes us look a little bit like a wholesale customer.

I think eventually that outfits like Home Depot and Walmart will stock filament. Then we can see the prices go from $4/lb down closer to the resin cost of $1.80/lb as volumes build up.

Edited 1 time(s). Last edit at 05/02/2007 01:45PM by Forrest Higgs.
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