Welcome! Log In Create A New Profile

Advanced

Adopting PLA as the core RepRap polymer

Posted by Adrian Bowyer 
Forum List Message List New Topic
Adrian Bowyer
Adopting PLA as the core RepRap polymer
March 26, 2008 04:58PM
Ed and I have been building with PCL, which is easy to work with and produces OK results. But Vik has been having lots of success with PLA. It looks as if we can get a supply of 3mm PLA filament (details follow), so should we switch to PLA as the recommended RepRap polymer (not to exclude others, of course)?

Being both bio-sourced and bio-degradable it has good green credentials too (cue comments about world grain prices and biofuels... No. We all know that argument. So let's not rehearse it here.)

Technical pros and antis?

best wishes

Adrian

[reprap.org]
[reprapltd.com]
Reply Quote
Forrest Higgs
Re: Adopting PLA as the core RepRap polymer
March 26, 2008 05:59PM
About the only anti that I can think of about PLA is that the surface of printed objects in it is a bit crude compared to what you get with PCL/CAPA.
Reply Quote
nophead
Re: Adopting PLA as the core RepRap polymer
March 26, 2008 08:11PM
Too early to call I think. Once we have a Darwin made of PCL and one made of PLA we can see the pros and cons. Looks like some high temp parts need to be made out of something else as well.

[www.hydraraptor.blogspot.com]
Reply Quote
VikOlliver
Re: Adopting PLA as the core RepRap polymer
March 27, 2008 05:19AM
Nearly there. I've got a modification to the Z motor mount to do, the beaded belt gears and a few plugs left. All I need now is the steel and the ability to cut it without clutching back in pain!

Vik :v)
Reply Quote
redskinsjbs
Re: Adopting PLA as the core RepRap polymer
March 27, 2008 09:05AM
Where can I get pcl or pla filament? Do you guys have any suggestions? I am in the US, so if there were a manufacturer here that you knew about it would be greatly appreciated.

Jay
Reply Quote
nophead
Re: Adopting PLA as the core RepRap polymer
March 27, 2008 09:11AM
PCL AKA CAPA:

[store.rrrf.org]

[www.hydraraptor.blogspot.com]
Reply Quote
redskinsjbs
Re: Adopting PLA as the core RepRap polymer
March 27, 2008 11:25AM
How long would a 2kg roll of CAPA last me? Is it enough to print another Darwin? Maybe two? This is where it would helpful if I could find that volume calculator that was in the forums a little while ago.

Jay
Reply Quote
degroof
Re: Adopting PLA as the core RepRap polymer
March 27, 2008 11:48AM
Here's the calculator: [degroof.googlepages.com]

I think a Darwin's RP parts are roughly 1000cc (anyone have an accurate measure?). CAPA's density is about 1.1 g/cc. So 2kg will get you 1800cc. You might be able to squeeze 2 Darwin's out of a roll.
Reply Quote
Forrest Higgs
Re: Adopting PLA as the core RepRap polymer
March 27, 2008 12:00PM
Vik has said that there is about 1.4 kg of plastic in a set of Darwin parts. Anybody got a better number? Ian? Adrian? Zach?
Reply Quote
degroof
Re: Adopting PLA as the core RepRap polymer
March 27, 2008 01:42PM
Maybe someone could take a kit, dump it in a bucket of water and measure the displacement. That'll get you volume and you can work out mass for each flavor of plastic.

Edited 1 time(s). Last edit at 03/27/2008 01:44PM by Steve DeGroof.
Reply Quote
redskinsjbs
Re: Adopting PLA as the core RepRap polymer
March 27, 2008 02:32PM
Thanks Steve and Forrest. I guess I should create a direct drive extruder that gets a lot hotter. That way I can cut my costs by about 3. (CAPA = 75$ per 2kg = < 2 Darwin ||| HDPE = 25$ per 2kg = < 2 Darwin) Therefore, since 75$/25$ = 3, I expend 1/3 of the cost for the plastic excluding the capital needed to soup up the extruder to HDPE standards.

Sorry about the goofy math. Its Spring Break and my mind is mush.

Jay
Reply Quote
Ian Adkins
Re: Adopting PLA as the core RepRap polymer
March 27, 2008 06:57PM
It sounds like PCL and PLA give better results than HDPE

Ian
[www.bitsfrombytes.com]
Reply Quote
redskinsjbs
Re: Adopting PLA as the core RepRap polymer
March 27, 2008 07:10PM
Yea, I think HDPE shrinks much more than the rest of the lot

Jay
Reply Quote
Adrian Bowyer
Re: Adopting PLA as the core RepRap polymer
March 27, 2008 07:22PM
Yes - it is just over a kilogram of ABS in the original. Ed has the accurate figure; I'll get it tomorrow.

best wishes

Adrian

[reprap.org]
[reprapltd.com]
Reply Quote
redskinsjbs
Re: Adopting PLA as the core RepRap polymer
March 27, 2008 09:08PM
Why don't we print in ABS? I haven't looked into that as much.

Jay
Reply Quote
Ian Adkins
Re: Adopting PLA as the core RepRap polymer
March 28, 2008 03:33AM
Much higher melting temperature i believe

Ian
[www.bitsfrombytes.com]
Reply Quote
nophead
Re: Adopting PLA as the core RepRap polymer
March 28, 2008 04:52AM
Actually I think the melting point is less than HDPE but it think it is more viscous. I hope to give it a go this weekend.

[www.hydraraptor.blogspot.com]
Reply Quote
Forrest Higgs
Re: Adopting PLA as the core RepRap polymer
March 28, 2008 01:33PM
A long time ago I chased down how ASTM measures the viscosity of polymers as a practical matter. I've reposted the little blog entry in my Lab Notebook.

[3dreplicators.com]
Reply Quote
redskinsjbs
Re: Adopting PLA as the core RepRap polymer
March 28, 2008 02:11PM
Forrest

I read your blog and I swear you are a genius. Those pellets are so mush easier to find than the filament. One thing I would like to mention is that I think if you reduce the extrusion barrel length from 8mm downwards, the diameter of the filament will be less predictable. This isn't from and experience, it just seems like the longer the plastic is in the barrel, the more it will want to stay in that shape. Maybe you could do some tests when you get this thing up and running. If it works, I'll guarantee you that i will be the first to build a second one.

Jay
Reply Quote
Forrest Higgs
Re: Adopting PLA as the core RepRap polymer
March 28, 2008 02:18PM
I looked at doing that two years ago and then abandoned it when I realised that there were firms with professional equipment which could make filament much cheaper and with much closer tolerances than I could ever hope to.

I'm pretty much against mounting a granule extruder on a reprap because it would weigh too much and require too much beef in the positioning system to move it around at reasonable speeds.

Sorry to disappoint.

Edited 1 time(s). Last edit at 03/28/2008 02:18PM by Forrest Higgs.
Reply Quote
redskinsjbs
Re: Adopting PLA as the core RepRap polymer
March 28, 2008 02:24PM
Ahh, no worries. Its just that Capa is just so darn expensive. I'll wait and see what results nophead gets with ABS.

Jay
Reply Quote
Forrest Higgs
Re: Adopting PLA as the core RepRap polymer
March 28, 2008 03:29PM
CAPA extruded in the UK is expensive. It's not nearly that bad extruded in the US.
Reply Quote
redskinsjbs
Re: Adopting PLA as the core RepRap polymer
March 28, 2008 07:06PM
~Forrest

So do you know of a supplier in the US?

Jay
Reply Quote
Forrest Higgs
Re: Adopting PLA as the core RepRap polymer
March 28, 2008 09:54PM
I know where you can have it made. The trick is ordering the raw resin from the supplier and getting it shipped to the plant where it's made into filament. Unless you buy a bunch, shipping costs eat you up.
Reply Quote
Ian Adkins
Re: Adopting PLA as the core RepRap polymer
March 29, 2008 05:31AM
If all the parts weigh 1kg then that makes it about $40.00 of CAPA OK no so chaep as HDPE but still not a bad price for all the Darwin RP parts just a little more than 1 motor!

The biggest problem with PCL is the cost of doing a second run due to minimum quantities.

If the demand was there then the price would fall at least by 50% but you would need to be talking tonnes not kg, usual commercial supply & demand dilemma.

Ian
[www.bitsfrombytes.com]
Reply Quote
nophead
Re: Adopting PLA as the core RepRap polymer
March 29, 2008 05:46AM
Does anybody have an idea what volumes of plastic welding rod are sold? It seems quite specialist compared to metal welding. Would we get to the stage where our demand is on a similar scale so a company that sells welding rod would start stocking PCL or PLA filament at similar prices?

Not that the price of welding rod is very good compared to raw plastic. My 5KG of HDPE was about

[www.hydraraptor.blogspot.com]
Reply Quote
Forrest Higgs
Re: Adopting PLA as the core RepRap polymer
March 29, 2008 11:58AM
It appears to me that the processing costs to convert resin to welding rod at New Image run about US$2.50-3.00/lb to judge from what they are charging for rods compared to what the cost of raw resin is.

Those UK prices make my hair stand on end. eye popping smiley

It's not hard to understand why Adrian wants a granule-fed extruder when you look at them. I'd feel the same way.

Edited 2 time(s). Last edit at 03/29/2008 08:02PM by Forrest Higgs.
Reply Quote
VikOlliver
Re: Adopting PLA as the core RepRap polymer
March 29, 2008 05:27PM
The cost of getting the filament extruded here is NZ10c/metre or roughly NZ$10/kg (US$3.60/lb)

Vik :v)
Reply Quote
reece.arnott
Re: Adopting PLA as the core RepRap polymer
March 31, 2008 01:31AM
I (in NZ) got my HDPE as 3mm filament from the Carr Group which is a NZ/Australia group of companies (www.carrgroup.co.nz). The cost itself was quite low and it came already as filament. BTW, people might want to be looking for 'weld rod' which may give a few more suppliers.

They have a number of different 3mm filaments on offer. A current price list is available at [www.carrgroup.co.nz]
Reply Quote
Gene Hacker
Re: Adopting PLA as the core RepRap polymer
April 03, 2008 11:46AM
Well, there is only one problem I see with PLA, it's biodegradable. A while back, Mercedes started putting wires with biodegradable insulation. As time passed the insulation degraded and caused shorts which caused engine failure.
[users.adelphia.net]

Speaking of PLA, the local grocery stores have just now started to sell food in containers made of it. So if anyone wants to try some PLA extrusion tests, try your local grocery store.

On filament extrusion, instead of extruding a round filament, why not extrude a flat sheet through something like a heated pasta roller. This might yield a more uniform bubble free filament than could be achieved with a round extrusion. Only problem is that it might require some modification to the extruder.
Reply Quote
Page 1 of 2    Pages: 12Next
Newer Topic Older Topic
Sorry, only registered users may post in this forum.

Click here to login