building a prusa mendel to print PET

Hi guys,

This is my first post here, asking for some advice.

I have had a (fully assembled) Afinia H for a few months now and i have been happy with its performance.
I am however looking at building a prusa mendel from a kit for the following reasons:

1. understand the level of performance achievable for a very low cost (435$ in mixshop.com) printer: less than 1/3 of afinia's cost.
2. I want to experiment with printing PET and PC plastics (Afiniah prints only abs and pla)
3. Be able to tweak the system and get a better understanding of its behavior.

I have a few questions, asking for your opinions/advice:

1. I found this kit here:
[mixshop.com]
Which mentions that the printed parts are not included. Does it mean that i will have to print the plastic parts in another
printer, or will the assembled kit be able to print the parts itself ?

2. For printing using high temperature plastics such as Polycarbonate and PET, what kind of hotend would you recommend ? Would i be able to use the same hot-end for lower temperature plastics ? Are there any other considerations besides the hot-end that i need ? can i use the same extrusion motor ?
I've noticed that the mixshop kit comes with Wade's Geared Extruder, would that work for high temp stuff ?

3. In terms of tools - i have basic tools like screwdrivers, dremel, saw and stuff, but no real machine shop (no mills or drill presses) - will i be able to assemble the kit given these constraints ?

An overall word of advice would be appreciated - at the current level of maturity for the prusa, and given that i have the afinia to back me up (if i need to print a plastic part) , should i be able to assemble this and have it printing say within 3-4 days or so ?

Kind regards,
Lenny

Ahh, PET! Good luck finding PET plastic welding rod! I am also considering this material because of its superb characteristics, but finding filament is rather difficult, to be honest.

1. "Printed parts not included" means that you have to print them before you can assemble the printer, so no problem since you already have a printer.

2. You definitely need an all-metal hot end. There are currently a few different choices:
- E3D Hot End (one of the cheapest I could find). The developers post their progress very frequently in this forum (look for SanjayM) and are very responsive to questions.
- Heaterbarrel V3 by Stoffel15. He also frequents this forum, but is more active in the German sub-forum. Development is also progressing at a steady rate.
- PrusaNozzle by Josef Prusa. A very hyped hot end. There are a lot of pictures floating around the web, but I have not seen development progress as detailed as from the other two hot ends (but then again, Prusa seems to be active on Google+ which I don't use at all, so maybe I have missed progress because of that).
- Magma Hot End by Trinitylabs. Have not heard much from this mainly due to them being located in the USA and me sitting in Europe. I am a little bit reluctant to buy from American shops due to increased shipping costs, but since RepRap discount (Chinese, with very good reputation and blazing fast, cheap shipping) also carries them now, this may be a very viable choice.

Other than an all-metal hot end, you don't have to change anything about the hardware.

3. You only need basic tools like screwdrivers, wrenches and maybe a drill (Dremel will also do the job).

The Prusa Mendel is quite mature in development, but a new generation of printers like the Prusa i3, Mendel90 etc. are already slowly replacing this older design. The main drawback of the Prusa Mendel is that at certain speeds and Z heights, it tends to shake itself up, which doesn't happen as drastically with the newer designs since they are much more sturdy. Being able to print your first object within 3-4 days seems like a reasonable time frame. We have built 10 Mendel90's with art students who were absolutely new to 3D printing and they got them running within 4 or 5 days.

Could any of the current pellets(/scrap?)-to-filament machines handle PET? Think i wouldnt recycle my bottles that way though, get too much money giving them back to the supermarket

I think if you shred the bottle a little bit before feeding it into the hopper, it might work.

uGen, thanks very much for your detailed reply.
As for your process with the 10 mendel90s ,

I am kind of hopping to do something similar with highschool students (in oakaland,ca).

Would you mind sharing where did you buy the kit ?
We are based in the US (california) and ordering it all the way from europe means +15/20% because of shipping)

Also, was there a specific step-by-step process you were following ? I am trying to make it somewhat structured,
and i have found this :
[reprap.org]

Thanks again for any advice,
Lenny

There are better instructions here: [github.com] but they are for the Dibond kit version that I sell. The instructions in the wiki are an older version of the machine.

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[www.hydraraptor.blogspot.com]

Thanks Nophead,
Just sent you a gmail message about the kit you are selling.

Looking forward for your reply.

Kind regards,
Arie

@Lenny: we sourced the parts ourselves. Most of the electronics were from ReprapWorld.com and a local electronics supplier. The MDF frame was milled out in a workshop in art school and the plastic parts printed on our own Mendel90, so this approach doesn't seem to be very transferable to you.

Also, we pretty much taught the students with our own build experience and printer as a template.

Sourcing electronics in the US shouldn't be a problem and the frame can also be manufactured by hand (there are drilling templates on github if I remember correctly). Alternatively, US-based SeeMeCNC is selling laser cut Prusa i3 frames (which should be roughly comparable with the Mendel90) and the electronics to boot.

You will have a very rough time extruding PET with a filament extruder. I've been trying off and on for a few months to get my filament extruder to handle it. Higher temps than ABS, at extruding temp PET is like a syrup and drops off from the extruder nozzle from it's own weight.

I haven't found anyone printing with PET, or successfully making PET filament with a home extruder. No sources for PET pellets or flakes, and no commercial suppliers of PET filament.

PLA does that when it too hot. What happens if you lower the temperature a bit?

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[www.hydraraptor.blogspot.com]

It's a fine balancing point on temperature. Too low and it barely extrudes and the output is cloudy, or hot syrup. It has to be aggressively cooled coming out of the nozzle, and requires a filament puller setup to get anything close to consistent filament diameter. I have extruded several unusable meters of it.

I think I can get it, eventually. I have searched alot on PET extrusion, but haven't found anyone that has done it successfully at home.

Sounds like it could be used for extremely thin layers like PLA...

You could look for PET plastic welding rods. *Tadaa~* (Yes, it's a little bit oversized, but here is another supplier with true 3mm rods from Australia.)

$87.95 a lb. is pretty pricey for such a commonly used plastic.

Edited 1 time(s). Last edit at 05/11/2013 03:14PM by Dirty Steve.

PET gets melted at 260 celcius degree therefore, gonna be a bit hard to get such high temp. thats it. Unless you design a better fuser to get over such technical temp in this order.
best regards!

I am printing PET from [www.plastic2print.com] with no problems [merlin-hotend.de]

I can print PET at 220C on my Mendel90 no probs.

Yes its curious because I print ABS at 250C on PET tape and it doesn't melt but when I tried printing it on a sheet of PET it did. Seems there are different sorts of PET.I Think PET tape is actually BOPET (Biaxially oriented), which makes it stronger and perhaps raises the melting point.

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[www.hydraraptor.blogspot.com]

"To my great surprise. In a nearby store for gardeners I discovered rod of 1.8 mm PET. It was a rod for trellising vines."
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