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Why is PEEK needed?

Posted by slang800 
Why is PEEK needed?
January 23, 2011 07:57PM
I am currently designing a wax extruder that is based off of a standard Mendel extruder (http://reprap.org/wiki/Geared_extruder_nozzle), and I was wondering why the PEEK block cannot be replaced with a thinner metal block or PTFE. I realize that PEEK can withstand very high temperatures, insulate well, and remain rigid; however it seems expensive/difficult to buy in comparison to its benefits.
Re: Why is PEEK needed?
January 23, 2011 08:16PM
PTFE will creep and expand, doesn't hold it's shape well at high temperatures, and is so slippery that things (the extruder barrel) have a tendancy to come unscrewed. It's OK for a thermal barrier, but not good for mechanical support.

Metal conducts heat too well - If the top of the barrel gets hot, the filament will start to melt before it goes into the barrel. It's under compression, so when it gets soft it swells and becomes to big to fit in, and the extruder jams.

We need something mechanically strong, that doesn't conduct heat well, and which can withstand the temperatures.

PTFE isn't the only option, of course. See, for instance, this. Stainless steel has a low enough heat conduction that in combination with a heatsink and a fan, we can keep the top end cool enough. There are other options out there as well, of course.


--
I'm building it with Baling Wire
Re: Why is PEEK needed?
January 25, 2011 02:26PM
BakeLite is also useable and cheap, used for saucepan handles.
Re: Why is PEEK needed?
January 26, 2011 05:07AM
Wax extrusion temperature should be quite low (<100C). It's very low compared to 220C for ABS extrusion. So there is probably no need for PEEK/PTFE. For example some Extralon should be fine (http://www.azom.com/Details.asp?ArticleID=4099). Even some epoxies should be fine.

I'll be much more woried with wax thermal properties. It shrinks a lot when solidifying, it has high thermal capacity and heat of fusion. I did make some simple wax moulds some time ago and it was quite a headache to get acceptable results... Maybe mixing wax with LDPE may help a bit ...
Re: Why is PEEK needed?
January 27, 2011 04:41AM
Grogyan Wrote:
-------------------------------------------------------
> BakeLite is also useable and cheap, used for
> saucepan handles.

Also called Tufnol, not done any tests, but the highest temperature grade I can find is 6g/92 which is rated for 250C.

Doesn't seem to be widely available though.
Re: Why is PEEK needed?
January 28, 2011 02:06PM
BakeLite is resistant to much higher temps.

For my reprap I bought a frying pan and turned its handle (bakelite) into a thermal break.

Initial tests included using a naked butane torch flame on the plastic, no deformation.

Edited 1 time(s). Last edit at 01/28/2011 04:40PM by Grogyan.
Re: Why is PEEK needed?
January 30, 2011 08:42AM
I have come across this material.

[uk.rs-online.com]

[docs-europe.electrocomponents.com]

It is a machinable ceramic that can withstand a continuous temperature of 800C! It is expensive of course but you would get more than one out of a rod. I could easily machine thin on my lath to make a super high temperature barrier. Have not machined this before but I have made things out of all sorts of materials and have a lot of experience in machining so am confident I would have no problem.

When I build my Mendel I may give this a go if I have any trouble with the available options.

If anybody wants one machined out of then then if you buy it and get it to me I will do it for you. Just provide detailed plans.
VDX
Re: Why is PEEK needed?
January 30, 2011 11:52AM
... i've successfully tested with milling and using Macor, but as it's really expensive, i searched a cheaper substitution and found soapstone (or limestone) even better, if you selsct the high-density grades used for tiles or ovens.

Search in the forum for this words with 'all dates' set - there are some discussions and samples ...


Viktor
Re: Why is PEEK needed?
January 30, 2011 01:12PM
Look at the thermal conductivity of ceramic compared to PEEK. I think it is about 10 times higher. That would mean using a a heatsink. Also I think you would need to line it with something slippery like PTFE.


[www.hydraraptor.blogspot.com]
Re: Why is PEEK needed?
June 11, 2011 09:01PM
nophead Wrote:
-------------------------------------------------------
> Look at the thermal conductivity of ceramic
> compared to PEEK. I think it is about 10 times
> higher. That would mean using a a heatsink. Also I
> think you would need to line it with something
> slippery like PTFE.

[www.makeitfrom.com] shows MACOR at 7.3 times the thermal conductivity of PEEK

[www.makeitfrom.com] shows Limestone at 10.5 times the thermal conductivity of PEEK.

Still, the higher maximum temperature of both could be an advantage when dealing with a runaway heater.
Re: Why is PEEK needed?
June 11, 2011 09:18PM
I came across this as well, but again, the manufacturer hasn't made it into the 21st century from an internet sales standpoint, so I have no idea how expensive (or inexpensive) it is.

[www.crystexcomposites.com]

[www.crystexllc.com]

With a thermal conductivity of .64, it's only 3.2 times that of PEEK. It's also moldable, so I could picture casting it directly onto (or into) the heater block, and casting the PTFE liner directly into it - eliminating any worries about leakage around the joins.

[edit]

I finally got a reply to my emails to crystallex - apparenty they don't sell their moldable ceramic in moldable form, but instead mold it for you. It also looks like the price for their machinable ceramics put them way out of reach for use here.

Edited 1 time(s). Last edit at 06/22/2011 12:49PM by raldrich.
Re: Why is PEEK needed?
August 01, 2011 02:42PM
I was wondering if a stack of blank copper clad boards ( FR4 ) could be used as a insulator /heat sink, simple to machine and made to tight tolerances

CS
Re: Why is PEEK needed?
August 01, 2011 03:27PM
FR4 is only good to 150C.
Re: Why is PEEK needed?
August 11, 2011 09:31PM
Use Wade's Extruder and you can skip the PEEK, because it does not need it. Two screws through the base of the PTFE will sufficiently hold the barrel.
Re: Why is PEEK needed?
August 24, 2011 07:20AM
The PEEK block is there to secure the nozzle to the PTFE or PEEK insulator also. If the insulator is PTFE, then it's necessary. If the insulator is PEEK and threaded instead of push-fitted, perhaps the PEEK block is not really needed.
Re: Why is PEEK needed?
September 05, 2011 10:07AM
I have not been using Peek for the Clamp part of the extruder for a while now I will post details up on the WIKI shortly the only part that I make out of Peek is the main insulator I will also post drawings of my simplified extruder insulator at the same time..
Its is a non RP extruder so it would be mainly for use on Rep-Straps or in my case Huxley or Modular Seedlings


Bodge It [reprap.org]
=======================================

BIQ Sanguinololu SD LCD board BIQ Stepcon BIQ Opto Endstop
BIQ Heater Block PCB BIQ Extruder Peek clamp replacement BIQ Huxley Seedling
BIQ Sanguinololu mounting BIQ standalone Sanguinololu or Ramps mounting Print It Stick It Cut it


My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]
Re: Why is PEEK needed?
October 14, 2011 10:46AM
Peek is a great temperature plastic. It is expensive but worth because of it's properties like low moisture absorption and resistance to chemicals.
Re: Why is PEEK needed?
December 04, 2011 07:01AM
It seems to me a hardwood like cherry or oak would do well - cheap and easily available in block or rod, low thermal conduction and good heat tolerance.
Re: Why is PEEK needed?
December 04, 2011 10:35PM
billmi Wrote:
-------------------------------------------------------
> It seems to me a hardwood like cherry or oak would
> do well - cheap and easily available in block or
> rod, low thermal conduction and good heat
> tolerance.

TechZone tried that approach - the problem is that oak is shot through with little pores, that allow plastic (Particularly PLA) to permeate the part. Once there, the plastic destroys the thermal characteristics of the oak. Believe me, it's one of those things that sound good on paper, but don't work out nearly as well as you might hope in practice.
Re: Why is PEEK needed?
December 05, 2011 07:16AM
I think we are talking about different parts.

Techzone's kit replaces the PTFE cylinder in an original extruder with a block of oak. I can definitely see how if there is not a seal between their PTFE sleeve and nozzle, that plastic would be injected into pores in oak (though there are plenty of readily available hardwoods that are not porous).

The post that started this thread though, is talking about a PEEK support block used to hold the nozzle, taking the load off the PTFE cylinder from the original extruder design - quite a different application, where porosity shouldn't be an issue. If plastic is going to leak between the nozzle and PTFE, it's going to glob out into open space, not be injected into the wood.
Re: Why is PEEK needed?
December 05, 2011 07:58AM
I don't think any wood handles 240C for prolonged periods. I think it chars eventually, turning to carbon and losing its mechanical properties.

Edited 1 time(s). Last edit at 12/05/2011 07:59AM by nophead.

[www.hydraraptor.blogspot.com]
Re: Why is PEEK needed?
December 05, 2011 08:31AM
So eventually it could be ok for PLA ?

I'm going to try that with bamboo wood one day.

Edited 1 time(s). Last edit at 12/05/2011 08:32AM by DeuxVis.
Re: Why is PEEK needed?
December 05, 2011 09:01AM
Well PLA seems to need about the same temperatures as ABS these days. I got some blue PLA from Faberdashery and at 220C is was struggling to extrude and came out much bigger than the nozzle. At 240C is was much happier.


[www.hydraraptor.blogspot.com]
Re: Why is PEEK needed?
December 06, 2011 07:22AM
That's hot ! My chinese PLA is extrudable at 150 °C - although for a better adhesion to bed I usually go for 170/175 °C

Glad you mentioned it, I just received some faberdashery's PLA - save me some time here thumbs up
Re: Why is PEEK needed?
December 07, 2011 05:04AM
We would recommend running Faberdashery PLA at 210C. If you are printing rapidly, you might want to crank it up to 220C.
It shouldn't be necessary to run at 240C... although we are still in the limits of error for temperature measurement... perhaps? We would never recommend using above 230C. A bed temp of 60C should work great in most instances

It surprises me that the cheap PLA (from China) can be extruded at 150C. Assuming it's the same extrusion grade of Natureworks 4043D, the only explanation is that the material has been degraded, leading to shorter chain lengths with lower MPt.

Cheers.


Faberdashery
Re: Why is PEEK needed?
December 07, 2011 05:31AM
I print all my PLA at 210°C! grinning smiley


Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse
Re: Why is PEEK needed?
December 07, 2011 06:05AM
The first PLA I got from Vik Olliver extruded at about 180C - 200C. Above that it was like Syrup. I then use some from Makerbot and that needed 220-240C but was very similar. A small temperature range between it not extruding and too runny, very little die swell.

The blue from Faberdashery was still very viscous at 220C and gave massive die swell, something I haven't seen with PLA. Even at 250C is didn't turn to syrup. Red seems to like lower temperatures and gets too runny at 240C, so more like Makerbot.

I am pretty sure my temperatures are accurate. I calibrate so that the temperature inside the nozzle matches a thermocouple within a degree or two. People that measure the temperature on the outside may will see lower readings.

@fabersdasher,
Incidentally why is your filament only 2.83mm? I though your web site claimed 3mm +- 0.1mm. Nobody seems to make 3mm filament any more but they all sell it as "3mm". What actual size is "1.75"mm filament?


[www.hydraraptor.blogspot.com]
Re: Why is PEEK needed?
December 07, 2011 06:36AM
I agree, most of my PLA is 2.8mm +/- 0.2mm (most of it bought from grrf.de).


Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse
Re: Why is PEEK needed?
December 07, 2011 07:13AM
nophead Wrote:
-------------------------------------------------------

>
> @fabersdasher,
> Incidentally why is your filament only 2.83mm? I
> though your web site claimed 3mm +- 0.1mm. Nobody
> seems to make 3mm filament any more but they all
> sell it as "3mm". What actual size is "1.75"mm
> filament?

All the people - like me - using a bowden cable setup are happy to get sure the filament is always under 3mm, even with variations along the spool, I think it's one of the reasons why.
this said, agreed that it might be nice to mention it in the product description, then.
Re: Why is PEEK needed?
December 07, 2011 07:44AM
This is really annoying! People like my who built their extruders back in the day when 3mm was 3mm+/- now find all the filament available is too small.

Does anybody know of a company that sells 3mm filament that is actually 3mm!


[www.hydraraptor.blogspot.com]
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