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Extruder Bits

Posted by Grogyan 
Extruder Bits
September 01, 2009 03:34AM
Just visited a CNC machinist today, gave them some drawings for extruder parts to get a price quote, I did submit the drawings to another company, Swages, their quoted prices were quite high for the nozzles, and fair for the barrel and thermal barrier.
Just got to send out the drawings to another place for another set of quotes.

After I got the quote from Swages, the quotes for the nozzles were probably so very high because the design I have, called for having text cut into the nozzle for easy identification of nozzle size, the quote request to Redwoods has the text removed.

I'm getting nozzles made with hole sizes, 0.5, 0.3 and 0.2mm.

Redwoods nearly had a fit when they saw that 0.2, but they reckon they could do it.
Will be hilarious to see a business' reaction when we finally ask them to drill a 0.1mm hole when a future RepRap design calls for it.

If, IF, they quotes are still high, i'll specify the use of a dome nut instead, that should, in theory bring the cost down.

I'll be getting 5 made, most of which i'll be donating to Vik, as he and Tim from MindKits want to try and setup a set of RepRap kits here in NZ, and these will be samples, when they do want to go for volume, they'll have all the info they need.

The biggest difference between what I have done to what is specified in the dxf drawings on the repository, is that the PTFE barrier will have flats machined into them to enable the tightening of the heater barrel to the thermal barrier and the nozzle. The flats also serve another purpose, that is all the wires that lead to the barrel can be cable tied to it, to keep everything tidy.
The barrel now has a specified chamfer angle on the edges of the heater barrel, to reduce the space between the barrel and the bottom of the thermal barrier and nozzle.
The whole assembly will also include an M6 flat washer, the reason for this is to enable the removal of the nozzle so that a smaller or larger or even a different nozzle size can be easily switched without needing a whole new extruder assembly.

As always the drawings will be made available to everyone. I've spent considerable amount of time over the last 2-3 weeks writing up drawings for the extruder bits and bits for my z axis, and one thing you'll notice straight off is the large amount of declared dimensions, this is critical to pass any design off to a machining company to reduce any chance of errors, which reminds me, i've got to specify tolerances on the drawings.

Sorry for the huge long post, just a lot has happened in the last week or two.
Re: Extruder Bits
September 11, 2009 11:23AM

Very interesting Project, but I think you will get pressure problems or will have to run very slow so that build times will increase significantly.

Please do not forget that a saller amount of Material devivers low heat energy to melt up the lane below an get stable merge state.

Maybe you can support with a very low speeded piped fan workin near the melting poit of your material to help the process.

You could also work with more heat on the Extruder to make the ABS more fluid, but be aware of not overheating the ABS.

Quite a tricky job.

My wish would be a solenoid-closed 0.1mm extruder-head and an implementation to the construction/controller.
Re: Extruder Bits
September 16, 2009 01:02AM
The 0.2mm will form the outside wall, where the infill would be 0.5mm.

Doing that would allow good tolerance on precision gears, which is still a problem on the current nozzle diameter that is in general use.
Re: Extruder Bits
September 28, 2009 05:16AM
I think there is an inverse mathematical relationship between the size of the machine's motors versus the size of the motor driving the extruder.yawning smiley
Re: Extruder Bits
October 06, 2009 12:10AM
I dunno about that statement grael, i've got no experience on that.

Well I think I can give an update of where I am at.
Bank statement came today, and the result is that I am unlikely to be able to buy any extruder bits this month, or anything else for that matter.

But one thing that I have read up on is it seems that PEEK with a max operating temperature of ~300 degrees C is far more robust than PTFE in terms of thermal creep and rigidity, so i'll change that in the drawing i've done, also I reckon i'll move the flats a bit so that they lay above the heater barrel, this should give extra strength while still be able to tighten everything with spanners
Re: Extruder Bits
July 08, 2010 01:55AM
How about using motor bike carburator jets.
The main jets for most dirtbikes looks quite like the nozzles being used and are readily available in small increments in the smaller sizes

Re: Extruder Bits
July 09, 2010 06:03PM
I have 2x old nozzles out of a dimension machine if you wanted one to reverse engineer or look at, you are most welcome (only hope i can still find them in my garage) let me know.
I think you will struggle to get anyone in NZ to conventionally machine anything smaller than a 0.4mm nozzle on an ongoing basis. The reason i suggest 0.4mm as a practical limit is that from my limited CNC mill knowledge the smallest common diameter of end mill/drill bit is 0.4mm.
Using some sort of jet out of a carbie or injector nozzle would be a great idea to look at further.

regards Andrew
Re: Extruder Bits
July 13, 2010 04:08AM
I bought a few nozzles from MakerBot as I had to justify the shipping cost of fiberglass coated nichrome wire.

I have a couple spare now, bought 3.

Later on I think i'll get my extruder bits from MakerGear.
Considering i've had my extruder up and over 300 degrees C, both PEEK and PTFE turn jello at 250, where my thermal break is BakeLite.

Here is a tip rather than forking out lots of cask for decent thermal break, buy a frying PAN and use a lathe to turn it down into a thermal break, that plastic handle is usually made out of BakeLite, but sometimes called "Cool to touch" which is the same thing.

Main thing here is to bug Tim Carr to stock fiberglass coated Nichrome wire (this is the most important), and maybe the barrel and nozzles too, right now he is spending a lot of time with his munchkin.
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