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Combination CNC Machine and 3D Printer

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Step 17: 2BEIGH3 3D Printer Hot-End

Picture of 2BEIGH3 3D Printer Hot-End
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The 2BEIGH3 hot-end is designed for quick replacement or swap out from job to job.  Just 2 screws mount the device to the Z Axis board.  The Heater connects with standard electrical spade lugs and the thermocouple uses one of the support 6/32 threaded rods.  Because there are minor differences, you'll need to re-zero your Z Axis.

The 2BEIGH3 uses two tip types.
The first is the lower resolution tip.  This is a .023" mig welding tip. See http://www.thingiverse.com/thing:7814
The small aluminum block is tapped to 1/4 - 28....there we go....knew we'd use that  1/4 28!
The mig welding tip is drilled out with a 1/8" bit to about .200" from the tip.
The white cylinders are the Teflon/PTFE tubes we ordered.  One inside the other.

  Careful with ABS
While this hot end is designed for NYLON, it can have issues you need to watch for with ABS.
ABS changes states much faster than NYLON, and when you use ABS with this hot-end, you must not let the ABS idle in the hot end as it will tend to pool inside and the extruded material will start to vary in thickness/dia.  What this means is that you should always retract a few mm's of ABS or PLA material while preparing for the next print.
I typically have a 1/8" tube blowing cool air on the lower section of the white cylinder where it meets the aluminum to keep ABS from pooling.

High Resolution Nozzle
The second Hot-end nozzle is a higher resolution unit that you may already have in your tool drawer.  I have a free handful from a vendor as it had his LOGO on it.....A pocket oiler
It is made of aluminum
It is threaded
It has a 0.5mm ID that we can roll to a smaller ID
It's cheap
They're everywhere.  Even Amazon has ump-teen flavors.
(Of course you need one like in my photo, not an all plastic oiler)

Since I got my printer up and running, I have been printing parts for work and friends.....it's almost always printing or cutting!   The 2BEIGH3 can print a 55 degree undercut, but starts to drop threads after that.  So you have to design with restraints in mind.  More on that later.

BOM
1 each         1/2 OD x 1/4 " ID Teflon/PTFE Tube - each hot-end needs about 4"  MMC PN 8547K31
1 each         1/4" OD x 1/8" ID Teflon/PTFE Tube - each hot-end needs about 5"  MMC PN 8547K23
1 each         #8 washer
1 each         Coupler MMC PN 51215K106 or any HW Store
4'                   3/8 neopreme tubing (Plumbing Section of your HW Store) Cut to fit your installation.
1 each         #6/32  x 24" threaded rod
4 each           6/32 nuts
1 each           120 volt heater cartridge MM Carr PN 3618K119
1 each           aluminum block  Cut from MMC PN 6023K291 -
                       Multipurpose Anodized Aluminum (Alloy 6061) 3/8" Thick X 2" Width, 1' Length
1 each           0.023" mig welding tip - Harbor Freight  $10 for 5 pc's
2 each           male 1/4" spade terminals for #16 awg wire
1 each          ring terminal for the thermocouple
1 each           Delrin 1" x 1" x 4+ "   MM Carr PN 8739K92  each hot-end needs about 4"
1 each           1-2 amp 120 volt Light Dimmer
                       The Heater cartridge draws .56 Amps at 120 volts and a nominal 300ma at the printing temp
                        It is still not a light bulb, so we need a good Light Dimmer capable of 1+ amps.
                         The Heater cartridge is isolated  and CSA approved but you still need to use covered Spade terminals for Safety.
NOTE: As to PTFE or as the rest of us know it “Teflon Non-Stick Coating for cooking utensils” is of course the famous Dupont coating used by millions for cooking. As any inventor or designer wants those that duplicate his efforts to be safe, I’ll take a few lines to explain where concerns originate.
Since it’s invention back in 1938, there has been something known as the “Teflon Controversy”.  And to this day it is taught in colleges and universities.  A Google search on the term “Teflon Controversy” will provide you a wealth of insight.
As for an in-depth and scientific description of Teflon Non-Stick Coating for cooking utensils, this site is a good start.
http://en.wikipedia.org/wiki/Polytetrafluoroethylene
As the author of this instructable and the designer of the 2BEIGH3, I am not a polymer specialist and can not speak for Teflon Non-Stick Coating or as some refer to it PTFE.
I can however, define the usage of Teflon in the actual 3D NYLON printing process.
1. While the heater cartridge can reach temperatures as noted 600F, this is not the actual printing temperature, as NYLON would boil at that value.
2. The actual temperature at print time is about 20 – 25 degrees above that of ABS.
3. The circular area of the Teflon Non-Stick Coating that comes in contact with heat is ½ inch”,  12mm dia. Or about 1/1000 of an
average frying pan.
4. The temperature at the point of contact on the hot-end is about 10 to 20 degrees higher than most people cook their meats but
certainly not as hot as an unattended frying pan left on the stove-top.
Again, this author respects and appreciates everyone's comments.

Assembly
Cut/Saw and Drill the Delrin per the print
Cut and Drill the Aluminum per the print
NOTE: The ID of the larger tube is slightly smaller than the OD of the smaller tube.  After you have cut to length, place the larger tube in a vice or clamp and run a 1/4" drill through it's center.  We want a snug fit, so don't go larger than 1/4.  Otherwise hot plastic will find a way between the two tubes and as it expands a bit will start to limit the smooth flow of material to the aluminum block.
Chamfer the Top outside edge of the 1/2" tube so it's meets snug with the delrin.
Chamfer the bottom outside edge of the 1/4" tube so it'll sit guided into the top of the 1/4-28 hole.
    Note, this is where your plastic and NYLON will leak if there's not a good pressure seal.  The design is such that as you screw in the top connector, it will push the 1/4 PTFE rod down and apply pressure to the chamfered end.  This is not fixed, as the PTFE will expand the first time we heat it up.  If you notice leaking around the 1/2" tube and aluminum block, tighten the connector to apply more pressure to the inner tube.  The washer keeps the inner tube from sliding up into the connector.
You'll need to tap threads into the top of the Delrin block.  This is an "NPT" thread.  As Delrin is easy to Tap, and Tap's are expensive, you can do as I did.   Just take a old peice of 1/2" pipe and use your dremel to cut about 12-14 slots in the threads as shown.  Works great!  Again, time vs money.
Wrap three turns of Teflon tape around the threads of the mig tip.
You will need to drill with a 1/8" bit into the mig tip to about .2" from the tip
Use a sharp bit.
Use a very slow speed on your varible speed drill.  The metal is very soft.
Use oil...then use more oil.  10W 30 works great.
The drill process will push some of the metal out the tip.  Pull it out .
The 0.023 hole will still be clogged.
Use a 1/16 drill bit and just tap the bottom of the drilled hole....like you were going to complete the hole with a smaller bit.
DO NOT push something from the tip in.....Take a small wire and push from the inside (where you drilled) out and the shavings will come out the tip.  Use compressed air to blow out any other flecks of metal.  If it won't open up, tap it with the 1/16 bit again.

Crimp the Spade terminals to the heater cartridge wires.  Do not solder as at 320c, they'll come UN-soldered.
Screw the tip into the aluminum block - tight.  Be careful not to strip the tapped hole.  The goal is for the heater cartridge, to heat the alum and therefore the tip.  Measure and cut your threaded rod, install the thermocouple and you're good to go.

The threaded rods are in my photos slightly bent.  This is due to an earlier insulator design that wouldn't hold up to the mechanical stress.  And rather than cut new rods, I just bent these into position.

As to the light dimmer, it was to get us up and printing, but of course we'll want a more accurate way of maintaining temperature.
I suggest  using a standard industrial PID controller.  There are several on EBay for about $20.00 or so.
Below is a photo and wires labled so you can see how one is connected.  These always lack "how to" info.
This uses a "K" thermocouple.  It will come with a fancy plug, but cut it off and simply cross the two wires.  Where they cross the first point....that's where they sense.  This means you can twist the wire a few turns, but only the first "touch" is sensed.



 
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ampeyro2 years ago
does your nylon extruder use ptfe parts?
i'm building one and i'm woried about the ptfe melting if i set it hot enough to melt the nylon