No lathe Plumstruder

Outdated now.

I'm going to cover the construction of a hotend made of common, readily available materials that requires no special tools to build. It uses Nopheads vitreous enamel resistor heater design to provide stable temperatures and is based on his Plumstruder which as of his post had printed 101 Mendels in 7 months without any issues (other than redrilling 0.5mm hole) and is still going 5 months later. I provide multiple options for most of the parts and construction in the hopes you will be able to build a reliable extruder without having to order any speciality parts.

extruded 12lbs of PLA so far without problem

Please note I am currently constructing multiple variations for testing and documentation. The instructions are currently incomplete and will change until all variations are complete.

Tools

Hand drill. (cordless or corded)
Vise grips or pliers
Drill bits
Hack saw
File
Utility knife ( optional )
Tap(s) and Die(s) ( optional )
Tube/Pipe cutter ( optional )

Materials

Heater barrel

Requirements
1/4" to 3/8" (6mm to 10mm)  Ideally 5/16" (8mm)
Conducts heat well
Easy to drill/machine

Possible choices
Brass bolt or rod
Copper mig welder contact tip

Brass bolt - Copper mig tip

Available from -
Industrial hardware suppliers.
Hardware stores.
Online

Nozzle

Requirements

Conducts heat well

Easy to drill/machine

Possible choices
Brass acorn nut
Copper mig welder contact tip
Gas jet forums.reprap.org

Brass acorn nut - Copper mig tip - Gas jet

Available from -
Industrial hardware suppliers.
Hardware stores.
Online.

PTFE (teflon)

Requirements

1/2" - 1" ( 12mm - 25mm ) Diameter
1.5" to 2.5" (40mm to 65mm) Length

PTFE (Teflon)

Known combinations
5/8" (16mm) PTFE rod fits 3/4" .065" wall tubing.

Available from -
Industrial hardware suppliers.
RepRap supply companies.
Plastics suppliers.
Online.

Tubing

Requirements
Must fit tightly over your PTFE rod. (if loose you can wrap the rod in teflon plumbers tape) 
1.5" to 2.5" (40mm to 65mm) Length 

Possible choices

Stainless Steel

Copper
Brass

Stainless steel - Copper - Brass

Known combinations
3/4" .065" wall tubing fits 5/8" (16mm) PTFE rod.

Available from -
Hydraulic supply companies.
Industrial hardware suppliers.
Hardware stores.
Plumbing supply stores. 
Online.

Support
Requirements
5/64" (2mm) to 3/16" (5mm)
Rigid but not brittle.
Capable of handling high temperatures.
Does not soften at high temperatures.
Low thermal conductivity. 

Possible choices
Fiberglass PCB material with copper removed
Phenolic (found in some circuit boards and used as an electrical insulator in older devices)
Hardwood
PEEK (hard to find and expensive)

Circuit board - Phenolic - PEEK

Available from -
Industrial hardware suppliers.
Plastics suppliers.
Electronic component suppliers.
Online.

Cap

Requirements
Fits over tubing being used. (loosely)
Dissipates heat well.
Easy to drill/machine.

Possible choices
Brass pipe cap. (used in my first version)
Copper pipe cap.
Brass tube nut for compression fitting. (best choice)

Brass pipe cap - Copper pipe cap - Brass tube nut

Known combinations
For 3/4" .065 tubing
1/2" brass pipe cap with threads removed
3/4" copper pipe cap fits with lots of clearance
5/8" brass tube nut for compression fitting fits with 1/16" clearance all the way around

Available from -
Hydraulic supply companies.
Industrial hardware suppliers.
Hardware stores.
Plumbing supply stores. 
Online.

Heater block

Requirements

Conducts heat well

Easy to drill/machine
Large enough to fit your heater barrel, resistor and thermistor/thermocouple

Possible choices

Aluminium solid stock  (square, rectangular, round, etc)

Brass solid stock  (square, rectangular, round, etc)

Copper solid stock  (square, rectangular, round, etc)

Aluminium - Brass - Copper

 
Available from -
Industrial hardware suppliers.
Metal suppliers.
Scrap metal recyclers.
Online.

Miscellaneous 

Machine screws
Nuts
Heatsink (optional)
L-brackets (optional)
Hose clamp (optional)

Construction

Heater barrel

      This will assume you do not have access to a lathe.

      The process here is similar to an afghan lathe, but requires less equipment and more effort.

  Bolt as barrel

1. Cut off bolt head.
2. Chuck bolt in drill chuck.
3. With the drill spinning file the end of the bolt flat.
4. With a 5/64" (2mm) drill bit between your fingers, carefully try creating a centre divot in the bolt while the drill is spinning.
5. Repeat steps 3 and 4 until you have it perfectly centred. (any imperfection now will be amplified during drilling)
6. With the drill bit in a pair of vise grips begin slowly drilling down the centre of the bolt. (the spinning nature of the work piece helps to keep the hole centred, you will still need to be careful to keep it straight)
7. Enlarge hole by one drill size at a time until you reach 9/64" (3.5mm)

  Mig tip as barrel

1. Chuck mig tip in the drill chuck with the threaded end out.
2. With the drill bit in a pair of vise grips begin slowly drilling down the centre of the tip. (the spinning nature of the work piece helps to keep the hole centred, you will still need to be careful to keep it straight)
3. Enlarge hole by one drill size at a time until you reach 9/64" (3.5mm)
4. Using a die, cut the threads on the threaded end to a total of 3/4" (19mm).
5. Using a die, cut threads on the un-threaded end to a total of 5/16" (8mm).

   Mig tip as barrel and tip

1. Chuck mig tip in the drill chuck with the threaded end out.
2. With the drill bit in a pair of vise grips begin slowly drilling down the centre of the tip. (the spinning nature of the work piece helps to keep the hole centred but you will still need to be very careful to keep it straight) (Be sure to stop 1mm from the end)
3. Enlarge hole by one drill size at a time until you reach 9/64" (3.5mm) diameter. (Be sure to stop 1mm from the end)
4. If using an .026 (0.6mm) tip and your happy with a 0.6mm nozzle you're done.
5. If a smaller tip is wanted you can solder the hole closed around a small diameter piece of stainless (solder doesn't stick to stainless) or using a hammer you can close the end of the copper and re-drill with a 0.25mm to 0.5mm drill bit.

Nozzle

1. Chuck a short length of bolt in the drill chuck with the threaded end out.
2. Thread your acorn nut on the end of the bolt in the drill.
3. With the drill spinning file a small flat on the end of the nut.
4. With a 1/16" (1.5mm) or smaller drill bit between your fingers, carefully try creating a centre divot in the acorn nut while the drill is spinning.
5. Repeat steps 3 and 4 until you have it perfectly centred.
6. With a 0.25mm to 0.5mm drill bit between your fingers carefully drill the hole.
7. With the drill spinning file away the divot left from step 4.
8. Using the largest bit that fits inside the threads of the nut carefully drill out the inside of the nut until the hole drilled in step 6 is 0.5mm deep/long.

Insulator

1. Cut the PTFE rod to length. 1.5" to 2.5" (40mm to 65mm) if required.
2. Cut tubing to same length as your PTFE.
3. Drill a 1/8" (3mm) diameter, 3/8" (10mm) deep pilot hole in centre of one end of the PTFE rod (do not drill any deeper)
4. Enlarge pilot hole to appropriate size for taping to fit your barrel. See tap Chart (do not drill any deeper)
5. Tap hole with appropriate bottoming tap for your barrel. (homemade tap)
6. Insert PTFE in to the tubing.
7. Thread finished heater barrel in to the hole as far as possible.

Support

1. Rough cut support material to 10% larger than tubing. one layer of 3/16" (5mm) or two layers of 5/64" (2mm).
2. Drill same size hole used for insulator in the centre of rough cut disk. 
3. Tap hole the same size as the insulator and barrel.
4. Thread rough cut support(s) onto heater barrel tight against the PTFE.
5. File rough cut support(s) even with tubing. 

Cap
   Pipe cap

1. Drill large hole in centre of cap. 75% the diameter of tubing.
2. File flats on every other corner. 120 degrees apart.
3. Drill holes for set screws on corners using flats for easy starting.
4. See tube nut instructions steps 4 - 7

   Copper pipe cap

1. Drill large hole in centre of cap. 75% the diameter of tubing.
2. Cut length to 5/8" (16mm) if its a lot longer.
3. Drill 6 holes for set screws.  60 degrees apart.
4. See tube nut instructions steps 4 -7

   Tube nut

1. File flats on every other corner. 120 degrees apart.
2. Drill holes for set screws on corners using flats for easy starting.
3. Drill three larger holes 5/16" (8mm) 60 degrees from set screws to reduce weight and improve cooling.
4. Tap holes for set screws ( or use self taping bolts ) 10-32 (M5) or similar.
5. Install set screws.
6. Slide cap over heater barrel, support and tubing. Secure with set screws.
7. Using the barrel as a drill guide, drill through the remaining PTFE with a 9/64" (3.5mm) drill bit.

Its easy to thread the barrel into the 9/64" (3.5mm) hole from this point on due to the pliable nature of PTFE so be careful not to turn the barrel. If you do turn the barrel be sure to thread it back in only as far as it was originally. Then run the drill through the hole again. It is very important that the transition between the barrel and PTFE is smooth.

Heater block

    Square/Rectangular

1. Calculate minimum length. = Barrel diameter + Resistor diameter + 1/4" (6mm)
2. Calculate minimum height. = Resistor diameter + 5/32" (4mm)
3. Calculate minimum width. = Resistor length + 5/64" (2mm)
4. Cut heater block to calculated size.
5. Calculate location for resistor. Resistor diameter / 2 + 5/64" (2mm) = A1
6. Mark location for resistor as per drawing A.
7. Calculate location for barrel. Barrel diameter / 2 + 5/64" (2mm) = A2
8. Mark location for barrel as per drawing A. 

   Round/Hex

1. Calculate minimum diameter. = Barrel diameter + Resistor diameter + 1/4" (6mm)
2. Calculate minimum height. = Resistor diameter + 5/32" (4mm)
3. Cut heater block to calculated size.
4. Calculate location for resistor. Resistor diameter / 2 + 5/64" (2mm) = B1
5. Mark location for resistor as per drawing B.
6. Calculate location for barrel. Barrel diameter / 2 + 5/64" (2mm) = B2
7. Mark location for barrel as per drawing B.

   Threaded

1. Drill hole for barrel as per tap Chart 
2. Tap hole for barrel.
3. Drill resistor hole same diameter as resistor.
4. Drill hole for thermistor as per drawings A or B
5. Drill holes for set screws to hold in resistor and/or thermistor (optional)
6. Tap holes for set screws if used.

   Crimp fit

1. Drill hole for barrel as close to barrel diameter as possible.
2. Cut slot(s) 1
3. Drill resistor hole same diameter as resistor.
4. Cut slot 2 (optional)
5. Drill hole for thermistor as per drawings A or B

Final assembly

    Threaded

1. Install resistor using set screw (do not over tighten)(if loose wrap in foil)
   
2. Install thermistor using set screw (do not over tighten)
3. Thread jam nut on to heater barrel.
4. Thread heater block on to heater barrel leaving 5/16" (8mm) threads sticking out.
   
5. Thread acorn nut nozzle all the way on to heater barrel.
6. Turn heater block back until it just touches the acorn nut nozzle.
7. Tighten jam nut against heater block.

   Press fit

1. Install resistor by crimping slot 2 closed around resistor. OR glue it in using ceramic adhesive (exhaust cement) or high temp silicone.
   
2. Glue thermistor in with ceramic adhesive (exhaust cement) or high temp silicone.
3. Slide heater block over heater barrel leaving 5/16" (8mm) sticking out.
4. Crimp slot(s) 1 closed around heater barrel.
5. Install nozzle if required.