Wallace G1

Parts for this section

  • Plastic parts:
    • Extruder Block
    • Idler Block
    • Push-on pinion
    • Big gear
  • M8 x 40mm hobbed bolt
  • 3x 608zz bearnings
  • 3x M8 washers
  • M8 nut
  • M8 x 30mm Idler bar (cut 8mm smooth rod)
  • M3 nut
  • 5x M3 x 10mm screws
  • 3x M3 washers
  • 4x M4 x 25mm screws
  • 4x M4 nuts
  • M5 x 45mm screw
  • M5 rubber washer
  • M5 nut
  • M5 wingnut 
  • Kapton tape
  • J-Head MK V-BV hotend kit (partlially assembled):
           - cooling cylinder
           - brass nozzle (0.50mm dia.)
           - brass heating block
           - Heat resistor (heating element)
           - Thermistor
           - PFTE tube for thermistor leads (wires)
           - PFTE tube for heat resistor leads (wires)
           - PFTE tube to guide filament into hot end
Take the "push-on pinion" plastic part , and insert the M3 nut sideways into the hole on the top of the "push-on pinion" so that it's completely inserted and flush with the top. Then insert an M3 x 10mm screw in the hole on the side of the pinion and tighten it slightly so that it holds in place. Don't over tighten it as it will block the hole on the top of the pinion and prevent you from inserting the shaft of the Nema 17 stepper motor later.
The idler bar in this picture is too long
The Extruder
 
This is the device that takes the filament, heats it, and then places it exactly where needed to make your 3D print. It's main parts are:
 
  • The hot end                    ... melts the plastic 
  • The extruder                  ... grabs filament from the spool and pushes to hot end 
  • The mounting                ... holds the extruder and hot end in place
 
 
Once assembled.
Insert the shaft of the Nema 17 stepper motor into the hole in the top of the pinion. Nw tighten the screw on the side to fasten the shaft to the pinion. This way when the shaft turns it will turn the pinion even if there's resistance on the pinion.
Insert the M8 nut into the hexagonal shaped hole in the center of the "big gear" plastic part.
Now place a 608zz bearing in the middle of the "idler block" plastic part. Once in place, insert the 8mm x 30mm idler bar through the center of the 608zz bearing.
In this picture the idler bar is too long. When it's the correct size, it should be flush with both sides of the "idler block".
You can make an 8mm x 30mm idler bar by cutting a 30mm length of an 8mm diameter smooth rod.
Place the "extruder block" plastic part on the assembled Nema 17 stepper motor pinion assembly. Fasten the "extruder block" to the Nema 17 stepper motor by inserting the four M3 x 10mm screws through four M3 washers and through the "extruder block" holes and then into the small holes in the corners of the stepper motors and tighten.
Next, place two 608zz bearnings on each side of the "extruder block".
The M8 x 40mm hobbed bolt goes through the 608zz bearings and the "extruder block" such that the hobbed section of the M8 bolt will be in the center of the opening in the "extruder block". 
Place three M8 washers on the foot of the M8 hobbed bolt and leave them loose.
Place the "big gear" plastic part with the M8 nut that was inserted on the foot of the M8 hobbed bolt and screw it tight.
Side view of the mounted "extruder block"
A view from a different vantage point,
Place the "big gear" plastic part with the M8 nut that was inserted on the foot of the M8 hobbed bolt and screw it tight.
When looking at idler block assembly you will see that one end has a curved profile while the other has a hole for a screw. Slide the curved side into the corresponding extruder block assembly that you just completed.
Once again the idler bar is way to long in this picture.
Once it's correctly in place, the combined idler block and extruder block assembly looks like this.
You can see a hole on the top of the idler block, that's where the M5 x 45mm screw  needs to be inserted. Speficially the foot of the screw will exit from this hole. The role of this screw is to pull the 608zz bearing in the idler block against the M8 hobbed bolt and squeeze the filament that passes in between. By squeezing the filament, the etched grooves in the M8 hobbed bolt will grip the filament and pull it through the extruder and into the hotend.
So, you can now insert the M5 x 45mm screw in the hole on the extruder block side and tighten the M5 nut as the M5 x 45mm screw exits the extruder block. From the left you cna see the head of the M5 x 45mm screw and red plastic and then the side of the M5 nut. Once the nut has been tightened, it will hold the screw firmly in place.
As the M5 nut is tightened, the M5 x 45mm screw's foot will go through the hole in the idler block. As it exits the idler block, place the M5 rubber washer and place the M5 wing nut on the foot of the screw as see on the picture.
When you tighten the M5 wing nut, it forces the 608zz bearing in the idler block into the opening in the extruder block and applies pressure against the filament. The filament gets squeezed between the 608zz bearing and the M8 hobbed bolt to form a grip.
Here's the assembly from a different view.

Hotend 

Extruder assembly

Since the J-Head hotend is partially assembled, here's a close-up of the brass parts.
The heat resistor is the item that looks like a big grey resistor. It's job is to heat the heat block. It's a heating element: the more power you send to it, the hotter it gets.
Gather the J-Head MK V-BV hotend kit which contains:
  • Brass nozzle         (screws in heating block)
  • Brass heating block
  • Cooling tower      (beige in the picture)
  • Heat resistor        (heating element)
  • Thermistor           (tiny thermometer)
  • PTFE linner           (helps guide filament)
  • PFTE tube             (to insulate the leads from heat resistor and thermistor)
Heat Resistor goes here
Brass nozzle
Heating
Block
Now insert the PTFE liner in the top of the J-heat hotend. 
Cut 2 lengths of PFTE tube that's the appropriate diameter to slide onto the leads (metal wires coming out of) the heat resistor. Cut a lenght that's a little shorter than the leads to allow soldering or otherwise connecting wires to them.
Next, insert the heat resistor in the hole in the brass heating block. Fitting in the parts is simply, but it is important to minimize the space or air between the heat resistor and the heating block. If its too lose, then wrap the heat resistor in aluminium foil before inserting in heating block. The foil conducts the heat from the heat resistor to the heating block.
If you looks closely at the heating block, one of the sides will have a very small hole. This is where you will insert the thermistor. The thermistor is a special type of resistor who's resistance level in ohms changes as it get warmer. The 3D printing software has a table that maps resistance levels to tempuratures, so the thermistor acts as a thermometer in the hotend for the 3D printer.
The thermistor is fragile, the head is a very small glass bead that can easily break if you pull the two leads appart with too much strength.
Since building the first printer we've come across a much better way of working with thermistor. You can get much greater details in the extruder section of the Neptune 500 project.
Take the thermistor and gently spread the leads, and fold a small section near the head.
The two M4 x 25mm screws and two M4 nuts will be inserted in two holes in the extruder block to attached and fasten the assembled extruder to the X - Carriage on the 3D printer.
The blue circles on the pictures above and below indicate the position where the M4 x 25mm screws go.
Congrats ... another stage is complete.
Now that they hotend is assembled, you can insert the top part of the hotend into the bottom part of the extruder assembly. You will notice that the top of the j-head cooling tower (beige part) has a ring around the top, then a narrower part, and then a wider diameter again. This narrower part allows the extruder block to the hotend.
Once inserted, then you can tinsert and tighten two M4 x 25mm screws in the holes in the extruder assembly indicated by the green arrows. These will hold the hotend in place.
The insert the thermistor in the little hole in the heating block. The thermistor is very small an finky, but critical to your printer. Make sure the small wires aren't crossed (short circuit) as that will give a false reading that tempurature is very high. You should look to tape in in place using Kapton tape. This tape won't burn as the tempurature of the heating block rises.
Attache a wire to each of the thermistor's leads. Then cut a rectangular piece of kapton tape. Carefully place the thermistor and wires on half of the rectangular piece kapton along its length. Fold the tape onto itself to seal everything shut. 
The nice thing about the kapton tape is that you can see through it very well and you can make sure that there's no contact between the leads at near the head of the thermistor, and everything is held firmly in place.