V1.0 (10 Jul 2012)

Document Version & Date: V1.0 10 Jul 2012

Goal: Provide a visual guide of the steps needed to construct a Romscraj Extruder.

Original Authors:Md Noh – design of the Romscraj Extruder

Special Mention:The design of the Romscraj Extruder has been made possible by ideas, concepts, designs and good work by:

Wade Bortz (Wade's Geared Extruder)Adrian Bowyer (Adrian's Geared Extruder)

Author of this Document: Md Noh

STL Model Files: https://github.com/romscraj/romscraj-extruder

Sketchup Model Credits:

Below are the Credits for the Sketchup models from 3D Warehouse(sketchup.google.com/3dwarehouse/), modified for use in this documentation where necessary, and are used in accordance to the Google 3D Warehouse - Terms of Service as of June 2012 under Section 11.1, Subsection (c):

- 'Retractable hobby knife' by J-m@nhttp://sketchup.google.com/3dwarehouse/details?mid=59481570acb7a0872d4ba5e1aa44cc40

- 'Premier Prismacolor® Markers' by Jonhttp://sketchup.google.com/3dwarehouse/details?mid=f352190b5a788ecff788b21b3d1cd437

- 'Straight dashed line and arrow, ground' by Googlehttp://sketchup.google.com/3dwarehouse/details?mid=f352190b5a788ecff788b21b3d1cd437

- 'stepper motor - nema 17' by russ_andersonhttp://sketchup.google.com/3dwarehouse/detailsmid=7b5ee9e35f85c343757b961dad12f52

Licensing:

Romscraj Extruder: GPL (http://reprap.org/wiki/GPL)This Document: GFDL (http://www.gnu.org/licenses/fdl.html)

The source files for this document are available at:

https://github.com/romscraj/romscraj-extruder

Issues with this document can be submitted to:romscraj@orangeknob.com

V1.0 (10 Jul 2012)- Initial version.

1x extruder-block 1x 53-tooth-driven-gear

1x idler-block 1x 9-tooth-drive gear

Note: Part drawings not shown to scale.

Quantity Description Remarks

1 M3 hex nut

6 M3 nylon flat washer (1mm thick) Used as insulating washers.

4 M3x10 bolt Socket Cap head recommended

1 M3x6 brass machine screw Pan head recommended.

1 M3x10 set screw / grub screw

1 M3 aluminium flat washer (large OD) 10mm OD

1 M3 silicone flat washer (large OD) 10mm OD, 2mm thick

6 M4 hex nut

2 M4 nyloc nut

12 M4 flat washer

1 M4 wing nut

1 M4x15 set screw

4 M4x45 hex head bolt

1 M4x50 bolt Stainless steel material recommended

2 M8 hex thin nut / jam nut 4mm thickness

3 624 ball bearing Typically 624ZZ

It is recommended to procure extra quantities of common parts to be on the safe side

Quantity Description Remarks

1 M4 threaded insert 6.5mm OD, 7mm length, with suitable external 'teeth'

1 NEMA 17 bipolar stepper motor + cable

1 Slidemount plate

For drawings, refer to: https://github.com/romscraj/romscraj-extruder

1 Hot end nozzle

1 Heater block

1 Insulator Barrel

1 Teflon tape / thread seal tape 12.7mm (1/2”) width, 50mm length

1 Heating element Typically a power resistor

1 Thermistor Typically an NTC, glass bead type

90mm PTFE (Teflon) tubing 3mm ID x 5mm OD (for use with Ø 3mm filament), 90mm length minimum

100mm PTFE / silicone glass fibre sleeving For insulating leads of hot end components.

1 High-temp glue / epoxy Able to withstand at least 80°C/176 °F. May not be required – refer to Part 1, Step 1.10

- Wires Adequate length to connect heating element and thermistor to printer's electronics

4 4mm ID spring10mm free length, 4 active coils, 25-35N load provided per spring. Extruder may work without these springs but they are recommended.

1 Ziptie Used to affix wires / cables. Minimum quantity 1pc as used in Part X, Step X.X

1 Marker pen Fine tip, permanent.

1 Penknife / box cutter / utility blade With a very sharp blade.

1 2.5mm Allen key For use with M3 socket cap head bolts

1 3mm Allen key For use with M4 socket cap head bolts

2 13mm spanner / wrenchIdeal tool to use for locking together the M8 thin nuts in Part 1, Step 1.5, as well as for tightening the nozzle in Step 1.6

1 Steel rule At least 15cm/6” long

1 Needle Nose / Snipe Nose Pliers

Assortment Files Needle files, plus assorted bastard files.

1 Safety eyewear Your eyes are the windows to your soul. Or something to that effect.

Note: Quantities stated are absolute mimimum requirements – it is recommended to procure extra quantities of common parts to be on the safe side.

Using a very sharp blade, carefully slice away approximately 2mm off only one end the 3mmID x 5mm OD PTFE tubing. The aim is to get a straight and perpendicular cut at the end of the tube. Be careful not to cut off too much tubing or it may end up being too short.

Insert the cut end of the tubing all the way into the filament channel from the underside of the extruder-block. Using a marker pen, mark the PTFE tubing at the point where it just enters the extruder-block.

Remove the PTFE tubing from the extruder-block. Measure the distance between the end of the tubing that was inserted earlier and the mark that was made. Record down this value.

Cut a 10cm length of the teflon (PTFE) tape provided. Take the hot end nozzle and orientate it such that the non-tapered end (the big hole) is facing you. Wrap the teflon tape tightly around the hot end nozzle in a clockwise manner, right at the edge of the non-tapered end. You should be able to wrap approximately four full rounds.

Insert the two M8 thin nuts into the hot end nozzle through the tip end (the end without the teflon tape). Position them near the nozzle tip and tighten them together using tools so that they cannot move.

Wrap the teflon tapein clockwise direction

Insert the cut end (that you have cut in Step 1.1) of the PTFE tubing into the hot end nozzle. Push it in as far as it can go – it should be about 15mm deep. While making sure the PTFE tube remains in the nozzle, insert the free end of the PTFE tube into the insulator barrel through the female M8 threaded end.

Screw in the end of the hot end nozzle with the teflon tape into the insulator barrel as far as it can go using tools. The fit should be tight but be careful not to tighten too excessively. Make sure that the PTFE tubing remains in the hot end nozzle throughout this step and the steps that follow.

Note: If the nozzle feels loose when screwed into the insulator barrel, add more layers of PTFE tape onto the nozzle as per Step 1.4, but this time wrap 5cm lengths at a time until the fit is tight.

Note for kits obtained from romscraj: If you have received your insulator barrel and slidemount plate already attached very firmly together, you need not (and should not) remove the slidemount plate.

Remove the two M8 nuts from the hot end nozzle. Add 10mm to the measurement from Step 1.3. Mark out this new length on the PTFE tubing, measured from the point where the tubing just enters the insulator barrel.

Using a very sharp blade, slice the PTFE tubing at the point you have just marked. Aim to get as straight and perpendicular a cut as possible, but it is very important not to cut off tubing beyond the marked point (i.e making it shorter than the measurement in the previous step), even if the cut is not very straight. Remember to ensure the PTFE tubing does not come out of the nozzle/insulator barrel or your measurement and cut will not be accurate.

(Note for kits obtained from romscraj: If you have received your insulator barrel and slidemount plate already attached very firmly together, skip this step.)

Check that the slidemount plate is able to slide into the groove on the insulator barrel. A little resistance is alright, but if it is too tight to slide in and force is exerted, the slidemount plate may crack or fracture. If the fit is too tight, do not force the parts together, instead carefully file the cut-out on slidemount plate until the fit feels right.

Distance=Measurement from Step 1.3 + 10mm

(Note for kits obtained from romscraj: If you have received your insulator barrel and slidemount plate already attached very firmly together, skip this step.)

Remove the slidemount plate from the insulator barrel. Apply a bead of high-temp glue / epoxy to the top and bottom edges around the cutout on the slidemount plate. Insert the slidemount plate into the insulator barrel, gluing the two parts together. Let the glue dry.

Note: you may also choose not to glue the slidemount plate to the insulator barrel if the fit is tight enough and there is no wobble or freeplay when the two parts are assembled.

Insert the heating element (resistor) into the 5mm diameter hole on the side of the heater block.

If it is too tight to fit, do not force it in as this may damage the resistor's enamel coating and may cause it to short out on contact against the insides of the heater block. Instead, carefully file out the hole to accomodate the resistor.

If the fit is loose, carefully wrap some kapton tape around the resistor body. The fit does not need to be tight at this point – we will address that later on.

(“X-ray” view)

Solder or crimp the hot end components (heating element and thermistor) to the hot end cable.

For kits obtained from romcraj: You may want to refer to the following steps as a guide.

Bend one of the thermistor leads as shown in the picture on the left below. After bending, cut the longer lead so that both the leads are the same length.

Cut two pieces of 1mm ID x 1.4mm OD PTFE tubing (these are the thinnest ones) – 15mm and 20mm long. Insert the tubings into the thermistor leads as shown in the picture on the right.

Bend the black wires of the hot end PTFE cable as shown below.

Cut the 2mm ID x 2.4mm OD PTFE tubing into four equal lengths. Each piece should be approximately 25mm long.

Insert two of the tubings that you have cut from the previous substep into each of the black wires. Solder the black wires to the thermistor leads.

Slide the PTFE tubing over the solder joints to insulate them. Carefully wrap some kapton tape to secure the black wires and PTFE tubings.

Remember to insert the 2mm ID x 2.4mm ODPTFE tubings before soldering the thermistor

Slide the PTFE tubings over thesolder joints to insulate them.

Carefully wrap kapton tape to secure thewires and PTFE tubings together.

Close up image of the thermistor end. Note how the PTFE tubings cover the thermistor leads and insulate them.

This is important to prevent shorting out the resistor against the heater-block.

Trim off the tinned leads on the ends of the red PTFE wires. Strip off and expose approximately 8mm of bare wire.

Cut two pieces of the 1mm ID x 1.4mm OD PTFE tubing – both pieces approximately 20mm long. Insert them into the resistor leads.

Insert the remaining two 2mm ID x 2.4mm OD PTFE tubings you have cut in substep 3 into the red wires.

Twist/wrap the red wires onto the resistor leads and solder the connection.

Slide the PTFE tubing over the solder joints to insulate them.

The completed hot end components so far:

Thread the heater block onto the nozzle. Leave approximately 4mm of exposed threads on the tip end of the nozzle. Insert one M8 thin nut and tighten it against the heater block so that it is unable to move.

Do not thread the heater block higher than necessary – it should be as close to the nozzle tip as possible while allowing just enough threads for the M8 thin nut to be screwed on.

Refer to the pictures on the following page.

(End of Part 1)

M8 thin nut positioned at the very endof the threaded portion of nozzle

Heater block and M8 thin nutpositioned too high up on nozzle.

This will result in printing problems.

(Resistor not shown in picture)

(Resistor not shown in picture)

Insert the M4 brass insert into the bolt. Thread it all the way in and tighten by hand against the other parts inserted earlier. It is important not to use tools as this may damage the 'teeth' on the brass insert. Next, insert 1 nut and tighten it against the brass insert (using a suitable tool for the nut).

Take the M4x50 bolt and insert the following:

1 washer – 1 624 bearing – 1 nut

Thread them all the way in and tighten them well against the bolt head using tools.

Insert the assembled parts into the extruder-block. Note the orientation: with the motor bracket facing away from you, insert the parts into the left bearing cavity until the 624 bearing is seated snugly inside. Refer to the pictures below:

Insert a 624 bearing into the open end of the M4x55 bolt until it fits snugly into the bearing pocket on the right side. Add an M4 washer followed by an M4 nyloc nut and tighten everything together. Note: the M4 nyloc nut will feel tight when being threaded in – use a hex wrench (allen key) and a 7mm wrench or small adjustable wrench (needle-nose pliers will work but not as well).

M4 nyloc nut

Turn the bolt shaft and ensure that it turns without much effort. Ideally the turning action should be very smooth if the bolt is very straight, the bearings and mating faces of the hardware are of high tolerance (very flat and parallel) and the extruder-block bearing pockets hold the bearings absolutely straight. However as the above ideals may not be easy to achieve, some degree of minor intermittent turning resistance is still acceptable – the shaft turns smoothly except for certain points when it encounters slight resistance. This should not affect the operation of the extruder.

In the case that the shaft is unable to turn relatively smoothly, or there is/are intermittent point(s) that feel very tight when turning, loosen the M4 nyloc nut slightly. This allows for more freeplay in the case of alignment problems (which is usually the cause of the turning resistance). Do not loosen the M4 nyloc nut more than necessary.

Insert the four M4x45 hex bolts into the extruder-block. Fasten some tape over the heads of the bolts to prevent them from coming out of the part.

Refer to the pictures on the following page.

Unscrew these two mounting screwsto remove vibration-damping mount

Note: If your motors came with a vibration-damping mount attached, this needs to be removed.

Ensure that the hole in the centre of the 9-tooth-drive-gear matches your motor shaft – it should slide on and fit very snugly. If it is too tight, carefully drill or file the hole.

Remove the 9-tooth-drive-gear from the motor shaft. Insert an M3 nut into the rectangular slot on the bottom of the pulley. You may need to widen the slot slightly to do this. Make sure that the centre of the nut is aligned with the channel in the pulley.

Insert the M3x8 grub screw into the channel on the rim of the hub, screwing it through the M3 nut until you see the end of the screw inside the centre hole, then unscrew it enough to slide the pulley onto the motor shaft.

Insert the pulley onto the motor shaft. Leave a gap of about 1mm between the pulley and the motor body, then tighten the grub screw.

1mm gap

Mount the motor onto the extruder-block using three M3x10 bolts and a total of six M3 nylon washers – place a washer between each bolt head and the extruder-block, and another between the extruder-block and the motor body.

Screw the bolts in to fasten the motor, but leave them loose enough such that you can slide the motor from side to side along the mounting holes.

Take the 53-tooth-driven gear and ensure the hole at the centre is 4mm in diameter – you may need to clean it out with a 4mm drill bit or a file. This is to ensure that it is able to slide into the M4x50 bolt smoothly.

Insert an M4 wing nut into the open end of the M4x50 bolt (with the 'wings' pointing out towards the open end of the bolt). Tighten the wing nut against the other parts on the bolt.

Insert the 53-tooth-driven-gear into the open end of the bolt. Push the rectangular slots on the gear against the wing nut so that the 'wings' of the wing nut is embedded into the gear. The fit should be snug and fairly tight. If it is too tight to fit in, carefully file the insides of the rectangular slots on the 53-tooth-drive-gear. Be careful not to remove too much plastic – the fit should not be too loose.

Add an M4 washer followed by an M4 nyloc nut to the open end of the bolt and tighten everything together.

Insert the idler-block into the four M4x45 bolts. The idler-block must be able to slide in and out of the bolts smoothly – if this is not the case, clean out the holes with a 4mm drill bit or a file. Once this is done, remove the idler block.

(Idler-block highlighted in red for visual clarity)

Insert the M4x15 set screw into one 624 bearing. Place the parts onto the recess on the idler-block, and secure with two zipties. Ensure that the 'head' of the zipties are on the side of the idler-block opposite the bearing.

'Head' of ziptie

(Side view)

Cut approximately 10cm length of feedstock filament and insert it into the filament channel on the extruder-block.

Insert the idler-block into the four M4x45 bolts, with the bearing facing the extruder-block.

Insert the following into the open end of each M4x45 bolt:

washer – 4mm ID spring – washer – nut

Tighten the nuts on each of the bolts, compressing the springs and pushing the idler-block bearing onto the filament. Turn the nuts until the springs are compressed to about half of their original length.

Insert filament into extruder-block

Slide the motor towards the 53-tooth-driven-gear until the teeth on both gears mesh. Verify that the teeth on the gears mesh smoothly together when rotated and there is no 'skipping' (i.e. points where certain teeth on the gears do not mesh when the gears are rotated). Turn the large gear a few revolutions to confirm this.

Once you are satisfied, tighten the three M3x10 bolts on the motor.

Loosen the nuts on the idler-block and remove the filament.

Insert the PTFE tubing end of the hot end assembly into the channel on the underside of the extruder-block. Orientate the hot end assembly such that the two holes on the slidemount plate aligns with the two holes on the extruder-block.

You may need to clean out by lightly filing the inside edges and surfaces of the underside of the extruder-block if the slidemount plate does not sit properly in its place.

Ensure these holes align

(Viewed from underside)

Insert the following into the M3x6 brass screw, all the way in:

large OD M3 aluminium washer – large OD M3 silicone washer

Thread in the brass screw into the M3 through hole on the long sides on the heater block (not the hole that goes to the heating element). You may use either end of the hole on either side of the heater block (we recommend the rear-facing hole). Leave a gap of approximately 1.5mm - 2mm between the silicone washer and the heater-block.

Leave gap between siliconewasher and heater block

Tuck the hot end wires towards the rear of the extruder-block (opposite side of the gears). This is to avoid problems with routing wires after mounting the thermistor.

Place the thermistor glass bead between the silicone washer and the heater block. Carefully screw in the M3x6 brass screw such that the soft silicone washer compresses against the thermistor and holds it in place. Do not tighten more than necessary or the thermistor will break (the glass bead is fragile).

Insert the M3x5 set screw into the M3 hole going to the heating element (resistor).

Thread in the set screw until it reaches the resistor body, then very carefully turn just by a small amount, just enough to hold the resistor in place. Do not overtighten.

Overtightening will damage the heating element.Alternative method: Instead of using the M3x5 set screw, carefully wrap bits of kapton tape around the resistor body until it fits snugly in the heater block. The fit should be relatively tight such that the resistor is not able to slide out when the leads/red wires are moved.

Tuck the hot end wires towards the rear of the extruder-block (opposite side of the gears). This is to avoid problems with routing wires after mounting the thermistor.

Place the thermistor glass bead between the silicone washer and the heater block. Carefully screw in the M3x6 brass screw such that the soft silicone washer compresses against the thermistor and holds it in place. Do not tighten more than necessary or the thermistor will break (the glass bead is fragile).

Mount the fan onto the rear of the extruder-block using the two M2.5x14 self-tapping screws. Orientate the fan such that the fan wires exit towards the top side, and the side of the fan with the sticker label faces inwards (into the extruder-block).

Side of fan with sticker labelto face into the extruder-block

Note: actual label may lookdifferent than pictured here

Side of fan without stickerlabel to face outwards

Your extruder assembly is now complete.

Some notes/tips on usage:- Cutting the tip of the filament at an angle (to make it 'pointed' somewhat like a spear head, or a

sharpened pencil) will make inserting it into the extruder easier. Loosen the idler springs fully before inserting (or removing) the filament.

- After inserting the filament, turn the nuts on each idler spring until they just start to compress them. Then tighten each nut on each spring 2 full turns.

- Always turn on the extruder cooling fan before heating up the nozzle (send 'M106' to turn on the fan – in pronterface type this into the box on the bottom right and click 'Send'). After printing, it is advisable to leave the extruder cooling fan on until the temperature drops below 100°C. When heating up for the first time, increase the temperature gradually in steps of 30°C at a time (60°C, 90°C, 120°C, 150°C, 180°C) and wait for 1 to 2 minutes between steps, observing for problems.

- The temperature for printing PLA may vary from 175°C to as high as 230°C due to several factors (some of which may be due to the electronics, eg. variation in thermistor batches). Set the nozzle temperature to 185°C and print a fairly large object at a moderate speed (30mm/s print speed, 50mm/s travel feed rate, 1.2mm filament retraction @ 13mm/s). If the extrusion is not consistent (with a lot of breaks) increase the temperature by 2°C at a time until it is. Also take note if the filament is stripped/not gripping well at the idler, which may happen if the temperature is too low and/or the print speed is too fast. If the plastic extrusion appears 'frothy' or 'foamy', the temperature is too high and you will need to lower it (this may also mean your PLA material has absorbed moisture). Some degree of trial and error is required, and printing temperatures may vary between different colours and different batches (even of the same colour from the same supplier or manufacturer).

(End of Part 2)