eX_34:

...not a silly pseudo-scientific name, just the iteration number. Yes, I've put a fair degree of effort in to this one - this is my daily driver for an extruder set up.

Update 30.4.19: I've uploaded an improved version: https://www.thingiverse.com/thing:3597342 The blurb below is still mostly relevant while the link above will take you to the update.

Goals: -A robust, reliable extruder -Capable of applying lots of force -Compatible with any filament, including bendy stuff -Filament run-out sensing -Filament lubrication -Easy to use -No faffing with filament swaps -Less prone to jamming -Somewhat self-maintaining -Reduce hot-end blockages -Straight forward design -Easy to print and construct -A minimum of extra parts required

Tough list of requirements..? I believe I've succeeded, suggestions always welcome.

This extruder is intended to screw to a 2020 frame but I have included the .123dx file if alterations are required.

Construction, Extruder: In addition to the printed parts you will need -A short length of (spare) Bowden tube -A Bowden-Hotend connector -A standard skateboard bearing -Five Allen bolts, four short, one medium -An extruder gear, of the type shown in the pictures -A reasonably robust spring -A 6x6x12mm Tact-switch and some wire if you intend to use the run-out functionality -A suitable stepper motor ...many of these parts can probably be taken from your current extruder!

1. Print the parts I would suggest three outer layers, and a minimum infill of 40% - this extruder is intended to be able to exert a lot of force so don't skimp. Also support (everywhere) will be needed. Carefully remove all the support material paying extra attention to the filament path holes, especially the connection between the filament path and the tact-switch housing. To improve reliability this design needs two small lengths of Bowden tube press-fitting in to the parts...

Note: When press-fitting the Bowden tube pieces you should find the fit is snug but not over-tight... but do take note that there is a small ring included in both the base and lever where the hole tightens a little. This is intended to help keep the tubing in place during operation, but may prove too tight during assembly. I would suggest a test fit and adjustment, if necessary, before starting assembly.

Lever For the lever I would suggest pushing the tube in from the input side until it is nearly up to the top of the output side - not too much, you want this to seat in the Bowden-hotend coupler but also need to be able to push sufficient Boweden tube in from the other side when running the extruder. Once in place take a sharp knife and cut the tube so the input side is as close to the contour of the plastic as you can - perfection is not required! Now time to fit the bearing... Take the small plastic hub and press-fit in to the bearing - you should find it's snug but not really tight. Note one end of the hub is square and pokes out the bottom of the bearing... you should see a similar shaped recess in the lower arm of the lever where the bearing will sit. Press-fit the bearing and hub in to the lever, you should feel it click in to place but a little fiddling to get it to line up may be needed. Once in place take one of your shorter Allen bolts and screw it in to the lever assembly until you can see the end of the bolt starting to poke out the other side. The last part is to screw the Bowden-Hotend coupler in to the top of the lever. This should be pretty tight but I'd hope just loose enough that it can be removed with strong fingers. The end of the Bowden tube should be just long enough to engage with the bottom of the coupler.

Body In the case of the main body take you need to perform a neat cut-out in the side of the Bowden tube before pressing it in to place. Bend the tube 180deg and carefully take a slice out of the elbow. When strait there should be a neat ellipse removed from the tube that's about half it's diameter. Press-fit this tube in to the filament path, this time from the output side, such that the hole you have made will line up with the hole between the filament path and the tact-switch housing, When done these should line up pretty-perfectly with a bit of tube sticking out both ends of the the filament path. As before trim the tube to reasonably match the contour of the output and I'd suggest leaving a little poking out the input side as this will help finding the hole when you inset filament.

Stepper Motor Screw the main printed part to the motor using three of the shorter Allen bolts. Be sure it's properly seated and firmly in place - gorillas not needed! Check you are happy with the orientation of the motor's connector when the completed extruder is fitted to your printer. Take your extruder gear and fit over the stepper motor shaft. You want the gear to be as perfectly lined up with the filament path as you can - I find using a piece of filament is a helpful guide. When happy tighten the gear in place.

Final Assembly A little fiddling may be required but the plan goes something like this - Take your spring (probably borrowed from your current extruder) and place that in the well in the main body. Now take your constructed lever and wiggle it in to place: -Other end of the spring fitting in to it's well -The 'nose' of the lever fitting in to the slot cut in the body's mounting arm -The lever fitting over, and pivoting on, the shaft sticking out of the body Take your final, longer, Allen bolt and screw that in to the coupling between the lever and the body... That bolt should be long enough to go all the way in to the stepper motor and screwed all the way down, but not so tightly that it impedes the lever's movement.

Remember the bolt that runs through the bearing? This also serves has a hight adjuster for the lever. (un)Screw this until you are happy everything is lined up nicely. Note: The reason the head of the top-left bolt sits slightly proud of the base is to serve as a spacer between the lever and the body and so help free movement.

The final job is to press-fit the knob on to the remaining stepper motor shaft - I'd suggest this part is needed so do print it.

Testing Take a piece of filament and push it in to the input. When you feel it stop (contact with the gear and bearing) press down on the lever to open the gear and pinch-wheel and push the filament in a little further. It's up to you but at this point I let go of the lever and use the wheel to wind the filament the rest of the way through.The axle of the pinch-wheel is off-set by 0.4mm to the stepper motor so when winding filament through it should enter the lever in perfect alignment.

It should all work as intended without any snags, but if not: -is the filament path properly lined up? -are the cut ends of your Bowden tube in need of further fettling?

All good? Time to hook it up to your printer and give it a test run. The only remaining 'gotcha' will be when you fit the hot-end Bowden tube to the extruder. It needs to go in far enough to engage with the coupler and but-up against the section of tube in the lever. The tube in the lever needs to be long enough to engage with the coupler so the two tubes line up properly. Also, depending on the set-up of your previous extruder, you may find your new extruder runs backwards! Don't despair, if this is the case you have two options: -Go in to your firmware, reverse the extruder direction setting, and upload your new version to the printer. -Pull the plug out of the stepper motor and shove it back in having twisted it by 180deg... ...this works absolutely fine, but it is a bit of a bodge and may require some modification to the connector.

Adjustment: If this extruder is using a different gear to the one from your original device you will need to do some speed adjustments, here's a quick how to: -Run some filament through the extruder with the Bowden-coupler removed -Cut the end of the filament flush with the top of the lever -Send the necessary commands to run 100mm of filament through -Measure what you've actually got -You new extruder esteps = 100 / what you got x old esteps -Enter the new value ...Google the details.

I run my printer with a Volcano Hot end and it's also running about 240% the speed the manufacturer intended - aren't Delta printers great? The result is I need a robust extruder that can exert a good deal of pressure on the filament to stop skipping... ...so how do you adjust this thing?

1. Get a stronger spring - not so helpful
2. Take a short Allen bolt, a nut, and a washer big enough your spring can seat on it that is small enough to fit in the well within the extruder body. Bolt + washer + nut and drop that in to the well thread side up. Now place the spring on top of your 'adjuster' and reassemble the extruder. You should find rather more force is being applied by the bearing - hurrah! The base design is intended to use the spring you probably snaffled from you old extruder and is hopefully set up to exert enough pressure for most normal circumstances. Also if you're using a soft/bendy filament you really don't want too much pressure. So why didn't I make for an easier adjustment process? -Two of my design choices were robustness and minimal extra parts -I'm often too tempted to fiddle where it's not necessary -It's not that difficult to change if you actually need to

Run-out Sensor One of those things you rarely need, but when you do you really wish you had! If you haven't already got one you will need access to your printer's firmware to switch on the relevant option(s). It's honestly not hard: -A quick Google for some instructions -A copy of your firmware -Upload the changed result to your printer

So... A multi-meter will be really helpful for this bit! Take your 7x7x12mm Tact-switch and using the multi-meter work out which pins do what when you press the button. You should find you only need two of the four pins on one side of the switch - snap the other two off or bend those pins in under the switch they will only get in the way. Solder some wire to the two remaining pins, sufficiently long to reach from your extruder's mounting position to the header on your control board for a run-out sensor. Gently press-fit the tact switch in to it's housing in the extruder body oriented to be sure the pins won't make contact with the stepper motor housing - we don't want any shorts!

Now comes the 'fun' bit... Push a piece of filament in to the extruder body and one in place continue to slowly push the tact-switch home until when checking your multi-meter you see the switch is actuated. Now remove the filament and recheck the multimeter? Is connection lost? Awesome!

Warnings and advice At this point you're going to want to glue the switch in place but don't until you've rechecked actuation a few times - you really want this to be reliable! Be sure the switch is always on with filament in place and always off with no filament. You will almost certainly need to do a bit of fiddling before this works properly, be patient and take your time. If you really can't get it to work it's almost certainly because either: -The hole in the Bowden tube is not correctly sized and/or lined up with the hole in the extruder body or -The end of the tact-switch isn't freely fitting through it's hole in the extruder body ...further adjustment required.

The Filament Oiler Did you think I forgot? Think of this as an optional but very useful addition, especially if like me you are pushing your printer quite hard. It serves two purposes: -It cleans and lubricates your filament before entering your hot end -It's intended to mount below the extruder to also act as a filament guide

Why? Give your filament a wipe with a bit of WD-40 and a cloth. A good deal dirtier than you thought, eh? That crud is a cause for hot-end jams, especially if you run your printer pretty hard. Also a little lubrication doesn't hurt for reliable function.

Use Fit the oiler as depicted in the pictures above. Insert a piece of cloth / cotton wool in to the well taking care not to block the filament's path. Add a few drops of WD-40, you don't need to go bananas. Replace the lid and run your filament through. Ta-da! More reliable prints. Obviously you will need to top-up the oil and change the cloth / cotton wool occasionally. Initially I'd suggest keeping a close eye to: -Gauge how often you need to re-oil -How quickly your cloth / cotton wool is getting dirty, and so in need of replacement.

Job done! :-D