Template:RepRapPro extruder drive assembly

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Goal

By the end of this stage your extruder drive will be mounted on the back of your Huxley like this:

Reprappro-huxley-extruder-drive-finished.jpg

Tools

  • 10mm (M6) spanner
  • Adjustable spanner
  • Allen key
  • Phillips screwdriver
  • Tweezers
  • 2mm drill

Step 1: Motor and hobbed stud assembly

RP parts Quantity Reprappro-huxley-extruder-drive-components-1.jpg
Reprappro-huxley-M6 block.jpg 1
Reprappro-huxley-large gear.jpg 1
Reprappro-huxley-small gear.jpg 1
Hardware Quantity
M6 hobbed stud 1
M6 full nut 1
M6 nyloc nut 2
M6 split washer 1
M6 plain washer 2
626 Bearing 2
NEMA 14 stepper motor 1
M3x10mm socket set screw (Grub) 1
M3 nut 1
M3x8mm screws 3

Use the 8mm M3 screws to attach the motor to the block. Put it as far from the centre as it will go in its slots. Don't do the screws up tight. The motor wires come out towards the bottom of the picture:

Reprappro-huxley-extruder-drive-motor-fitting.jpg

Push the M6 nut (plain, not one of the nylocks) into the hexagonal recess in the big gear.

Put a bearing on the hobbed 6mm stud (note the relative positions of the short and long threads), followed by two plain M6 washers, followed by the gear with its nut. The nut should face away from the bearing.

You are going to adjust things so the gears mesh.

Put the M3 nut into the slot in the small gear and run the M3 set screw through it.The small gear may need reaming out by hand with a 5mm bit.

Some motors have a flat on the shaft that runs all the way to the motor case. If yours is one of these, put the small gear on the shaft with its hub towards the motor. Then put the bearing in its hole so the big gear meshes with the small one.

If the flat stops short of the case, put the bearing and the big gear on first, then put the small gear on the other way round (as in the picture below).

Take things apart and put them together again, adjusting the motor's position in its slots, until the gears mesh nicely.

Reprappro-huxley-extruder-drive-motor-fitted.jpg

When you are happy tighten all the motor screws, reassemble everything else, and tighten the small-gear set screw. Make sure that the small gear hub is not rubbing on the big gear - there should be about half a millimetre clearance between them.

Put the other bearing in on the other side of the block.

Put the split M6 washer on the side with the big gear so it bears on the gear's nut, then put M6 nylock nuts on both ends.

Tighten the nylocks, while checking the hobbing against the 2mm hole down through the block where the filament will run. The hobbing should be centred on this. Undo or do up the big gear with its nut, and the two nylocks until this is so.

Don't tighten the nylocks so far that the gears, stud, and motor can't rotate freely.

Step 2: Idler

RP parts Quantity Reprappro-huxley-extruder-drive-components-2.jpg
Reprappro-huxley-idler.jpg 1
Hardware Quantity
M3x30mm screw 1
626 bearing 1
M3x45 screws 2
M6x20mm socket set screw 1
M3 washers 6
M3 full nuts 2
M3 nylock nut 1
Springs 2

Put the bearing on the M6 set screw and drop it into the slot on the printed part. Check that it rotates freely. If it does not, use a blade to remove a little material where it is binding.

Fit the idler to the drive with the 30mm M3 screw, two washers - one each side - and the nylock nut. Don't over-tighten it - it must move freely:

Reprappro-huxley-extruder-drive-idler-fitted.jpg

Put the springs on the long screws. Sandwich each spring between a pair of washers.

Put the screws through as shown. If you drop the nuts into their holes with tweezers first, then hold a screwdriver blade over them while you tighten the screws this is less fiddly.

Step 3: The Bowden tube

RP parts Quantity Reprappro-huxley-extruder-drive-components-3.jpg
Don't confuse the 300mm PTFE tube (shown) with the shorter
translucent heatshrink also supplied with the kit.
Reprappro-huxley-extruder-drive-tongue.png 1
Hardware Quantity
slotted brass retainer 1
PTFE tube 1

Use a sharp blade to trim a few millimetres off the end of the tube at right angles to get a clean square end.

Screw the tube into the brass retainer. Look in the other end to see when it gets to the end of the internal thread, then stop.

Screwing the tube in will have reduced its internal diameter slightly. Gently twist a 2mm drill by hand in the end of the brass to thin the tube where it is inside the screw thread. If you have a small hand-chuck this is made easier. The picture shows this being done for the other brass connector that you will install on the next page. The method is the same:

Reprappro-huxley-hotend-enlarging-ptfe.jpg

Push a short length of 1.75mm build filament down the tube from its free end to clear out any PTFE swarf.

Push the brass retainer into the drive, and secure it with the printed tongue. The thin end of the tongue goes to the right in this picture:

Reprappro-huxley-extruder-drive-tube-fitted.jpg

Feed in the short length of 1.75mm filament. The compression screws should be done up just tight enough that when the filament is trapped in the drive you cannot pull it out by hand - no tighter. (Hold the big gear still when you tug to test this.) Turn the device by hand. The filament should feed slowly and smoothly down the tube.

Step 4: Fitting the drive

Hardware Quantity
M3x20mm screw 1
M3 washers 6
M3 nylock nut 1
small cable tie 1

Attach the drive to the bracket on the machine. Put four washers as spacers between the drive and its bracket. Use the cable tie in the bottom hole to secure the lower end:

Reprappro-huxley-extruder-drive-finished.jpg

Clip the excess off the cable tie.

Finally, take a pair of long-nosed pliers and use them gently to remove the tongue. Take out the PTFE tube and its brass fitting. You will need these separate for the next step...