Template:RepRapPro mini extruder drive assembly

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Revision as of 07:48, 17 January 2013 by Adrianbowyer (talk | contribs) (Step 2 - Assembly)
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Step 1 - Components

You will need one drive for each colour/material that your Mendel will print, up to a maximum of three. This section describes the parts for one drive.

Reprappro-multi-materials-extruder-drive-parts.jpg
Item Quantity
Large internal gear (printed) 1
Small push-fit gear (printed) 1
Main block (printed) 1
Tongue (printed) 1
PCB clips (printed) 2
Slotted custom PCB clip (printed) 1
Flat motor spacer (printed) 1
M3 nuts 5
M3 nyloc nuts 3
30mm M3 caps 2
35mm M3 caps 1
25mm M3 caps 1
25mm M3 screw (threaded to the top) 1
20mm M3 caps 3
12mm M3 caps 1
M3 spring washer 1
M3 washers 13
3mm 623 bearings 10mm OD x 4mm thick 3
8mm M3 hobbed drive 1
Short NEMA 17 motor 1

Step 2 - Assembly

Reprappro-multi-materials-extruder-drive-geared-shaft.jpg

Start by assembling the geared filament drive.

Fit an M3 nut in the recess in the gear. The easiest way to do this is to put the 12mm screw through from the back with a washer under its head, and to use it to pull the nut into its recess. Make sure the nut flats are aligned with the hexagon of the recess.

Put the screw with the thread running all the way to the top through the nut then screw on the other parts. The order goes:

  1. Screw head
  2. Nut
  3. Gear
  4. M3 washer
  5. 623 bearing
  6. M3 washer
  7. M3 spring washer
  8. Hobbed insert

You will notice that the hobbing on the insert is not in its centre. Put the insert on so that the hobbing is away from the gear end.

Do the hobbed insert up as tight as you can with your fingers. Take care not to scratch yourself with the hobbing - it is intended to be sharp. Wrap a piece of tissue round the insert to protect yourself.

Reprappro-multi-materials-back-bearing.jpg

Next put a 623 bearing in the back of the drive block as shown. You may need to clean the hole a little. Use a 10mm drill bit twisted carefully in the hole by hand. While you are at it, clean the hole at the other side too.

Push the gear and hobbed insert assembly that you just made into the opposite side of the block to the one that you just put the bearing into. Check that the hobbing is centred where the filament will run by looking in the unoccupied idler bearing hole in the side of the drive block (poke a length of filament down the 2mm hole in the top of the block if you can't tell where this is). If the hobbing is off-centre adjust its position by putting extra washers between its bearing and the spring washer, or by turning it over so the hobbed side is nearest its gear.

Take the gear and hobbed insert assembly out of the block for the moment.

Reprappro-multi-materials-extruder-drive-block-mounting.jpg

Mount the block on the motor as shown above using two screws and washers. Put the spacer between the block and the motor with its notch under the bearing you fitted in the back of the block. The motor wires are at the back in this picture.

Reprappro-multi-materials-idler-gears.jpg

Fit the idler bearing using the 12mm screw as shown (the screw needs no nut to retain it).

Fit the small gear. You may find this easier if you use a sharp blade to put a slight chamfer on the underside of the gear where it meets the motor shaft.

Push the small gear onto the shaft such that its top is flush with the end of the shaft.

Reprappro-multi-materials-fitting-drive.jpg

Push the gear and hobbed insert assembly into its hole in the block. Rotate the gear as you do this so that it meshes with the small gear on the motor.

Note that the gear and hobbed insert assembly is designed so that the action of driving the filament tends to tighten the hobbed insert on the M3 thread. It can also be easily removed for cleaning when there is no filament in the drive. But when it is operating the filament that it is driving retains it in place by lying in the slight dent formed by the hobbing.