2.1. MyoBone ‘Parallel Assemblies’ - Four Round Tube Fibres

2.1.1. Prepare parts

2.1.1.1. Step 1: Cut fibres to the desired length

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Tips:

  • Lathe can create a precise cut and avoids damaging the tube

2.1.1.2. Step 2: Mill the tube ends

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Mill the inside hole of both tube ends in order to create a rough surface for gluing.

Tips:

  • Use a round moulding cutter with an automatic screwdriver
  • Use gloves to protect you from dust

2.1.1.3. Step 3: Positioning of the tube length

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Insert the tubes in the tube holding-support and position the tubes with the distance support. Fix the tubes with the screws.

2.1.1.4. Step 4: Gluing threaded pin in tube ends

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Add glue evenly to the threaded pin and hole. Use the distances according to the MYO-Bone class.

Tips:

  • While drying, use a fixture to keep the thread pin and fibre centred and at the correct distance
  • Wear protective gloves

2.1.1.5. Step 5: Remove the leftover glue

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Remove the glue with a cutter knife. Consider the hardening-time of the glue.

Production of spacers

2.1.1.6. Step 1: Water-jet

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Order water-jet cut part shape (aluminium).

2.1.1.7. Step 2: Drilling and threading of holes

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Drill and thread the holes of the flexure clamps.

Tips:

  • Put small fibers in the flexure clamps to avoid deformation caused by the pressure exerted by the drill bit

2.1.1.8. Production of end plates and flanges

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End Spacer:

  • Selective Laser Sintering (Polyamide)

SB Flange plate:

  • Machining (Aluminium)
  • Selective Laser Sintering (Polyamide)

Screws, nuts and washers are standard parts.

2.1.2. Assembly

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Material needed

4 x CFRP tubes with threaded ends

4 x spacers

16 x M2.5x10 countersunk head screw (DIN 965)

2 x end spacer

8 x M4 thin nut (DIN 39)

8 x M4 spring washer (DIN 127)

2 x SB flange plates

8 x M3x25 countersunk head screw (DIN 7991)

8 x M3 thin nut (DIN 39)

8 x M3 spring washer (DIN 6798)

2.1.2.1. Step 1: Assemble fibres and spacers

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Slide the fibres (1) in the flexure clamps (2) of the spacers.

Tips:

  • Slide one fibre through all spacers, and then go on with the next fibre
  • Flexure clamp screws should be loose
  • In preparation for the next step, regroup the spacers next to each other

2.1.2.2. Step 2: Plug fibres in the end-spacer

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Plug each fibre in one of the holes of the end-spacer.

Tips:

  • Apply sufficient pressure so that the end of the cfc tube is in contact with the shoulder at the bottom of the hole
  • Do not press the fibers firmly into the holes

2.1.2.3. Step 3: Screw fibres to the end spacer

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Screw each of the fibers to the end-spacer using the M4 nuts and the large spring washers.

Tips:

  • Screw the nut until the spring washer is nearly flat, not more
  • (if you screw further, you may pull the threaded pin out of the tube)

2.1.2.4. Step 4: Attach the other end-spacer

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Repeat steps 2 & 3 for the other end-spacer.

Tips:

  • Make sure the end-spacers are as much as possible:
  • Parallel to each other
  • Perpendicular to the fibres
  • Lay the bone on the table to ensure that it is not twisted

2.1.2.5. Step 5: Adjust the spacers

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Arrange the spacers equidistantly between the two end-spacers.

Tips:

  • Distance between spacers: 51 to 52 mm
  • Ensure that the spacers are perpendicular to the fibres

2.1.2.6. Step 6: Check straightness

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Check that the MYO-Bone is straight and that both end-spacers are parallel to each other.

If necessary proceed to adjustments.

2.1.2.7. Step 7: Attach the SB flange plates

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Screw the SB flange plates to the end-spacers with the M3 screws.

Use the small spring washers together with the M3 nuts (backside).