Partially Flexible Foot Piece

This online tutorial describes the production of a partially flexible foot piece. The partially flexible foot piece runs from the heel to the tiptoes. The area from the heel to the metatarsophalangeal joints is produced rigidly, meaning stiff. The area from the metatarsophalangeal joints to the tiptoes is produced flexibly.

Use the Orthosis Configurator to choose a foot piece. You will receive a recommendation for the production of a foot piece based on the patient data.

Click here to go to the online tutorial for producing a rigid foot piece.

 Biomechanical Basics

Step 1/1

 Reinforcing the Foot Piece

Step 1/20

In order to increase the load capacity and useful life of the material of a partially flexible foot piece, reinforce the forefoot and rolling-off area (blue area) flexible and without a brim.
Note: A toes bank, or similar, can be attached subsequently if required.

Step 2/20

We recommend using electrical scissors (e.g. Easy Cutter) to cut the separate fabric layers (carbon as well as aramid).
Note: Use adhesive transfer tape without backing material to secure the cutting edges. This way, the edges will not fray.

Step 3/20

Dry the aramid fibre fabric at 120°C in an oven for at least one hour.
This way, you remove any moisture that has been absorbed during storage and improve the fabric’s properties for further processing.

Step 4/20

Consider the foot’s rolling-off area when laminating a partially flexible foot piece. It encompasses the area from anterior of the metatarsophalangeal joint (d1) of the big toe to posterior of the metatarsophalangeal joint (d2) of the little toe.

Step 5/20

Consider the order of the different reinforcing layers when laminating a partially flexible foot piece. The quantity of the reinforcing layers should match the individual needs of your patient. The following reinforcing steps indicate where you can adhere more reinforcing layers, if necessary.
Note: Aramide is a flexible material that is particularly well suited for areas bearing dynamic loads.

Step 6/20

Scarcely cover an aramid fibre fabric pre-cut with adhesive spray and adhere it to the entire sole. Use as many layers of aramid fibre fabric as you need (this is an exemplary picture).
Important! Make sure to use the fibres stretched! 

Step 7/20

Scarcely cover a carbon fibre fabric pre-cut with adhesive spray and adhere it up to the rolling-off area. Then, cover the foot piece’s sole and sides with a carbon fibre fabric pre-cut.
Important! Make sure to use the fibres stretched!

Step 8/20

Keep on reinforcing with carbon fibre fabric. Each layer of the pre-cuts should end further ahead (distally) in the rolling-off area. Use as many layers of carbon fibre fabric as you need (this is an exemplary picture).
Note: Always only spray the pre-cut which still needs to be adhered and not the already adhered reinforcement.

Step 9/20

Attach unidirectional carbon fibre band below the joint retainer at the foot piece. Mind the direction of the fibres (arrows).

Step 10/20

Keep on reinforcing in a v-shape way. Mind the direction of the fibres (arrows).

Step 11/20

Make sure not to cover the edges of the rolling-off area with carbon fibre band when adhering the unidirectional carbon fibre band in a v-shape way.

Step 12/20

Reinforce the midfoot and forefoot area with unidirectional carbon fibre band. Spare the edges.

Step 13/20

Apply some insulating wax to the thread of the joint retainer in order to seal it airtight.

Step 14/20

Mount the assembly/lamination dummy with system string to the joint retainer. Find the correct position (the shape of the joint retainer matches the hollow for the bearing nut of the joint's upper part). Screw the retaining screw through the base film into the joint retainer and screw it tight.

Step 15/20

Attach unidirectional carbon fibre band in a v-shape below the joint retainer at the foot piece again. Mind the direction of the fibres (arrows).

Step 16/20

Make sure not to cover the edges of the rolling-off area with carbon fibre band when adhering the unidirectional carbon fibre band in a v-shape way.

Step 17/20

Attach carbon fibre fabric below the joint retainer. Mind the direction of the fibres (arrows).

Step 18/20

Keep on reinforcing. Each layer of the pre-cuts should end further ahead (distally) in the rolling-off area. Use as many layers of carbon fibre band as you need (this is an exemplary picture). Attach a final layer of carbon fibre fabric to the foot piece. Cover the entire rolling-off area without exceeding it with the reinforcement. Also, cover half of the assembly/lamination dummy.

Step 19/20

Finish reinforcing the partially flexible foot piece with aramid fibre fabric. While doing so, cover the entire sole. Use as many layers of aramid fibre fabric as you need (this is an exemplary picture).

Step 20/20

Finally, in order to attach the reinforcement layers, pull a decorative fabric or a PA reinforcement stocking (for a carbon look) over the model. Thus, the PVA film tube can easily be pulled over as top film layer.
Note: We recommend using a 0.10mm thick film layer.

 Laminating the Foot Piece

Step 1/5

This production technique is specifically adapted to our epoxy resin and hardener.
Important! Please consider the processing instructions and the safety data sheets for our epoxy resin and hardener. Precisely stick to the mixture ratio and thoroughly mix resin and hardener.

Step 2/5

Mix a sufficient amount of resin and hardener. Let the fabrics soak completely and rub surplus resin out.

Step 3/5

Press out the foot piece in order to receive the highest possible fibre volume ratio. While doing so, protect the film with some padding material and make sure to maintain the form of the modified pitch.

Step 4/5

The shaping dummy increases the fibre volume ratio at the system joint area and facilitates mounting the NEURO SWING cover plate later. Align the shaping dummy, fitting the joint's upper part, and secure it with adhesive tape.

Step 5/5

Let the model harden over night (at least 10 hours), under vacuum and at room temperature.
Important! Also note the processing instructions for epoxy resin.

 Cutting the Foot Piece

Step 1/3

Use an oscillating saw to saw along the cutting lines in order to remove the orthosis parts from the model. You can see the recommended saw blade in the picture. Thus, you can saw very close to the system joint without damaging it.

Step 2/3

Remove all laminate parts which are no longer necessary.

Step 3/3

Carefully remove the orthosis parts from the model. Those are not yet completely hardened. Consider this while removing the orthosis parts, in order to avoid deformations.

 Tempering and Grinding the Foot Piece

Step 1/3

Clean all the joint areas as well as the system stirrup before you temper the parts of the orthosis. Heat all wax residues with a hot air blower (1) and blow
the liquefied insulating wax out of the hollows (2). Remove all residues with a cloth (3). Remove the PVA film tube as well.

Step 2/3

Temper all parts of the orthosis before you grind them. Place the orthosis parts into a cold oven and heat it up slowly. When tempered, the parts of the orthosis are stable and can be worked in the best possible way.
Important! Also note the processing instructions for epoxy resin.

Step 3/3

Grind the edges of the orthosis parts (e.g. with an angle grinder). However, it is essential to avoid predetermined breaking points in the metal! Also make sure that the flexible area of the foot piece is even (without brinks).
Note: Even after tempering, you can still work aramid fibres with sharp scissors.