Pre-nesting of the active area on plates to reduce thickness variation
A method for preparing a bipolar plate assembly for a fuel cell stack is provided. The method first includes the steps of providing a first unipolar plate having a first active area with a plurality of channels formed on a first inner surface thereof, and a second unipolar plate having a second active area with a plurality of lands formed on a second inner surface thereof. The first unipolar plate and the second unipolar plate are aligned to dispose the first active area adjacent the second active area. A first pressure is then applied to the first and second active areas to pre-nest the first active area and the second active area. The perimeters of the first and second unipolar plates are then joined. A clamping fixture and associated method for assembling the bipolar plate assembly is also provided.
1. A method for preparing a bipolar plate assembly for a fuel cell stack, comprising the steps of:
providing a first unipolar plate having a first active area with a plurality of channels formed on a first inner surface thereof and a first perimeter flange;
providing a second unipolar plate having a second active area with a plurality of lands formed on a second inner surface thereof and a second perimeter flange;
aligning the first unipolar plate and the second unipolar plate to dispose the first active area adjacent the second active area;
applying a first pressure directly to the first and second active areas to pre-nest the first unipolar plate and the second unipolar plate; and
joining the first perimeter flange of the first unipolar plate to the second perimeter flange of the second unipolar plate.
2. The method of claim 1 , further comprising a step of constraining the first unipolar plate and the second unipolar plate after the pre-nesting of the first unipolar plate and the second unipolar plate.
3. The method of claim 2 , wherein the first and second unipolar plates are constrained by applying a second pressure to the first and second perimeter flanges to militate against a relative movement between the first and second unipolar plates.
4. The method of claim 1 , wherein an excess plate material is displaced to at least one of the first and second perimeter flanges during the step of applying the first pressure to the first and second active areas.
5. The method of claim 1 , wherein the pressure is applied to the first and second active areas with at least one of a mechanical force, a pneumatic force, a hydraulic force, and a magnetic force.
6. The method of claim 1 , wherein a substantially hermetic seal is formed by the joining of the first perimeter flange and the second perimeter flange.
7. The method of claim 6 , wherein the seal is formed from one of a weld, a solder joint, a braze joint, and an adhesive.
8. The method according to claim 7 , wherein the weld is formed by one of arc welding, gas welding, resistance welding, energy beam welding, and solid-state welding.
9. The method according to claim 8 , wherein the energy beam welding includes one of laser welding and electron beam welding.
10. The method of claim 1 , wherein the first and second unipolar plates are aligned with a clamping fixture.
11. The method of claim 1 , further comprising the step of bonding the first unipolar plate and the second unipolar plate with a plurality of localized electrically conductive nodes.
12. The method of claim 11 , wherein the step of bonding the first unipolar plate and the second unipolar plate includes spot welding to form the localized electrically conductive nodes.