The company is raising capital from existing partners as it ramps up its operations.Archer Aviation (ACHR -9.27%) has secured important new funding from a partner as it moves toward production of its small electric plane. But the funding came at a steep price for existing shareholders.Archer stock is down 10% as of 10:30 a.m. ET on Friday following the announcement.Building the cash pile ahead of productionArcher is one of a handful of companies working to commercialize electric vertical takeoff and landing ...