With (laser or traditional) welding of metals it gets to the point where you need to flood the area with shielding gases (eg. argon/helium/nitrogen) during the

With (laser or traditional) welding of metals it gets to the point where you need to flood the area with shielding gases (eg. argon/helium/nitrogen) during the weld to prohibit poor surface qualities (due to plasma formation, oxidation, etc), and that the flow rate requirement and geometric matching of the airflow-assist structure ('shoe') becomes critical (sometimes on both sides). Basically, a generic solution has severe limitations in material, speed and finish terms. I am no chemist but would generally assume the same to be true for many food related substances. Polymers bonding will often respond better to a mix of focused ultrasonics and pressure than simply thermal energy. Alternative, use glue.