Percussion weld monitoring
AssigneeGeneral Electric Company
InventorMichael K. Cueman
Life of this patent
Estimating the term…
Abstract
The quality of a percussion weld is sensed by measuring and analyzing certain features of the weld current signature. Instantaneous current is measured by a Hall sensor and permits isolation of the welder from the monitoring system. Weld quality is strongly correlated to the time to vaporize the nib separating the parts, and the dwell time to forge the parts together after nib explosion. A weld is assumed defective if nib time is too short or dwell time is too long. These quality parameters may be supplemented by weld and forge timing, line voltage, and acoustic information; a weld is rejected if any of these are outside of acceptance limits. Experiments on the percussion welding of silver-cadmium oxide to brass show that cadmium-oxide is decomposed and expelled by the forge pressure and the joint is a silver to brass weld.
Claims16
A method of monitoring the quality of percussion welds made on a percussion welding machine comprising:
- sensing a weld current passed through parts to be welded, one of which has a nib in contact with the other, as said parts are heated and said nib explodes, and as forge pressure is applied to impact and unite said parts;
- measuring nib time from the start of said weld current to nib explosion and dwell time from the nib explosion until said parts are forged together;
- and
- determining weld quality by comparing said nib and dwell times to preselected acceptance limits.
An improved method of monitoring the quality of the percussion weld of a silver-cadmium oxide part to a second part, comprising:
- sensing the instantaneous weld current fed to said parts, one of which has a nib in contact with the other, as a nib current pulse heats said parts and explodes said nib, and as a plasma forms and cadmium oxide in a shallow layer of the first-mentioned part is decomposed and expelled upon application of forge pressure to impact and unite said parts,
- analyzing said weld current and measuring nib time from the start of said nib pulse to a rapid decrease in current at nib explosion, and dwell time from nib explosion to a rapid increase in current to a second peak as said parts are forged together;
- and
- comparing said nib and dwell times to predetermined upper and lower limits for acceptable welds.
A percussion weld monitor for determining the quality of welds produced on a percussion welding machine which has means to supply a weld current pulse and forge force to parts to be welded, one part having a nib in contact with the second part, said monitor comprising:
- means for sensing the instantaneous weld current as a nib pulse is applied to heat said parts and explode said nib, and during a dwell interval before joining of the heated surfaces by impact of the forge force;
- means for analyzing the weld current waveform and measuring nib pulse time and said dwell interval;
- and means for comparing said nib time and dwell interval to predetermined maximum and minimum values of acceptable welds.
Dependencies are inferred from the claim text.