Solution - Thermal Force Feedback (TFF®) System

Explanation of the TFF® feature

The TFF® system monitors and controls the weld processor to assure production of spot welds that meet specifications. The TFF® system controls the process from the moment of gun closure through each stage of the weld: i) close gun, ii) build weld force, iii) development of the weld nugget, iv) indentation of electrodes, v) shut off weld current, and vi) open of weld gun.

The TFF® monitoring system is based on the physical law that metal subject to heat will expand. If expansion is restricted by physical means, thermal forces will develop proportional to the temperature and the amount of weld expansion.

The TFF® system uses the fact that those thermal forces precisely reflect the state of the metal during the welding process. A rapid rise in thermal forces indicates that the metal is rapidly expanding (2 & 3) A slowdown in the increase in thermal forces shows that the metal has begun to soften (4) When the increase in thermal force has stopped, the metals have reached the molten state. Then the electrodes indent into the nugget and fuse the metal pieces. (5 & 6) The TFF® senses the decrease in thermal forces which indicate that indentation has begun, and tells the MedWeld 3005 weld control to stop providing weld current because no further heat is required.

The thermal forces are measured by instrumenting the servo gun between the expanding metal and the mechanical restriction. The algorithm of the servo gun provides the mechanical restriction. The blocking prevents the piston from moving back into the cylinder during the expansion period. This arrangement causes the development of thermal forces, which are monitored by the force sensor. WTC has modularized the TFF® system for the MedWeld 3000 system. It integrates easily in any permutation of MedWeld 3000 welding control system.

Video Interview of Mr. Ariel Stiebel, inventor and owner of TFF patent technology. Supported by WTC engineering member, Mr. John "Jack" Farrow.

Choose to download either size file. Video Length: 15:38 minutes

(16.23 MB) mpeg file.

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This video interview of the inventor of this technology was produced by WTC's Medar welding control group. Although dated back to the early 1990's, much of the information presented in this video still applies with current technologies such as electrical servo welding guns..