Dotwelder Operation

PREPARATION OF CAVITY

In order to create a good bond between the pellet metal and base metal, it is necessary to enlarge the section to be welded by use of a center punch, drill or carbide cutter. Enlarge the cavity so that it will accommodate approximately 2/3 of the size of pellet to be used. A clean cavity and pellet insures a solid weld; carbon tetrachloride has been successfully used to remove dirt, grease, dust or foreign material from the cavity. Another type of cavity enlargement which has been found to be of value where strength of the Dot Weld is important, is the dove-tail technique based on the same principal as is used by a dentist in forming a secure anchor for a tooth filling; the dove-tail enlargement is a portion of the cavity enlarged below the surface opening. To make such an enlargement a drill or rotating burr type instrument is used to rout out base metal below the narrow neck of the cavity opening. The cavity surface face should be smooth to form a secure footing for the pellet metal. Care must be taken in handling the pellets. It is recommended they be stored in a dry spot to prevent oxidation. When dropping the pellets into the cavity a tweezer should be used to prevent picking up the oils from the fingers. This oil is only microscopic but can cause impurities in the weld.

READYING THE MACHINE

After the cavity has been prepared insert the primary plug into the receptacle and connect the ground and electrode cables to the terminal cam loks provided for them on the face of the machine. Since this is an alternating current machine it is unimportant whether the ground cable or electrode cable is connected to left or right terminal. Insert the remote cable plug into the remote jack between the two terminals. Turn the "ON-OFF" switch to "ON" and the red pilot light should illuminate. The machine is now ready to use.

DOT WELDING PROCEDURE

Attach on the ground clamp to the piece of metal to be Dot Welded. Best results are obtained when the ground connection is located as close to the cavity as possible. If the work to be welded is a large mold and the ground clamp will not fit, an additional "C" clamp may be fastened to the work and the ground clamp attached to the "C" clamp. Adjust the variable Electronic Timer, located at right hand of front panel and the heat setting at left hand of front panel in accordance with suggested heat and time setting table,
These are average settings and depend upon the quality and length of the ground path. Experiments should be made on equivalent scrap material and optimum settings should be made. Experience in setting both the timer and the heat selector switch will be acquired with practice; these values are suggested to serve as a guide.
After the timer and the heat selector switch are set place the probe above the pellet in the cavity and with sufficient pressure to make good electrical contact, press the remote control switch to actuate the contractor. Once the switch has been pressed the process is automatic. The timer will cause the contractor to cut complete. The length or manner of pressing the switch has no effect. After the weld has been made it may be rough ground and finished in prescribed shop procedure.