Solutions Through Welding Technology...

NBC-9654
Projection (Upset) Welding

EQUIPMENT DESCRIPTION:

This machine, a DC resistance upset welder, is capable of delivering 2,000 to 250,000 amperes for up to one second with a weld force of 1,000 to 100,000 pounds in a vacuum of 10 microns. The DC current comes from two, three phase to DC rectifiers controlled by a weld control and auto-transformer. The weld force is derived from a Servo hydraulic cylinder and accumulator, complete with a hydraulic pump unit. A complete vacuum chamber and vacuum pumping system provide the vacuum for welding and a gas supply with two available sources is provided for back-fill after the weld. A data acquisition system collects data on all weld parameters, as well as the temperature of the part being welded.

The mechanical portion of the upset welder consists of the press, or force delivery system, the vacuum chamber, the secondary weld current conductors, and electrodes.

The press is a four-post arrangement separating upper and lower platens. A linear roller bearing guide is mounted from the upper platen to provide vertical guidance for the welding ram. A fabricated steel ram is motivated up and down by an 8" bore by 15" stroke servo-hydraulic cylinder with a 100,000 pound capacity load cell sandwiched between the cylinder and ram. Attached to, and insulated from the underside of the steel ram, is a RWMA Class 2 ram extension which extends through a gland on the top of the vacuum chamber. The upper electrode is fastened to the bottom of this ram extension. The ram extension has a stainless steel outer sleeve to provide the necessary wear characteristics with the quad-ring seal gland.

Flexible copper laminated shunts mount to each side of the upper ram extension and allow for the 15" stroke of the ram. The opposite end of the shunts are terminated on the upper conductors, which in turn, lead to the upper connection pads on the two DC power packs. Due to the duty cycle of one weld per hour, no water cooling is provided for the secondary circuit.

A common lower conductor connects the lower pads of the DC power packs to the lower electrode and ties the two packs together at ground potential.

Front View of Welder

Rear View of Welder

DATA ACQUISITION:

A PC provides complete data acquisition and machine control through a keyboard and mouse. Operator and part information is loaded with a bar code scanner. Complete operating parameters are entered or loaded from files and automatically downloaded to the weld control and hydraulic servo system. There are three levels of pass-coded security for operator access.

During the weld, data is collected at up to 5000 samples per second. The system records displacement, force, pressure, vacuum level, primary and secondary voltages, primary and secondary currents, and up to four thermocouple inputs. The system also calculates the pre-weld resistance of the part and the cold displacement. After the weld, plots of all the data can be automatically generated and printed on a color printer. A summary sheet reports the average data and whether or not all parameters were within acceptable limits, predetermined by the operator.

VACUUM SYSTEM:

The vacuum chamber has a gland on top to accommodate the sliding ram extension. This gland has a fill and vent port located between the top and second quadring to feed vacuum oil for lubrication and sealing purposes. The entire front of the chamber is an access door, equipped with a 10" diameter lexan viewing port. On the left side of the chamber are three access ports; one for voltage measurement feed through, and two for thermocouple feed through. On the top of the chamber is a 3/8" NPT hole for mounting a pressure relief valve and a nipple for mounting the vacuum gage. The rear of the chamber has a 4" diameter flanged connection for the vacuum system.