Weld Box Units

AISI H-13 Tool Steel Weld Rolls in SS Clevis		15" 3-Roll Quick Set Weld Box

 

Weld box units perform two primary functions:

• Stabilizing and guiding of the strip edges as they enter the weld apex
• Applying pressure to forge the heated edges of the formed strip together to produce a good weld. The weld rolls must be capable of providing enough pressure to upset the edges sufficiently to ensure that impurities are squeezed out. There are several types of weld roll configurations that are commonly used in the industry. Each has certain advantages and disadvantages that need to be recognized to properly select a weld roll configuration for a given situation.

Quick Centering Mechanism – An Addison Exclusive

The Addison Three-Roll Weld Box has the first ever Quick Centering Mechanism incorporated into the unit to provide quick and positive roll centering at setup and changeover. This patented feature allows the operator to achieve a round tube at the weld box without the use of a setup plug, which may be impractical or impossible to use due to mill configuration.  In less than a minute, the operator can set the weld rolls without the use of a plug gage or guessing. The rapid setup feature provides significantly reduced scrap, down time, and size changeover times. 

Quick centering is accomplished by the use of a quick release clevis pin and three precisely located holes. The operator inserts one of the pins into a hole in the roll clevis and then moves the weld rolls away from the tube using the universal adjustment. When the pin drops into the locating hole, the operator uses the individual adjustments on the remaining two clevises to repeat the procedure of inserting their pins into the locating holes. Once all three clevises are located, the operator removes the three pins and using the universal adjustment, moving the weld rolls to the proper position as determined by a feeler gage between any two-roll rims.  The weld rolls are now positioned properly per the manufacturers setup chart. A slight final adjustment may be necessary to position each individual clevis/roll set accurately.

Three-Roll Configuration Advantages

• Swirl marks are virtually eliminated
• Provides adjustment for correcting edge misalignment should this be necessary
• Small rolls allow the weld coil to be placed closer to the weld point
• Rolls can be adjustment independently or simultaneously
• Roll-mounting fixture can be rotated to a position with a single roll vertically above the centerline with a groove in the center to aid edge registration of thin walled tube
• Roll changeover is much quicker

Because the bearings are smaller and mount in the rolls to keep roll size small, the three-roll configuration (Figure 5-6) is generally limited to .187" wall thickness.

The Addison Three-Roll Hi-Frequency Weld Box has been recognized as a leader in the tube producing industry for more than many years. This leadership stems from the outstanding features designed and built into each three-roll weld box. The unit is mounted on a ridged fabricated steel weldment that is machined to stringent dimensional requirements. A keyway, as specified by the customer, can be machined into the base plate of the unit to assure proper alignment. An optional subbase can be supplied that allows for perpendicular adjustment of the entire unit. This feature corrects for minor mill misalignment or wear and can be used to offset slight seam rolling.

Mounted to the fabricated base is a Addison universal three-jaw chuck. The universal feature allows each weld roll clevis to be adjusted independently or all three clevises adjusted simultaneously. The simplicity of these adjustments allows the mill operator to make quick and accurate set-ups. During the process of manufacturing each weld box, the universal chuck is completely disassembled and evaluated for required accuracy. After this inspection is satisfied, the chuck is mounted on the plate and gib arrangement that locates the chuck assembly true to the tube centerline if a keyway or locating device has been machined in the base plate.

Securely mounted on the face of the chuck are three heavy-duty weld roll clevises. The clevises are cast from 304 non-magnetic stainless steel. Each clevis is precision machined to accurately mount on the master jaw of the chuck with no more than .003" clearance from the face of the chuck to the bottom of the clevis. Optionally, wiper plates can be attached to each clevis. The purpose of the wiper plates is two-fold. First, to create a retainer for stainless steel wool placed at the rear of each weld roll as a pick-up remover. Second, mill coolant can be directed to the backside of each weld roll by utilizing the tube fitting that is attached to each wiper plate. This feature is most useful when mill coolant must be restricted at the point of welding.

The weld roll shaft assembly is unique in its method of accurately locating the weld rolls in the center of each clevis. Pressed into one flange of each clevis is a hardened locating bushing. This bushing contacts the inner race of the weld roll bearing as the weld roll shaft is installed through the clevis and weld roll. The shoulder of the weld roll shaft contacts the inner race of the opposite bearing. A single socket head cap screw locks the assembly in a consistent center location time after time.

One feature many tube manufacturers have found useful is the chuck rotation mechanism. Simply by loosening the three chuck mounting bolts on the chuck face, the entire assembly can be rotated to allow a single grooved roll on top to straddle the welded seam. This configuration most useful for light wall applications.

The weld rolls are manufactured on state-of-the-art machining centers. Each roll is produced from H13 heat resistant tool steel, precision machined, hardened, and ground completely. Contours are machined after heat-treating to assure the highest degree of accuracy and then polished to a high luster finish.

Four-Roll Configuration Advantages

The four-roll configuration (Figure 5-7) functions in much the same way as the two-roll configuration, except that two additional (head) rolls mount vertically above and to each side of the weld seam. The four-roll configuration is recommended for sizes above 2" x .135" thick and above 3" x .187" thick. This configuration has the following advantages:

• Much stronger configuration for running heavier walls.
• Top rolls are adjustable individually and universally for optimum control of strip edge registration for both thin and thick wall thicknesses.
• Top rolls are adjustable individually to adjust roll gap.
• Top rolls can be removed to create a two-roll configuration when running very small diameters.
• Roll wear is reduced on roll lips, which reduces swirl marks.
• Top rolls guide the edges and prevent them from moving outward because of the pressure from the side rolls.

In the Addison weld box, the lower unit and the upper unit are both fabricated steel weldment. The lower unit houses the horizontal squeeze rolls. The squeeze rolls are mounted on live shafts. Each shaft is assembled to the bearing block utilizing Timken bearings. Both squeeze rolls are adjustable in and out to allow for the proper squeeze pressure and adjustable as a unit to maintain true tube centerline location. These adjustments are gear assisted to give a mechanical advantage when turning these screws.

The head rolls are mounted in fabricated steel clevises. Each head roll is complete with a preassembled Timken bearing assembly. The head rolls are adjustable in both the vertical and horizontal plane and can be adjusted simultaneously or individually in both planes. The individual adjustment feature in the horizontal plane allows the operator to modify the gap between the head rolls when there are several gauge changes.

The upper unit assembly is vertically adjustable via a machine screw actuator, manually operated for fine adjustment, and can be supplied with a second input shaft for a DC motor drive system to make larger adjustments quicker. A 1/3 HP motor supplied with a Seco DC Motor Controller Model 163 with start/stop, run/jog, forward/reverse switches and speed potentiometer mounted in a NEMA 4/12 enclosure is used.

The Four-Roll TIG Weld Box is a heavy-duty side closer unit designed with heavy-duty live spindles. The spindles are supported by angular contact ball thrust bearings, which are housed in adjustable slide block housings. Each spindle is manufactured from alloy steel, heat-treated, and precision ground. A coaxial adjustment screw allows each pair of inboard and outboard weld rolls to be closed or opened about the tube centerline either individually or separately. Each slide block housing is cooled during operation via a manifold system located inside the weld box assembly. During the welding process, the weld box is totally enclosed to create the necessary internal gas atmosphere. Provided are optically-protected view ports to allow the operator to monitor the welding technique.

Either the three-roll or four-roll configurations described above may be satisfactory for a broad range of tube sizes and wall thickness. The selection depends on the exact product produced. Economic considerations and operator preference may also be factors. The four-roll configuration is always recommended for larger diameters, heavier wall thicknesses, and higher strength materials.

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