Are Tactile Seam Tracking Systems Right for You?
Brian Butler, Automation Manager, Arc Products, Inc.
In the last few years, many manufacturers once again have become aware of the advantages of using seam tracking systems. For companies to stay competitive in today’s market, production facilities must become lean and efficient. Tactile seam tracking systems help manufacturers achieve this goal with a relatively small capital investment. Companies in countries that have historically added more labor to a particular welding project, in hopes of meeting required production rates, also have realized the benefits tactile seam tracking systems offer.
Step 1 –Payload Requirement: Determine the weight the system will carry and select the appropriate cross slide. Cross slides are offered in weight capacities of 40 (18), 250 (113) and 450 (204) pound (kg) models. Be sure to select a model with a rating higher than your requirement. Pricing differences between models is usually not significant, so if your requirements are near the rating of one of the cross slides, upgrade to the next model to provide much longer service life and less maintenance.
Step 2 –Stroke Length Requirement: Determine the stroke length of the cross slide you will need. The 40-pound (18 kg) model is typically offered in 3” x 3” (8 cm x 8 cm) and 6” x 6” (15 cm x 15 cm) stroke lengths, whereas the larger models are offered in standard 5” x 5” (13 cm x 13 cm) or 10” x 10” (25 cm x 25 cm) stroke lengths. The first number represents the horizontal stroke length and the second is the vertical stroke length (use “H” before “V”, just as in the alphabet, to be sure your order is built correctly).
Custom stroke lengths are available in 5” (13 cm) increments up to 60” for the 250 (113) and 450 (204) models. The cross slides can be configured with each axis having a different stroke length to accommodate specific applications, where, most commonly, more horizontal stroke length is needed—a 20” x 10” (51 cm x 25 cm) or 30” x 5” (76 cm x 13 cm), for example.
Step 3 –Level of Automation: Select the level of automation—fully automatic or semi-automatic. Selecting fully automatic will require use of an advanced model, which can take full advantage of the remote inputs and outputs. The standard model would fit the semi-automatic selection, providing basic seam tracking but requiring the operator to manually start and stop the welding process.
Step 4 –Sensor Tip Selection: Selecting the appropriate tip is simple, primarily involving matching a tip size to the seam type and the material thickness.
Each system is provided as a kit consisting of several components; see Table 1 for a list of components and typical price ranges for pre-configured systems. As you will notice in this table, the standard seam tracking systems are the most affordable. The return on investment can be as short as 5 to 6 months, depending upon current production rates and rework at your facility.
Table 2 lists the features and capabilities of each model of seam tracking systems. As mentioned earlier, the standard systems offer basic seam tracking features. This standard model will search for the seam by driving straight down until the sensor contacts the work piece. In fillet welds or lap joints the Sidetrack function is enabled to provide a left or right bias to keep the sensor’s tip against the seam’s edge. In this case, the system will drive downward at a 45-degree angle until the sensor contacts the work piece and is stopped horizontally by the seam’s edge.
In either case, once this basic system finds the seam, the operator must start the welding process, i.e., start the welding power source, wire feeder, carriage / welding lathe, etc. The standard seam tracking system is ideal for simple applications to gain quality, reliability and productivity without the added expense of fully automating the welding station.
Another application that may create an obstacle is multi-pass welding. Multi-pass welding has been an issue for seam tracking systems because the seam is not well defined after the first pass. However, by using a “Y”-type sensor tip, the system will track the seam very well. In fillet welds for beam fabrication, for example, a “Y”-type sensor tip could be employed to sense the seam at two different points. One tracking point of the “Y” tip would sense horizontal movement from the flange, while the other would sense vertical movement from the webbing. In tracking the seam in this manner (out of the seam), the multi-pass weld beads will not affect the system’s ability to track the seam. A larger diameter ball tip can be used instead of a “Y” tip with similar results.
Multi-pass welds on “V” grooves, or deep grooves, offer a greater challenge, but these also can be overcome with great results. With advanced systems, the sensor can track the first pass, usually the most critical, without issue. Subsequent hot and fill passes can be tracked using a left or right bias (sidetrack) to stagger the beads as the passes are run. But on cap passes, the system must be locked out horizontally, to prevent automatic torch movement from the sensor, because there is no longer a well-defined seam to hold the sensor’s tip captive. An input called horizontal auto-disable is used and, when enabled, locks the sensor’s ability to move the torch left or right while still tracking vertically and maintaining a consistent torch height. Enabling this feature allows the operator to manually position the torch left or right for cap passes using the joystick. By using this method, the critical passes are tracked reliably and quality is improved significantly over positioning each weld pass manually.
With the advancements in welding technology, weld travel speeds are increasing beyond manual torch positioning and require some type of automation to achieve greater torch accuracy. Seam tracking systems offer this with a relatively small capital investment. Take the short quiz in Table 4
to see if a seam tracking system can benefit your company.
Can Seam Tracking Systems benefit your welding application? Take this short quiz to determine if seam tracking is right for your application.
1. Are your parts the same basic shape with similar seam configuration, varying only in size—diameter and/or length?
2. Is your welding application repetitive in nature—many of the same part are welded before the welding station is retooled for another part type?
3. For circumferential welding projects, like tanks, cylinders and/or pressure vessels: a. Are operators required to manually weld the end-caps or manually position a torch while welding?
b. Would you like to weld both end-caps at a time?
4. For beam fabrication: a. Are operators required to manually weld the beam or manually position a torch throughout the full length?
b. Would you like to weld both sides of the beam at the same time?
5. Is your seam configuration a lap joint, v-groove or fillet weld, either single or multi-pass?
6. Is your fit-up good, but some variation exists that prevent the joint from being welded reliably by hand? For example, on large tanks the shell / cylinder sag under the weight or walks on the turning rolls.
If you’ve answered YES to any of the questions above, adding a seam tracking system to your application could offer significant benefits over your current welding process.
Brian Butler is the automation manager for Arc Products Inc., a Lincoln Electric Company.