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Home / Three Common Questions Concerning Laser Welding in Sheet Metal Fabrication

Three Common Questions Concerning Laser Welding in Sheet Metal Fabrication

Many sheet metal fabrication shops still hesitate to invest in laser welding. They are missing out on the numerous competitive advantages and opportunities that it offers over conventional welding processes. Here are some insights that they need to know.

Figure 4. Electrical housing, .060 in mild steel, laser welding vs. MIG welding. Laser welding this electrical housing made of .060 in thick mild steel cut production time to just 9.9 hours per year compared to MIG welding. The cycle time shortened by 77 percent, cost fell by 17 percent, and the smoother surface on the laser welded seams increased product quality. (second view)
Figure 4. Electrical housing, .060 in mild steel, laser welding vs. MIG welding. Laser welding this electrical housing made of .060 in thick mild steel cut production time to just 9.9 hours per year compared to MIG welding. The cycle time shortened by 77 percent, cost fell by 17 percent, and the smoother surface on the laser welded seams increased product quality. (first view)
Figure 1. Cover, .060 in mild steel, heat conduction welding. Laser welding reduced the production time of this mild steel cover by 91 percent compared to TIG welding, and part costs dropped 69 percent even though the hourly rate of the laser welding cell is higher than the TIG welding. Heat conduction welding creates cosmetic weld seams with smooth surfaces that often eliminate or greatly reduce secondary processes like grinding or straightening. Even complex joint geometries like curved shapes or materials with different sheet thicknesses can be laser welded.
Figure 2. Water tank, stainless steel, deep penetration welding. Deep penetration welding is used when full penetration, high part stiffness or sealed and tight weld seams are required, such as the stainless steel pressure tank shown here. Weld speeds of 40 ipm to 200 ipm, combined with high weld strength, can be realized.
Figure 3. Flange-to-tube connection, .120 in mild steel, deep penetration welding. The consistent weld seam quality, decreased heat input and negligible distortion of welded components make deep penetration welding ideal for brackets or flanges. Laser welding cut the production time on this mild steel flange by 81 percent and reduced the total cost by 51 percent.
Figure 5. Laser beam sharing of 2D laser cutting system and laser welding cell. Shops can minimize their investment costs in a laser welding cell by up to 40 percent by creating a laser network that uses an existing laser resonator from a 2D laser cutting machine to support laser welding operations.
Table 1. Cost and Time Comparisons: Laser Welding vs. Conventional Welding
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Laser welding has been widely accepted by the automotive industry for decades, but in sheet metal fabrication many shops are still hesitant to take the leap. The latest advancements have made laser welding a more viable solution, reducing the cost of entry and providing sheet metal fabricators greater access to the numerous advantages laser welding offers compared to conventional welding processes. Here we address the common questions sheet metal fabricators ask when looking to add laser welding to their shop.

WHAT SHOULD I KNOW ABOUT LASER WELDING BEFORE I LOOK TO INVEST?
In sheet metal fabrication, a solid state laser emitting light at a wavelength of approximately 1 µm can be used to join materials. The focused laser beam melts the material locally and with minimal heat input resulting in minimal distortion of the material. Three main parameters determine the laser welding process: laser power, weld speed and focal positioning.

In heat conduction welding, cosmetic weld seams with smooth surfaces result and often eliminate or dramatically reduce secondary processes like grinding or straightening. Typical applications include covers (Figure 1) and boxes, or fixtures such as counters and sinks for the medical or food service industries. With deep penetration welding, weld speeds of 40 ipm to 200 ipm, in combination with high weld strength, can be realized. This welding technique is used when full penetration, high part stiffness or sealed and tight weld seams are required. Applications include pressure tanks (Figure 2), brackets or flanges (Figure 3). Both techniques offer consistent weld seam quality, decreased heat input and negligible distortion of welded components. Due to the small spot size of the laser, the heat input is typically 200 times lower than with arc welding processes like MIG, MAG or TIG welding.

To fully reap the benefits of laser welding, a fabricator must commit to high-quality sheet metal processing prior to welding. As a rule of thumb, material gaps in the weld zone should be limited to approximately .008 in, although this can vary based on the application. Luckily, these tolerances are easily met by modern 2D laser cutting machines and press brakes. Although parts can typically be converted from arc welding to laser welding with just minor adjustments to the design, laser welding does provide design engineers with new opportunities, such as overlap welds, corner welds and flange welds. Even complex joint geometries like curved shapes (Figure 1) or materials with different sheet thicknesses can be laser welded.

WHAT MATERIALS AND SHEET THICKNESSES CAN BE JOINED WITH A LASER WELDING CELL?
While mild steel, carbon steel, stainless steel or aluminum are most commonly seen in laser welding, fabricators are not restricted to these materials. It is also possible to join dissimilar material or materials like coated steel, copper or titanium. With laser welding, the maximum sheet thickness depends on the welding technique as well as the material. Typical sheet thicknesses for heat conduction welding with a 3 kW laser are approximately 3 mm (.120 in) for steel and 2.5 mm (.100 in) for aluminum due to the material’s high reflectivity and thermal conductivity. The weldable sheet thicknesses increase when deep penetration welding or a higher laser power is used.

HOW DO THE ADVANTAGES OF LASER WELDING INFLUENCE PART COSTS AND ROI OF A LASER WELDING CELL?
For most laser welded sheet metal parts, the weld quality and the speed of processing are superior to conventional welding processes, and this ultimately results in increased profit margins. If you consider the complete sheet metal fabrication process (i.e. cutting, bending, punching and welding), welding and refinishing affect approximately 70 percent of the cost per part. This is mainly due to the length of time required and the high consumption costs associated with these processes. These main cost drivers are reduced by laser welding’s consistent quality and cosmetic seams.

This is illustrated by the sample parts mentioned previously (Table 1). Each sample considers welding and refinishing time, including programming and setup, as well as consequent costs such as fixturing. For each sample, it is assumed that 500 parts are manufactured per year. Production time of the mild steel cover shown in Figure 1 was reduced by 91 percent by laser welding instead of TIG welding. In addition, part costs were reduced by 69 percent, considering the hourly rate of the laser welding cell is higher than that of TIG welding. For the mild steel flange depicted in Figure 3, production time was reduced by 81 percent while total cost diminished by 51 percent.

Welding the electrical housing made of .060 in thick mild steel, shown in Figure 4, cut production time to just 9.9 hours per year with laser welding for a time reduction of 77 percent and a cost reduction of 17 percent, compared to MIG welding. Furthermore, quality increased by way of a smoother surface for its laser welded seams. While these calculations are based on average values and the results will vary based on the application, the time and cost savings associated with laser welding tend to be impressive.

Since sheet metal fabricators benefit from the laser welding process in various ways, the ROI varies based on the production requirements of the shop. However, a laser welding cell can achieve a very high return on investment based on typical calculations. For example, pay-off time is roughly three years when a fabricator processes parts similar to those discussed above. This is true even when machine utilization is less than 50 percent and only active one shift per day. In addition, it is also possible to minimize investment costs by creating a laser network (Figure 5). Using an existing laser resonator from a 2D laser cutting machine to support laser welding operations can reduce investment costs of the laser welding cell by up to 40 percent.

While most sheet metal fabricators will benefit from the numerous advantages of laser welding, many are still hesitant to make the investment. To overcome this concern, consider the needs of your sheet metal shop and how laser welding might impact production. Consult with industry experts who can help evaluate your parts, answer questions and show you how laser welding opens up new opportunities.

9 Comments

Leave a Comment:

  • Pilyong Oh wrote:

    Hi, I have an interest in Figure 1. Bead looks very nice but is there any good solution not to have any oxidation in the bead?

    • Figure 1 represents a mild steel cover after laser welding process. Due to corrosion, mild steel parts are typically painted after welding process to avoid rust. Thus, oxidation of weld seam is negligible since it is not visible any more after painting. Compared to conventional welding processes (like TIG or MAG welding), the quality is of laser welded seams is superior even without any refinishing.

      If welding stainless steel, one has to avoid oxidation to achieve best possible weld quality. This is possible by use of shielding gas and rapidly cooling the weld zone by e.g. copper plates. However, smallest content of O2 on weld process zone can cause discoloration.

      From my perspective, it is a topic depending on the specific requirements of the part in terms of weld quality.

  • Agis Liberakis wrote:

    How does E-Coating and painting over carbon steel affect the quality in laser welding? Thanks.

    • Dr. Philipp Rettenmeier wrote:

      In Figure 1, the cover is laser welded before (!) being painted. Thus, there is no influence of the painting to the laser weld quality.

      Laser welding of coated mild steel is also possible. Due to the large variation of coatings, laser weld tests might be applicable to test the interaction of the welding process and the specific coating. However, for typical coatings (e. g. zinc coating), numerous successful laser weld tests were already performed by TRUMPF.

      Thanks for contacting us in case of specific inquiries.

  • Umesh More wrote:

    Can laser welding be done on a typical motor cycle petrol tank where presently it is done with the seam welding process? The important requirement is that it must be leak-proof and sealed. The sheet metal thickness is 0.8 mm. Thoughts?

    • Priyank Joshi wrote:

      Dear Mr. Umesh,
      Are you from India? I would like to discuss this in detail to provide a suitable solution. please call 020-66759800.
      Priyank Joshi
      Trumpf India

      • Umesh More wrote:

        Hi Priyank, Tried to call you but your number is disconnecting pl. call on this number 020-67336818.

  • Dr. Sanjeev Joshi wrote:

    Is the discussion on laser welding of petrol tank still active? Interested to know what is updated on this topic in the last two years. How to avoid porosity in fusion zone due to Zn coating on sheet? Thanks.

  • CHIDANAND MAGADUM wrote:

    High strength steels can be welded by laser?

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