3M Dual Lock Reclosable Fastener SJ3550

Laser Processing of 3M™ Dual Lock™ Reclosable Fastener SJ3550

Introduction

3M™ Dual Lock™ SJ3550 is part of a product line of reclosable fasteners produced by 3M. Dual Lock SJ3550 is comprised of an array of polyolefin stems designed to interlock when two sheets of the material are pressed together. This creates a strong bond that can be used to replace conventional fastening methods. Dual Lock SJ3550 consists of a 75µm plastic liner, a 630µm thick acrylic adhesive, and a 2.5mm thick array of polyolefin stems and mushroom heads. A diagram depicting Dual Lock SJ3550 is shown in Figure 1.

Figure 1. Dual Lock SJ3550 diagram showing plastic liner (75µm), acrylic adhesive (630µm), and polyolefin fastener array (2.5mm).

Dual Lock SJ3550 is used in aerospace, automotive, industrial, and commercial applications. The fastening strength, flexibility, vibration reduction, and temperature, moisture, and UV resistance that Dual Lock SJ3550 provides make it an ideal replacement for many traditional fastening methods. The non-contact nature of laser processing allows applications to be processed with small features and fine geometry which might be difficult to achieve with traditional mechanical methods. Dual Lock is only suitable for laser cutting which produces consistent edges and minimal heat affected zones. Other laser processes are not suggested as they are not conducive to the intended use of this material. Universal Laser Systems makes it simple to consistently and repeatedly process this material to a high degree of dimensional accuracy because the non-contact nature of laser processing eliminates material deformation during processing.

Laser Processing Notes

Dual Lock SJ3550 was tested to assess laser processing compatibility and determine the best configuration of peak laser power and wavelength. Dual Lock SJ3550 appears to absorb both the 9.3µm and 10.6µm laser wavelengths efficiently with a minor difference in results. A microscopy image taken at 300x magnification of the Dual Lock SJ3550 edge after laser cutting is shown in Figure 2.

Figure 2. Microscopy image (300x) of the edge after laser cutting Dual Lock SJ3550. The heat affected zone measures 100µm. The image above depicts the liner up as the material is processed with the fastener array down.

Dual Lock SJ3550 was tested with both 9.3µm and 10.6µm laser wavelengths. The results of these tests were compared by analyzing the heat effects, quality of the processed edge, and post-processing requirements. The comparison of these system configurations is listed in tabular form in Table 1 and shown photographically in Figure 3. The 9.3µm configuration produces a noticeably better edge when cutting this material and is the recommended configuration.

Table 1 System Configuration Comparison

System Configuration	Heat-Affected Zone	Process Characteristics	Post-Processing Requirements
9.3µm (Recommended)	Minimal heat-affected zone of approximately 100µm	This configuration results in a smooth edge that exhibits minimal heat effects and no discoloration	No post-processing required
10.6µm	Increased heat-affected zone of approximately 350µm	This configuration results in overall increased heat effects along the processed edge	No post-processing required

Figure 3. Comparison microscopy images (300x) of the edge resulting from 9.3µm (left) and 10.6µm (right) wavelengths.

Processing Example

Dual Lock SJ3550 applications requiring fine geometry and intricate detail without degrading the physical properties of the material can be accomplished with Universal Laser Systems technology. An example demonstrating the results of laser cutting Dual Lock SJ3550 using the recommended system configuration is shown in Figure 4.

Figure 4. Example of the geometry possible with laser cutting of Dual Lock SJ3550.

Conclusion

Dual Lock SJ3550 is suitable for laser processing and was extensively tested to determine the optimal processing configuration. Through this testing it was determined that laser cutting is viable with this material and a 75 watt 9.3µm CO₂ laser source is the recommended configuration for the. Dual Lock SJ3550 which efficiently absorbs the 9.3 µm wavelength laser energy to produce a processed edge that has minimal heat affected zone and discoloration.