Case Studies

Schweitzer Engineering Laboratories (SEL)

Schweitzer Engineering Laboratories (SEL) invents, designs, and builds digital products and systems that protect power grids around the world. Their technology prevents blackouts and enables customers to improve power system reliability and safety at a reduced cost. SEL offers a variety of fault indicators for use on subsurface or pad-mounted transformers, subsurface or pad-mounted switchgear and sectionalizing cabinets, junction boxes, and splices.  Recently, SEL was facing difficulty in assembling one of the many Reset Fault Indicators they offer. The product is made of Polycarbonate-Makrolon 2607 and project was to weld the clear lens display screen to the body of assembly. Since the product is designed for use in harsh, submersed, and corrosive environments, the hermetic seal of the ultrasonically welded housing is tested to sustain temperature ranging from -40 deg C to +65 deg C.

Unacceptably low process yield using pneumatic ultrasonic welder:

SEL was experiencing unacceptably low yield from their pneumatic ultrasonic welding process. The welds were inconsistent, resulting in leaking non-hermitic welds.  Welding process, DOE’s (Design of Experiments) were conducted over period of three years always pointing to the same small welding process window with high down speeds and very short weld times. Engineers at SEL were thinking to redesign the plastic injection molds for even flatter welding surface.  However, before making costly changes to the injection molds they brought multiple sets of parts to Dukane’s Applications Lab.

Problem identified using iQ Servo Ultrasonic Welding Graph feature:

Dukane’s 20 kHz frequency iQ Series Servo controlled Ultrasonic Welding system with Melt-Match®  technology was used to perform tests on sample parts. iQ Servo welder graphs showed the part was acting like a spring because of a hollow area under the weld zone and was collapsing faster than the horn movement resulting in inconsistent and leaking welds. Therefore, it was necessary to use varying weld speeds.

Servo driven Ultrasonic Welding precise control & repeatability produced 100% yield:

Ken Holt, Sr. Application Engineer, Dukane states, “This grade of Polycarbonate, Makrolon 2607, welds very well when the initial weld speed is slow and is gradually increased over the weld distance. Although old pneumatic systems are capable of varying the force during the weld, the rate of change is restricted due to the time required to move air in or out of the air cylinder. Whereas, the servo system is capable of accelerations of 50in/s2, which is equivalent to changing speed by 1in/s in 0.020s. Dukane’s patented Melt-Match® technology further expands this capability by allowing 10 discrete velocity values during the weld process.”

iQ Servo’s ability to precisely control and vary the weld speed (velocity of the collapse of the weld joint) proved the key factor for welding leak proof parts. Numerous set ups were attempted, until a varying of the weld velocity speed was optimized.  The final speed profile setting from .020”/sec. to .090”/sec. proved to be very robust and allowed for variations on weld distance and amplitude without adversely affecting weld results.

Melt-Detect™ also known as Force Drop is an important component of Melt-Match® technology, which was enabled to ensure complete initiation of melt before prompting the horn to initiate downward movement. The overall “U” shape of the force curve (fig1) indicates that high force was applied at trigger; horn movement was initiated when force dropped to a pre-set value signaling that the part had begun to melt and collapse; finally, force and horn movement was increased gradually providing consistent strong bonding. The gradual increase of the distance vs. time curve (fig. 1) shows no abrupt changes as the weld progresses.

Rick Lewis, Manufacturing Engineering Supervisor, Schweitzer Engineering Laboratories, Inc states, “We had an old 1980’s era pneumatic welder that needed to be replaced.  A new servo welder was the obvious choice because of its greater capability’s. The new servo welder is integrated into a robotic cell and is working flawlessly. The repeatability of the servo welder and the welding and graphing functions make it easier for setting up new welding programs.  It reduces the engineering time and the number of scrap parts required to set up a new welding process.” he adds, “The ability to use the application lab in St Charles and meeting Ken Holt, at Dukane provided a wealth of knowledge that will be used on all of our future welding projects.”

Thus, by using Dukane’s technology SEL was able to get hermetic seal on their existing part and did not have make any costly part design changes to their fault indicators.

Electrical Component

Medical-Diagnostic Test Strips

A leading medical device manufacturing company uses Dukane’s iQ Series Servo driven Ultrasonic Welding System to assemble Test Strips and gets sophisticated results. Assembling mini medical devices as test strips require precise, repeatable and consistent process control. The test strips are made of two thin layers of Polyethylene Terephthalate (PET) film. Between the two layers is a mesh membrane layer carrying the diagnostic chemical. Once assembled, the test strips are placed in an analyzer. These test strips measure Total Cholesterol, HDL, Glucose and Triglycerides.

Prior to investing in iQ Servo Ultrasonic Welder, the biggest challenge for manufacturer was misalignment of thin PET films during assembly process. Scrap rate was more than 30%. Dukane’s iQ Series Servo driven Ultrasonic Welding System with patented Melt-Match® technology, fixed part alignment problem and provided accurate, repeatable and reliable process control. As a result, scrap rate came down to less than 5%. iQ Series Servo Ultrasonic Welders have provided 20+ million cycles in less than three years by using a highly effective and efficient iQ Servo digital process control.

In general, Ultrasonic process allows thin film lamination to move through assembly without product misalignment. Multiple parameters are available for defining triggering sequence for iQ Servo system. In this particular application,iQ Servo system is programmed to trigger by minimal force. Ultrasonic horn travels at a certain speed, and then slows down to a programmed controlled speed prior to coming in contact with part. When system reaches programmed trigger force value, horn’s downward movement stops completely and Ultrasound signal starts.  Next, system detects a programmed drop in force, indicating that parts have begun to melt and weld continues as servo motion restarts. Part compression continues for programmed distance and speed. The above feature to control horn speed and detect melt initiation reduces unnecessary force on thin film walls and improves weld quality.

In final weld phase, Servo gives the flexibility to program dynamic and/or static hold. In this application, iQ Servo System has been programmed to provide ‘Static Hold’. As a result, press holds its final weld position for a given amount of time, without moving. This gives materials enough time to solidify without misaligning. Horn then returns to home position or top stroke ready for a new cycle. This was the most helpful feature for these thin PET strips.

Another major advantage of using iQ Servo system is the ability to duplicate a known process on multiple iQ Servo Systems without any variation in weld results. In this application, this feature was of major benefit for the manufacturing company. They were able to install multiple iQ Servo System with their growing need without investing extra time or effort in fine-tuning the process for each set up.

Along with great product Dukane’s sales and engineering team, collaboratively work with customers to provide with the best solution for their given application. For more information on iQ Series Servo Ultrasonic Welder and other Ultrasonic Welding products visit http://www.dukane.com/us/ or call 630-797-4900.

Medical Industry

Tonneau Cover Assembly

Dukane feeling honored and proud to be part of this award winning team for Tonneau cover assembly on the 2016 Toyota Tacoma pickup. This winning team in eleven months designed and created a Tonneau cover that is not only flexible and light weight but also provides the required strength & security to the end user. All these unique features have made the Tonneau cover a winner in Parts Competition in Exterior Trim Category at 2015 SPE TPO Automotive Engineered Polyolefins Conference. 

New Toyota Tonneau cover has a trifold design, which can be easily secured or removed from the vehicle. Thermoplastic polyolefin is injection molded to form the upper and lower panel of these three folds. Injection molding was the choice, to get consistent thin wall and dimensional stability.  Further these panels are trimmed for additional weight savings. Aluminum bars, “T” nuts and nut plates are placed on the panels for required strength.  All the three panels have more weld area on the right and left side to prevent the use of a crow bar to pick up or pry open the assembly and provides security from theft.

Initially, leading suppliers of Vibration Welding technology from the plastic welding industry, including Dukane, felt that this application was a low frequency weld application. Due to the high cost of the low frequency Vibration Welders and the extra expense required to build the larger tooling, it was evident that using low frequency equipment would be a very expensive way to weld these panels.  However, Dukane’s technical experts kept an open mind and tested the application using both high and low frequency Vibration Welders, proving it could be done by a high frequency welder.  Finally, Dukane built a standard 240 Hz Dukane Vibration Welding machine and kept the cost to a minimum.

Two versions of the assemblies were designed one for short bed truck and another for long bed truck. Dukane built three panels per version which means six vibration tools to weld the six individual parts. Dukane’s customer Nyloncraft, welds these parts in batches. The quick tool change feature of Dukane’s Vibration Welders allow Nyloncraft to weld all the three panels of bed cover using the same welder. Tools are typically changed in less than ½ an hour much less than the changing of the mold tools.

Inductive part sensing capabilities of Dukane’s Vibration Welders are used to make sure that all aluminum bars, “T” nuts and nut plates are placed securely before welding the upper and lower parts. Dukane’s proprietary HMI software is programmed to look for up to 15 parts before welding the upper and lower molds of the cover panels. There is somewhere between 55 and 70 square inches of weld area on each assembly.  Some panels are larger so they are closer to the 70 square inches of weld.

Initial challenges on this project were met with team work, persistence and clear vision. The result is an award winning product that helps Toyota meet stringent CAFÉ (Corporate Average Fuel Economy) standards for mpg of fleet vehicles.

 

 

Automotive