Resistance spot welding monitors and checkers measure the electrical and mechanical aspects of the welding process; they analyze weld quality enabling the user to make adjustments and improvements resulting in process stability, and, ultimately, improved yields. Here’s a quick look at the three most important reasons to consider adding a weld monitor or weld checker to your resistance welding line:
Weld monitors give you a 360° view of your weld making both R&D and production analysis work more effective
In the process development phase, weld monitoring is indispensable for evaluation and research, process optimization, and process validation. Recently, a process engineer from one of our medical device customers was doing some R&D work using a Miyachi Unitek UB25 linear DC welder (which can monitor current, voltage, power, resistance, and time), along with a Series 300 electromagnetic weld head, monitoring displacement. The legacy process used epoxy to join two small workpieces, and the company wanted to reduce manufacturing costs by developing a more automated method using resistance welding, but the engineer wasn’t having any luck getting it to work properly. His welds were inconsistent and the material was changing in form and structure during cooling, leading to unacceptable variations. The failure rate was an astonishing (and unacceptable) 50 percent! He had some data - bits and pieces of information from each of the devices he was using, but he wasn’t looking at them together on the same screen.
Enter the Advanced Data Analysis Monitor (ADAM). We set the ADAM up with the UB25 and Series 300 to monitor force and displacement along with the other parameters the engineer was already monitoring (voltage, current, power, time). We put them all together on one large screen and within the first couple of welds got some eye-opening information. The screen looked something like this (note: this is NOT the actual data).
- The part was collapsing after the weld energy had shut off – about 2-3 milliseconds (ms) after the end of the weld energy.
- Material displacement was very rapid, causing a spike of 40 pounds (lbs) in the force profile – when the welding force was only 8 lbs! The difference was due to the weld head acceleration as it tried to maintain force on the part while it was collapsing. As the material cooled, the increased acceleration caused the large 40 lb. impact force, which was having a negative effect on the weld, and causing variations in the formation of the part-to-part interface.
2. Stability = accountability
With an ever-increasing emphasis on process accountability, manufacturers in ALL industries need the best possible information to support process development and production monitoring. They also need data to document quality requirements contained in ISO (International Organization for Standardization), GMP (good manufacturing practice) and TQM (total quality management) programs. Weld monitors enable them to get the information back up they need.
Armed with the information gleaned from ADAM, we were able to focus our efforts to bring the process under control. We started by changing the process parameters - reducing weld energy, and introducing upslope to the weld profile to bring the energy in more slowly. We also increased the weld time slightly. These small changes resulted in less rapid displacement, allowing the weld head force control to become stable. Within a short time, and 20-30 adjustments, we had increased the success rate to 85%! (image shown is NOT actual data).
3. Improved Yields
Obtaining high yields is the key to manufacturing success – and using a weld monitor is one fast and easy way to make that happen. As outlined above, weld monitoring helped our customer achieve an 85% yield in just a few short hours. After purchasing his own ADAM, and further tweaking the process, he obtained a 99 percent yield. The company is now in production with the part.
So there you have it. Makes a pretty persuasive case for the benefits of weld monitoring, doesn't it? Bottom line: Analysis - Stability - Yield. 3 very good reasons for adding weld monitoring to your process.