Reducing Production Waste with Laser Profiling and Characterization
Since the Scientific Revolution of the 1500’s and the Industrial Revolution of the 1700’s, both science and industry have moved and merged at a rapid pace. Every time you look through a trade journal, listen to the daily news, or explore the Web, you see announcements about discoveries and inventions. Remember thinking how fantastical the technologies showcased in the movie Star Wars were? Yet today we are beginning to see some of them emerge. What was once deemed science fiction or fantasy is now becoming reality.
One of the key principles driving the success of science and industry is the adoption of production processes and the tools supporting it. Humankind has been able to take what we now think of as basic production concepts and tools and change or evolve them to accomplish things never before thought possible. Using various, and occasionally exotic, materials, methods, and disciplines, we have seen many aweinspiring things come to fruition. In some cases, manufacturing processes no longer even require direct human intervention to accomplish the desired end result.
|Thanks to the efforts and imagination of Theodore Maiman of the Hughes Research Laboratory in California on May 16, 1960, we now have the laser, a mainstay of many industries (image source: laserfest.org). Since its discovery, the laser has undergone significant changes and iterations. And industry has duly taken advantage of these changes and applied them to many different applications. Lasers are now widely used and present in many industries, phases of production, and fields of endeavor. Lasers assist industry in producing parts at higher volumes and with greater accuracy than ever previously imagined.||
For the most part, industry and business are driven by profit. In order to positively impact overall profitability and thus remain competitive and viable, processes have to run at a higher rate of speed, reliability, reproducibility, and accuracy. But there are pitfalls. One of the largest is variable cost, which is unavoidable. In a general sense, variable cost is any cost that can vary depending on production volume, rising and falling as production increases or decreases. Raw materials are a major component of variable cost and little can be produced in today’s world without them. Another key component of variable cost is management of the waste stream.
Lean manufacturing was developed as a philosophy to help science and industry address some of these concerns by establishing sets of tools that assist in characterizing and optimizing a given process. Lean defines seven degrees of waste: transportation, inventory, motion, waiting, overproduction, over-processing, and defects. In the past, many manufacturers lacked the proper knowledge and/or tools to adequately understand, characterize, and optimize their various processes. In many cases they only had a cursory understanding as to why bad parts or scrap was occasionally being generated. As a general rule, most industries would initially set up their product lines for a production run, run some preliminary sacrificial product, and then, if all checked out, they would begin running production. This is all well and good until something unexpected occurs and negatively impacts product quality and/or volume. On a modern, high speed, precision process, if something malfunctions it can quickly affect hundreds or even thousands of valuable parts creating a mountain of scrap—many times at great cost.
Product Quality and Laser Profiling
Knowing which process parameters or key control characteristics to measure within a laser manufacturing process and how they relate to product quality and waste are critical. A laser profiling system can be of great benefit in helping to characterize and identify which variables affect product quality and waste minimization. Yet it is not uncommon to discuss a customer’s laser process and come to the realization that they have never evaluated the quality of their beam beyond the initial delivery and assessment of their laser’s commissioning document, i.e., certification document. Many companies, after initial system set-up, merely run a few test parts and, if all is well, continue to run until bad parts are inevitably produced. When this happens, operators, process engineers, maintenance personnel, and supervisors actively engage in adjusting various knobs and controls in the hopes of impacting their process so it gets back to “normal”. In some cases, this can go on for days before patience is lost or scrap expenses are overwhelming. This is when a frantic call goes out to an outside service organization in order to get data on what potentially went wrong, incurring further expense and extended downtime. Unfortunately, this approach is merely a band aid that rarely leads to the identification and permanent elimination of the problem.
This does not have to be the case. Wouldn’t it be better to avoid some of these problems or pitfalls before beginning production by having the proper tools in-house and using these tools to characterize and optimize a process in advance so that product quality and process variability could be understood and maintained?
Understanding Laser Variables to Control Waste and Cost
Six Sigma teaches that if you map the process and understand the key variables associated with each step within a given process, as well as understand the sources of variability associated with these variables, you can ultimately control waste and lower overall cost. Understanding variables within the process and correlating these to end product specifications and suitability (fit for use) is paramount to reducing waste. In the case of laser applications, a key variable may be something such as beam diameter, beam tomography or modal structure, spatial power, energy density and distribution, collimation, or alignment.
Understanding, measuring, and correlating these variables will have a positive impact on final product quality (fit and finish), and waste reduction. Waiting for a failure to randomly occur or relying on the final product to act as the “bell weather” or “canary in the mineshaft” should be a thing of the past. The ability to gather accurate process data before and after a production run or product campaign provides critical process knowledge and the traceability now required by many industries.
Yet many people using lasers are unaware that there are a number of tools available beyond the basic power meter and sensor combination to help measure, characterize, and understand, in real-time, what their laser is outputting. Since its founding in 1976, Ophir-Spiricon has developed world class instruments that allow researchers and manufactures to measure and understand their lasers. The following is a brief general summary of some of the many profiling instruments available and their capabilities.
|Scanning-Slit Profilers (microwatts – 1000’s watts)
NanoScan is a high accuracy instrument which can be used to measure both CW and KHz pulsed laser sources with beams sizes ranging between 7μm to 6mm, depending on the power and wavelength. Wavelengths between 190nm out to 100μm (Far Infrared) can be measured effectively. This is accomplished by choosing one of the three different single element detector choices available: silicon (190μm – 950nm), germanium (700nm – 1800nm), and pyroelectric (190μ - 100μ).
Once aligned with the laser source, results are instantaneous and sow accurate 1D, 2D, 3D, and usercustomizable results such as beam width, centroid position, beam divergence, ellipticity, Gaussian fit, pointing stability, and more. Results charting, data logging, and reports can be done within the NanoScan software package.
Because this is a scanning slit device, in most cases additional attenuation is not required. This is a very portable device that uses direct USB connectivity so there are no external controllers or power supplies required.
Camera-Based Profiling Systems (microwatts – 1000 watts)
There are many different camera-based systems available and as a general rule each system is comprised of a camera, beam attenuator accessory, and software. These systems allow the user to evaluate both CW and pulsed sources. As with the scanning-slit profilers previously discussed, wavelengths between 190nm (UV) – 3000μm (Far Infrared) can be accommodated, the main difference being that these cameras systems use an arrayed detector as opposed to a single element. The same detector types apply here as well. Because these cameras have detector arrays, they are somewhat limited as to the smallest beam they can accurately measure without additional optical enhancement. This is primarily a function of pixel size. As a general rule we like to have a minimum block of 10 x 10 pixels illuminated in order to insure that the laser source is accurately represented.
|Depending on the camera and the array selected, beam sizes between 40μm and 24mm can be analyzed. Most of the cameras have USB interfaces so they are very easily connected to either a laptop or desktop computer.|
BeamGage profiling software provides the output interface and helps to analyze the laser source in real time. BeamGage is currently available in two versions – Standard or Professional. BeamGage PRO is an upgraded version of BeamGage STD but has additional key functionality: Automation Interface (LabVIEW, .NET VB, and Excel), Custom Calculations (programmable and user determined), and Image Partitioning. After alignment and attenuation, data acquisition is instantaneous with a high degree of resolution and accuracy.
Non-Contact (500 watts – 120kW)
A recent addition to our profiling family is a high power non-contact focus spot size and position monitor—BeamWatch. This instrument was designed to measure lasers with wavelengths between 980nm – 1080nm. The beauty of this instrument is that it can effectively measure lasers output as low as 500 watts and because this in a non-contact instrument there is no reported upper limit.
BeamWatch uses disruptive technology and measures the signal generated from Rayleigh scattering around the laser’s beam waist. This allows the user of the device to instantaneously and dynamically measure the focus spot size, focus spot location, beam wander or shift, centroid location, Beam Parameter Product, and other key spatial and beam quality parameters. BeamWatch can be coupled to automation with tools that support various Automation Clients. Communication is done through a PC using GigE Ethernet connectivity.
Understanding and Controlling Your Process
Employing one of the Ophir-Spiricon beam profiling solutions is an excellent step in understanding and controlling your process. These world-class tools are recognized and well established within the laser industry. It does not take long to become proficient in their use and by doing so a laser owner and operator can gather accurate and highly reproducible information quickly and efficiently.
Many industries are already routinely using this laser measurement equipment to conduct root-cause analysis studies, verify alignment and set-up, understand laser sub-component effects, conduct screening experiments and correlation studies, establish preventative maintenance schedules based on actual data as opposed to random recommendations, and develop process application windows, etc. Knowing that a process is stable, consistent, predictable, and capable goes a long way toward generating sustainable profit, waste minimization, and end customer satisfaction.