in Vol. 15 - November Issue - Year 2014
Advanced Stress Testing Tools For Shot Peened Surfaces
GearScan 500 is our newest product created to help customers to check their gears, says Lasse Suominen
Prism equipment (ESPI) for hole-drilling measurements. Example of measurements of a shot-peened sample on top .
Lasse Suominen checking the status of the CrankScan 500 under manufacturing
Xstress Robot making stress measurements on a pinion gear
MFN had the opportunity to talk to Lasse Suominen, President of Stresstech Oy - providing quality control tools for 30 years.
(?) MFN: Mr. Lasse Suominen, it is good to interview you. Could you introduce yourself first?
(!) L.S.: Sure but first I'd like to thank you for the invitation to this interview.
Today I am the President and part owner of Stresstech Oy, and have been with the company for more than 20 years, first as a research scientist and since 1998 as President. Even before joining the company, I worked with stress-related subjects in my previous jobs. I have been developing our X-ray products from the beginning. My basic education is Master of Science in Technology, and I have specialized in Materials Science.
(?) MFN: Stresstech Oy has been in the industry over 30 years, please talk about your company's history.
(!) L.S.: The company was first founded in 1983 to USA with the name American Stress Technologies Inc. by Seppo and Kirsti Tiitto to market the method that was based on Seppo Tiitto's dissertation on Barkhausen Noise. After the first sales were received, Stresstech Oy was founded in Finland to manufacture the equipment for measuring stresses.
We started with the magnetic method called Barkhausen noise, which method we commercialized. In 1990, we added X-ray diffraction to our expertise, and now we have a hole-drilling method in our selection. All of these methods have such unique features, which no one else has ever before applied. Nowadays we also provide measurement services around the world.
We have an efficient worldwide organization that, in addition to the head office in Finland, includes sales and marketing offices in Germany, USA and India, and a branch office in Sweden. These offices are strong centers that support our customers locally and provide measurement services. We also have representatives in more than 20 countries worldwide, who have our products in their selection.
Stresstech Group is well known around the world among our customer base. Most of our customers belong to the transportation industry, e.g. to car, truck, heavy equipment and aircraft manufacturers. Recently, the energy sector has also become more important for us. The newest interesting field is welded structures made from high strength steels.
(?) MFN: There are not many companies that have been doing business with residual stresses for over 30 years. Which strategies do you use to meet the market's needs?
(!) L.S.: From the very beginning, our main goal has been to measure residual stresses. We have been able to keep this goal very well over thirty years. We have systematically expanded our product line so that we can give solutions to as many residual stress measurement cases as possible to our customers. Barkhausen noise technology can be applied only to ferromagnetic material, so we expanded to X-ray diffraction to get better coverage. Because the XRD method has limitations with non-crystalline materials, we wanted also to have a solution in cases, where the XRD does not work. Therefore, we decided to expand our product line with the hole-drilling method.
As the quality of their products is always the key issue for our customers, our goal is to make achieving and keeping that as easy as possible. A very important part of the quality is the residual stress born in the production process. We have invested many resources to make it easier to perform stress measurements by the means of ease of using software and automated measurements. This results in less user effects. All our products and new ideas are tested in our measurement laboratory, where we also do service measurements for customers that need only occasional measurements or want to know if our methods can satisfy their needs.
Our main goal is to help our customers improve the performance of their products. We offer our customers tools to measure stresses by providing them instruments to easily study stresses in their products to get to the positive result in their own manufacturing processes. With the help of our products, our customers can easily spot the weak points in their production or process or verify that the process works the best possible way, and that their products fill the set quality demands. Defects in their products or problems in their processes can cause remarkable costs or irreplaceable damage to their image.
We work very closely with our customers either with the help of our representatives or by ourselves, as especially, our sensors and stands are usually custom made according to the specific needs of the part or surface to be measured, or e.g. automation demands.
(?) MFN: What are Stresstech's main products on the market?
(!) L.S.: We have three main product types for measuring stresses and for verifying the quality. All of our methods are environmentally friendly, using no acids or other harmful chemicals.
Barkhausen noise method is a magnetic method that is very suitable for even 100 % production control as being fast and able to separate defected parts from good ones. Based on this method we provide sensors, Rollscan Barkhausen noise meters, ViewScan software and more and more custom-made inspection stands for handling the parts. These components are today most often integrated together as inspection systems by us to ensure the best possible performance. Parts that our equipment can measure range from small injection nozzles to large parts such as crankshafts weighing hundreds of kilos. The smallest unit is a handheld sensor and the biggest, a fully automatic measurement station in the production line.
With X-ray diffraction method, you can find absolute values for stresses. X-ray measurement is a static measurement, which is why it is most often used in production development e.g. for finding correct shot peening parameters. Our Xstress instruments using this method consist of a main unit, three alternative types of goniometers for handling the measurement head, and XTronic software for calculating the stresses. The newest version of the goniometers is the robot goniometer, in which a robot handles all goniometer movements such as tilting and rotation. Different types of accessories from safety cabinets to work tables have been designed for making the measurements as safe and convenient as possible.
The hole-drilling method is typically applied in cases where the X-ray method does not work. Such situations are e.g. casting, extruded aluminium or non-crystalline materials. Prism instruments consist of equipment for drilling the hole and taking photos before and after drilling, based on which the special software PrismS analyses the stresses.
(?) MFN: How is your system different from other systems on the market?
(!) L.S.: We have two basic principles when we start to develop our new products. One is that no one else has exactly similar solutions. We always bring some new advances to our designs. The other principle is simple solutions and through that, easy-to-use equipment. When we started, the Barkhausen noise system was new in the market. On the X-ray side, we had and have unique detector technology and geometry. In the hole-drilling side, our technology has dropped out the strain gages that were traditionally used to find stresses with this method. We started to use microprocessor controlled meters from the middle of the 1980's. When using microprocessors, you can design simpler systems with less cabling as every unit can work independently. For example, our X-ray unit needs only HV cable and one control cable between the main unit and goniometer.
(?) MFN: Can you present to us at least some of its advantages?
(!) L.S.: BN technology is pre-eminent compared to the traditional temper etching method, as it uses no chemicals, is easy to automate, and documents test results. BN gives an indication of the defect at an early stage when nidal etch does not give any indication.
On the XRD side, we have invested a lot to keep things simple, of which an example is automatic determination of the measurement distance. Also, an important thing is the simple hardware design, which makes it easy to handle our equipment in the field conditions.
The main advantage of our hole-drilling equipment is no need for strain gages. This alone makes total measurement many times faster than with the traditional hole-drilling method with strain gages. With our method, you also get information around the hole in every direction, whereas with the method using strain gages, you typically measure only in three directions.
(?) MFN: How did you approach the product development and quality assurance process?
(!) L.S.: We have had ISO 9001 certification since 2001. We have designers and quality persons that are specially focused and concentrating full time on quality issues.
Product development is every day work for us. The most important driving force is customers' feedback.
(?) MFN: What about the company's performance?
(!) L.S.: We have been growing steadily for over thirty years and we have made positive results annually more than nine times out of ten. If calculated with an even growth rate, we have been growing at over a 10% annual rate, and we are continuing to grow at least with the same rate at present.
(?) MFN: How much experience is required to serve the customer with the optimal solution?
(!) L.S.: In the first contact, everything often looks simple, but when you go into details, everything demands a lot of knowledge and experience. Our main strong point is that we can do everything from mechanical, electric, electronic and most important software design and manufacturing in our own house. On top of this, we have our own application specialists in all our three measurement methods. This gives us a lot of flexibility and also the capability to respond rapidly to our customers' needs. Experience is a key factor, and in addition to that, we have our own testing laboratory where we can test and verify customer's applications. 30 years in business has already given us quite a good picture of what kind of challenges our customers have regarding keeping their quality. Designing custom solutions for almost each customer has each time increased our expertise. So today, there are already basic solutions for many kinds of components and problems in our knowledge base. Updating these to the latest technical advances is today's business.
(?) MFN: Give us an insight into the market that you serve.
(!) L.S.: The transportation industry is clearly our biggest customer base. We already have solutions for engine components of all kinds of vehicles that move on the land or in the air. Similar components such as gearboxes and bearings can be found also in factories and wind mills. The components we are dealing with are expensive and critical, e.g. high strength materials such as camshafts, crankshafts, bearings, gears, landing gears, etc. Shot peening is one of the most important applications in the surface treatment field.
(?) MFN: What developments are you planning for the future?
(!) L.S.: Research and development is essential to our business. Typically, we have two large projects, in which we develop something totally new, going on simultaneously. We just finished the new Rollscan meter project. We are developing new data acquisition and analyzing software for the Barkhausen noise applications. The time frame of this type of large project is from two to four years. On the software side, the development has in general been so fast that you practically have to scrap an old software program and start to build a new one almost from zero. In addition to the large R&D projects, we are at the same time running five to ten smaller development projects; the time frame of which is under one year.
(?) MFN: Any final thoughts?
(!) L.S.: We have an exciting future in front of us. Demand for measuring residual stresses is expanding strongly. There are clearly two driving forces behind this. Industry today is using strong materials, which are sensitive to defects such as wrong residual stresses. One example of this is welding high strength steels. The toe area of the welds needs to be peened to achieve benefits of material strength. Another example is new materials, for example composites in aircraft structures. You have to know the residual stresses to be able to simulate fatigue strength of structures accurately.
MFN would like to thank Lasse Suominen for the interview!