Matti Manninen

Evaluation of Different Monitoring Methods of Laser Additive Manufacturing of Stainless Steel

Different monitoring methods for the laser additive manufacturing process were studied in this study. Possibilities and downfalls of three different methods were compared to each other to define their applicability in future on-line and adaptive monitoring use in LAM processes. The material used on all the LAM process tests was EOS StainlessSteel PH1 in fine powder form. In this study, e.g. parameters like scanning speed, layer thickness and hatch space were tested. Based on the results of this study, the pyrometer seems to be more easily adaptable to continuous monitoring than the spectrometer or systems based on active illumination imaging system. It seems that the pyrometer is a promising method for quality control. The ability to control quality through on-line measurements can be further utilized in future e.g. for on-line quality control and dynamic process control, i.e. the ability to change and correct parameters on the fly.

Design of a microdistillation column

Distillation is the predominantly used separation method in chemical engineering. The device presented in this paper is called a microdistillation column, because the distilled volumes are measured in milliliters and dimensions in millimeters or less. There are two main reasons for a small distillation unit; firstly, it could theoretically be used in production, maybe in series with many such units. It could be used for example for hazardous or expensive materials, or in any case for applications which do not require large volumes to be distilled. More importantly, however, it could be used to study the distillation process in very small scale for the industrial scale device. Process development could then move from laboratory scale straight to industrial scale without need for expensive pilot plants.This study focuses on the design and manufacturing process of such a microdistillation column. To the knowledge of the authors it is the smallest continuous distillation column in the world at the moment. As such, the small size of the device posed several challenges in manufacturing. This case serves as a single and relatively simple example on how to design for advanced manufacturing methods; in this case laser processing. Another purpose of this paper is to give a clearer view of the advantages as well as disadvantages and limits of laser processing in small scale manufacturing. It is important to understand where and when the use of laser processing is really justified and when more conventional methods are more suitable.Distillation is the predominantly used separation method in chemical engineering. The device presented in this paper is called a microdistillation column, because the distilled volumes are measured in milliliters and dimensions in millimeters or less. There are two main reasons for a small distillation unit; firstly, it could theoretically be used in production, maybe in series with many such units. It could be used for example for hazardous or expensive materials, or in any case for applications which do not require large volumes to be distilled. More importantly, however, it could be used to study the distillation process in very small scale for the industrial scale device. Process development could then move from laboratory scale straight to industrial scale without need for expensive pilot plants.This study focuses on the design and manufacturing process of such a microdistillation column. To the knowledge of the authors it is the smallest continuous distillation column in the world at the moment. As ...

Laser assisted manufacturing of microscale chemical device of TT reactor

The latest development trend even in chemical industry is to use smaller components even in mill and micro meter scale. Microscale devices and systems have a number of advantages for process development and reaction studies in chemical engineering. Microreactors are small-scale reactors or other processing units for chemical industry with typical channel or chamber diameters in the range of 10-500 micrometers. One of the main features of microreactors is their high surface area to volume ratio, which leads to high heat and mass transfer rates. The advantages of microreactors compared to the conventional reactors are e.g. more optimal reaction conditions, efficient temperature control and smaller volume of raw materials. In process development, number-up by microreactor units would guarantee identical process conditions and eliminate costly redesign and pilot experiments that are usually routines in conventional scale-up and thereby the development time from laboratory to production is shortened.The laser micro processing is one of the fastest spreading and developing areas of laser processing. The processes of laser micromachining are numerous: micro cutting, welding, marking, drilling etc. This wide field of different processes makes laser a novel tool for micro processing and gives lots of new ideas, solutions and applications for designing of microscale process devices for chemical industry. With the use of lasers engineers are given an opportunity to design reactors based on process rather than manufacturing technologies.Aim and purpose of this study was to manufacture a microstructured TT-reactor with laser processing. Material used for this study was HDPE (high density polyethylene) and laser equipment used were IPG 200 W fibre laser and Laserline 200 W diode laser. The lasers were selected in order to test the productivity and reached quality of low power CW lasers.It was concluded that laser processing provides a unique tool for industrial manufacturing of these devices, even in planning and testing stage of these devices in laboratory cases. When a certain structure is proven to be most efficient in a laboratory, number-up means only production of larger number of similar structures.The latest development trend even in chemical industry is to use smaller components even in mill and micro meter scale. Microscale devices and systems have a number of advantages for process development and reaction studies in chemical engineering. Microreactors are small-scale reactors or other processing units for chemical industry with typical channel or chamber diameters in the range of 10-500 micrometers. One of the main features of microreactors is their high surface area to volume ratio, which leads to high heat and mass transfer rates. The advantages of microreactors compared to the conventional reactors are e.g. more optimal reaction conditions, efficient temperature control and smaller volume of raw materials. In process development, number-up by microreactor units would guarantee identical process conditions and eliminate costly redesign and pilot experiments that are usually routines in conventional scale-up and thereby the development time from laboratory to production is shortened.The laser ...

Characterisation of Pulsed-Fibre-Laser-Perforated Polymeric Food Package Films

A packaging material requires a proper interaction with regard to water vapour transmission between the product and the outside environment. For many fresh food products such as bakery goods, fruits, and vegetables, microperforation is utilised to extend the shelf life of the foodstuff and to provide better food quality. The microperforation potential of five commercial polymeric films has been evaluated using a pulsed fibre laser technique, and significant differences were found between the films in the penetration of the laser beam and in the diameter of the perforation. Breathable polymeric packaging films were prepared with an average laser power of 20 W and a pulse duration of 200 ns. The numbers of holes (80 μm in diameter) in the films were approx. 2000 holes/m2 and 4000 holes/m2. As expected, the number of perforations affected the water vapour transmission (WVT): the WVT was 11 g/m2/d for unperforated film, and 60 g/m2/d for the film with 4000 holes/m2, indicating that the fibre laser can be used successfully for microperforating this type of polymeric films. However, microscopic and microtomographic analyses revealed major differences in hole formation behaviour and in the wall structures of the microperforations.

Real-time online monitoring of nanosecond pulsed laser scribing process utilizing spectrometer

This study proposes a novel configuration and algorithm to develop real-time online monitoring of an ultrafast scribing process utilizing a spectrometer. The target process was the ultrafast low energy scribing process performed by using a nanosecond laser. A new configuration in which the spectrometer probe incorporated into the scanner head unit and received the reflection light of microprocessing via a special monitoring adapter has been developed. The scan head adapter enables the scan head-based observation of a galvanometer and polygon scan heads working field. Typical applications include process monitoring or determination of a work pieces orientation during laser processing.

TWINQUASI – A new method for quasi-simultaneous laser welding of polymers

Quasi-simultaneous laser welding (QSLW) of polymers has been studied, developed and used both in academia and industry for many years. The process has high flexibility and lot of advantages but it has some limitations especially when short welding time is required. The short welding time requires a scanner with extremely high speed and accuracy which usually limits the maximum dimensions of the joint and products to be welded. This paper presents a new method to utilize a QSLW-process with two lasers and optical scanners (TWINQUASI) for quasi-simultaneous laser welding of polymers which enables welding of larger components within a short welding time. The paper demonstrates TWINQUASI and compares its performance to those of traditional QSLW. Results show that with this method the length of the weld can be doubled within the same welding time while still keeping equal scanning frequency to that of the conventional QSLW-process. It is shown that with the TWINQUASI method, larger components can be welded with quasi-simultaneous method compared to shown earlier. Another advantage of the process is the ability to program scanning paths of both lasers individually. Because of this, the TWINQUASI method enables also variation of the weld width within one weld seam giving even more flexibility to the process.Quasi-simultaneous laser welding (QSLW) of polymers has been studied, developed and used both in academia and industry for many years. The process has high flexibility and lot of advantages but it has some limitations especially when short welding time is required. The short welding time requires a scanner with extremely high speed and accuracy which usually limits the maximum dimensions of the joint and products to be welded. This paper presents a new method to utilize a QSLW-process with two lasers and optical scanners (TWINQUASI) for quasi-simultaneous laser welding of polymers which enables welding of larger components within a short welding time. The paper demonstrates TWINQUASI and compares its performance to those of traditional QSLW. Results show that with this method the length of the weld can be doubled within the same welding time while still keeping equal scanning frequency to that of the conventional QSLW-process. It is shown that with the TWINQUASI method, larger components can be welded wit...

Laser welding of micro-VLE-measurement device and its practical application

The knowledge of phase equilibrium is critical for the modeling and operation of reactors and separation units. The use of incorrect vapor-liquid equilibrium (VLE) data for distillation leads to tower malfunction with varying end results. The only reliable method for obtaining valid VLE data for a non-ideal system is to measure it. When studying components that are either very expensive or hazardous the amount of chemicals used is preferably minimized. Typical volume of chemicals used in a VLE-measurement is 100 cm3 or above. In a VLE-measurement the temperature, pressure and composition of both phases are determined for a range of concentrations.The laser micro/fine processing is one of the fastest spreading and developing areas of all laser processes in the world. The wide field of applications makes laser a novel tool for micro processing and gives lots of new ideas, solutions, opportunities and applications for designing these milli and micro scale process devices for chemical industry.In this study an exceptionally small VLE-measurement device was designed and manufactured by utilization of laser processing. Even though the application itself is in micro scale the laser processing used in fine processing scale gave opportunity to reach the minimum volume. Laser welding has unique possibilities for this kind of welding when heat input can be controlled and only small heat affected zone and thereby minor distortions are caused. Laser welding also enables welding of demanding structures, like this micro-VLE-device.The volume of the measurement cell of micro-VLE-device was approximately 2.5 cm3, which was made possible by using the pressure transducer cavity as the equilibrium cell. The chemical consumption is therefore reduced by up to a factor of 50. The valves were also welded to the structure. The welding would not have been possible with conventional methods due to overheating of the transducer electronics. The cell was initially tested by measuring pure component vapor pressures of alkanes.The knowledge of phase equilibrium is critical for the modeling and operation of reactors and separation units. The use of incorrect vapor-liquid equilibrium (VLE) data for distillation leads to tower malfunction with varying end results. The only reliable method for obtaining valid VLE data for a non-ideal system is to measure it. When studying components that are either very expensive or hazardous the amount of chemicals used is preferably minimized. Typical volume of chemicals used in a VLE-measurement is 100 cm3 or above. In a VLE-measurement the temperature, pressure and composition of both phases are determined for a range of concentrations.The laser micro/fine processing is one of the fastest spreading and developing areas of all laser processes in the world. The wide field of applications makes laser a novel tool for micro processing and gives lots of new ideas, solutions, opportunities and applications for designing these milli and micro scale process devices for chemical industry.In this study a...

Laser scribing of stainless steel with and without work media

The advantages such as tight restrictions for heat and mass transfer make micro-/milli scale devices of mixing and droplet formation viable to become widely used in specialty chemical industry. Small dimensions and simple geometry ensure laminar flow and mixing through diffusion, ensuring well-defined behavior of mixing and short reaction times. Combining dry etching by laser beam with wet chemical etching is expected to reduce the production costs of these novel devices.In this study the manufacturing of grooves in stainless steel SS 316L by means of laser micro-/milli processing was investigated. Deep and narrow channels with depth to width ratio of 1:1 at least are preferable, width is allowed to vary from 10-500 micrometer. Lasers used for this study were: 5 kW IPG YLR-5000 S, 200 W IPG YLS-200-SM-WC, 1 kW IPG YLR-1000-SM fiber lasers, 400 W Powerlase diode pumped Nd:YAG laser and 14 W diode pumped Nd:YVO4 laser. Chemical assisted laser scribing is also included in this study.Preliminary results show possibility to obtain channels with desired parameters in pulsed mode laser machining. However, investment cost for CW (continuous wave) lasers per kilowatt are in order of magnitude smaller than for pulsed lasers, that’s why the study was essentially focusing on lasers operating in CW mode. Optimal scribing parameters were defined by adjusting laser power, number of repetitions and speed. Preliminary experiments done without any media resulted in low quality grooves with moderate depth and burned edges. It was concluded in this study that finding a suitable chemical to improve to scribing process is a key moment of getting channels with acceptable quality.The advantages such as tight restrictions for heat and mass transfer make micro-/milli scale devices of mixing and droplet formation viable to become widely used in specialty chemical industry. Small dimensions and simple geometry ensure laminar flow and mixing through diffusion, ensuring well-defined behavior of mixing and short reaction times. Combining dry etching by laser beam with wet chemical etching is expected to reduce the production costs of these novel devices.In this study the manufacturing of grooves in stainless steel SS 316L by means of laser micro-/milli processing was investigated. Deep and narrow channels with depth to width ratio of 1:1 at least are preferable, width is allowed to vary from 10-500 micrometer. Lasers used for this study were: 5 kW IPG YLR-5000 S, 200 W IPG YLS-200-SM-WC, 1 kW IPG YLR-1000-SM fiber lasers, 400 W Powerlase diode pumped Nd:YAG laser and 14 W diode pumped Nd:YVO4 laser. Chemical assisted laser scribing is also included in this study.Preliminary results show ...

An overview of the conventional microprocessing and laser assisted techniques for fabricating microscale features

In this literature review conventional methods and techniques for microscale processing are introduced and compared to laser micromachining. Conventional techniques studied include wet bulk etching, many dry etching techniques, LIGA processes, abrasive jet machining, electrical discharge machining, and mechanical micro-machining.During the last decade the tangible advantages of laser material processing have sparked much interest and scientific study. These studies show that, given correct parameters, laser can be used to fabricate very small features and, as such, can be utilized in microscale processing. Especially, excimer and fiber lasers are seen as potential candidates, former being the more costly but also more well-known – and arguably more capable – choice. Other lasers included are Nd:YAG, Nd:YVO4, and Ti:sapphire solid-state lasers.In this literature review conventional methods and techniques for microscale processing are introduced and compared to laser micromachining. Conventional techniques studied include wet bulk etching, many dry etching techniques, LIGA processes, abrasive jet machining, electrical discharge machining, and mechanical micro-machining.During the last decade the tangible advantages of laser material processing have sparked much interest and scientific study. These studies show that, given correct parameters, laser can be used to fabricate very small features and, as such, can be utilized in microscale processing. Especially, excimer and fiber lasers are seen as potential candidates, former being the more costly but also more well-known – and arguably more capable – choice. Other lasers included are Nd:YAG, Nd:YVO4, and Ti:sapphire solid-state lasers.