Blanking Tool Research Articles

Optimization of Process Parameters of Wire Electric Discharge Machining Process for Machining AISI A2 Tool Steel

In this investigation, AISI A2 tool steel is considered as the workpiece material, which is typically used to manufacture blanking tools, punches die etc., due to its good toughness and wear resistance. In this work, the effect of controlling parameters of the Wire Electric Discharge Machining (WEDM) process is investigated. Molybdenum tool electrodes of 0.18mm diameter and de-ionized water dielectric medium are utilized. Peak current, on-time, off-time and voltage are considered as the controlling parameters. Surface roughness average and material erosion rate are considered as the response parameters. The type of design of experiments considered for this work is Taguchi’s L27 orthogonal array. Analysis of variance indicates the percentage contribution of each machining parameter on response parameters. The optimum combination of machining parameters yields a minimum surface roughness of 2.87 μm and the highest material removal rate obtained in this work is 774 mm3/hr.

Image-based feature extraction for inline quality assurance and wear classification in high-speed blanking processes

Wear is one of the key factors that determine the efficiency of multi-stage processes that include blanking operations. Since wear in these processes not only causes unplanned downtime but also directly affects product quality, inline detection of wear and its effect on product quality is of major importance. However, current quality assurance (QA) methods are limited to manual offline inspection by operators at predefined intervals, so that 100% inspection of the product and description of the state of wear is not found in industrial practice. The aim of this work is therefore to develop an optical system that enables in-line acquisition of product images and the associated control of blanking-specific quality features up to stroke rates of 300 strokes per minute (spm). In order to make the system attractive to small- and medium-sized enterprises (SME), the system is designed to minimize integration and investment costs using commercially available components. By combining the system with a methodology for extracting blanking-specific features, so-called key performance parameters (KPPs), the condition of the blanked surface as a relevant quality parameter is derived directly from the workpiece image. To demonstrate the transferability of the methodology to industrial applications, two use cases are investigated. In the first case, the KPPs are used directly to determine the quality of the blanked workpiece and are compared with reference measurements. Here, the KPPs are quantified with a mean absolute error of 18 μm compared to a ground truth. In the second case, the KPPs are used to build a machine learning (ML) model to estimate the wear of the blanking tool. Here, an accuracy of 92% is achieved in classifying the actual wear state.

Numerical modeling of multipoint blanking process of electrical steel

AbstractA new method of forming using multipoint blanking, which can reduce cutting forces was discussed. In the processes of punching and blanking magnetic materials, an important problem is excessive and irregular wear of the cutting edges of the punches. The contribution proposes multipoint initiated punching using specially designed punches, which aims to significantly reduce the punching forces needed to separate the material. The FEM method was used to analyze the physical phenomena occurring during the process. The updated Lagrange description was used to describe the phenomena at a typical incremental step. The states of strain and strain rate are described by nonlinear relationships without linearization. The description of the nonlinearity of the material was made with an incremental model taking into account the influence of the history of strain and the strain rate. The condition of the material after the previous treatments was also taken into account by introducing the initial states: displacements, stresses, strains, and their velocities. Analyses of the impact of the geometry of blanking tools on the values of stresses, deformations, and blanking forces were carried out. Fatigue analyses were carried out for the proposed tools. The research results may be useful for the design of modern blanking tools used in the processing of electrical materials.

THE POSSIBILITY OF USING STRUCTURAL DAMPING IN THE DESIGN OF A PREFABRICATED TURNING CUTTER TO REDUCE THE AMPLITUDE OF SELF-OSCILLATIONS IN THE PROCESS OF METAL CUTTING

A mathematical model of four mass oscillating circuit cutting machine was developed and studied in this paper. The influence of the internal friction in the joints of structural elements on the machine tool vibration amplitude and details. Effective self-oscillation amplitude blanking tool is possible by choosing the optimal parameters of the tool body frictional connection with tool holders

Reduction of adhesive wear with use of tool coating reducing thermoelectric currents

Blanking is one of the main processes in producing sheet metal components. The impact of adhesive wear of the blanking tools on the cost efficiency is high, especially when processing aluminum. As an influencing factor on adhesive wear in blanking, thermoelectric currents have been considered to a very small extent. Recent investigations have shown that thermoelectric currents occur in every blanking tool due to the rise of temperature in the shear zone in interaction with a difference of the material-specific Seebeck coefficients of tool and sheet metal. A reduction in the amount of wear was observed in case of a smaller difference of Seebeck coefficients and therefore lower levels of flowing thermoelectric currents. This paper follows the approach of adjusting the Seebeck coefficient of the tool material CF-H40S+ to the one of the sheet material by means of coating with CrAlN, in order to reduce the flowing thermoelectric currents and consequently adhesive wear. For this purpose, the effect of coating on the Seebeck coefficients, the thermoelectric currents during blanking as well as resulting wear quantities were investigated. Basic correlations could be revealed.

Viscoplastic constitutive modeling of boron steel under large strain conditions and its application in hot semi-cutting

Abstract To overcome the long process time of laser cutting and the high costs for repairing cold blanking tools of ultra-high strength hot stamping components, the hot semi-cutting process was proposed. The reliable testing and parameter identification method of the constitutive behavior under large strain conditions are essential for an accurate simulation of hot stamping and hot semi-cutting process. In the present work, a new testing and parameter identification method for the viscoplastic constitutive behavior of boron steel is proposed based on the Gleeble system, which includes a new grip design, shear specimen selection, and its relevant high-temperature and high-speed digital image correlation (DIC) technology. To obtain the stress-strain curves under large deformation, the FEM-based optimization method is also proposed to identify the hardening parameters. To cover a greater strain range, a new viscoplastic hardening model is proposed based on the dislocation density evolution under elevated temperature deformation conditions. The reliability of the proposed testing method and hardening model is verified by the analysis of uniformity of temperature and strain rate, and the comparison of predicted stress-strain curves with parameters identified from shear and tensile testing. The thermomechanical tension of the center-hole and notched specimen, and the hot semi-cutting process are carried out to verify the proposed testing method and hardening model. The results show that the shear specimen has a more uniform temperature and strain rate distribution in the deformation zone than the tensile specimen. Shear specimens can be used to test the hardening behavior under various process conditions until failure at the large strain. The insensitivity to phase transformations of shear testing is another advantage for identifying the constitutive behavior of the product phase formed during continuous cooling. The constitutive behavior of the boron steel under a large strain range can be accurately identified by using the FEM-based optimization method proposed in this paper. Besides, the mechanical response of the center-hole specimen, notched specimen, and the hot semi-cutting deformation predicted by the proposed hardening model shows accurate results.

The effect of different types of quenching methods on the burr zone characteristics on Ti-6Al-4V material

Heat treatment is a process that aimed to increase the ductility, reduce internal strain, smoothen the crystallite, increase the tensile strength, improve the Carbon (C) atom components, and increase the hardness. This research aimed to find the heat treated results using carburizing and quenching in blanking tool with low-carbon steel in the form of hardness level growth using carbon charcoal media mixed with BaCo3 energizer in pack carburizing process at 900°C temperature for 120 minutes holding time. This is continued with quenching process using oil, saltwater, and water. The blanking tool was tested in blanking experiment with 2.5% clearance, 3000 mm min−1 cutting speed using Ti-6Al-4V sheet metal with 0.6 mm thickness. The result parameter from the experiment was the burr zone level measurement of the product. Heat treatment process increased Carbon (C) atom component in the blanking tool. The raw material had a 0.17% component, and the quench media of oil, saltwater, and water had 0.19%, 0.22%, and 0.3% carbon components respectively. The hardness value also increases using oil, salt water, and water as the quenching media, resulted in 283.7, 423.8, and 462.4 HV respectively. The burr zone level was also obtained using the quench media of oil, salt water, and water with the results of 0.218, 0.206, and 0.119 mm.

A Study on Effects of the Press Speed on Sheared Edge Formability

In this study, the effect of shearing speed on edge formability was investigated with two different grades of advanced high strength steel (AHSS), DP780 and GEN3-980. A straight blanking tool with adjustable shear clearance was used to shear the selected materials in two different type presses, a high-speed pneumatic press, and a mechanical servo-press. The four different shearing speeds from 0.01 meter per second up to 1.5 meters per second were realized and measured. The different shearing speed conditions result in different edge quality and work hardening levels. The half specimen dome test and micro-hardness analysis were conducted to evaluate the edge formability. The samples sheared with a pneumatic press at a higher speed showed significantly better edge quality, less hardness increase, and smoother sheared edge than the samples sheared with the servo press. The developed high-speed shearing condition has a very good potential to shear AHSS without creating significant damage and work hardening on the sheared edge, providing further advantages for the post stamping operations.

Design and Analysis of Punch and Die of a Micro Blanking Tool

Stamping dies one of the essential industries in engineering. The sheet metal blanking procedure is a shearing operations. In the blanking procedure the sheet metal is detached from the bulky portion of stock through the application of shearing force on the sheet. Nowadays, the increase of gadgets and smart phone is because of the 4th industrial revolution. This situation leads the demand for micro parts that will include in electronic devices. The main problem occurred in sheet metal stamping is damage to the punch after running thousands of stamping process. This paper focuses on designing a micro blanking dieset that meet the industrial demand. The study is conducted using solidworks to design the micro blanking dieset and perform analysis using FEM. The result of FEA will be calculated using e-fatigue to get the lifecycle for the punch.

Influence of wear on particle emission in aluminum blanking

The pollution of blanked parts with particles emitted by the blanking operation itself can be encountered in different cases of blanking, in particular aluminum blanking. The consequences of this pollution are a degradation of the quality of the parts produced (appearance, function) and, possibly, a degradation of the behavior of the blanking tool. In this context, we studied the effect of the wear of the punch in the case of AW5754 H111 blanking. Press tests were conducted with a complex part shape and with different press test configurations. The results highlighted two types of wear. The first one is called “run-in” (punch surface accommodation) and leads to a reduction of the emission of particles. On the contrary, the second type of wear, called “pick-up” (material transfer from the sheet), leads to increase particle emission. The mechanisms corresponding to the two particle emission modes are studied. The first mechanism is well known and results from the transition from a blanked edge geometry with secondary shear zone to a more conventional geometry without this secondary shear zone. The second mechanism is new, with sheet material being picked up by the punch and then the picked up material being scraped off, eventually leading to particles being deposited on the die and the part. The study also focuses on the effect of lubrication, clearance and punch shape on these mechanisms. The two mechanisms differ by the influence of lubrication: The second mechanism becomes preponderant as soon as lubrication becomes insufficient, and a solution must be found rapidly because of the larger particle emission and the risk of galling of the punch.

Evaluation of the fine blanking tool for the precise clutch cam of automobile seat lifter pumping device

In this paper, the multi-step forming process was studied with the fine blanking (FB) tool and the FB experiments for the precise clutch cam of automobile seat lifer pumping device (PCC). In order to form the PCC, the multi-step compound FB tooling system was taken; the three forces were directly gained from the rams of the FB press and the other force was gained from the auxiliary hydraulic device in the FB press. The FB tool was optimally designed through the FB simulation and fabricated. From the FB experiments with the FB press (Mori Iron Co., Ltd, FB400), the 5 samples of the PCC were taken and measured. All samples fulfilled the tolerance conditions.

Evolution of White Layer during Wire-Cutting and Comparison of Several Methods to Improve Surface Integrity for Fineblanking Tools

Powder metallurgical high speed steel (such as S390) has superior mechanical properties and been used as fineblanking tools. The electrical discharge machining has been widely used for cutting fine blanking tools which are made of especially hard tool steels. Whereas, its thermal nature causes great concerns regarding surface integrity, which matters a lot to tool life. In the present study, the evolution of surface integrity of the S390 with multi-cutting is comprehensively compared. The result shows that the surface roughness, white layer thickness and surface residual stress decrease with the increase of cutting pass. Additionally, the effectiveness to remove white layer on HSS S390 by manual and towed polishing and electrolytic polishing are compared. At last, a device of abrasive water jet polishing is designated to remove the white layer resulted from wire-cutting.

Tensile stresses in fine blanking tools and their relevance to tool fracture behavior

Abstract In order to enhance the productivity of the fine blanking process there is a tendency to apply high strength tool materials with superior resistance to wear and plastic deformation such as WC-Co hard metals. Due to the mean stress sensitivity of these high strength materials under fatigue loading conditions, there is a need to describe the tool load situation including previously unconsidered tensile tool load components and mean stress. To this end a finite element-based tool load analysis was performed that describes the cutting process and the tool's retraction from the remaining sheet material. The tool load was revealed to contain significant tensile components that occur during tool retraction. Their location on the lateral punch surface coincides with origins of tool fracture in two thirds of investigated fine blanking punches that failed close to the cutting edge in an industrial production scale fine blanking environment. The influence of friction between punch and sheet on the magnitude of the cyclic stress range and mean stress that act locally at the tool surface was investigated. As one of the main results, a first approximation for a surface quality requirement for fine blanking tools made of WC-Co hard metal was quantitatively estimated as a function of the friction coefficient based on linear elastic fracture mechanics.

Dependencies of the die-roll height during fine blanking of case hardening steel 16MnCr5 without V-ring using a nesting strategy

For economic reasons, fine blanking of asymmetric parts is performed with shifted and rotated part nesting. It was observed that both the part position and the part orientation on the sheet metal strip affect the die-roll height. Therefore, the influence of the bridge width between the produced cutting line and the strip edge or existing sheared edges was studied in this work. Additionally, the effects of the stroke number, the convexity of the radii and the sheet metal anisotropy were considered. The parts were manufactured in a production series of 40,000 parts with a fine blanking tool ejecting four parts simultaneously. From each nest, 20 parts were separated at four equidistant steps. The die-roll height was determined in three regions with different convexity radii of parts from varying nests. A normal distribution was found for the die-roll height, categorized by convexity radius and position of the nest. The die-roll height was found to be promoted by convexity radius, small bridge width, and in transverse blank direction. The number of strokes had a minor impact. Interaction effects occur particularly at small convexity radii and small bridge widths. As a conclusion, the nesting must be considered in order to reduce the die-roll height. Small bridge widths, small convexity radii, and the orientation in transverse blank direction have a negative impact, whereas the stroke number has a marginal influence. The understanding of the correlation between die-roll formation and nesting helps to reduce waste in mass manufacturing.

Experimental evaluation of tool wear throughout a continuous stroke blanking process of quenched 22MnB5 ultra-high-strength steel

Steel is the most common material used in vehicles’ chassis, which makes its research an important topic for the automotive industry. Recently developed ultra-high-strength steels (UHSS) provide extreme tensile strength up to 1,500 MPa and combine great crashworthiness with good weight reduction potential. However, in order to reach the final shape of sheet metal parts additional cutting steps such as trimming and piercing are often required. The final trimming of quenched metal sheets presents a huge challenge to a conventional process, mainly because of the required extreme cutting force. The high cutting impact, due to the materials’ brittleness, causes excessive tool wear or even sudden tool failure. Therefore, a laser is commonly used for the cutting process, which is time and energy consuming. The purpose of this paper is to demonstrate the capability of a conventional blanking tool design in a continuous stroke piercing process using boron steel 22MnB5 sheets. Two different types of tool steel were tested for their suitability as active cutting elements: electro-slag remelted (ESR) cold work tool steel Bohler K340 ISODUR and powder-metallurgic (PM) high speed steel Bohler S390 MICROCLEAN. A FEM study provided information about an optimized punch design, which withstands buckling under high cutting forces. The wear behaviour of the process was assessed by the tool wear of the active cutting elements as well as the quality of cut surfaces.

An Investigation of the trimming of boron nitride steel (22MnB5) during the die-quenching process

Abstract The in-die hot trimming cuts the heated blanks during the phase transformation from an austenite phase to a martensite one. This process could reduce the total cycle time of the hot stamping process and enhance the tool life. The aim of the present work is to identify key parameters of the in-die hot trimming, and therefore to secure the control chart for the sound surface-quality and the low die-wear in the blanking process of boron steels. The numerous experiments were carried out while varying the temperature of boron steel and the clearance between the punch and die. The pyrometer mounted on the blanking tool could measure directly the actual temperature of the boron steel located at the trimming site during the rapid cooling. Profiles, percentage of depth ratios, hardness, and microstructure of sheared zones are measured to characterize the influence of process parameters. From our investigation, the trimmed zone which has a desired surface quality and dimensional accuracy could be achieved in the temperature range from 500 to 550℃ and below the clearance of 5%.

Increase of Lifetime for Fine Blanking Tools

To improve the lifetime of blanking tools, the application of high quality steel, heat treatment and coatings has become an interesting issue for many European companies dealing with stamping, punching and blanking operations. Important trends such as longer lifetime, higher accuracy and higher complexity of the products are challenging and require more special materials and techniques.The technological solutions to improve the existing processes are not obvious because of the enormous amount of possibilities in available materials, heat and surface treatments such as PVD coatings for the envisaged industrial processes and applications. An in-depth research to understand the manufacturing processes with the consequence of an increased performance and lifetime of the tools as well as the opportunity of further optimization was the main goal of this project.In many blanking processes where heavy duty conditions are applied, the use of hard metals, durable coatings and wear resistant tool steel is already established to extend the lifetime. The tools studied in this project were applied without coatings. The increasing production rate and the use of high strength steel sheet induce wear, crack formation and flaking of blanking tools with consequent low lifetimes. This project studied the tribological synergy of the substrate-heat treatment-surface preparation relationship and their influence on lifetime in heavy load conditions. A preliminary study was performed on the cutting edges of special designed triangular punches made of several high alloyed steels which were heat treated in a conventional way and by deep cryogenic treatment after quenching.After this research some demonstration tools were tested in industrial conditions to show the feasibility of certain selected combinations.

Effect of different machining processes on the tool surface integrity and fatigue life

Ultra-precision grinding, wire-cut electro discharge machining and lapping are often used to machine the tools in fine blanking industry. And the surface integrity from these machining processes causes great concerns in the research field. To study the effect of processing surface integrity on the fine blanking tool life, the surface integrity of different tool materials under different processing conditions and its influence on fatigue life were thoroughly analyzed in the present study. The result shows that the surface integrity of different materials was quite different on the same processing condition. For the same tool material, the surface integrity on varying processing conditions was quite different too and deeply influenced the fatigue life.

Conceptual Design of Blanking Tool for Washer Special

Conceptual Design of Blanking Tool for Washer Special

The Influence of Punch-Die Clearance on Blanked Edge Quality in Fine Blanking of Automotive Sheets

Fine blanking is a widely used process that permits the production of precise finished components which are cleanly sheared through the whole cutting surface. It can be eliminated secondary operations, such as milling, grinding, etc. Many studies on the weight reduction of automobile for fuel saving were underway. The clearance of the punch-die of a fine blanking tool is an important design factor that affects the sheared surface of a product. If the clearance is too big, a fractured surface would occur in the product while if it is too small, bulging would occur. The main objective of this paper is to provide an overview of the effect of clearance between punch and die in a fine blanking tool on quality of sheared surface. A well as to specify the effect of mechanical properties of sheared steel sheet on blanked edge quality given by ratio of hv/a0.