Metal Stamping Research Articles

Numerical design of load response in magneto-rheological actuators for sheet metal stamping

Auxiliary systems for sheet forming processes are widely used to improve products accuracy and increase tools life. As example, in blanking hydraulic dampers are widely used to reduce shocks and vibrations; nitrogen springs are often integrated in deep drawing tools to correct the ram tilt or to locally increase the blank-holder force, obtaining geometrical features on the stamped blank with one press pass. In this paper, a Magneto-Rheological (MR) semi-active actuator is developed for sheet forming operations and the interaction between MR fluid and electromagnetic field is investigated by Finite Element (FE) analysis. To overcome the limitations of gas springs and hydraulic actuator, the static electromagnetic circuits is reconfigured with respect of conventional MR actuators known in the state-of-the-art. The novel MR actuator has an inner bore where the electric windings are placed, while the narrow gap, in which the active MR fluid flows, is obtained between the inner bore and the cylinder internal surface. The resulting magnetic fields H and induction fields B, as well as the selection of components materials, are studied through the magneto-static FE model. The results from FE simulations show a longer activation length along the gap resulting in higher controllable forces values, without increasing the overall dimensions of the proposed prototype.

Assessment of micro-abrasive wear tribological properties of H10 tool-steel under conditions of “constant normal force ⇒ variable pressure” and “constant pressure ⇒ variable normal force”

In industrial applications, tools of H10 tool-steel used in mechanical and metallurgical manufacturing processes, such as rolling, extrusion, forging, sheet metal stamping, milling and turning, frequently present significant levels of micro-abrasive wear, which occurs under specific circumstances of “constant normal force”, resulting in a “variable pressure” physical condition, or “constant pressure”, resulting in a “variable normal force” physical condition. Consequently, results of micro-abrasive wear generated under these tribological conditions can help engineers design materials and tools with a longer working life span when they are working under mechanical and metallurgical manufacturing processes. Observing the relevance of this subject, the purpose of this work is to assess the micro-abrasive wear tribological properties of H10 tool-steel submitted to experimental conditions of “constant normal force ⇒ variable pressure” or “constant pressure ⇒ variable normal force”. Ball-cratering wear tests were conducted on quenched and tempered AISI H10 tool-steel; the counter-body was a quenched and stress-relieved AISI 52100 bearing steel sphere and the abrasive slurries were prepared mixing abrasive particles of silicon carbide with distilled water. During the micro-abrasive wear tests, the abrasive slurry was, continuously, agitated and fed between the sphere and the tested material; values of coefficient of friction were, simultaneously, acquired, as well. After the tests, each wear crater was analyzed by optical microscopy, SEM and CAD software. The results were discussed based on the behavior of the “Steady-State Wear Regime”, “wear volume”, “wear rate”, “micro-abrasive wear modes”, “pitch between grooves”, “coefficient of friction” and, finally, validated by ANOVA. With the attainment of the Steady-State Wear Regime, it was possible to present the following conclusions: (i) wear volume and wear rate increased under conditions of “constant pressure ⇒ variable normal force”, (ii) there was the predominance of “grooving abrasion”, with the action of “micro-rolling abrasion” wear phenomenon, (iii) the pitch between grooves presented, approximately, the same value of the average abrasive particles size and (iv) the coefficient of friction remained in a tribological condition classified, statistically, as “constant”.

Finite Element Analysis of Reinforcement Rocker Part Made from JAC780Y Steel Sheets

The manufacturing industries for automotive parts aim to develop technologies for reducing vehicle weight in order to decrease fuel consumption. However, passive safety function for drivers and passengers must not be impaired or should be even improved. Therefore, advanced high strength steel sheet plays more and more important role in designing automotive components. Nowadays, prediction of formability for sheet metal stamping has high capability more than the past. The major challenge is springback prediction. Moreover, it assists in the tooling design to correctly compensate for springback. Especially in automotive production, springback effects have been generally exhibited distinct after forming process of the high strength steel sheets. The springback effect occurred in the deformed state of metal parts must be taken into account by designing any sheet metal panels. Then, the purpose of the present research is to investigate the springback phenomenon of an automotive part named Reinforcement Rocker RL made from an advanced high strength steel grade JAC780Y, after stamping. In addition, the tools design has been carried out. Finite Element (FE) program known as DYNAFORM (based on LS-DYNA solver), has been applied to analyze and improve the springback effect on such forming part. An anisotropic material model according to type 36 (MAT_036 3-PARAMETER_BARAT) was applied. The results obtained from simulations were compared with required parts in each section. Then, the die surface from compensation in 2nd step forming was modified to use. Finally, the simulation part was verified with the real stamping part. It was found that the finite element simulation showed high capability for prediction and compensation of springback in high strength steel sheets forming.

Extraction of Formal Manufacturing Rules from Unstructured English Text

Semantics-based approaches – founded on the idea of explicitly encoding meaning separately from the data or the application code – are being applied to manufacturing, for example, to enable early manufacturability feedback. These approaches rely on formal, i.e., computer-interpretable, knowledge and rules along with the context or semantics, which facilitates the reuse and sharing of the knowledge via semantic web technologies. On the other hand, manufacturing knowledge has been maintained primarily in the form of unstructured English text. It is considered impractical for engineers to author accurate, formal, and structured manufacturing rules. However, previous efforts on extracting semantics from unstructured text in manufacturing have mainly focused on basic concept names and hierarchies for ontology creation, rather than extracting complex manufacturing rules. In this context, this paper focuses on the development of a semantics-based framework for acquiring formal manufacturing rules from English text, such as those written in manufacturing handbooks, by guiding standard Natural Language Processing (NLP) techniques with formal manufacturing knowledge (i.e., controlled vocabulary and domain ontology). Specifically, this paper studies the problem of rule extraction in the manufacturing domain, proposes the formal rule extraction framework, and demonstrates its feasibility. From the dataset of 133 sentences with a manufacturing rule, the proposed framework was able to extract correct rules from approximately 57% of the sentences. This paper also demonstrates the extensibility of the framework. Specifically, the framework was initially developed using the three sections of a manufacturing handbook, including milling, metal stamping, and die-casting sections, and could be successfully applied to the rest of the book after just updating the formal manufacturing knowledge to cover the other sections. This paper provides meaningful results in terms of formalization, thus will contribute to the development, sharing, and reuse of formal manufacturing knowledge that includes complex manufacturing rules.

Active control of blankholder in sheet metal stamping

The continuous demand of shape complexity, product accuracy and extended tools life has led to a widespread use of auxiliary systems in sheet metal stamping. Nevertheless, their performances are often inadequate, making their use a compromise between process efficiency and stability. The paper focuses on a new magneto-rheological actuator design. Both analytical and numerical approaches are developed to evaluate load response and to optimize the magnetic field interaction. A physical prototype according to the design outputs is manufactured and tested at different dynamic conditions. Finally, magnetic force values obtained from FE model and experimental tests are compared.

Improvement in nano‐pattern replication of injection molding by polyamide/dendrimer blend

AbstractIn general, lower viscosity of materials leads to desirable nano‐pattern replication characteristics in injection molding processes. However, such materials do not meet the properties required for manufacturable products owing to their poor mechanical properties. In this study, we blended a small amount of dendrimer with high‐viscosity polyamide 6 to lower viscosity and enhance flowability of the polymer blend while maintaining desirable mechanical properties. It was observed that the flowability of the polyamide 6/dendrimer blend increased significantly with an increase in dendrimer content without affecting the mechanical properties of high‐viscosity polyamide 6. To investigate the nano‐pattern replication characteristics of the blend, injection molding process and the mold of metal stamp were used to manufacture a nano‐pattern specimen. Blending more than 0.6 wt% of dendrimer with high‐viscosity polyamide 6 significantly improved its nano‐pattern replication characteristics and flowability.

Characterization of Shorted Dipole Antennas for Low-Cost RFID Reader Applications

This article presents a comprehensive study on shorted dipole antennas aiming for low-cost radio frequency identification (RFID) reader applications. Starting from a low-profile shorted bowtie dipole antenna, it is found that by varying the shorting wall position, three different types of resonant antennas could be realized with different radiation features. A low-profile planar inverted F antenna (PIFA) -type dipole is obtained by moving the shorting wall toward the feeding, which exhibits a low resonance frequency without obvious back lobe radiation or sidelobes. When the shorting wall is placed in the middle of the radiating patch, a mushroom-type dipole antenna can be built. A zeroth-order mode is also observed. This structure differs from the magnetoelectric dipole due to a low-profile structure. Placing the wall toward the end of the dipole arm leads to a loop-type antenna with a broader beam and a reduced gain. It also shifts the resonance toward the higher frequency. Based on the PIFA- and mushroom-type structures, two circularly polarized antennas with crossed shorted dipoles are designed and investigated carefully. Finally, two optimized, compact, and low-cost RFID reader antennas based on simple metal stamping process and screws are designed, fabricated, and tested, showing an excellent RF reading range. This study demonstrates that for the shorted dipole antennas, miniaturization and bandwidth control can be achieved simultaneously. Particularly, for higher gain and smaller size, the shorting wall should be placed close to the feeding to suppress the loop mode. For omnidirectional radiation, the loop mode should be enhanced by moving the shorting wall close to the end of the dipole arm.

A novel testing method to evaluate edge formability nondestructively with eddy current

Eddy current (EC) testing is one of the most extensively used NDE techniques in the automotive industry for automatic in-line inspection of ferrous materials such as advanced high strength steels (AHSS). In addition, shearing is a very common forming operation in the automotive industry. With the increase of shearing clearance, the sheared-edge experiences significant work-hardening that normally decreases the formability of the sheared edge. This paper introduces a novel and real-time monitoring NDE method based on the EC sensor to characterize variations in shear edge quality for two different grade advanced high strength steels, DP780 and 980GEN3. The developed NDE method was applied to scan the edges sheared at various clearances between 5 and 25% of the material thickness. The NDE signal received was correlated with pre-straining introduced during the shearing process at various clearances. Microhardness measurements were taken to compare the trends obtained from the NDE tool with the hardness values. To evaluate the edge formability, half-specimen dome testing (HSDT) was conducted for the edges sheared at various clearances. A digital image correlation (DIC) system was used to measure failure strain during the HSDT. The failure strain of sheared edges was correlated with the NDE measurements for each clearance to assess the application of an NDE measurement in determining edge quality. The NDE method can potentially be used to inspect the sheared edge quality for sheet metal stamping process.

Development and experimental studies of new types of sheet metal stamping equipment

In this paper, developed devices for gas sheet stamping are presented. The devices allow to significantly reduce the cost of products. They can be used both for food manufacturing, petrochemical industry and other branches of industry. Prototypes of products obtained experimentally are presented.

Optimization of the pulsating curve for servo stamping of rectangular cup

Abstract The introduction of the servo press in recent years has opened up options for metal stamping; within this context, enhancing material formability and reducing stamping time are important goals. Focusing on a case study of rectangular cup stamping, this study optimized the pulsating curve for a servo press. First, the forming depths, thinning ratios, and forming time resulting from a pulsating curve and a crank curve were compared. Experiment results indicated that the pulsating curve could produce 92.3 % greater forming depth and an 8% smaller thinning ratio at the same forming depth as the crank curve. Next, finite element software was used to optimize the lifting velocity, press-in velocity, lifting distance, and press-in distance of the pulsating curve with forming time, thinning ratio, and forming force as single objectives. For single-objective optimization, the smaller-the-better formula of the Taguchi method was used and the analysis values of the optimal parameter combinations were compared with the optimal analysis values of nine analysis. The optimal parameter combinations produced a shorter forming time (0.06 s less), a lower thinning ratio lower (0.1425 % less), and a smaller forming force (808 N smaller). Using ANOVA and multiple regression analysis, the influence of the four process parameters on the quality characteristics and derived their mathematical relationships were calculated and their mathematical relationships derived. Next, with forming time, thinning ratio, and forming force as the quality objectives, multi-objective optimization was conducted using the Taguchi method. The grey-entropy method, and grey relational analysis were also used. Experimental verification results revealed that the grey relational grade of the optimal parameter combination was higher than those of the nine analysis. Furthermore, lifting velocity exerted the greatest influence on the multiple quality characteristics with a contribution of 55.01 %.

Symbiotic Circularity in Buildings: An Alternative Path for Valorizing Sheet Metal Waste Stream as Metal Building Facades

This study suggests an alternative approach to valorize non-hazardous industrial solid waste flow into construction materials, in particular as metal facade systems by quantifying the creative reuse of consistent and predicated sized scrap metal cutouts (known as Offal) that were generated from the automotive sheet metal stamping and blanking manufacturing processes. This study is an expansion on two papers presented at the 10th International Conference on the Environmental and Technical Implications of Construction with Alternative Materials (WASCON). Automotive sheet metal waste stream was transformed into two novel building facade system designs and a “cradle to gate” Life Cycle Assessment was carried out to analyze their environmental impacts and its resultant effect on design, manufacturing and economy. A Material Design Circularity Factor was introduced to compare both facade systems. Design #1 had greater impacts for all indicators except for operational energy due to the possibility of infiltration. Economically, design #1 had almost double the savings of design #2 at approximately four million dollars annually. The avoided carbon emissions made it evident that the creative reuse of Offal had significant environmental impacts. The two facade systems avoided 7.8 and 5.3 million kg CO2-eq. of greenhouse gas emissions for design #1 and design #2 respectively. Industrial Symbiosis is a viable concept that can lead to the adoption of circular economy principles to activate reuse over recycling for industrial by-products, which was promoted by creativity, saved manufacturing energy and the reduced costs of production of construction materials. This study proved that reusing automotive metal scrap for building envelopes is environmentally optimal and economically affordable.

Bursa Arkeoloji Müzesi’nden Bir Orta Bizans Damgası

This article tries to determine the place and identity of the owner of a metal stamp located in the Bursa Archaeological Museum collection in the Byzantine stamping objects typology. The stamp that we consider in this article is one of the rare examples, in which the inscription specifies the name of the owner as well as the offices and titles he held. The owner of the stamp, dated to approximately 9th –10th centuries, is Iohannes, the imperial protospatharios and epi ton oikeiakon. It is understood from the title protospatharios that Iohannes was a member of the central government and a wealthy aristocrat. The title epi ton oikeiakon, appearing together with Iohannes, may be a title that shows that he is a more privileged individual than other officials and that he may be from the imperial court. On the other hand, we also know of an administrative task under the sekreton of oikeiakon since the last quarter of the 10th century. In light of this, we have the following question: did Iohannes use his stamp for his personal affairs or did he use it in accordance with his responsibilities, which were part of his administrative position of management of imperial properties? In either case, we think that his stamp was stamped on a soft object such as clay and that it may be a brick stamp.

Comparison of apparatus and methods for tactile marking of polymeric films with Braille alphabet

This article analyzes contact and non-contact methods for local heat treatment of heat shrink films in tactile marking devices. The characteristics of polymeric film heating processes under heat transfer from metal stamps and laser emitters were investigated. The article contains diagrams obtained by differential scanning calorimetry of polymeric heat shrink film exposed to thermal effect of different tactile marking devices. The article also describes stereometry of Braille elements obtained by using a metal stamp and a laser emitter.

Crack Detection on Sheared-Edge of Ultra-High Strength Steel Sheet by Using Acid Immersion

In trimming of ultra-high strength steel (UHSS) sheet, the high strength of the sheet usually results in large fracture and low burnish surfaces on the sheared-edge. For metal stamping industries, large fracture surfaces are unwanted, as it not only deteriorates sheared-edge quality but also leads to delayed-crack. In this study, crack detection by using acid immersion on the sheared-edge of ultra-high strength steel sheet caused by the trimming process was investigated. The ultra-high strength steel sheet of JSC780YN, JSC980YN, and JSC1180YN having different strengths were trimmed and immersed in 35% hydrochloric acid under a controlled time interval. The steel sheet with higher strength was found to produce larger fracture surface after trimming, i.e. more than 50% of the entire sheared-edge is fracture surface. Besides, the larger fracture surface of the steel sheet results in higher crack exposure and higher crack propagation, which in the long run, it can cause failure to the part manufactured using UHSS.

Analysis of the risk of galling in sheet metal stamping dies with drawbeads

Sheet metal stamping of complex geometries normally involves the use of drawbeads to control the metal flow in the forming die. Drawbeads are, however, often the most tribologically severe part of the stamping dies. Selection of a suitable tribosystem for this type of forming operation depends on parameters such as local contact pressures, sliding speed, tool/workpiece interface temperature, tool and workpiece materials, and surface topographies. Furthermore, it depends on the required tool life and acceptable maintenance costs. This study demonstrates a methodology for offline evaluation of tribosystem applicability for a specific production platform for stamping of a three-dimensional component using a forming die with drawbeads. Based on an industrial case study, this work combines experimental and numerical analyses of the risk of galling in the different regions of an industrial forming die.

Inspection of Imprint Defects in Stamped Metal Surfaces Using Deep Learning and Tracking

This article focuses on the automatic detection and classification of imprint defects on the surface of metal parts. This innovative research had collaboration with a multinational industry, which provided a system to capture images of vehicle parts as well as information about defects, their frequency, and quality requirements. As our main contribution, we propose a framework that combines detection, classification, and tracking in a synergistic way to assist the automotive industry. We use a state-of-the-art convolutional neural network, known as RetinaNet, to detect and classify imprint defects. We explore the temporal coherence in consecutive frames by tracking detected regions so as to reduce false alarms—unstable candidate regions that are rarely (re)detected many times—or to fix the classification of regions that are alternated classified as mild or severe imprint across frames. In our experiments, we achieve a mean average precision of $76\%$ to detect and classify mild and severe defects, outperforming state-of-the-art detectors for static images. For severe imprints only, we achieve precision and recall values of $90\%$ and $92\%$ , respectively. These are promising results that could also benefit other industrial applications such as inspection of fissures, holes, wrinkles, and scratches, that also use image sequences.

Research on the influencing factors of small bending radius elbow stamping based on CAE simulation

The elbow with small bending radius is widely used in heating system and line collecting system, but its processing is difficult. Using the way of sheet metal stamping processing half elbows, and then welding the two half elbows is an effective method. There are a series of key parameters in the process of elbow stamping, which directly affect the forming result. Using sheet metal stamping software for stamping simulation, and comparing the effects of the parameters on thinning and principal stresses, we can see the specific effects of different parameters on the shaping. The main influencing factors of elbow stamping include friction coefficient, clearance, blank holding force and sheet metal thickness. For the friction coefficient and blank holder force, it should be selected near the minimum value. For clearance and sheet metal thickness, it is proportional to the forming effect.

Investigation of Galling Wear Using Acoustic Emission Frequency Characteristics

In the sheet metal stamping process, during sliding contact between the tool and sheet, it is expected that severe events such as tool wear or fracture on the sheet generate acoustic emission (AE) burst waveforms. Attempts have been made in the literature to correlate the AE burst waveform with the wear mechanisms. However, there is a need for additional studies to understand the frequency characteristics of the AE burst waveform due to the severity and progression of the galling wear. This paper will determine the AE frequency characteristics that can be used to monitor galling wear, independent of the experimental process examined. The AE burst waveforms generated during the stamping and scratch tests are analysed in this paper to understand the change in the AE frequency characteristics with the galling severity. These AE burst waveforms were investigated using the Hilbert Huang Transform (HHT) time-frequency technique, band power, and mean-frequency. Subsequently, these AE frequency features are correlated with the wear behaviour observed via high-resolution profilometer images of the stamped parts and scratch surfaces. Initially, the HHT technique is applied to the AE burst waveform to understand the influence of wear severity in the power distribution over the wide AE frequency range. Later, the AE bandpower feature is used to quantitatively analyse the power in each frequency interval during the unworn and worn tool conditions. Finally, the mean-frequency of AE signal is identified to be able to determine the onset of galling wear. The new knowledge defined in this paper is the AE frequency features and wear measurement feature that can be used to indicate the onset of galling wear, irrespective of the processes examined.

Technology for producing wear-resistant bimetal bearing based on cast aluminum

The paper presents the results of research the new technological process for producing bimetallic materials in the composition of “aluminum cast alloy - sintered iron powder” by the method of joint stamping of liquid metal. The purpose of this research is obtain parts with high wear-resistant properties, special sintered powder materials are used, which have an internal porosity to retain lubricant. However, such materials do not fit well with traditional aluminum alloys. This problem is may be solved by creating new bimetallic alloys, part of which is an outer casing, and the other materials is the functional bearing. To accomplish this task, we conducted a study of a new technology for joint stamping of liquid metal. In order to optimize and increase the reliability of the experiment, the pressing pressure, the pressure holding time, and the tooling temperature of the matrix were taken as quantitative factors. The effect of the applied pressure on the mechanical properties of the base material and the facing layer was determined on a longitudinal section of the obtained samples by the Vickers method. It was revealed that the gradient of increasing hardness is directed to the outer radius of the workpiece, that is, to the opposite crystallization front. The high level of bimetal adhesion is explained by the presence of a uniform moderate zone of mutual solubility, including due to the violation of the porous surface layer of the powder billet.

Argon Flow Rate Effect on Hardness of Carbon Thin Films on SKD11 Steel Using Target Material from Battery Carbon Rods with Plasma Sputtering Method

Processes for increasing the hardness value of steel are among the most challenging in industrial applications. SKD11 steel is one of the steels that is commonly used in industry (building, transportation facility construction, and production of various kinds of scissors such as knife-edge mold, scissors, circular saw blades, and metal stamping mold). However, SKD11 steel has a hardness value of only around 58–60 HV. Even though it is often used for building and transportation facility construction, which requires material with a high hardness performance. It will be better if the hardness performance is increased. The deposition of carbon thin films with plasma sputtering is a physical vapor deposition method that is effective for improving the hardness value of material. The purpose of this study is to obtain the maximum average hardness value of carbon thin films on SKD11 through the optimization of the argon gas flow rate parameter on plasma sputtering. The effect of the argon gas flow rate parameter on the hardness value of carbon thin films for SKD11 steel is investigated using a Vickers hardness tester. The research method involves the use of target material from battery waste (carbon rods) using argon gas low-frequency plasma sputtering with variations in the argon gas flow rate of 20, 40, 60, 80, and 100 mL/min for 2 hours at 300˚C. The method allows for the improvement of the hardness performance of carbon thin films because the argon gas flow rate affects the probability of carbon atom collision with particles in the chamber and the number of argon ions formed. This can cause different structures and hardness values of thin films. Based on the results, it can be concluded that the optimum argon gas flow rate parameter is 80 mL/min, which is associated with the highest average hardness value of 335.9 HV.