Punches And Dies Material Of Construction PdfBy Charles B. In and pdf 12.04.2021 at 19:15 9 min read
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- A Definitive Guide to Tablet Press Tooling Design (Learn How to Choose & Maintain Die/Punch System)
- Rectangular punch
- Punches Dies
A Definitive Guide to Tablet Press Tooling Design (Learn How to Choose & Maintain Die/Punch System)
Punch optimization is important in improving the technological process of belt perforation. Research about this process can rarely be found in the scientific literature. The objective of this paper is to determine the effective geometry of the piercing punches with a spherical bowl used for polymer composite belts. In order to fulfill this goal, the complex research of the influence of the geometrical features of the piercing punch on the perforation force, the hole quality, and the tool life has been conducted.
For derivation of the proposed model, the authors have used the combination of analytical and FEM analyses, along with the experimental tests validation. Based on the results, there are clear correlations between the depth of the spherical bowl punch and the perforation force or the hole diameter deviation. By analyzing the ratio of the perforation and transverse force, we are able to evaluate how the tool life will change for different sets of geometrical parameters.
All these correlations have been used to derive the indicators of the perforation force, tool life, and hole quality. Based on those, the optimization function has been specified. Finding the minimum value of this function makes it possible to define the optimal tool geometry. Since the model has been built based on the indicators, it is easy to adjust it to match any specific requirements of the belt manufacturers, which makes it useful for tool designers.
Perforation of the conveyor belts, due to the variety of materials used for manufacturing multilayer composite belts and the range of their mechanical properties, became a serious issue for manufacturers worldwide. Conventional tools are no longer suitable for the punching process, considering its efficiency, durability, and quality of the holes. Wojtkowiak et al. This indicates that the simplest mechanical method of belt perforation—punching with two cutting edges a piercing punch which cooperates with a die —may be considered as an optimal one, if the effective geometry of the piercing punch will be determined.
Based on the previous research presented in [ 2 ], the concave piercing punches, especially the one with spherical bowl, may greatly reduce the perforation force. The structure of the belts may be either multilayer or fibre-reinforced. Among the materials of which separate layers are made of most common are polyamide, polyester, polyurethane, rubber, PVC, and aramid or carbon fibers. The main focus in the presented research is put on the rigid belts with increased strength whose core is made of polyamide film covered by polyamide fabric protective gaskets and nitrile rubber NBR covers.
According to the previous research presented in [ 4 ], this type of belts needs the highest perforation force and the quality of the hole strictly depends on the geometry and wear of the cutting edge, due to the combination of fabrics and rigid film in their structure. As far as tool optimization performed for such tools as twist drills, mills, turning tools, or punches is concerned, research can be widely found in the scientific literature; however, there is no research connected with belt perforation tools.
Abele and Fujara [ 5 ] presented a new holistic method of using computing power for twist drill design and optimization. Li et al. Zong et al. Jensen et al. Performing the tool optimization based only on the experimental research requires to manufacture a series of tool sets with variable geometries, which is very expensive.
Based on the analyses, we can choose a few sets of geometrical features, which will be later manufactured and tested to validate the model used and the results obtained. This approach will greatly reduce the costs and will expand the range of tested parameters.
During the tool optimization, various objective functions, designs, and state variables may be used. Venkata Rao and Savsani [ 9 ] presented in their work multiple advanced optimization techniques, which was explained on few examples of the optimization of different mechanical designs gear train, robot gripper, etc.
In general, we can distinguish three main groups of objective functions for tools: exploitation parameters tool life or wear, process efficiency, tool stiffness, etc. If we consider the belt punching process, the most important objectives are the lowest perforation force, the longest tool life, and the best quality of the holes. As design variables, the geometrical features like bowl radius, punch-die clearance, punch diameter, or tool angle will be used.
Based on the chosen tool geometry, the state variables equivalent stress, strain, or frictional work can be obtained and used to determine the objective functions. Among the searched parameters, the hardest to determine is the tool life.
Experimental tests, which will make it possible to specify the tool life, could take a few years and millions of cycles before any usable results are obtained.
Because of that, it is necessary to use models for tool life prediction, based on the above-mentioned state variables. In the scientific literature, we can find the correlations between the tool life and the following parameters: cutting edge stress, lateral to normal force ratio, cutting force, temperature, tool wear after low-cycle tests, or some stochastic or genetic algorithms based on previous population of results for specific types of tool.
Oraby and Hayhurst [ 11 ] used the ratio of force components acting at the tool tip radial and feed component of the force in order to develop the models for tool wear and life estimation.
Zhang and Guo [ 12 ] proposed a tool wear model, which uses the prediction of the cutting force and the energy consumption in the turning process and validated this model with the experimental results available in scientific literature. Yen et al. They claimed that using the FEM simulations to determine the above-mentioned variables, it is possible to predict the tool wear evolution and tool life with acceptable accuracy.
Hu et al. Salonitis and Kolios [ 15 ] presented a methodology for the efficient reliability assessment of cutting tool wear based on the combination of stochastic response surface and surrogate modeling methods combined with Monte Carlo simulations and first-order reliability methods for the estimation of reliability indices taking into an account cutting speed and feed rate. They claimed that the proposed techniques have potential for determining optimal tool life with reduced experimental testing in comparison with pure experimental methods.
Kovac et al. All above-mentioned tool life estimation models cannot be directly used for an estimation of the punch wear. The important difference between the belt punching process and machining is the magnitude of the tool life.
In belt punching, the tool life may exceed 1,, holes, which takes hours and a lot of wasted material, while in machining, the tool life is measured in minutes. Because of that, for the punch optimization, we should use methods based strictly on FEM analyses, which will provide as results to the perforation force to transverse force ratio or the contact pressure on the cutting edge.
The main goal of the presented research is to determine the effective geometry of the piercing punches with a spherical bowl used in the belt perforation process. Any additionally derived characteristics should enable to simply adjust the optimization model to match specific requirements of the manufacturers worldwide.
In the presented research, the combination of analytical derivations, FEM simulations, and experimental research was used in order to determine the effective geometry of the piercing punch.
All presented results were obtained using the test stand designed by authors Fig. Its construction was described in details in [ 2 ]. The main advantage of the test stand is the zero backlash linear guide, which makes it possible to use a very small clearance between the punch and the die down to 0.
All the experimental tests were performed on the MTS Insight testing system with load capacity 50 kN, where traverse speed 0. Punching die and the set of tools used in presented tests with their geometrical parameters: 1—base, 2—head block, 3—guiding column, 4—sleeve, 5—ball bushing, 6—punch plate, 7—punch chuck, 8—piercing punch, 9—piercing die, 10—belt specimen, 11—pressure plate, D —diameter of the piercing punch, H —depth of the spherical bowl, L —punch-die clearance, R —radius of the piercing punch.
In order to derive the optimization model, only one type of belt TFL10S will be used. This type of belt was chosen because it has a combination of the most difficult properties for a perforated belt manufacturers—it is very rigid and has increased strength, which indicates it needs one of the highest perforation forces and the tool wear during its processing should be the worst.
Additionally, it has protective gaskets made of the polyamide fabrics which implies that it should be subjected to the tool sharpness and almost all defects common for the belt perforation will occur for this type of belt.
The quality of the punched holes may be evaluated using both quantity and quality criteria. Since the diameters measured in perpendicular dimensions differ due to the orthotropic properties of the polymer composite belts and much more elasticity is visible in the longitudinal direction of the belt than the transverse one, the diameter D L measured in the longitudinal direction will be taken into account during further analysis.
Based on the obtained results, the deviations in the longitudinal directions are 10 times higher than those in the transverse direction, which means that slight ovality of the holes is present. To determine the correlation between the depth of the piercing punch bowl H and the punch-die clearance L with the above-mentioned quantity criteria, the measurement of the hole diameters was taken with a slide caliper with accuracy of 0. For each geometry, five holes were measured in both directions and then the average was derived.
The methodology of the measurement is presented in Fig. Based on the results, there is a negative linear correlation between both analyzed parameters and the depth of the punch bowl H. This indicates that the sharper the cutting edge, the better the quality of the hole we can obtain.
Analyzing the influence of the punch-die clearance, we can observe that by increasing the gap between two cutting edges, diameter deviations rise nonlinearly. On the other hand, changing the punch-die clearance has no effect on the ovality of the hole. As can be observed, the hole diameter for the flat punches is always lower than the nominal value, since the belt is extended during the process and shrinks after the punch goes back to its initial position.
On the other hand, for the spherical bowl punches, the holes have slightly greater diameters than the tool. Because some correlations between the hole deviation and the geometry of the tool are present, it could be possible to determine the nominal diameter of the piercing punch, which would compensate the hole deviation. Thanks to that, we would be able to obtain perfect diameter of the holes in the belt, even with less sharp tools.
The problem with this approach is the fact that presented correlations are specific for a single type of the belt and may slightly differ for another one. In order to adjust the equipment of the perforating machine for various belts, it will be necessary to use not only different piercing punches but also the dies. It would generate very high cost of exploitation.
Using the effective geometry of the tool, which should be properly designed for a universal application, can greatly reduce that cost. Even if the tool life of the sharper piercing punch will be shorter, the wear of the die is much lower than the punch. Applying the constant nominal diameter of the piercing punch will make it possible to use one die for the multiple types of punches. For the quality analysis, the most important factor taken into account is the presence or absence of the typical defects that occur in the perforated belts.
Based on the previous research [ 2 ] as the common defects of belt perforation, we can distinguish: conicity or ovality of the holes, fiber pull-out, uneven edge or side surface, and deformation of the covers of the belt. In Fig. Comparing the flat punch with all spherical bowl punches, it can be clearly observed that the roughness of the side surface and the shape of the hole contour are greatly improved regardless of the depth of the bowl and clearance.
Analyzing the correlation between these parameters and the overall quality of the holes, we can observe that increasing the clearance has a negative effect since the pulled-out fibers occur much more often. Increasing the depth of the bowl should theoretically reduce the fiber pull-out as it makes the punches sharper, but the surface finish and tool condition may affect the quality as well.
Based on the above-mentioned analysis and the overall experience of the authors obtained by the contact with the industry, the map of hole quality was made Fig. It should be mentioned that the presented data should be used more for understanding the tendency of how the hole quality varies when using different tool sets rather than for a quantity analysis of the perforation process.
One can find a lot of research that presents an influence of the punch-die clearance on the punching process parameters in metal stamping, such as maximum force, tool wear, and hole quality. Soares et al. However, they also mentioned that for very small clearances 0. Subramonian et al. They also stated that this stress level may be used as an indicator of a punch wear and together with the geometry curve can be used to improve the tool life.
Lo et al. However, the above-mentioned correlation for more elastic materials, like polymer composite belts, was not specified. Based on the experimental results, a slight difference in the force magnitude is visible, but no explicit nature of the correlation may be determined. Since the differences between extreme values for the experimental tests are 6.
This thesis is also proved by FEM analyses results.
The die materials used for the main parts of medium-sized and large-sized dies are described here. Although there are several types of die structures, explanations are given here are based on the widely used movable stripper structure. The plate configuration of the die shown in Fig. The punch and die holder are not only for fixing the die to the press machine but also for supporting the rigidity of the die. They also have the role of adjusting the die height and providing the space for springs, etc. Usually, the materials used are SS or S50C. There is no big difference between the two.
Again and again and again. Always identical, again and again. The convincing properties of our components are their excellent cutting quantities and unbelievable precision. We only deal with cutting units, they are the meaning of our work.
We are a comprehensive supplier for the entire tableting process, extending from research and development, through production, using the latest instrumentation technology, as well as marketing, application consultation, and intensive product training for the customer. Fette Compacting has spent years developing industry-leading technology for both tablet presses and the critical components needed to support them. Our revolutionary designs in tooling and turret design have paved the way for faster production, reduced downtime, and increased quality.
Punch optimization is important in improving the technological process of belt perforation. Research about this process can rarely be found in the scientific literature. The objective of this paper is to determine the effective geometry of the piercing punches with a spherical bowl used for polymer composite belts. In order to fulfill this goal, the complex research of the influence of the geometrical features of the piercing punch on the perforation force, the hole quality, and the tool life has been conducted. For derivation of the proposed model, the authors have used the combination of analytical and FEM analyses, along with the experimental tests validation.
Лжец! - выкрикнула Сьюзан. - Я видела твою электронную почту. Хейл замер, потом повернул Сьюзан лицом к. - Ты вскрыла мою электронную почту. - А ты отключил моего Следопыта.
Это не был тщательно загримированный покойник в обитом шелком гробу. Обнаженное тело, бесцеремонно брошенное на алюминиевый стол. Глаза, которые еще не приобрели отсутствующего безжизненного взгляда, закатились вверх и уставились в потолок с застывшим в них выражением ужаса и печали. - Dоnde estan sus efectos? - спросил Беккер на беглом кастильском наречии.
Сьюзан стало дурно оттого, что она увидела.