Heuristic design of U-shaped die cooling channel for producing ultra-high strength steel using hot press forming

This paper proposes an optimised cooling channel design for a U-shaped die in the hot sheet metal forming process using a heuristic method. Unlike in previous works, the parameters used in this study for optimising the cooling channel design not only consider the pitch between and diameter of cooling channels but also their distance from the tool surface and wall tool. The cooling channel design is optimised by coupling the heuristic method with finite element thermal and static analyses. The main factors to be considered in the optimisation include the highest heat transfer and the lowest stress that can be achieved by the optimum cooling channel die design. The optimum design was determined by conducting a simulation and was validated by conducting an experiment. The temperature distribution of the FEA model was at most 5% different from the experimental results. The optimum cooling channel design of hot press sheet metal forming can produce ultra-high strength steels which tensile strength and hardness are 51 and 83% greater than those of original boron steels. The heuristic method can also be applied to optimise the cooling channel die design for the production of ultra-high strength steels in the automotive manufacturing industry

Effect of rake angle and feed rate on tool wear and surface topography for different chip size in machining carbon steels

This paper proposes tool wear and surface topography analyses in cutting carbon steels 1045 that producing different chip types. The problem of continuous chip due to the different rake angle and feed rate cause the reduction of the surface quality and tool life. The cutting rake angle is set based on the difference angle of shim support for the tool holder. Beside rake angle, different feed rate can improve the surface topography and the tool wear. Tests are carried out using carbon steel 1045 as workpiece material and chip breaker CNMG 120412 as tool insert under dry machining conditions. Results indicated that the lowest the tool wear, the better surface topography produced from the segmented chip at feed rate 0.4 mm/rev and a rake angle −9°. The effect of rake angle and feed rate overcome the problem of continuous chip that associated with low tool wear and surface topography

Design of cooling channel in hot stamping tool by heuristic approach

Owing to the demand for reducing gas emissions, energy savings, and the production of safer vehicles, the development of Ultra High Strength Steel (UHSS) materials is non-trivial. To strengthen a UHSS material such as boron steel, it is required to undergo a number of processes namely, heating it via hot stamping at a certain temperature and time as well as cooling it through quenching. In the hot stamping process, a similar die is used as in the cold stamping process, but with additional cooling channels. The cooling channel systems are integrated into the die design to control the heat transfer rate for quenching process of hot blanks. During quenching process, an effective die design contributes towards the achievement of the optimum heat transfer rate and homogeneous temperature distribution on hot blanks. In this study, the parameters of the cooling channel design i.e. the diameter of cooling channel (CA), the pitch between cooling channel (CB), the cooling channel distance to tool surface (CC), and the cooling channel distance to wall tool (CD) are optimised for a flat and U-shape tool using heuristic method. The heuristic method is coupled with the thermal and static analysis of finite element analysis (FEA) via ANSYS to determine the optimum design of hot stamping cooling channels. The static analysis are performed to ensure that the tool is able to withstand the applied pressure, whilst the thermal analysis was carried out to ensure homogeneous temperature distribution. Each parameter of the cooling channels optimised and benchmarked with traditional Taguchi method. Then, hot stamping process experiment is conducted to get the temperature distribution of the blank product and tool. Next, the simulation results were compared with experimental works for validation purpose. The result of the temperature distributation between FEA and experiment expected error less than 20 %. It is found that the optimum design of the hot stamping tool with a high heat transfer and lower von Mises stress (VMS), the following parameters (previously defined as CA, CB, CC, CD in mm) are required (8,8,10) mm for the flat tool, (8,8,8,10) mm for the upper U-shape tool and (8,8,8,8) mm for the lower U-shape tool, respectively. It is also evident that the pattern of the temperature distribution of the FEA model agrees the experimental results. Based on the flat shape tool, the average percentage error for the blank heat distribution is 1.83 % and for the tool is 2.67 %. As for the U-shape tool, the average percentage error for the upper tool, lower tool, and the blank heat distribution are 16.65 % 17.95 % and 7.92 %, respectively. The tensile strength and the hardness value of the blank products (flat and U-shaped samples) are measured to be approximately 1200 MPa and 600 HV, respectively. In conclusion, based on the aforementioned optimised parameters in the study, it is apparent that a high tensile strength with high value of hardness product could be produced from the heuristic method

Development of hot stamping tool by using indirect hot stamping for basic bending part (u-shape)

In hot stamping process, (UHSS) blank was cut into the rough shape. The blank is then heated to the temperature (900 - 950 °C) for 5 to 10 minutes inside the furnace. Then, the blank must be transferred quickly to the press to avoid the part is cooled before forming. After that, the blank is formed and cooled simultaneously by the water cooled die for 5 to lOs. Due to the contact between hot blank and the cool tool, the blank is cooled in the closed tool [1]. Today, hot stamping exists in two different types of methods which are direct and indirect. For indirect hot stamping method, before the blank is heated inside the furnace, it then undergoes cold pre-forming process. This process is done once after the blank is cut

Heuristic Optimization of Cooling Channel Design in the Hot Stamping Die for Hot Stamping Process

In hot stamping process, similar die is used as in cold stamping process but with additional cooling channels. The cooling channel systems are integrated into the die design to control the cooling rate for quenching process of hot blanks. During quenching process, the die is effectively cooled to achieve the optimum cooling rate and homogeneous temperature distribution on hot blanks. In this paper, heuristic method with finite element analysis (FEA) of statis analysis and thermal analysis are applied to determine the cooling channel size, pitch size between channels and channel distance to the blanks surface. This static analysis identifies either the tool able to stand the pressure applied or not, while the thermal analysis is to ensure the die obtains the high cooling efficiency with homogenous temperature distribution. In this heuristic method, each parameter of the cooling channels inside the die are optimized and benchmarked with traditional Taguchi method. The results showed that the heuristic method coincides with Taguchi method even better and achieved the acceptance error between FEA in temperature distributions

Effect of rake angle and feed rate on chip segmentation in machining carbon steel 1050

A chip breaker plays important role to break the chip and enhance productivity and quality during turning process. However, chip break as tool are not able to break the chip and formulate the continuous chip causes the tool wear and the excessive heat generated for interrupting the surface machining quality. These chips formation are influenced by cutting conditions and tool geometries such as spindle speed, feed rate, depth of cut and rake angle. In this study, experiments were carried out on carbon steel 1050 with chip breaker at a constant cutting speed 275 m/mm at depth of cut 0.9 mm. The effect of different feed rate and rake angle to chip length produced were further investigated in the experiment. The results obtained that the chip segmented at 0.4 mm/rev of feed rate and -9° of rake angle. Thus, the feed rate and rake angle can play the important role in breaking the chip with a chip breaker to enhance the productivity and quality in the machining process

Effect of rake angle and feed rate on wear and roughness in machining carbon steel 1045

In metal industry, the optimum usage of insert in turning process is a common practice to reduce the machining cost. Hence, the endurance limit for the insert will be low and will affect the quality of the surface finish. Several studies have discovered the tool wear and surface roughness when machining parameter of the process is properly considered. This study present analysis of tool wear of carbide inserts in finish turning of carbon steel 1045. This paper contribution concerns the experimental occurrence of tool wear and roughness for a continuous cutting condition of tool holder that has a variable rake angle and variable of feed rate. So, these parameters become critical to minimize the tool life and roughness of the work part

Evaluation of minimal quantity lubrication effects on surface roughness in milling with coated and uncoated tools using kurtosis quantification method approach

The present work’s main contribution is applying kurtosis quantification to analyse complicated or random type of milling vibration signals under dry and minimal quantity lubrication (MQL) to achieve good surface quality. The milling process is carried out using coated and uncoated cutting tools on ductile iron under the selected MQL volume flow rate parameter. The results obtained from kurtosis and skewness measurement are then verified with average surface roughness measurement (Ra). From the experimental work, it was found that kurtosis demonstrate the effectiveness on feature extraction. The dry milling using uncoated tools contributes high values of vibration signals and surface roughness. Meanwhile, the Ra values improvement, which reduces by 70% when MQL is applied

Comparison of Cooling Performance Between High Thermal Conductivity Steel (HTCS 150) and Hot Work Tool Steel (SKD 61) Insert for Experimental Tool Using Finite Element Analysis

In hot stamping, the tool cooling system plays an important role in optimizing the process cycle time as well as maintaining the tool temperature distribution. Since the chilled water is forced to circulate through the cooling channels, there is a need to find the optimal parameters of the cooling channels that will cool down the tool efficiently. In this research paper, the cooling channel parameters that significantly influence the tool cooling performance such as size of the cooling holes, distance between the cooling holes and distance between the cooling holes and the tool surface contour are analyzed using the finite element method for both static and thermal analysis. Finally the cooling performance of two types of materials is compared based on the optimized cooling channel parameters

Experimental Validation for Hot Stamping Process by Using Taguchi Method

Due to the demand for reduction in gas emissions, energy saving and producing safer vehicles has driven the development of Ultra High Strength Steel (UHSS) material. To strengthen UHSS material such as boron steel, it needed to undergo a process of hot stamping for heating at certain temperature and time. In this paper, Taguchi method is applied to determine the appropriate parameter of thickness, heating temperature and heating time to achieve optimum strength of boron steel. The experiment is conducted by using flat square shape of hot stamping tool with tensile dog bone as a blank product. Then, the value of tensile strength and hardness is measured as response. The results showed that the lower thickness, higher heating temperature and heating time give the higher strength and hardness for the final product. In conclusion, boron steel blank are able to achieve up to 1200 MPa tensile strength and 650 HV of hardness