Hole Piercing Research Articles

Micromachining of 316LVM stainless steel tubes using periodic acousto-optic modulation of pulsed Nd:YAG lasers for cardiovascular stent applications

Optoelectronic techniques can be used in laser applications in biomedical instrumentation to achieve better flexibility and control of the available optical power. These techniques enable the processing and manufacturing of biomedical implants like cardiovascular stents and micrometallic components with reduced heat-affected zone (HAZ) and extremely precise edge cutting. The present investigations deal with the study of laser piercing routines and further profile cutting of thin stainless steel sheet tubes for biomedical implant manufacturing. The process is performed using an acousto-optic (AO) modulator-based pulsed Nd:YAG laser. The AO modulator used in the experiments is a Bragg diffraction device. During the piercing of holes, the focused laser power is gradually increased from a low value and finally reaches the maximum as the beam goes deeper into the material. The most suitable value of dwell time is found to be 50 ms. A nine step staircase modulating voltage with a maximum ac component of 800 mV is used, and the laser power is 4 W in TEM00 operation. The acousto-optic modulator-based pulsed Nd:YAG laser is capable of cutting extremely complex geometries of stents on 316LVM tubing. Laser cutting results in a kerf width of 20.5±0.5 µm. Precise strut dimensions of 115±15 µm for subsidiary strut, 150±15 µm for main strut, and 150±15 µm for the link are also obtained. With the piercing routine, extremely fine holes with reduced heat-affected zones are produced, and this quality is reflected during consequent machining of required profiles for implants.

Coefficient of Friction between Tool and Material in Shearing

In this study, we propose a method of determining the coefficient of friction between a tool flank and a sheared surface in shearing. In this method, the vertical force and horizontal force need to be measured after completion of the separation process, after which the coefficient of friction is defined as the ratio of vertical force to horizontal force. In this study, the influences of punch speed, kinematic viscosity of lubricating oil and clearance on the coefficient of friction were investigated. Using the proposed method, a coefficient of friction of about 0.35 was obtained when ordinary lubricating oil was used. The coefficient of friction between the tool face and the material surface was also determined from sliding friction tests. The results of Finite Element Method taking into account the coefficients of friction obtained by the method showed good agreement with experimental results for the piercing of small holes.

Study on Coefficient of Friction between Tool and Material in Shearing

Determining method of a coefficient of friction (hereafter coefficient) between tool flank and sheared surface in shearing is proposed. In the method, measuring of vertical force and horizontal force are needed at a stage after separation process completed. Then, the coefficient is defined as the ratio of vertical force versus horizontal force. The influences of punch speed, kinematics viscosity of lubricating oil and clearance on the coefficient were investigated. By the method proposed, the coefficient of about 0.35 was obtained when ordinary lubricating oil is used. The coefficient between tool face and material surface is also determined from sliding friction test. The results of FEM analysis in consideration of the coefficients obtained by the method showed good agreement with the experimental results of the piercing of small holes.

Influence of Punch Geometry on Small Hole Piercing Characteristics

Experiments and FEM analysis on small hole piercing were carried out. In this paper, small hole piercing is defined as piercing performed using punches that have smaller diameter than the material thickness. The results of this study clarified the followings ; 1) Shearing force, stripping force and pushing force are considerably affected by the friction between the punch flank and inner surface of pierced hole, 2) The use of tapered punch is effective for reducing frictional force, and 3) Increasing the linear portion at the punch tip increases the shearing force. The experimental and analytical results were also found to agree for these findings.

Elastic-Plastic FEM Analysis for Piercing of Small Holes.

Experiments and FEM analysis on the piercing of small holes were carried out. Small hole, in this paper, means that the diameter is smaller than the thickness of the material. Material deformation in the piercing differs from that of conventional shearing. So, the piercing processes were calculated by rigid-plastic FEM analysis and elastic-plastic FEM analysis, experimental and FEM analytical results were compared, and material deformations and piercing forces were investigated. The results of elastic-plastic FEM analysis showed good agreement with the experiment results even more than the results of rigid-plastic FEM analysis.

An exploration of the piercing of round holes in metal sheets in the presence of frictionally induced radial compressive stress

A new concept of using an annular urethane disc to apply radial compressive stress in blanking or piercing is presented. As the punch advances prior to piercing a hole in the sheet metal, it compresses a urethane disc which is enclosed within a die ring. Friction between the urethane and the sheet metal being pierced induces radial compressive stress in the sheet metal. The tooling used for the process and the results of experiments conducted with mild steel and brass are presented. A theoretical model is used to estimate the induced compressive stress and the force needed for the piercing operation. The results show that some improvement in the quality of the hole is produced, as compared with conventional piercing.

An exploration of the piercing of round holes in metal sheets in the presence of frictionally induced radial compressive stress

An exploration of the piercing of round holes in metal sheets in the presence of frictionally induced radial compressive stress

4851634 Device for electrical discharge piercing of holes in components : Khaidar A Vakhidov, Erkin T Abdukarimov, Tashkent, Union Of Soviet Socialist Republics

4851634 Device for electrical discharge piercing of holes in components : Khaidar A Vakhidov, Erkin T Abdukarimov, Tashkent, Union Of Soviet Socialist Republics

Formation of a finely dispersed structure in piercing of holes in aluminum-alloy sheet blanks

Formation of a finely dispersed structure in piercing of holes in aluminum-alloy sheet blanks

A manufacturing process using the impact compression of a viscoplastic pressure medium. Application to the piercing of fine holes.

Recent developments in the electronics industry require a piercing technique for making fine holes at a high production rate. The present research attempts to apply to such piercing a new manufacturing process utilizing the impact compression of a viscoplastic pressure medium recently proposed by the authors. As a result, the process is shown to be successful in piercing various fine holes, unobtainable by the conventional shearing process : for example, circular holes of 0.05 mm and 0.1 mm in diameter and a slit of 0.05 mm in width. The piercing pressure is examined theoretically and experimentally.

A Sheet Metal Forming Process Employing Viscous Material as a Pressure-transmitting Medium : Examination into Mechanical Properties of the Medium

Using a drop hammer apparatus, four kinds of impact compression and forming tests are carried out with nonmetallic materials (i.e., clay, plasticine, silicone polymer and rubber) which have various viscous/elastic/plastic characteristics, and their applicability to the new forming process previously proposed by the authors is discussed. It is concluded that a viscous medium with a high strain rate sensitivity m is advantageous for piercing and shallow stretch-forming. Some new applications (i.e., piercing of small holes and glass sheets) are presented.

A manufacturing process using the impact compression of a viscoplastic pressure medium (Application to piercing of fine holes)

The recent development of electronics industries requires a piercing technique for fine holes with a high production rate. The present research attempts to apply to such piercing a new manufacturing process utilizing the impact compression of a viscoplastic pressure medium, recently proposed by the authors. As a result, the process has succeeded in making various fine holes, unobtainable by the conventional shearing process : for example, circular holes with a 0.05 ∼0.1 mm order in diameter and a slit of 0.05 mm in width. The piercing pressure is examined theoretically and experimentally.

PIERCING OF METAL SHEET WITH RUBBER PADS

SUMMARY Experimental results are presented for the piercing of circular holes in sheet metal using pads of conventional rubber or polyurethane. An empirical equation has been obtained for calculating the required loads and an attempt has been made to interpret this equation in terms of rubber hardness and the work-hardening characteristic of the metal. It is shown that the deformation behaviour of the polyurethane is different from that of the rubber and that it is misleading to treat polyurethane as though it is merely a rubber with a higher Shore hardness.