Pocket Corner Research Articles

Adaptive speed control for waterjet milling in pocket corners

Milling thin titanium alloy workpieces using conventional manufacturing processes is a delicate operation. During machining, the cutting forces can deform the part, while resulting compressive stresses could actually enhance its mechanical properties. Nevertheless, when parts are both large in size and thin, deformation generated by machining will be incompatible with the geometrical specifications. From this perspective, abrasive waterjet milling offers a suitable alternative solution. Numerous works present the results relating to the depths milled, the surface characteristics and machining strategies when milling pockets. Such studies show that the change of direction when milling closed pockets generates defects arising from the distribution of the jet’s energy over the milled surface or the kinematics of the machine. When a pocket corner radius is imposed, changes of direction are made following circular arcs with a radius lower than the specified one. In the present paper, an analysis of the width milled during successive circular trajectories is presented and a predictive model for the depth is adopted. This model is then used to propose a milling method that allows both the imposed radius and tolerance on the pocket depth to be respected.

The algorithm of layering calculation for corner plunge milling tool path

Cavity corner is one of the most common machining features in the complex structural components of aircraft, and processing pocket corner by plunge milling has the advantages of higher metal removal rate, smaller machining distortion, and higher machining precision, and especially is suitable for cavity corner machining with large depth. However, there are some problems in current corner plunge milling approach, such as sidewall over-cut, invalid tool location points, and uncontrollable residual height. Therefore, a universal layering algorithm for plunge milling tool path generation is projected and established. First, define and represent two-dimensional corner model. Next, the terminologies about machining layer circle, cutter circle, and cuspidal point circle are introduced and layering model is built. Then, construct cutter circle arrangement program on the basis of the intersection between layer circle and corner model. Meanwhile, the relationship between residual height and layering model is determined. Finally, the layering tool path is recursively generated in line with radial cutting width. Two groups of contrast experiments prove effectively that the proposed method excels the conventional methods in guaranteeing residual height and avoiding invalid tool location points. In addition, the layering method can maintain an efficient processing tool path ratio of more than 80%. Furthermore, the application of a CAD solid model of an aircraft panel demonstrates the feasibility and effectiveness of the layering approach.

Cutting Temperature Investigation of AISI H13 in High Speed End Milling

Heat produced at the tool-chip interface during high speed milling operations have been known as a significant factor that affect to tool life and workpiece geometry or properties. This paper aims to investigate cutting temperature behaviours of AISI H13 (48 HRC) under high speed machining circumstances during pocketing. The experiments were conducted on CNC vertical machining centre by using PVD coated carbide insert. Milling processes were done at cutting speeds 150, 200 and 250 m/min and feed rate were 0.05, 0.1 and 0.15 mm/tooth. Depths of cut applied were 0.1, 0.15 and 0.2 mm. Tool path method applied in this experiment was contour in. Results presented in this paper indicate that by increasing cutting speed the cutting temperature is lower than low cutting speed. However, by decreasing feed rate leads to cutting temperature low. Cutting temperature phenomena at the corner of pocket milling were also investigated. The phenomena showed that cutting temperature tends to decrease a moment when cutter comes to the corner of pocket and turning point of tool path and increase extremely a moment before leaving the corner and turning point.

Tool path generation and optimization method for pocket flank milling of aircraft structural parts based on the constraints of cutting force and dynamic characteristics of machine tools

The cutting force and vibration will be increased dramatically due to the sharp change of cutting engagement angle during the process of pocket flank milling for aircraft structural parts. And the sharp change of the curvature of tool path curves of pocket corner brings higher requirements for the performance of dynamic characteristics of the machine tool, while the machining quality of the surface will be affected heavily once the dynamic characteristics of the machine tool cannot meet the machining dynamic characteristics requirements. It is very important to consider the constraints of cutting force and dynamic characteristics of the machine tool during tool path generation. However, it is a contradictory problem to satisfy the requirement proposed by the two constraints on tool path, and it is not easy to compromise the two constraints. In order to address the difficult issue mentioned above, a new tool path generation and optimization method for pocket flank milling is proposed. The essential idea of this paper is the combination strategy of corner-looping milling and clothoid curve transition, where the contradictory requirement of the above two constraints can be compromised and optimized. The machining experiment results show that the conditions of cutting force can be improved, vibration during the process of machining can be reduce, as well as the machining quality of the surface is improved.

Precise prediction of forces in milling circular corners

Pocket corner is the most typical characters of aerospace structure components. To achieve high-quality product and stable machining operation, manufacturer constantly seek to control the cutting forces in pocket corner milling process. This paper presents the cutting force in corner milling considering the precision instantaneous achievements of tool engagement angle and undeformed chip thickness. To achieve the actual milling tool engagement angle in corner milling process, the details of tool–corner engagement relationship are analyzed considering the elements of tool trajectory, tool radius, and corner radius. The actual undeformed chip thicknesses in up and down milling operations are approached on account of the trochoid paths of adjacent teeth by a presented iteration algorithm. Error analysis shows that the presented models of tool engagement angle and undeformed chip thickness have higher precision comparing with the traditional models. Combined with the cutting force coefficients fitted by a series of slot milling tests, the predicted cutting force in milling titanium pocket with different corner structure and milling parameters are achieved, and the prediction accuracy of the model was validated experimentally and the obtained predict and the experiment results were found in good agreement.

Prevention of Synmastia in Breast Augmentation of Sunken Chest: Muscle Splitting Concept

Background Synmastia is serious condition but rare. Synmastia is a technical complication caused by over dissection of the medial pocket over the sternum. In sunken chest, the medial portion of Pectoralis muscle tends to be elevated easily from the sternocostal area. So it should be more careful to prevent from overdissection in breast augmentation of sunken chest. Methods An idea was obtained from buttock augmentation with implant. For buttock augmentation, implants are placed intramuscularly for the protection of sciatic nerve and for the prevention of implant displacement. Muscle splitting concept for intramuscular placing of implant in sunken chest adds tissue to sunken area and provide guarding barrier to reduce detaching tendency at the parasternal area. Results As I had the concept of intramuscular placement at the medial side for the breast augmentation in case of sunken chest, I experienced steady medial breast contour in 5 cases of sunken chest. Conclusions Muscle splitting as coronal plane of medial portion of pectoral muscle make muscular pouch at the medial corner of subpectoral pocket which is effective for the prevention of medial displacement of implant in breast augmentation of sunken chest by guarding effect of irregularly arranged muscle fibers which resist against the detaching force of pectoral muscle from the sternocostal origin. Keywords: Sunken chest, Synmastia, Muscle splitting, Breast augmentation

Effective corner machining via a constant feed rate looping tool path

In the finish machining of a pocket corner, varying radial depth of cut is generally encountered by the end milling tool during the entry into and exit from the corner. This leads to substantial variability of the machining process. This paper presents the generation and application of a multiple looping tool path for corner machining with the objective to reduce the machining variability and improve the machining efficiency. Material removal rate is selected as the measure for the machining variability. To reduce the material removal rate for a straightforward corner machining tool path, feed rate needs to be decreased as the end mill approaches the corner apex and increased as it exits the corner. Instantaneous changes of feed rate are not possible in practice due to practical limitations on the servo drive system of common machine tools. A tool path of constant feed rate is thus preferred for effective corner machining. The looping tool path proposed in this work is composed of a series of smoothly connected linear and circular segments to ensure its applicability for all machine tools. For a given corner geometry, a single-cutter as well as a double-cutter strategy have been introduced to maximise the machining efficiency. Various case studies were carried out to examine the resulting material removal rate and total machining time for different machining operations.

Influence on Cutting Forces and Vibration in High Speed Machining Pocket Corner

High speed milling hardened mould steel (above HRC50) at pocket corner generates the cutting forces increase and vibration gets fiercely because of the sudden change of cutting direction. It will cause serious wear and possible breakage of cutting tool, and poor quality of parts. Hence, the need to select reasonable cutting parameters and adopt appropriate cutting strategies will help them to achieve their goal. In this paper, the effects cutting parameters including cutting speed, pocket corner angle, feed rate per tooth and radial depth of cut on cutting force and vibration are studied. The results show that sharper pocket corner results in the increase of cutting force and makes vibration strong. Cutting force increase with the increase of cutting speeding, feed per tooth and radial depth of cut. The optimum of cutting speed leads to the decrease of vibration. It is proposed that cutting parameters should be optimized to improve tool life and processing efficiency.

Experimental Study on Cutting Force of Pocket Corner in HSM

Pocket corner in the high-speed milling (HSM) often occur under-cut, over-cut, vibration and other phenomena. This not only reduces tool life, seriously affected the work-piece machining accuracy and processing efficiency. In the paper, the impact of cutting speed on cutting forces is studied in the pocket corner based on the high-speed milling experiments. The results show that cutting force increased slightly with the increase in cutting speed, and that cutting force no significant change with the increase in radial depth of cut.

Investigation of Cutting Forces and Vibration in High Speed Milling of Pocket Corner

Investigation of Cutting Forces and Vibration in High Speed Milling of Pocket Corner

Cutting Forces and Vibration of Pockets Corner by High Speed Milling

When the pocket in die and mould is machined by high speed milling (HSM), the cutting forces increase and vibration fluctuates at the pocket corner because of the sudden change of cutting direction in general. It will cause serious wear and possible breakage of cutting tool, and poor quality of parts. By means of experiments, the cutting forces and vibration at the pocket corner with different HSM conditions are measured. The results show that the sharper pocket corner, higher cutting speeds, larger feed rate per tooth and radial depth of cut, will result in increasing of cutting forces and vibration amplitude. Thus, it will lead to be unstable during the process of high speed milling pocket corner.

Toolpath Optimization on Automatic Removal Uncut and Application

In milling pocket corner, there maybe residual material left at sharp corners when stepover is extremely large in contour-parallel toolpath. This paper describes an improved pocket toolpath by inserting biarc transitions segments in contour-parallel toolpath. When reaching the sharp corner, the cutter moves along the biarc transitions toolpath so that the corner material is removed. The efficient toolpath is continuous for clearing residual material at sharp corner. Milling test has been conducted to demonstrate and verify the significance of the proposed method.

Toolpath Optimization on Automatic Removal Uncut and Application

In milling pocket corner, there maybe residual material left at sharp corners when stepover is extremely large in contour-parallel toolpath. This paper describes an improved pocket toolpath by inserting biarc transitions segments in contour-parallel toolpath. When reaching the sharp corner, the cutter moves along the biarc transitions toolpath so that the corner material is removed. The efficient toolpath is continuous for clearing residual material at sharp corner. Milling test has been conducted to demonstrate and verify the significance of the proposed method.

放射線防護のための迷路計算法(その2) : 模型実験報告とその検討

Effects of labyrinth for protection of Gamma-rays are well known and practically applied already. This experimental study aim is to confirm quantitatively pocket corner effects of labyrinth to use it for entrance of Gamma-ray hot cell facilities. The 1/3 scale model labyrinth made with ordinary concrete blocks is used in this experiment and is measured the dose rate by the pocket chambers and cobalt-60 point source. The pocket corner effects of the labyrinth (walls and ceiling) in this experiment are estimated by the method of the calculation already stated. After measuring the dose rate in the labyrinth, compared the two group dose rates (calculated and measured in this experiment) to confirm the evaluation of the corner effects of the labyrinth. This experiment results are followings: 1. The pocket corners are effective and dose albedo changing methods to zero for pocketing walls, ceil and floor are confirmed quantitatively. 2. This estimating method of the effects of the pocket corner of labyrinth for gamma-ray protection will be applied practically.