Straight Chip Research Articles

Enhanced chip analysis with computed tomography for estimation of chip segmentation frequency

This work presents an enhancement of a method for analyzing metallic chips produced during turning processes in order to estimate the chip segmentation frequency. Therefore, the resulting 3D image of a computer tomography scan of the chip can be transformed virtually into a straight chip by describing the course of the chip in three-dimensional space by a trajectory. Along this trajectory, the chip point cloud is sliced in thin layers which can be transformed to a straight chip. To estimate the segment rate, the height course describing the segmentation of the chip is extracted on the serrated side of the point cloud by means of nearest neighbor interpolation. The resulting signals are compared with the measurements of the chip surface using an optical microscope, whereby only two straight chips could be analyzed. The comparison shows a nearly perfect match between the two signals and is confirmed by a Pearson correlation coefficient of over {86}% for both signals. Furthermore, a statistical comparison with the acoustic emissions of the turning process reveals satisfying similarities for the chip segmentation frequency with respect to the compression factor.

Optimized design of structural parameters of Si3N4-based ceramic tools with variable cross-section

Through theoretical analysis and finite element simulation experiments, this paper proposes an optimal design method for the structural parameters of ceramic tools with variable cross-sections. On this basis, the tool angles of Si3N4-based ceramic tools for cutting inconel 718 high-temperature alloy are investigated, including rake angle γ0 = −5°, clearance angle α0 = 5°, cutting edge inclination λs = −2°, cutting edge angle Kr = 45°. By comparing the main cutting force, temperature and chip-breaking effect of flat face and three different groove ceramic tools, it is found that straight chip breaker has the most obvious optimization effect, main cutting force is 14.5% lower than that of the flat face, the temperature is reduced by 10.2%, and radius of chip curl curvature is the smallest, which is easy to break chips.

Design, development and test of a novel broach for long polypropylene tubes

Polymers are frequently used for a variety of applications in industry. One relevant field is plastic tubing. As plastic tubes are manufactured from thermoplastic material through hot-extrusion their dimensional accuracy is only moderate. Wherever high accuracy on tube diameters and roundness are required, the conventional production techniques reach their limits and more complex technologies are needed. Known approaches from metal machining are deep hole drilling and internal broaching. However, machining processes with chip removal on polymeric materials are not so common. Therefore, the authors studied cutting operations of polypropylene experimentally. Based on their findings they designed and built an internal broach for the machining of polypropylene tubes. Finally, the authors tested their developed broaching tool in a relevant industrial environment. The tool not only fulfills the dimensional machining requirements but also solves the present chip evacuation problem in a unique way. It enables free cutting through the whole operation and creates continuous straight chips with no need for chip breakers. Consequently, the timely cleaning step, required in traditional broaching, can be eliminated, which reduces the lead time significantly. Furthermore, the set of materials allows dry broaching. Coolant is not necessary. This leads to less waste, a cleaner production line, and avoids damage through aggressive liquids. Lastly, their design ensures that no loss of dimension occurs when resharpening the tool.

Development of a Chip Pulling System for Efficient Turning

Combined with the chip guiding, this paper presents a new “assisted turning method” where the cut chip is pulled using an external pulling device to improve the performance of turning process. In the proposed method, straight unbroken chip is generated by utilizing special tool tips and guided through a guide tunnel for automated chip pulling. The first prototype of chip pulling device is designed that can pull the guided straight chip continuously as the turning operation is carried on. Design of the chip pulling system, proposed pulling device and its automatic control are presented in this research. A brief insight on the effect of chip pulling to the turning process is discussed by inspecting fundamental process parameters. Experimental results show that by pulling the chip in a controlled manner, process can be improved dramatically. Cutting forces and temperature are effectively reduced in actual “chip pulling turning”.

Rational axial shift of gear cutter

The relation between the axial shift and n is not always unique. In milling a single blank with each adjustment of the cutter, decrease in axial shift is accompanied by corresponding increase in n , so long as the tooth wear of the cutter is within permissible limits. However, in milling two or three blanks with each cutter adjustment, n will be proportional to the product of the number of axial shifts and the number of gears machined in each cutter adjustment and will also depend on the nonuniform wear of the cutting teeth. We know that the teeth on the input section of the cutter are subject to more wear. The wear of each tooth in cutting is different. Accordingly, reducing the axial shift to some critical value may entail reduction in the number of gears machined per cutter adjustment so as not to exceed the permissible tooth wear. The number of gears machined over the cutter’s working life may be reduced (since the product of the number of axial shifts and the number of gears machined per cutter adjustment is reduced), even though the number of axial shifts may increase. Conversely, increasing the axial shift to some critical value may increase the number of gears machined per adjustment and hence increase the number of gears machined within the working life. Existing recommendations regarding the axial shift are obtained experimentally or taken from hobbing practice. Thus, recommended values were presented as a function of the tooth inclination and the number of number of gear teeth to be cut, for the standard series of modules (2‐26 mm), in [1]. It was shown that factors significantly affecting the axial shift include the module, the tooth inclination, and the number of tooth to be cut on the gear. However, the discrete values of these factors do not permit the use of these recommendations to determine the rational axial shift of the cutter in other machining conditions [1]. Accordingly, we need to determine the rational axial shift for specific values of the relevant factors. We may use 3D simulation to determine the rational axial shift. As we know, increasing the cutting path length of the cutter tooth or the total volume of metal removed by each tool will increase the cutter wear. Therefore, we have developed a 3D model of tooth cutting that permits accurate determination of both the cutting path length for each cutter tooth and the total metal volume removed by the tooth. On the basis of the simulation, we may sample possible axial shifts so as to determine the value best ensuring equal cutting path lengths for each cutter tooth or equal metal volume removed by each cutter tooth, for the maximum possible number of teeth. This approach to determining the rational axial shift is considered for the example of producing a straighttooth gear using a single-setting cutter. The gear parameters are as follows: height H = 20 mm; module m = 3 mm; number of teeth z 1 = 45. The parameters of the gear cutter are as follows: number of straight chip channels 14; external diameter d a 0 = 112 mm; length of mill’s working section L f = 90 mm; cutting speed v cu = 25 m/min; cutter speed n 0 = 71.05 rpm; axial supply of cutter s ax.c = 2 mm/turn. Each tooth of the cutter is assigned an index n z , which may increase or decrease relative to the symmetry axis of the cutter tooth’s axial profile (with index n z = 0). The symmetry axis of the cutter tooth’s axial profile (with n z = 0) lies in the plane of cutter rotation, passing through the intercenter distance of the cutter and blank.

A study of micropool lubricated cutting tool in machining of mild steel

This paper presents an experimental study of the performance of micropool lubricated cutting tool in machining mild steel. Microholes are made using femtosecond laser on the rake face of uncoated tungsten carbide (WC) cutting inserts. Finite element analysis is conducted to assess the effect of microholes on the mechanical integrity of the cutting inserts. Liquid (oil) and solid (tungsten disulfide) lubricants are used to fill the microholes to form micropools. A comparative study is conducted between micropool lubricated (surface-textured) cutting tools and dry/flood-cooled conventional (untextured) cutting tools. Three cutting force components are measured and compared. Tool–chip contact length and chip morphology are examined using optical microscope. It is found that the mean cutting forces ( F f, F t, and F c) are reduced by 10–30% with micropool lubrication. The chip–tool contact length is reduced by about 30%. Coiling chips are produced with micropool lubricated cutting tool while long and straight chips are formed with the conventional cutting tool. Liquid and solid lubricants are found to be equally effective in reducing the contact length and coefficient of friction at the chip–tool interface. There is no adverse effect on the performance of the insert with microholes on the rake face.

Spatial Structure Injection Molding Analysis of Suspended Bio-Carriers

The realizability for spatial structure of suspended bio-carriers should be considered in the process of structure designing. Injection molding analysis could obtain the injection performance of spatial structure, and provide the references for economic benefit of structure realization and structure optimization, so it become an important tool for structure designing and optimization. In oder to apply the injection molding analysis to the process of bio-carriers designing, three structures, multi-plane spherical structure, straight chip columnar structure, wing panel structure are designed. Their injection performances, such as best location of injection, fill time, and injection pressure are be compared, the results show that the multi-plane spherical structure has the best injection economic benefit.

Creation of Flat-End V-Shaped Microgrooves by Non-Rotational Cutting Tools

The study deals with the creation of V-shaped microgrooves with flat-end, which play an important role in case of generating intermittent grooves. Microgrooves by use of rotational cutting tool have a long radius in disengagement from the workpiece. Thus, two cutting methods by use of non-rotational cutting tool are devised so that V-shaped microgrooves with flat-end can be created. The first method makes use of straight chips generated under some cutting condition. Non-rotational cutting tool compresses the chips at the groove end and cuts the excessive parts of chips over the plane. The second method is to transcribe the surface of a tool indented vertically into a workpiece. As a result, it is experimentally found that the methods enable the creation of flat-end microgrooves.

Characteristic Variations of Chip Morphology and Cutting Forces in Face Milling with Flat-Faced and Grooved Tool Inserts

The modeling of face milling operations has been traditionally focused on using flat faced tools with an assumption of perfectly straight chip formation. However, curled chip formation is a common phenomenon in practical milling operations, and it has a profound effect on machining performances. A new analytical model that takes into account the chip curling effect in milling operations is proposed in this paper. It is shown that chip morphology and machining parameters, such as the chip up-curl radius, the chip thickness, and the tool-chip contact length, simultaneously change with varying undeformed chip thickness during each tooth cycle. The proposed model is validated through milling tests. Good agreement between theory and experiments has been reached. A comparison of the average resultant force among three types of commercially available tool inserts is made to demonstrate the effect of tool insert chip-groove geometry on milling performances.

Machining with applied chip tension—Part I: Theory

Machining with applied chip tension is the basis of a process, strip peeling, for making small batches of metal special strip products. An approximate slip-line field numerical analysis of the process, related to the matrix method, is presented which shows how pulling stress and its direction affect chip thickness and curvature and tool forces. Pulling parallel to, or within 5° of, the rake face produces straight chips but results in less reduction of chip thickness and tool forces than pulling at more than 5° to the rake face. In the latter case chips are formed curled and are subsequently plastically straightened by the pulling force. Chip failure by plastic straightening and other causes is discussed and it is recommended that the pulling direction should be between 5 and 20° from the rake face. Influences of rake angle and friction stress are also considered.

Some new slip-line solutions for two-dimensional steady-state machining

For restricted and unrestricted cutting tool faces, certain new slip-line fields have been obtained where there is completely or nearly uniform frictional resistance and which produce a straight chip and are valid beyond the limitations of previous solutions. Some possibly correct solutions showing chip curl have also been presented, e.g. where the frictional resistance decreases along the tool face from the tip to the tool-material separation point. Using these, cutting resistance or force, curl radius, chip thickness ratio and natural contact-length have been determined in relation to the rake angle and friction stress. Slip-line fields containing a built-up edge were obtainable only where the rake angle was negative and where there was chip curl.

A study on the machinability of wrought aluminium alloy (1st Report)

As shown in the previous report, the rods of wrought aluminium 17S-T4 and 56S-F were of lower machinability under a low cutting speed of 37-183m/min and so this time we put then under a high speed as far as 330m/min. and examined the turning machinability about the cutting resistance, the surface roughness, the chip treatment and so on. As the machinability is said to be affected by the materials or the figures of the used tool, authors examined a high speed steel one side tool, a carbon steel and tangalloy tools which have the same dimention, and discussed the influences of the figures of tools on the machinability changing dimentions of them.The results are summarized as follows:1. It is found that the cutting resistances under high speed turning are nearly equal to those of low speed turning as shown in previous report, and show nearly constant values according to the materials but regardless of the cutting speed. In this case, the cutting resistances of 17S is greater than those of 56S.2. According to the turning at a high speed, the good cutting surface near to the theoretical roughness of feed mark is obtained, even in the 17S and 56S which are not so easy to obtain the good surface by the turning at a low speed according to the plenty growth and dalling of built-up edge. The roughness of the cutting surface is improved rapidly with increase of the cutting speed, as far as critical speed of cutting, then arrives nearly constant roughness. It seems that the above mentioned critical speed of cutting may be a factor of machinability and, from this point of view, machinability of 17S is better than that of 56S.3. When both 17S and 56S are turned at a high speed, straight chips or ribbon-like chips are introduced continuously and wind round a part of the machine or the tool, on the other hand these chips sometimes leave a scar on a turned surface.4. The tangential force of the carbon steel tool is sleightly larger than that of the other two kinds of tools: the high speed steel and the tangalloy, whose tangential forces are not different. But it is observed that the traversing force of the tangalloy tool is very large especially when the side rake angle is small. But, in the chip treatment, the easily treatable chips may be obtained in using the tangalloy tool.5. The suitable edge angle of the end cutting is about 10°according to the cutting resistance and the surface roughness.6. On the tool tip figure, the cutting resistance of round nose is larger than that of broad nose, but about the cutting surface, the former is much better.This study owed its expenses to the Scholarship Commitee of the Institute of Light Metal Foundation to which we are extremely greatful.