5-axis Grinding Research Articles

An error compensation method for single point oblique axis grinding considering the grinding wheel wear

With the increasing amount of high quality optical products, the manufacturing requirement for the high-precision optical glass lenses is on the rise. Grinding is typically the main manufacturing process for the optical mold. The degree of wheel wear has a direct impact on the precision of the grinding process. In this paper, the wear rule of grinding wheel in the grinding process of optical aspheric surface is studied with the in-site wear measurement system. A new image processing method and a wear degree evaluation method are proposed. The wear prediction model for the grinding wheel is established. Then a modified compensation method of optical aspheric surface considering grinding wheel wear is proposed. The optical aspheric surface is then compensated using a modified multinomial equation considering grinding wheel wear. The results demonstrate that the profile error of optical aspheric surface can be reduced to less than 150 nm. The proposed compensation method that takes into account the grinding wheel wear can highly improve the grinding precision and efficiency of optical aspheric surface as compared with the conventional compensation method.

Big data-oriented wheel position and geometry calculation for cutting tool groove manufacturing based on AI algorithms

Groove is a key structure of high-performance integral cutting tools. It has to be manufactured by 5-axis grinding machine due to its complex spatial geometry and hard materials. The crucial manufacturing parameters (CMP) are grinding wheel positions and geometries. However, it is a challenging problem to solve the CMP for the designed groove. The traditional trial-and-error or analytical methods have defects such as time-consuming, limited-applying, and low accuracy. In this study, the problem is translated into a multiple output regression model of groove manufacture (MORGM) based on the big data technology and AI algorithms. The inputs are 34 groove geometry features, and the outputs are 5 CMP. Firstly, two groove machining big data sets with different range are established, each of which is includes 46,656 records. They are used as data resource for MORGM. Secondly, 7 AI algorithms, including linear regression, k nearest-neighbor regression, decision trees, random forest regression, support vector regression, and ANN algorithms, are discussed to build the model. Then, 28 experiments are carried out to test the big data set and algorithms. Finally, the best MORGM is built by ANN algorithm and the big data set with a larger range. The results show that CMP can be calculated accurately and conveniently by the built MORGM.

Parallel axis precision grinding of micro-tooth internal thread with the coarse-grains CBN wheels

As an important part of precision transmission system, internal threads with high precision, high hardness and small pitch are widely used in the fields of aerospace, numerical control machine tools, medical equipment and construction machinery. Aiming at micro-tooth internal thread, the research on parallel axis precision grinding of micro-tooth internal thread with the coarse-grains CBN wheels is carried out. Firstly, the grinding wheel section is designed based on the principle of parallel axis grinding of micro-tooth thread, and the theoretical error is systematically analyzed. Secondly, the maximum undeformed chip thickness of parallel axis thread grinding based on coarse-grains is established. Finally, the precision grinding experiment of internal thread is carried out. The optimal parameters can be obtained: the grinding wheel diameter is 17.08 mm, the grinding wheel angle is 90.13°, the lead is 3 mm, the pitch diameter is 21.06 mm. In this case, the maximum axial error is about 0.1 μm, the tooth profile angle error is 0.01° and the rounded radius error is about 3.5 μm. Considering the machining effect and efficiency, the truing depth is 150 μm, the feed rate is 0.2 mm/s, the grinding speed is 17,000 r/min and the grinding depth is 5 μm.

Razvoj nove CNC brusilice za 3+2 osno brušenje profilnih koturatih glodala

Due to the great expansion of woodworking, profile tools manufacturing has become current and in demand. In wood industry there are two large groups of tools: rotary and spindle milling cutters that can be profile or flat. The technology of making profile rotary milling cutters requires, apart from cutting, turning, milling, 5-axis grinding operation that is performed on a 5-axis CNC grinding machine with the A'OXYZC configuration.It is a machine of a very complex kinematics and high cost-price. The paper presents a new machine that has been built for 3+2-axis grinding - Profilator 100,used for industrial manufacturing of rotary and spindle profile milling cutters. The accuracy of measures and shapes of the profile cutters built on Profilator 100 is of a high level and in industrial exploitation the difference is not observed between the profile cutters built on 5-axis CNC grinding machines. Regarding technoeconomic cost-effectiveness, production costs of Profilator 100 are lower even by ten times compared to the cost-price of 5-axis CNC grinding machines of renowned world manufacturers such as Schneeberger and Volmer.

Tehnologija izrade profilnih koturastih glodala 3+2 osnim brušenjem na horizontalnom obradnom centru

The paper presents the technology of making brazed shaper milling cutters and with special reference to 5-axis grinding process (making of profile blades) on CNC grinding machine tool. Based on the analysis of the kinematics of the 5-axis grinding process, a new concept of profile milling tool production by a 3+2 axis grinding process on horizontal milling center was established. By Applying new concept, one tooth of profile tool was machined by grinding process. By obtained results, new approach for manufacturing of profile milling tools was verified.

Effect of the cutting conditions on surface roughness during 5-axis grinding of Maraging steel MS1

This work deals with the effect of the cutting conditions and the spindle tilt on the surface roughness when grinding complex shaped surfaces of Maraging steel MS1 on an ANCA MX7 5-axis tool grinding machine. It is necessary to grind complex shaped surfaces where high surface quality is important and requested. For this experiment was selected a component with a complex shaped surface which was printed on the 3D printer machine from maraging steel MS1. Since grinding of complex surfaces is being investigated, it is necessary to use CAM software for creat-ing an NC program. The aim of this work is to study the effects of the cutting conditions on the grinding of a com-plex shaped surface in relation to the resulting surface roughness. To do this, it was necessary to design an experi-ment with the appropriate grinding technology, create a clamp, and create NC data in NX CAM software for grinding the complex shape surfaces on the part.

Grinding of maraging steel 1.2709 with SiC grinding wheels and effect of grinding conditions on the surface roughness and wear of the wheels

Grinding is one of the basic finishing operations which can be used for parts made from different materials where high quality and surface accuracy is required. One of these materials is maraging steel 1.2709, which is used for the test samples for tensile testing. In this case, it is very important to achieve good surface quality. Wear of a grinding wheel is best expressed as G-ratio which shows us if the grinding parameters are selected correctly. This article deals with the influence of grinding conditions and grinding wheels on surface roughness and wear of the grinding wheels when grinding tool steel VACO 180 on a 5-axis grinding machine. The experiment was designed to investigate the influence of changes in cutting speed, depth of cut and using two different grinding wheels for these two values. At the end of the article, the results from the experiment are summarized and compared.

5-axis grinding path generation for free-form surface based on plane instantaneous grinding engagements

Grinding is an important process to remove the material efficiently. Before the finish machining, it is necessary to remove the cusps by the wider grinding band for obtaining more uniform allowance. In this paper, the grinding wheel hold by the multi-axis machine tool is introduced into the free-form surface grinding. The engagement between the wheel and the to-be-ground surface is established for generating the paths. An instantaneous engagement model is proposed in terms of machine tool kinematic chain, and the spatial engagement is represented on a group of planes. Based on the engagement model, the grinding path generation for enlarging bands is transformed into an optimization. Different with traditional path generation, a slight local overcut is allowed on the wheel locations. However, the envelope of grinding engagements is limited in the required boundaries to satisfy the design tolerance. They are realized by adjusting the contact locations and orientations of the wheel. At last, a compressor blade is used to verify the advantages about the proposed path generation method.

Influence of tilt and lead angles on 5-axis grinding with spherical mounted points

Through the kinematics involved on the grinding process, part of the grinding wheel topography is imprinted on the machined component in the form of grain scratches. During 5-axis grinding using spherical mounted points, the tilt \(\beta _{fN}\) and lead \(\beta _{f}\) angles can be used to locate the tool and align these scratches to achieve a desired angle in relation to the feed direction, creating a defined structure and decreasing the roughness on the ground surface. Moreover, different tool orientations change the force distribution over the tool, affecting the geometric deviation of the workpiece. The current work reveals a reduction of 50% of the roughness and geometric deviation for grinding of hot isostatically pressed silicon nitride HIPSN through optimization of the tilt \(\beta _{fN}\) and lead \(\beta _{f}\) angles.

Force and Temperature Modeling in 5 - axis Grinding

Building upon a recently published (J. Manuf. Sci. Eng. 2017;. doi:10.1115/1.4037969) general geometrical framework for specific removal rate, the current paper develops the physics in 5 - axis grinding (5AG). Relating the grain-level chip thickness h to the wheel-local material removal rate per unit area m”, grinding force components from chip-formation, plowing and sliding, resolved normal and tangential to the tool surface locally were considered. A new approach to model steady-state workpiece temperatures for small tool-workpiece contact areas is shown. A composite Green’s function for a moving heat-source from two solutions in the literature, near- and far-field, was synthesized. A representative 2D patch on a nominal plane and its travel speed were formulated from the instantaneous 3D tool-work contact area and local feed-rate variation. From the local sliding power, prescribed heat-partition and linear superposition of heat sources, temperature variation over the complete 2D patch was calculated. For shallow-cut surface grinding (SCSG), the force model was validated with experimental data in grinding of nickel alloy with electroplated CBN wheels. Peak temperature for SCSG with the new thermal model was found to be in reasonable agreement with the classical Jaeger moving heat-source model. Examples of heat-flux and workpiece temperature distribution for a few individual moves in general 5AG with smaller contact areas is shown.

Influence of servo characteristics on crack generation in ultra-precision grinding of optical glass lenses

Generally, manufacturing process of optical glass lenses, which are used for single lens reflex cameras, is classified into grinding and polishing for removing cracks generated by grinding. Thus, it is desired not to generate the cracks in grinding as much as possible. Because grinding condition with cracks differs depending on the material properties of the workpiece, suitable grinding condition needs to be selected based on a lot of experimental verifications. In addition, the controller’s gain of the tool spindle with grinding wheel may be intentionally set to low value in ultra-precision grinding. Thus, the spindle speed may decrease even under servo control because of grinding load. In this study, the influence of servo characteristics on crack generation is evaluated in ultra-precision grinding of optical glass lenses. Concretely, an optical glass lens was machined using an ultra-precision 5-axis grinding machine and servo information of tool spindle was monitored during the process. Comparison of the obtained servo information and the surface observation of the workpiece revealed that the spindle speed decreased and the number of the cracks increased at the outside of the workpiece. The experimental results suggested the possibility of estimating the grinding load and predicting the surface quality by monitoring the variation in the spindle speed.

Ultraprecision grinding of small-aperture concave aspheric mould insert with tilt axis method

With the widespread application of various small aspheric optical components, high-precision manufacturing technology of forming molds is deeply demanded. However, the ultra-precision grinding technology of small-aperture aspheric mould is still undeveloped. An ultraprecision grinding technique called tilt axis grinding which is based on the grinding spindle is tilt with the axis of aspheric surface and profile error compensation of aspheric mould are studied. Through constructing geometric model of the tilt axis grinding, the tool path and the interference conditions were calculated. The form error was compensated with the data measured by profiler. An experimental test is conducted to grind an aspheric tungsten carbide mould of aperture 5 mm, and the profile accuracy is gradually improved from 0.652 μm to 89.3 nm in PV after two compensation cycles. The surface roughness is 10 nm in Ra.

Development on Synergistic Process and Machine Tools Integrated Inclined Axis Grinding and Magnetorheological Polishing for Small Aspheric Surface

Development on Synergistic Process and Machine Tools Integrated Inclined Axis Grinding and Magnetorheological Polishing for Small Aspheric Surface

Study on a 5-axis precision and mirror grinding of glass freeform surface without on-machine wheel-profile truing

The precision freeform grinding depends on the on-machine truing of diamond wheel, leading to the inefficiency of grinding system. Hence, a virtual ball-end algorithm along with a fixed tool posture angle is proposed for the 5-axis grinding of glass by using a self-dressing diamond wheel. The objective is to realize the precision and mirror freeform grinding without any wheel-profile truing. First, virtual ball-end grinding, ground freeform surface and freeform errors compensation were modeled in 5-axis grinding system, respectively; then tool interference, envelope trace height, grain cutting depth and ground surface roughness were systemically investigated in connection with tool posture angle, tool sizes, grain protrusion variables, abrasive parameters and self-dressing coefficient; finally, the 5-axis grinding experiments of F-theta freeform glass lens were performed. It is shown that the virtual ball-end algorithm is valid for the 5-axis freeform grinding with a self-dressing abrasive tool. Increasing tool posture angle decreases the grain cutting depth to the critical cutting depth from brittle cutting to ductile cutting, but it increases the risk of tool interference. The mirror freeform grinding may be parameterized by material behavior, tool size and posture, grinding conditions and abrasive tool performance. On the base of virtual ball-end algorithm, the form errors compensation enhances the mirror-ground freeform accuracy by 26%. It is confirmed that the 3-μm-size diamond grinding without on-machine truing is feasible to fabricate the precision and mirror freeform glass along with the tool posture angle of 30°.

Research on modelling of ball-nosed end mill with chamfered cutting edge for 5-axis grinding

This paper presents models related to the manufacturing of ball-nosed end mills of solid carbide (BEMSC) with a chamfered cutting edge (CCE). A parallel grinding wheel (PGW) is selected, and the relationship between CCE face and PGW working face is determined. Based on the geometry models of BEMSC established in our previous work, the centre and axis vectors of PGW are calculated for the grinding of CCE face on bath the ball-nosed end and the cylinder, which is validated through a numerical simulation. In order to produce the tool, a grinding machine, SAACKE UMIF, is chosen. Targeting the grinding data of BEMSC, the transformations are carried out between the coordinate systems of workpiece and the NC programme according to the structural features of the machine. An algorithm is derived for dispersing grinding paths. As a result, the centre data and axis vector are generated with respect to the grinding machine. The BEMSC with CCE is machined using the selected machine, which demonstrates the correctness of the established models. Finally, the performance of the machined cutting tool is validated in comparison with a common BEMSC without CCE in the milling of a mould of a multi-hardness joint structure.

Fabrication of small aspheric moulds using single point inclined axis grinding

Single point inclined axis grinding techniques, including the wheel setting, wheel–workpiece interference, error source determination and compensation approaches, were studied to fabricate small aspheric moulds of high profile accuracy. The interference of a cylindrical grinding wheel with the workpiece was analysed and the criteria for selection of wheel geometry for avoiding the interference was proposed. The grinding process was performed with compensation focused on two major error sources, wheel setting error and wheel wear. The grinding results showed that the compensation approach was efficient and the developed grinding process was capable to generate small aspheric concave surfaces on tungsten carbide material with a profile error of smaller than 200nm in PV value after two to three compensation cycles.

Current Concept of Geometrical Accuracy

Abstract Within the solving VEGA 1/0615/12 research project "Influence of 5-axis grinding parameters on the shank cutter´s geometric accuracy", the research team will measure and evaluate geometrical accuracy of the produced parts. They will use the contemporary measurement technology (for example the optical 3D scanners). During the past few years, significant changes have occurred in the field of geometrical accuracy. The objective of this contribution is to analyse the current standards in the field of geometric tolerance. It is necessary to bring an overview of the basic concepts and definitions in the field. It will prevent the use of outdated and invalidated terms and definitions in the field. The knowledge presented in the contribution will provide the new perspective of the measurement that will be evaluated according to the current standards.

An Automated and Accurate CNC Programming Approach to Five-Axis Flute Grinding of Cylindrical End-Mills Using the Direct Method

In solid carbide end-mills, the flutes significantly affect the tool's cutting performance and life, and the core radius mainly affects the tool's rigidity. The current CNC programming techniques can correctly determine the orientation of the wheel so that it grinds the rake face with the specified rake angle; however, it cannot accurately determine the wheel location for the direct method and, consequently, the desired core radius is not guaranteed. To address this problem, a new CNC programming approach is proposed to accurately calculate the wheel orientation and location (WOL) in 5-axis grinding of the cylindrical end-mill flutes. In this work, a new concept of 5-axis CNC grinding—effective grinding edge (EGE)—is first proposed to represent the instantaneous grinding edge of the wheel, and the parametric equations of the effective grinding edge are formulated. The wheel orientation and location in 5-axis flute grinding are calculated automatically and accurately so that the rake angle of the rake face and the core radius are ensured. The new approach is verified with several examples in this work. Therefore, it can improve the end-mill quality and lays a good foundation for the computer-aided design/computer-aided engineering/computer-aided manufacturing (CAD/CAE/CAM) of end-mills.

Determination of the relative position between grinding wheel and a cylindrical workpiece on a 7 axis grinding machine by acoustic emission

The contact between grinding wheel and workpiece in the grinding process is recognized by acoustic emission (AE). Two acoustic emission monitoring systems (MS) were integrated into a 3 axis CNC grinding machine. A laptop allows the signal acquisition and visualization. The acquired AERMS signals from the contact between tool and workpiece are analyzed permitting to establish the most suitable AE monitoring system to recognize the contact in a particular grinding machine. In a second experimental setup the selected MS was installed on a 7 axis tool grinding machine at an industrial partner. At this partner, the relative position between grinding wheel and workpiece was previously determined manually. This procedure has a direct influence on the results depending on the technical skills of the operator. The automation of this activity supported by acoustic emission has led to satisfactory results regarding the relative position between grinding wheel and workpiece and contributed to the setup time reduction.

Inclined Axis Ultra-Precision Grinding for Spherical Surface

Through establishing the mathematical models of velocity and grinding force to optimize the installation angle with inclined axis grinding technology, the spherical surface of the ultra-hard alloy material was ground by formed electroplated diamond wheel. After analyzing the abrasion of grinding wheel, the results show that the inclined axis grinding technology of the formed grinding wheel can avoid the rotation dead spots of grinding wheel, and can make the grinding wheel surface contacted with work-piece fully which could make the worn more evenly. Finally, it obtains a surface in a high quality with the surface roughness of Ra is 12.88nm, and the form accuracy of PV is 124nm.