Manufacture and measurement of oil sludge model fo

2022-08-07
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Making and measurement of oil sludge model for passenger cars

Abstract: through the comparative analysis of materials for making oil sludge model for passenger cars, this paper puts forward the making method and measurement method of oil sludge model. This method is simple, convenient, easy to form, low cost and can be preserved for a long time. According to the proposed measurement method, the oil sludge model is measured by a large CNC three-dimensional coordinate measuring machine, and accurate bus modeling data can be obtained, which provides an intuitive, scientific and rapid design method for bus modeling design, bus CAD and bus product development

key words: passenger car sludge model design and measurement

1 introduction

today, with the increasing development of market economy and science and technology, the passenger car design technology and manufacturing level are constantly improving. In order to meet the new requirements of the market for passenger cars, the passenger car design has also broken through the traditional procedures and moved towards a new era of independent development, adapting to the target market and improving design efficiency. A typical bus design procedure is shown in Figure 1

Figure 1 bus design and development procedure

it can be seen from Figure 1 that it is extremely important to determine the bus shape curve that meets the functional, aesthetic and market requirements in the process of bus development, and the production and measurement of the model is the key link

the making of scaled sludge model is a crucial step in the design frontier. Its purpose is to reproduce the idea of modeling design with real objects, verify the three-dimensional effect of the effect drawing, optimize and demonstrate the scheme, and can also be used for comparative wind tunnel tests. By measuring and processing the 3D coordinates of the selected modeling model, the coordinate data of modeling curve and surface can be obtained efficiently and accurately, which can be directly used in bus CAD to improve the design level

2 design and production of model

the design and production process of sludge model includes market investigation, material selection, budget estimation, production of wheel axles and accessories, production, molding and finishing of moulding bed, color treatment, etc

2.1 selection of model materials

the materials that can be used to make the passenger car sludge model mainly include: sludge, keel, foam, etc

at present, the commonly used sludge materials mainly include the following. The first is industrial clay (talc powder) 60%, flexible binder (grease or butter) 30%, and solid binder (paraffin or Vaseline) 10%. The second is wax 9% ~ 10%, sulfur 50% ~ 55%, ash 9% ~ 10%, grease (butter) 20% ~ 25%, and a little resin and pigment. The third kind is oil sludge for construction, which is composed of clay and tung oil

different sludge has different physical and chemical properties. The ratio of solid binder to flexible binder is difficult to control with regional changes during the production of the first sludge. The composition of the second kind of sludge is complex, and the expansion coefficient of sludge changes greatly with temperature, so it is not suitable for long-term storage. The third kind of sludge is easy to use, low cost, good viscosity, good plasticity, easy to form, and can be consolidated after drying for storage and measurement; However, this kind of oil sludge has slight toxicity, the drying process is long, and it must be placed in a well ventilated and cool place to avoid cracks and "flow samples" caused by high temperature. Therefore, attention should be paid during use

the keel is a strip wood, which is used to make moulding bed and underframe, bear various loads and install axles. The cross-sectional dimensions of the keel can be different for different scale sludge models

foam is selected as the tire base because it has the advantages of light weight and convenient manufacturing and forming of the tire frame

2.2 production of wheel axles and accessories

model wheels should be directly used as load-bearing parts, so appropriate production materials must be considered. The wheels can be made of aluminum, and then pasted with cloth dry glue of appropriate color, but the rims are difficult to process and form. In addition, it can be processed from wood or gypsum, and then processed into patterns. These methods are limited by the process conditions, the cost is high and the shape is not very realistic. In order to overcome these shortcomings, the "external application method" is adopted to make the wheel this time. In this way, the tire core is made by using the bearing material inside according to the specification and size, and its thickness is about 1/3 of the tire width, then the oil sludge that is easy to form is applied outside, and finally the tire pattern is finely carved on the oil sludge. In this way, wheels that can carry loads and have realistic shapes can be made under simple conditions

the model axle is also used as a bearing part, which mainly bears large bending moment. Therefore, steel, such as A3 steel, can be selected and processed according to the design size and wheel hole

the production of accessories includes the production of rear-view mirrors, wipers, logos, etc., which can be carved from wood or other materials that are easy to carve. The production of accessories should be fine to avoid affecting the overall shape of the clay model

the scale of the passenger car reduced sludge model is generally 1:2, 1:5, 1:10 and 1:20

2.3 production of moulding bed

according to the overall parameters of the designed passenger car, make a wooden underframe with appropriate size to install the axle and bear various loads. Figure 2 shows the installation position of the underframe. It can be seen from Figure 2 that the size of the wooden underframe should be reasonable, the front and rear length should not affect the shape of the whole vehicle, and the left and right width should ensure that the plastic foam will not expand too much when the empty groove is excavated and backfilled

prepare the underframe according to the design, and install the front and rear axles at the corresponding positions. Color the wooden underframe. Place the foam block on the wooden underframe so that the shape of the wooden underframe is printed on the foam board. Then the plastic block can be "grooved". During grooving, pay attention to control the depth of the groove to meet the minimum ground clearance as the standard. The cut groove shall be dipped with emulsion to form a hard film to prevent the plastic deformation of plastic foam from reducing the ground clearance of the whole model in the process of making the clay model or preserving it. Install the prepared wooden underframe with axle in the cut groove of plastic foam block, spray emulsion to bond firmly, and then backfill with foam

place the foam block installed with the wooden underframe horizontally on the grid coordinate platform. According to the preliminary general layout drawing, modeling curve and effect drawing of the car body, roughly cut the foam block into a rough shape. During cutting, it is necessary to ensure that there is a certain sludge application thickness (at least 5mm before the Pb point) for later forming and fine carving

Figure 2 Schematic diagram of moulding bed structure

2.4 forming and finishing

before applying the oil sludge, in order to make the bubbles in the oil sludge overflow, it is necessary to knead on the flat plate, and at the same time, the oil sludge can be mixed more evenly. Apply the rubbed sludge layer by layer from the middle to the head and tail of the model. Proper force shall be applied during application, so as to ensure the adhesion between the oil sludge layers and prevent the deformation of the whole model due to excessive force until the applied oil sludge makes the model exceed the preliminary design curve by 2 ~ 5mm. Then, according to the height measuring instrument and the design, the tool knife is used for cutting, so that the surface is generally smooth and the shape is generally similar

the benchmark for body engraving is the body grid, so the coordinate grid must be drawn on the body surface. It is very convenient to do this work by gantry carving frame or scriber; When there is no gantry carving frame, the method of ruler positioning and snapping and drawing the body coordinate grid can be adopted

the refined sludge model is carried out after the model basically conforms to the general layout curve and effect drawing. In the process of refinishing, it should be based on personal subjective feelings, aesthetic views and various artistic effects brought by poor vision, and strive to make the curvature transition of the whole body surface smooth and smooth. We should also seek the opinions of relevant experts to make the model more perfect. For the carving of such details as the windshield, side window, passenger door, driver's door, trunk and fuel tank, attention shall be paid to the uniform thickness of the lines, and the moderate concavity and convexity, so as to make the sludge model have a realistic effect. The finishing shall be completed within the time suitable for engraving, so as to prevent cracks during finishing due to the hardening of the sludge surface

2.5 surface color treatment of sludge model. The finished clay model surface shall be painted after several times of puttying and fine sanding. Two points shall be paid attention to when painting: the first is that the painting is uniform and does not flow; Second, color does not interfere. Maintaining proper spray distance is the key to uniform spray; The key to non-interference is to cover the non painted surface

With the wide application of cad/cam technology, the universal application of CNC 3D coordinate measuring machine has become an inevitable trend. At present, numerical control measurement technology has been widely used not only in foreign countries, but also in major domestic automobile manufacturers, especially in the design and manufacturing process of car bodies

3.1 introduction to MT3 2040 3D coordinate measuring machine

mt3 2040 3D coordinate measuring machine is manufactured by MFO company of France, and the control part is jointly produced by Qingdao qitech company. The equipment has reached the international advanced level in the 1990s

mt32040 three-dimensional coordinate measuring machine is a large horizontal arm CNC measuring machine. It is a high-precision, high-efficiency and universal precision measuring equipment integrating optics, mechatronics and computer technology. It can measure and analyze the coordinates of the measured parts through the connection between the control system and the computer and its corresponding software. It is suitable for the mapping of models, molds and products, especially in the automotive industry. For example, it can map the body surface curve and connect with the bus CAD system

mt3 2040 three-dimensional coordinate measuring machine has a measuring range of 6000 mm in X direction, 1500 mm in Y direction and 2000 mm in Z direction; The measurement uncertainty is: 0.04+l/40 000mm in X direction, 0.03+l/15 000mm in Y direction and 0.03+l/15 000mm in Z direction (where l is the measurement length)

3.2 measurement preparation and accuracy assurance

preparation before measurement is the prerequisite for successfully completing the measurement task and ensuring the measurement accuracy. Preparation for measurement mainly includes: a) preparation before measurement of the measured object; B) Preparation for laboratory measurement; C) Preparation of measuring machine before measurement

the preparation before measurement of the measured object is mainly to be familiar with the design drawings, draw up the measurement scheme, determine the specific objects to be measured, i.e. the elements to be measured, control the temperature of the measured object, place the measured object, etc. The temperature of the measured object is controlled within the allowable range in order to ensure the measurement accuracy. Therefore, the measured object must be moved to the measurement laboratory in advance before measurement to maintain the allowable constant temperature of 0 channel if the allowable value is 000; The measured object shall be placed in accordance with the "Abbe length measurement principle (i.e. the series principle)", which is also to ensure the measurement accuracy

the preparation before measurement in the laboratory mainly includes the control of temperature and humidity and the inspection of power supply and air source. The temperature of the laboratory is the most important external factor affecting the measurement accuracy, so the temperature and humidity of the laboratory should be controlled according to the "CMMA" standard. The preparation before measurement of the measuring machine mainly includes: cleaning the guide rail of the measuring machine, selecting appropriate probe and rod accessories for installation, and calibrating the probe. When installing the probe, pay attention to press the emergency stop key, handle it gently and use appropriate force. After the installation is complete, it needs to run to test whether the protection function of the probe is normal; The probe is standard in theory, but there are errors in practice. Therefore, it is necessary to verify the "three-dimensional uncertainty" of the probe in order to ensure the accuracy. The calibration method is to measure the standard ball with a measuring gauge

3.3 measurement steps

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