In fixture design, most of our common products are car cylinder block, cylinder head, so today for everyone's popular science cylinder block, cylinder head processing production line, how to choose tools?
Characteristics of tool selection for modular machine tools
1. Multi-axis and multi-tool processing
The headstock of the combined machine tool is designed according to the process preparation of the process content, generally adopt the form of multi-spindle multi-cutter processing, different aperture processing hole can be designed in a headstock, such as MR479Q cylinder production line, OP130 process, fine boring 52? Mm main bearing hole, fine hinge after oil seal cover 2- 6? Mm positioning hole and fine hinge transmission 2-10? Mm positioning hole, power box through the spindle box of multi-layer gear transmission, to achieve the spindle to obtain their different rotation speed and each axis reasonable but different cutting speed V, to meet the requirements of the process.
2. The workpiece hole depth is different, and the multi-spindle adjustment is flexible
According to the relative position map of each spindle tool at the feeding terminal of the combined machine tool, adjust the position of the tool connection rod, and then fix the tool pressing screw (the external taper of the tool handle is consistent with the internal taper of the connection rod), so as to meet the requirements of different elements of the design and different depth dimensions of the tool. To meet the hydraulic (mechanical) sliding platform of modular machine tools unified feed and unified return of high efficiency characteristics.
3. The fixture of the modular machine tool is basically equipped with the guide device of the tool
The aim is to improve the rigidity and position accuracy of the tool itself.
Machining center tool selection characteristics
1 processing center machine tool belongs to a single spindle machine tool, through the manipulator to quickly change the tool to complete drilling, reaming and tapping thread, etc., and can be arranged in a process, in a number of steps to complete, although the processing content is not limited, but how much the completion of the processing content by the entire production line and the tool tool library capacity.
2. How to improve the efficiency of machine tools in the machining center and ensure the short beat of the entire production line? Often using a composite tool is effective, will be multiple work steps into a composite tool, in a feed to complete multiple work steps.
3. The workpiece jig of the machine tool in the processing center, because there is no tool guide, for the processing of the hole with a large length-diameter ratio, it is guided by the workpiece body hole. For example, fine boring cylinder block main bearing hole, need to be half fine boring block main bearing hole, a single half fine boring tool to return to the tool library.
Generally fine boring cylinder block main bearing bore boring tool using semi - fine boring tool, fine boring tool and guide bar three combinations of the composite tool. At the beginning of feed, semi-fine boring tool does not participate in the cutting of the main bearing bore of the block block, generally the main bearing bore of the block block is only used as the orientation hole of the half fine boring tool, and then the fine boring tool processing, to guide, semi-fine boring machining the second block main bearing bore of the block block, and then fine boring...... Until it's done. Compared with the combined boring machine, the cutting distance is long and the processing efficiency is low, which is far less than the processing efficiency of the main bearing bore combined boring machine.
Tool type selection
The cutting tools are divided into general cutting tools and special cutting tools. Special tool is divided into single tool and composite tool, tool according to the drawing and process related requirements, commissioned special tool factory design. In design, the supply and demand sides discuss the processing technology, the beat of the whole production line, the tool structure and the distribution of the cutting margin. It is worth noting that the special tool structure is complex, small batch and high cost, not suitable for single production, should be used in a large number of cylinder block, cylinder head production line.
In view of the special cutting tools for cylinder block and cylinder head processing production line, we discuss the choice of special cutting tools in combination with the problems of cutting tools in construction line, acceptance and production practice.
1. The cutting allowance of a single tool should be reasonably distributed
For example, coarse boring cylinder head valve 16- vertical column hole tool, the original structure of a single tool, the overall structure, cylinder head vertical column hole blank aperture for 15? Mm, coarse boring to 30.5? Mm, unilateral allowance up to 7.5? Mm above, the cutting load increases, when the trial production, there is a machining center machine tool spindle boring, cutting temperature rises, boring valve lifter hole tool and cylinder head machining hole bonding together, often appear to pull the stiffener hole has been processed on the inner surface of the situation.
The reason is that the excessive cutting allowance of one cutting tool causes the high cutting resistance. If divided into rough boring and semi - fine boring two work steps, and will increase the beat time. So, we changed the single tool to the compound tool of ladder structure, the cutting allowance made a reasonable allocation again, the front-end tool rough boring side allowance up to 5? Mm, the semi-fine boring margin of the back-end tool is 2.5? Mm, valve taming column hole due to the first rough boring, after half fine boring, cutting load is relatively reduced, plus the reasonable distribution of cutting margin, and improved coolant supply conditions, good heat dissipation, processing quality is stable, no longer appear machine tool spindle boring phenomenon.
2. Tooling in composite process
The structure of cylinder block and cylinder head is more complicated. According to the processing sequence of work steps, multiple work steps of related elements are often combined into a special tool. Under the condition of workpiece positioning and clamping at one time, a cutter is used to complete the processing of multiple related elements, so as to ensure their position accuracy and operation rhythm.
For example, OP-50 cylinder head machining fine boring valve seat ring installation hole and valve tube installation hole, the two work steps are designed as a composite tool (see figure 2), because the process requirements for valve tube installation hole and valve seat ring installation hole have a high degree of position. The use of composite tools can not only ensure the coaxiality, but also improve the efficiency. Compound tool is also after the sequence of finishing pipe hole 6? Mm and seat ring 90 degrees sealing surface provides process assurance, meet the design of valve seat ring 90 degrees sealing facing the inner hole of the catheter 6? Radial run-out of mm center line 0.03? Mm requirements. On the other hand, if the two steps are processed separately, it will inevitably affect the pace of this process. In addition, if the machining accuracy drops, it is difficult to guarantee the coaxiality of valve seat ring installation and valve tube installation.
3. Special plane milling cutter milling, should ensure a reasonable cutting speed
70 Mm installation surface is the diameter 60? Mm welding structure end milling cutter (see figure 3), there are three problems: the milling speed is low, the oil filter installation surface roughness, flatness can not meet the requirements; Cutting tool phi 60? Mm projection area is less than oil filter 70? Mm mounting surface, need to go many times, long time; Welding structure end milling cutter, one of the cutter tooth damage, the whole scrap tool, tool replacement time, laborious. Later used walter machine clip end milling cutter, milling cutter diameter also by 60? Mm to phi 110? Mm, the increase in the diameter of the milling cutter to improve the speed of milling, can be a cutter to complete the plane milling, by the welding structure to block and screw machine clamping structure, the blade is also changed to 4 side can be transferred, the replacement of the blade to save time, save effort, extend the life of the tool, so the oil filter installation surface roughness and surface degree exceeded the design requirements.
Welding structure milling cutter for installation face of cylinder block filter
Tool material selection
The workpiece material determines the tool material. The cylinder head is made of aluminum alloy with good plasticity, but the cutting chips are easy to adhere to the tool to form a chip tumor during cutting, which leads to the deterioration of the machining surface quality. The cylinder block material is alloy cast iron, brittleness is big, but the cutting tool is easy to collapse, the cutting tool material generally chooses the cubic boron nitride (CBN) with good cutting performance and brittleness resistance.
Tool structure selection
1. Welding tools
In principle, welding tool is used in the processing of small diameter tool, tool body and blade material different occasions, such as cylinder head fine boring valve seat ring installation hole and valve pipe installation hole composite tool, because of the structure of the cutter, is not suitable or unable to use mechanical clamping way, can only use welding structure. Such as small diameter 10? Mm H7 cylinder transmission shell positioning hole of the machine reamer, blade and cutter body is also generally used welding structure.
2. Stop cutting tool clip machine
Cheese block machine tool widely used in the structure of space allows, large diameter cutter, such as milling behind the former of the cylinder body, top bottom big plane milling cutter, such as using the cheese block machine structure form, the characteristic is: due to participate in cutting blades, each blade is reduced greatly as a cutting load, the blade of a single customization, with reasonable cutting Angle, each blade in a polygon, with 4 ~ 8 a cutting edge, the blade can transfer, repetition machine clip, dispense with the grinding blade working hours. Due to the large diameter and high cutting speed of the milling cutter, the milling out of the plane roughness is good, high planeness.
Solid carbide internal cold spiral reamer
3. Adopt solid carbide tool
Cylinder head line processing 6? Mm catheter hole, at the beginning of the line, the use of foreign brand boring tool, because of the small hole, boring bar fine, small blade, cantilever long, boring tool rigidity and easy to vibration, machining the surface of the tube hole often appear ring vibration, roughness is not qualified. Later we in view of the boring bar, small blade, long cantilever and vibration problems, from improving boring tool rigidity, switch to domestic whole 4 blade spiral teeth carbide within the whole cold reamer (see figure 4), increase the spiral cutter tooth contact with catheter hole length, improve the stability of cutting tool and cutting rigidity, cold also improved tool in the coolant supply conditions, phi 6? The machining of mm pipe hole meets the requirements of the roughness of the design and prolongs the tool life.
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