Deep Hole Machining In Cnc Machining Process

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Holes are important surfaces on boxes, brackets, sleeves, rings, and disc parts, and are often encountered in machining. When the machining accuracy and the surface roughness are the same, the machining of the hole is more difficult than the machining of the outer circular surface, and the productivity is low and the cost is high. This is because the size of the tool is limited by the size of the hole to be machined, so the rigidity of the tool is poor, and the large cutting amount cannot be used. When the hole is machined, the cutting area is inside the workpiece, and the cutting fluid is not easy to enter the cutting area, chip removal and heat dissipation. Poor conditions, machining accuracy and surface quality are difficult to control.

Hole processing methods include drilling, reaming, reaming, boring, drawing, grinding, and hole finishing. In addition, the processing method for replacing conventional drilling holes is to drill deep holes and heat. Drilling, laser drilling, electron beam drilling, electric spark drilling, etc. Different parts and materials, different sizes, different precision requirements, different tools are selected; different efficiency requirements, different mass production requirements, different straightness ratios, and different processing techniques.

Deep Hole Machining

Deep hole machining is a type of machining that is dominated by tools designed for existing applications. Deep hole machining is involved in many different industries. Today, success in this field of processing is often based on mixed-use standards and specialized tool components with experience in designing dedicated deep hole machining tools. These tools feature an extended, high-precision shank with support and integrated reamer, combined with the latest cutting edge geometry and insert material and efficient coolant and chip control for maximum penetration and Get the high quality you need under processing safety.

Deep Hole Machining Difficulties

• (1) The cutting condition cannot be directly observed. The parameters of the chip and the bit are judged by listening to the sound, looking at the chip, observing the machine load and oil pressure.
• (2) The cutting heat is not easily transmitted.
• (3) It is difficult to remove chips, which may cause damage to the drill bit if it is blocked by chips.
• (4) Due to the long length of the drill pipe, poor rigidity and easy vibration, the axis of the hole is easily deflected, which affects the machining accuracy and production efficiency.

Precautions for deep hole machining

Deep hole machining operation points: The coaxiality of the center line of the spindle and the tool guide sleeve, the tool holder support sleeve, and the workpiece support sleeve should meet the requirements; the cutting fluid system should be unblocked; the machining end surface of the workpiece should not have a center. Holes, and avoid drilling holes on the slope; the shape of the chips should be kept normal to avoid the formation of straight-band chips; the through-holes are machined at a higher speed, and when the drill is about to drill through, the speed should be reduced or stopped to prevent damage to the drill bit.

Deep hole machining cutting fluid: A lot of cutting heat is generated during deep hole machining, and it is not easy to spread. It is necessary to supply sufficient cutting fluid to lubricate the cooling tool. Generally use 1:100 emulsion or extreme pressure emulsion; when high processing precision and surface quality or processing toughness materials are required, extreme pressure emulsion or high concentration extreme pressure emulsion is used, and the moving viscosity of cutting oil is usually selected (40 °C) 10 ~ 20cm2 / s, cutting fluid flow rate is 15 ~ 18m / s; when the processing diameter is small, the cutting oil with low viscosity is used; for deep hole processing with high precision, the cutting oil ratio can be selected as 40% extreme pressure vulcanized oil +40% kerosene + 20% chlorinated paraffin.

Notes on using deep hole drilling:

• A. The end face of the workpiece is perpendicular to the axis of the workpiece to ensure reliable end face sealing.
• B. Pre-drill a shallow hole in the hole position of the workpiece before the formal machining, and guide the centering action when drilling.
• C. In order to ensure the service life of the tool, it is best to use automatic walking.
• D. If the guide elements in the inlet and the movable center support are worn, they should be replaced in time to avoid affecting the drilling accuracy.

Link to this article： Discussion on deep hole machining in cnc machining process

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