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CNC lathe machining knowledge-rapid prototyping aluminium

Sep 28,20

CNC lathe machining knowledge-rapid prototyping aluminium

Zhongda Lathe has more than ten years of experience. Here are some machining techniques for CNC lathes:CNC lathe is a kind of high precision, high efficiency of machine tool automation, using a CNC lathe can improve machining efficiency and create more value, the appearance of the numerical control lathe enterprises to get rid of the backward processing technology, numerical control lathe machining process is similar to the processing technology of the engine lathe, but as a result of the numerical control lathe is a clamping, automatic processing to complete all turning process, thus the following aspects should be paid attention to.

Reasonable choice of cutting parameters
For high-efficiency metal cutting, the material to be machined, cutting tools and cutting conditions are the three main factors.These determine the processing time, tool life and processing quality.An economical and effective machining method must be a reasonable choice of cutting conditions.
Three factors of cutting conditions: cutting speed, feed and cutting depth directly cause tool damage.With the increase of cutting speed, the tip temperature will rise, resulting in mechanical, chemical, thermal wear.Cutting speed increases by 20% and tool life decreases by half.
The relation between the feed conditions and the wear behind the tool occurs in a very small range.But large feed, cutting temperature rise, behind the wear.It has less effect on the tool than the cutting speed.The influence of cutting depth on the tool is not as large as the cutting speed and feed, but in the micro cutting deep cutting, the cutting material produced hardening layer, will also affect the tool life.
The user shall choose the cutting speed according to the material to be machined, hardness, cutting state, material type, feed, cutting depth, etc.

The selection of the most suitable processing conditions is based on these factors.Regular, steady wear to life is the ideal condition.
However, in practice, the choice of tool life is related to tool wear, size change, surface quality, cutting noise, machining heat, etc.In determining the processing conditions, the research should be carried out according to the actual situation.For refractory materials such as stainless steel and heat resistant alloys, you can use a coolant or choose a rigid blade.

How to determine the three elements of machining
How to correctly select these three elements is a main content of the course of metal cutting principles. WeChat of metal processing extracts some key points and chooses the basic principles of these three elements:
(1) Cutting speed (linear speed, circular speed) V (m/min)
To select the spindle RPM, you must first know what the cutting line velocity V should be.Choice of V: depends on tool material, workpiece material, processing conditions, etc.

Tool material:
Hard alloy, V can obtain higher, generally can be more than 100 meters/minute, generally when the purchase of blades are provided with technical parameters:
How many large linear velocities can be selected when processing what materials.High speed steel: V can only be low, generally no more than 70 m/min, in most cases, take 20~30 m/min or less.

Workpiece materials:
High hardness, V is low;Cast iron, V take low, tool material for carbide can be 70~80 m/min;Low carbon steel, V desirable 100 m/min above, non-ferrous metal, V desirable higher (100~200 m/min).Quenched steel, stainless steel, V should be lower.

Processing conditions:
Rough machining, V lower;Finishing, V higher.The rigidity system of machine tool, workpiece and cutting tool is poor, and V is low.If the nc program USES S as the RPM of the spindle, then S: S (RPM of the spindle) should be calculated based on the workpiece diameter and the cutting line velocity V =V (cutting line velocity) *1000/ (3.1416* workpiece diameter). If the NC program USES constant line velocity, then S can use the cutting line velocity V (m/min) directly.

(2) Feed amount (feed amount)
F mainly depends on the workpiece surface roughness requirement.During finishing, the surface requirements are high and the cutting amount is small: 0.06~0.12mm/ spindle per turn.When roughing, it is advisable to make it larger.Mainly depends on the strength of the tool, generally take more than 0.3, the tool after the main Angle is larger when the tool strength difference, feed quantity can not be too big.In addition should also consider the power of the machine tool, the workpiece and the rigidity of the tool.CNC program USES two units of feed: mm/ min, mm/ spindle per turn, the above units are mm/ spindle per turn, such as the use of mm/ min, available formula conversion: feed per minute = feed per turn * spindle revolutions per minute.

(3) Cutting depth (cutting depth)
When finishing, generally take 0.5 (radius value) below.During rough machining, according to the workpiece, tool and machine tool, the general small lathe (the maximum machining diameter is below 400mm) turning the normalizing state of no. 45 steel, the radius direction of the cutter depth is generally not more than 5mm.In addition, also note that if the lathe spindle speed is the use of ordinary frequency conversion speed, then when the spindle per minute speed is very low (less than 100~200 RPM), the motor output power will be significantly reduced, the depth of the knife and feed can only get very small.

Rational choice of tool
1. When the rough car, to choose a high strength, good durability of the tool, in order to meet the rough car when the big back of the knife, large feed requirements.
2. When finishing the car, it is necessary to choose a tool with high precision and good durability to ensure the machining accuracy.
3. In order to reduce the time of tool changing and facilitate tool matching, the machine clamping knife and the machine clamping blade should be used as far as possible.

Reasonable selection of fixture
1. Try to use universal fixture to hold the workpiece, avoid using special fixture;
2. Parts positioning datum coincide to reduce positioning errors.
Determine the processing route
The machining route is the track and direction of the tool relative to the parts in the process of the exponential control machine tool.
1. Requirements for machining accuracy and surface roughness shall be ensured;
2. The processing route should be shortened as far as possible to reduce the empty travel time of the cutting tool.
The connection between machining route and machining allowance
At present, in the CNC lathe has not reached the conditions of widespread use, the general blank should be too much margin, especially the margin of forging, casting hard cortex arranged in the ordinary lathe processing.If you must use CNC lathe processing, you need to pay attention to the flexible arrangement of the program.
Key points of fixture installation
At present, the connection between hydraulic chuck and hydraulic clamping oil cylinder is realized by pulling rod. The critical point of hydraulic chuck clamping is as follows: first, remove the nut on hydraulic cylinder and pull tube by hand, and draw out from the back end of the spindle, and then remove the fixing screw of chuck by hand. Then, the chuck can be removed.