04。车削加工工艺

(S=Rω, ω =2π N)
These data are obtained through experiment
Cutting Depth
Cutting Depth d=( D-D1 )/2
Basic Consideration of Cutting Depth
In roughing the big depth is set, but in finishing, a small depth is set.
-Much higher accuracy than manually operated lathe in terms of finished part
-……
Terminologies of Turning Process
For understanding any machining process it is very important to make sense of movement relationship between work-piece and cutting tool.
To machine a taper :
-Calculate the topslide angle based on the formula shown. -Fix the topslide in a calculated angle by clamping handle.
What if CNC lathe is used to machine a taper?
Capacity of the lathe
Capacity of the lathe covers two aspects: -Power consumed
-Geometrical parameters If CNC lathe, because of no gear train, the second item is almost ignored (ball screw and ball guideway). To purchase a lathe you have to check geometrical parameters shown on the bottom left.
What if CNC lathe is used to machine a taper?
How to read a mathematical expression?
Continue d
Cutting Speed and Spindle Speed
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Basics of cutting data: S-Cutting speed meter/ minute(based on experiments) N-Spindle speed RPM d-Cutting depth mm f-Feed rate mm /r
Movements of Lathe
The key step to understand a machine tool: -To make sense clearly of Relationship between work-piece and cutting tool. In other words, how many movements the machine tool possesses is subject to formation of the work-piece.
In CNC context, do we need a gear train to ensure the ratio of spindle and carriage?
Half Nut and Gear Train for Screw
Cutting Tool for Screw
Setting up for screw cutting
-prepare cutting tool -install cutting tool to the tool post -position and clamp the stock on the chuck -calculate some parameters if necessary -set cutting parameters -cutting -take finished part from lathe
Tool Post vs Tool Library
Turning Operation
Turning a taper
Basics of taper:
Taper K=(D-D1) / L=2tga Taper included angle: 2a K is donated by m::n, like 7:24
The cutting depth also depends on:
-the material and tool angles -the material of part to be machined
-machine tool power available(power is consumed during cutting)
Turning Process
Three Elements To be Considered: -Work-piece: Cylindrical or Conical Objects -Cutting Tool: Single Point Cutting Tool
-Machine Tool: Lathe
for each revolution of
workpiece,the cutting tool must move a pitch.
Nspindle / Nleadscrew =i i = i headstock × i feedgearbox ×iother
Mechanism to perform screw cutting.
-If CNC lathe
Steps: -develop a turning process -program the part to be turned -deliver the document to the operator
Summary for Turning Process
-Turning processes -Movements relationship between cutting tool and work-piece -Configuration of Lathe -CNC lathe -CNC lathe tool bank
Feedrate
Feedrate is a distance of forward movement of cutting tool when work-piece rotates one revolution. Feedrate usually influences surface finish and stock removal rate.
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CNC Turning Machine or CNC CNC Turning Machine lathe or CNC Lathe
The Feature of the CNC Lathe: -All Operations are done automatically
-All Operations are controlled by numbers and symbols
Holding work-piece
Work-holding Principle
Three Jaw
Collet for Holding
Supporting a Work
Fixed Steady
Practicals
-If manually operated lathe
Steps:
-develop a turning process
-start(multi-start threads)
-lead=number of start*pitch -right and left hand screw
How is a screw formed? -by rotation of work-piece and cutting tool feeding along workpiece axis. -the cutting tool must be shaped like screw thread profile. -Set lathe to the condition that
Screw Turning
When the work-piece rotates one revolution the cutting tool must move forward exactly a distance equaling to pitch.
What is screw? -pitch
Designed to be selflocked Key
Carriage
Carriage is to transmit both longitudinal and cross movement of cutting tool
Pinion is small gear engaged with rack
Three Elements for Developing Machining Processes -What you are going to shape—Work-piece -What tool you are going to employ —Cutting Tool -What equipment is to be used —Machine Tool
Configuration of Lathe
-Headstock -Lathe Bed -Tailstock
-Carriage