Estimation of Machining Time for Shaping
Let L = Length of stroke or Tool travel, in metres,
l = Length or breadth of job, over which the tool passes, in metres,
l1 = Tool approach, that means. the distance it has to travel before starting actual cutting in metres,
l2 = Overtravel, i.e. the distance through which the tool travels beyond the work surface in metres,
f = Feed per cycle, in mm,
m = Ratio of return time to cutting time,
v1 = Average cutting speed, in metres per min.,
v2 = Average return speed, in metres per min., and
n = No. of cycles required
Now, Cutting speed (v) = Length of cutting stroke/ Time taken in cutting stroke
Cutting time = Length of cutting stroke/ Cutting speed in m / min .
= L/ v1 min.
or,
= (l + l1 + l2)/ v1 min.
And, non-cutting time or idle time
= Length of cutting in metres/ Return speed in m/min = L/ v2
= l + l1 + l2 / v2 min.
Now, Total time per cycle = Cutting time + Idle time
Equation 1
![86_Estimation of Machining Time for Shaping 1.png](https://www.expertsmind.com/CMSImages/86_Estimation%20of%20Machining%20Time%20for%20Shaping%201.png)
{where K = ratio of idle stroke time to cutting stroke time)
Equation 2
![2497_Estimation of Machining Time for Shaping 2.png](https://www.expertsmind.com/CMSImages/2497_Estimation%20of%20Machining%20Time%20for%20Shaping%202.png)
For shaping a workpiece an allowance of around 5 mm is left on either side of it. Therefore, the shaping width of the workpiece is attaining as:
Shaping width B = Width of workpiece + 2 × allowance
No. of cycles required (n) = Shaping width/ Feed per cycle = B/ f
Machining time = No. of cycles × time required for each cycle
Equation 3
![231_Estimation of Machining Time for Shaping 3.png](https://www.expertsmind.com/CMSImages/231_Estimation%20of%20Machining%20Time%20for%20Shaping%203.png)