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In the context of this article, let us consider: Real-world scenario
At a site in a remote place, the
tc = total machining time for full coil machine was down because
td = downtime in minutes the machine pressure wasn’t
tl = loading time building up. The machine op-
ts = machine setting up time erator needed support from
lc = length of coil the OEM to bring the machine
Cd = cost of downtime back to operational state. Nor-
Rh = revenue potential per hour mally, this would have meant,
Rc = revenue potential per coil someone from the OEM’s team
Nh = number of coils per hour travels to the site and bring
Mc = weight of coil in kilograms the machine back to the op-
Cc = cost of coil (raw material) erational state. However, this
Ce = energy cost being a remote site, the jour-
Co = other costs ney alone would take at least a
SD = surface density constant of material day. That implies that the
ID = Inner Diameter (mm) machine has to be down until
OD = Outer Diameter (mm) that time.
T = Thickness (mm) To understand the commercial
W = Width (mm) aspects of the machine’s oper-
ations and downtimes in this
From the concepts of geometry of solid bodies, we arrive at case, let’s consider the following
equations for the length, lc and weight, Mc machine and material properties
(refer Table 1).
length, lc (mtrs) = π * OD2 — ID2 This was a unit that operated in As new
4 T 3 shifts. This means the machine technol-
would not have been avail- ogies are
Weight, Mc (kg) = lc * Wc * T * SD able for at least 24 hours of the being made
1000 planned production time. available,
From the equations discussed MSMEs
Based on practical observations, we arrive at the relations above, we deduced that an hour- should
between material properties and revenue as follows: ly downtime cost would be ap- come
proximately `18,306 (~US$ 250) forward to
Cost of coil, Cc = Material Rate * Mc for the machine and material adopt them
properties we chose. Now, with and stay
Typical revenue per coil, Rc = margin * [1 + Cc] a 24 hours downtime, the cost of competitive
the downtime would be signifi- in the glob-
cantly high, nearly 24 times the al manu-
hourly cost in this case. facturing
landscape.
Typical revenue per hour, Rh = Nh * Rc
Coils per hour, Nh = 1 * 60
tc
lc
Processing time, tp = speed
Total machining time for full coil, tc = tp + tl + ts
Energy cost, Ce = Unit Rate * units consumed per hour
Therefore, to estimate the cost of downtime, we arrive at the
following equation:
Cost of downtime, Cd = td [Rh — (N * Cc) — Ce — Co]
60
Source: yzThings Technologies Pvt Ltd
In most metal processing applications, other costs are neglible
compared to the raw material and energy costs hence are being
ignored in our case study here.
(Note: These are not to be treated as bench marking formula;
only used for rough cost benefit assessment.)
www.mmindia.co.in | 23May-June 2021