Information Technology Reference
In-Depth Information
Lathe
CNC
SPM
Time
(sec)
Time (sec)
Time (sec)
Counterboring time
5.0
3.0
3.0
Drilling time
8.0
4.0
4.0
Tapping time
10.0
5.0
5.0
Cutting time
23.0
12.0
5.6 1
Tool changing per part
6.0
0.12 2
Free tool traveling per part 6.0 0.6 3
Indexing time per part 1.2
Loading/unloading 15.0 2.40 4 5.0 5
Non-cutting time 27.0 3.12 1.2
Total time per part 50.0 15.12 6.8
Parts per hour 72 238.10 529.41
1 : On the SPM the longest operation time determines the time required for each operation
2 : Tool changing time for the CNC machine is 3 times of 2 seconds each for 50 pieces (0.12 sec/part)
3 : Free tool traveling for the CNC machine is 30 seconds for 50 pieces (0.6 sec/ part)
4 : Loading/unloading time of one pallet carrying 50 pieces is 2 minutes (2.4 sec/part)
5 : Loading/unloading on the SPM will be performed by an automated system and at the same time
machining is in progress in other stations
Table 2. Comparison of machining times for traditional lathe, CNC, and SPM
Fig. 17. Part exchange time on traditional lathe, CNC, and SPM.
Table 3 represents machining unit cost for all of the three methods and provides all cost
components. When traditional lathe is used there is a need to use seven machines in order to
achieve required annual output. This significantly increases labour and overhead costs that
would result in a unit cost of $4.7423. In the case of CNC machine there is a need to use two
machines in order to achieve the required output. This would reduce the unit cost to $0.5211
that is significantly lower. Yet SPM would further decrease this figure. Due to high
productivity of SPMs only one machine with a single operator is needed to achieve the
required output. This decreases most cost components including labour and overhead costs.
Consequently the cost per part is reduced to only $0.2138. In other words, the use of SPM
results in a significant 59% reduction of unit cost in comparison with CNC, and an amazing
95.5% cost reduction is achieved when compared to traditional lathe.
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