The purpose of this paper is to prove the impact of design and control schemes on flexible system of incorporate fabrication. A computing machine simulation theoretical account is developed to measure the effects of aforesaid schemes on the make-span clip, which is taken as the system public presentation step. This system does non hold dedicated buffer but alternatively has cardinal buffer. The impact of hold clip for storage and retrieval of parts from the cardinal buffer on the public presentation of the system is besides studied. The consequence of the simulation shows that there is definite scope of palettes for each degree of routing flexibleness at which the systems performs satisfactorily. It is besides observed that different combinations of despatching and sequencing regulations give different degrees of public presentation. Besides there is some impact of hold clip on the system public presentation.
Keywords: flexible fabrication system, make-span, routing flexibleness, simulation,
1. Introduction
In the present epoch, quality, invention and assortment are the primary characteristics of merchandise success. To accomplish these demands, fabricating companies need to be flexible and antiphonal to alterations in order to bring forth assortment of merchandises in a short clip span. Among all the bing fabrication system, makers are following flexible fabrication system ( FMS ) . FMS is the system, which is equipped with the several computer-controlled machines, holding the installation of automatic changing of tools and parts. The machines are interconnected by automatic guided vehicles, palettes and several storage buffers. The procedure of implementing an FMS is dearly-won as it requires heavy capital investing in machinery and equipment. Hence the design and control of FMS requires an intensive work on be aftering an efficient and effectual system.
Within the survey of design schemes, the diverse types of flexiblenesss are studied. Browne et.al.1984 have comprehended eight types of fabrication flexiblenesss, which are known as: machine flexibleness, procedure flexibleness, routing flexibleness, operation flexibleness, merchandise flexibleness, volume flexibleness, enlargement flexibleness and production flexibleness. Among all these, the routing flexibleness is one possible manifestation of fabricating flexibleness at the store floor.
The commanding action in any fabrication system is holding increasing importance. Equally far as the function of control schemes is concerned it manifests it self in the signifier of sequencing and despatching determination of the parts in the system. Buffer is besides an of import constituent of any fabrication system. In general the advantage of high buffer capacity doing high use is offset by the disadvantage of extra floor infinite and stock list as stated by Saad and Byrne [ 1 ] . While low buffer capacities cut down the floor infinite and higher stock list demand, they are frequently non preferred because of decreased use and increased hold.
This paper presents a simulation survey with the combination of assorted design and control schemes. In the design scheme, the impact of routing flexibleness, location of buffer and figure of palettes in the system has been taken into consideration. The sequencing and dispatching regulations have been selected as the control schemes. In this survey, SPT and MBPT are considered as the sequencing regulation whereas the dispatching regulations are NR ( let go of the portion to the idle machines ) , MINQ ( minimal figure in waiting line ) and MWTQ ( minimal waiting clip in waiting line ) . The brand span clip is considered as the public presentation step for the FMS. The different combinations of assorted schemes are studied with the aid of ARENA simulator.
The balance of the present paper has been organized in the undermentioned mode: Section 2 trades with literature reappraisal, followed by subdivision 3 which delineates the description of the job under survey. Section 4 reveals the obtained consequences with the different fabrication schemes. Finally, the decisions are reported in the subdivision 5.
2. Literature Reappraisal
A literature reappraisal was carried out to place the old research attempts and way related to this work. The literature reappraisal addressed two wide spheres of FMS i.e. , design and control schemes.
The design schemes consist of routing flexibleness, buffer location and figure of palettes in the system. The control strategies consist of sequencing and despatching regulations. The routing flexibleness measures the ability to execute operations by more than one machining centre to manage machine dislocations. Exploiting the routing flexibleness in the distinct portion fabricating systems is studied by many research workers. Matsui et Al. [ 2 ] surveies the public presentation of flexible fabricating systems with finite local buffers and fixed or dynamic routing regulations. They showed that for a fixed routing theoretical account the system throughput in the instance of finite local buffers is greater than in the instance of infinite local buffers. Buyurgan et al [ 3 ] studied a conjectural FMS holding a cardinal buffering scheme had been adopted where machining centres have no input or end product buffers. Partss enter the system from a cardinal input buffer and issue from a cardinal end product buffer. A limited buffer capacity in both input and end product topographic points of workstations gives the possibility for the system to see a dead end state of affairs where no stuff can travel as stated by Caumond et al. , [ 4 ] . Ali and Wadhwa [ 5 ] studied the impact of routing flexibleness on the make-span public presentation of a flexible fabrication system. They considered three degrees of routing flexibleness, i.e. , no routing flexibleness, partial routing flexibleness, and full routing flexibleness. They observed that partial routing flexibleness based system performed better that full flexibleness system. Ali and Wadhwa [ 6 ] exploited the routing flexibleness in the distinct portion fabricating systems affecting assortment production towards heightening the make-span public presentation by incorporating different entities fluxing in the system. Matta et Al. [ 7 ] , states that it is non easy to gauge the consequence that an addition or a lessening of the figure of palettes can hold on the impregnation of machines.
Buitenhek et Al. [ 8 ] have stated that the control mechanism in FMS specifies which portion to treat following at a machine upon the competition of the current operation. Chan et Al. [ 9 ] surveies the consequence of dispatching and routing determinations on the public presentation of flexible fabricating systems. They studied the impact of buffer capacities on the public presentation of the system by using three routing policies. The public presentation steps considered is make-span, mean machine use, flow clip and mean hold at the local input buffers. Abou-Ali and Shouman, [ 10 ] studied the consequence of dynamic and inactive dispatching schemes on dynamically planned and unplanned flexible fabrication system. Ali [ 11 ] has studied existent clip scheduling method for a system with uninterrupted occupation arrival form. He has concluded that keeping a balance of work load on each machine reduces the WIP stock list and that on an mean SPT regulation performed better than other sequencing regulations. Matsui et Al. [ 12 ] evaluates the public presentation of flexible fabricating systems with finite local buffers and fixed or dynamic routing regulations, and addresses the optimum design or system constellation job of maximising the system throughput. Das and Canel [ 13 ] studied the job of scheduling batches of parts in a flexible fabrication system ( FMS ) and developed a theoretical account could be used to minimise the entire production clip ( make-span ) i.e. minimise production clip, minimisation of inter-batch apparatus times becomes an of import undertaking. Altinkilic [ 14 ] has presented a usage of simulation to better store floor public presentation. The public presentation of the bing system is evaluated by utilizing ARENA. Saygin et Al. [ 15 ] considered real-time use of alternate routings in flexible fabrication systems through simulation survey. Similarly Shingoli et Al. [ 16 ] surveies the impact of fabricating flexibleness on flexible fabrication system with aid of simulation technique. Yan and Zhong [ 17 ] usage Petri cyberspaces technique to decide the job of dead ends in machine-controlled flexible fabrication systems.
The above literature high spots, that the public presentation of FMS which is extremely dependent upon the design and control determinations. However more work demands to be done in this way. An effort has been made in this paper to see the impact of design and control schemes on the public presentation of flexible system of incorporate fabricating a bomber sphere of flexible fabrication system.
3. Problem Description:
In the present flexible system of incorporate fabrication, a system constellation consists of 6 flexible machines ( M1, M2, M3, M4, M5 and M6 ) . All these machines are capable of bring forthing any portion types. Figure 1 depicts the layout of the system. It is provided with cardinal buffer ( CB ) with finite capacity. However the capacity of CB is modeled as variable. The sequencing determination point ( SD ) and a dispatching determination point ( DD ) are attached to cardinal buffer.
M1
M4
M5
M6
M2
M3
CB
South dakota
Doctor of divinity
Figure 1: Sample Flexible Manufacturing Systems
In all 6 portion types ( P1, P2, P3, P4, P5 and P6 ) , are manufactured in this system. The figure of operations required for treating the portion type has been taken as 4 to 6. The entire operations are 30. The item of figure of operations to be performed on each of the portion type are as follows: Part 1=4 operations ; Part 2=5 operations ; Part 3=6 operations ; Part 4=4 operations ; Part 5=5 operations and Part P6=6 operations severally. The parts can be routed through the different machines, for treating depending on the degree of routing flexibleness available in the system. The public presentation step is considered as make-span. Make-span for 600 parts ( 100 of each six portion types ) is collected to measure the public presentation of flexible system of incorporate fabrication. First, different parts arrive in the system. These portion types are held up at the lading country boulder clay it is released whenever the possible machine becomes available. Once the parts are released from the lading country, they are sent to respective machining Stationss for operation. If the machine is non idle, the parts are sent to the cardinal buffer. Table 1 allotment of machines with processing clip in brackets at routing flexibleness degree 1.
Table 1: Routing for sequence of operation and processing clip for routing flexibleness ( RF=1 )
Partss
O1
O2
O3
O4
O5
O6
P1
M1 ( 40 )
M2 ( 40 )
M3 ( 24 )
M5 ( 24 )
M4 ( 52 )
M1 ( 52 )
M6 ( 33 )
M3 ( 33 )
#
#
P2
M4 ( 17 )
M3 ( 17 )
M2 ( 39 )
M1 ( 39 )
M3 ( 41 )
M4 ( 41 )
M5 ( 38 )
M2 ( 38 )
M1 ( 26 )
M5 ( 26 )
#
P3
M5 ( 72 )
M6 ( 72 )
M1 ( 49 )
M4 ( 49 )
M3 ( 37 )
M5 ( 37 )
M2 ( 94 )
M1 ( 94 )
M4 ( 39 )
M6 ( 39 )
M6 ( 70 )
M1 ( 70 )
P4
M2 ( 55 )
M1 ( 55 )
M5 ( 92 )
M3 ( 92 )
M6 ( 38 )
M2 ( 38 )
M3 ( 92 )
M6 ( 92 )
#
#
P5
M6 ( 67 )
M5 ( 67 )
M4 ( 65 )
M6 ( 65 )
M2 ( 40 )
M3 ( 40 )
M5 ( 94 )
M4 ( 94 )
M1 ( 15 )
M2 ( 15 )
#
P6
M3 ( 64 )
M4 ( 64 )
M5 ( 52 )
M2 ( 52 )
M4 ( 66 )
M6 ( 66 )
M1 ( 36 )
M5 ( 36 )
M6 ( 63 )
M3 ( 63 )
M2 ( 50 )
M4 ( 50 )
The simulation theoretical account has been developed in the ARENA-11 simulation bundle. ARENA bundle was selected for patterning as it provides a good graphical interface and besides the life public-service corporations. In ARENA bundle, there is no available characteristic to explicitly pattern the flexibleness features. An extended attempt has been carried out to accomplish this characteristic besides. Now the mold of different schemes is described which will foreground the underlying logic of the theoretical account and the associated premises.
The degrees of routing flexibleness are explained as: RF=0, means that there is precisely one machine for an operation on a given portion i.e. there is 0 ( zero ) options. RF=1, implies that there are two possible machines for treating the same operation i.e. there is precisely 1 more alternate machine ( other than the machine which is available at RF=0 ) for any operation on any portion. RF=2, implies that there are in all three possible machines for treating the same operation i.e. there are precisely 2 more machines available for treating the same operation ( other than the machine which is available at RF=0 ) . Similarly RF=3 and RF=4 imply 3 and 4 alternate machines are available severally for any part/operation.
The dispatching determination is referred as the choice of the machine for treating the following operation on the portion out of available alternate machines. The machine is selected on the footing of the dispatching regulation enforced. The two sequencing regulations and three dispatching regulations have been used in the control schemes are explained here.
Sequencing Rules: SPT: Choose the portion that has Shortest Processing Time on the machine ; MBPT: Select the portion which has Maximum Balance Processing Time left for finishing the entire processing.
Dispatching Rules: MINQ: Choose the following machine for treating the following operation on the portion which has Minimum figure of parts in the input buffer ; MWTQ: Select the following machine for treating the following operation on the portion which has Minimum amount of the processing times ( on that machine ) of all the parts waiting in the input buffer i.e. Minimum Waiting Time in Queue ; NR: Let go of the portion to the idle machines.
Confirmation and proof are two technique employed during the development of simulation mold of system. In the present survey, the confirmation of the simulation theoretical account has been carried out with the aid of built in characteristic of ARENA bundle and by uninterrupted monitoring of the values of some of import variables. The installation of graphical life of system during simulation run provides great support for confirmation of the theoretical account. The other installations provided in ARENA, which help in confirmation, are SIMAN cryptography, which is in generated analogue, when the theoretical account is run. This helps for speedy mentions. The 2nd facet of simulation theoretical account is proof. The proof of present simulation theoretical account is done harmonizing to the attack suggested by Fryer [ 18 ] that conjectural simulation theoretical account, should execute in conformity with the premise and logic. This is achieved by following measure by measure of the simulation run to formalize, that the theoretical account is executing in conformity with premise and under lying logic.
4. Simulation Consequences
In the undermentioned subdivisions, we analyze and discuss the consequences obtained by executing simulation experiments maintaining in position the above mentioned issues. We consider the undermentioned issues:
Impact of MST on RF at given NP with different DR/SR combination of regulations.
Impact of DT for Storage and Retrieval of parts from CB.
Impact of NP and RF with different combinations of DR/SR
In this subdivision, we present the consequences of the simulation experiments conducted under different combinations of despatching and sequencing regulations ( i.e. , control schemes ) . The simulation consequences indicate that by maintaining the capacity of the centralised buffer fixed, different degrees of routing flexibleness and given figure of palettes indicates different consequences for alternate control schemes. The consequence of NR/MBPT combination of sequencing and despatching regulations are shown in Figures 2.
Figure 2: Impact of MST on NP at different degrees of RF with NR/MBPT
It is seen from Figure 2, that for all the degrees of routing flexibleness there is lessening in make-span when the figure of palettes is increased from 6 to 12. When figure of palettes is farther increased from 12 to 60, the make-span remains about changeless at given degree of routing flexibleness. The systems blocks when the figure of palettes is increased beyond 60 at RF=0, 1, 2 and 3. However at RF=4, and 5, the system blocks at 66 palettes. This shows, that with addition in flexibleness degrees, more palettes are allowed in the system. However the addition in figure of palettes, does non better system public presentation. When routing flexibleness is increased to 1 we observe significant lessening in the make-span at all the degrees of palettes. We can detect from Figure 2, that there is fixed scope of palettes within which the system performs satisfactorily i.e. , 60 palettes for RF=0, 1, 2, and 3 and it is 66 for RF=4 and 5.
Table 2, below shows the sum-up of impact of assorted factors on the system public presentation. For illustration at RF=1, PR =6 to 60, NPMB = 24, NPB & A ; gt ; 60 and decrease in MST is 20.44 % , when figure of palettes is increased from 6 to 24. Table 2 shows the comparing of public presentation of the system with NR/MBPT and NR/SPT as the combination of sequencing and despatching regulations.
Table 2: Impact of RF and NP on System Performance
Degree of Routing Flexibility
Praseodymium
NPMB
NPB
Max. % Decrease in MST
0
6-60
36
& A ; gt ; 60
24.35 %
1
6-60
24
& A ; gt ; 60
20.44 %
2
6-60
42
& A ; gt ; 60
13.11 %
3
6-60
54
& A ; gt ; 60
8.98 %
4
6-66
48
& A ; gt ; 66
4.79 %
5
6-66
36
& A ; gt ; 66
0.21 %
Table 3 shows the different combination of despatching and sequencing regulations gives different degree of public presentation. The maximal betterment in the system public presentation depends on the degree of routing flexibleness, figure of palettes and control schemes. With NR/MBPT, the maximal benefit ( 24.35 % ) is obtained at RF=0, and NPMB =36. With NP/SPT, the maximal benefit ( 19.45 % ) is obtained at RF=1, and NPMB =12. It is seen that simply increasing the figure of palettes in the system does non needfully better system public presentation.
Table 3: Comparison of impact between NP, RF and DR/SR on MST
DR/SR
Releasing factor
Lead
NPMB
NPB
% Reduction in MST
NP/MBPT
0
6-60
36
& A ; gt ; 60
24.35 %
1
6-60
24
& A ; gt ; 60
20.44 %
2
6-60
42
& A ; gt ; 60
13.11 %
3
6-60
54
& A ; gt ; 60
08.98 %
4
6-66
48
& A ; gt ; 66
04.79 %
5
6-66
36
& A ; gt ; 66
00.21 %
NP/SPT
0
6-60
12
& A ; gt ; 60
7.24 %
1
6-60
12
& A ; gt ; 60
19.45 %
2
6-60
24
& A ; gt ; 60
12.68 %
3
6-60
36
& A ; gt ; 60
08.56 %
4
6-66
66
& A ; gt ; 60
04.45 %
5
6-66
36
& A ; gt ; 66
00.21 %
Next we change the dispatching regulation from NR to MWTQ and measure the public presentation of the system. It is seen from Figure 3 besides, that for all degrees of routing flexibleness there is lessening in MST when NP is increased from 6 to 12. At RF & A ; gt ; =1, with addition in figure of palettes beyond 66 the system starts barricading. If we compare this figure with Figure 2 we see that in this instance besides, it is fruitful to increase routing flexibleness from 0 to 1 to acquire maximal benefit.
Figure 3: Impact of MST on NP at different degrees of RF with MWTQ/MBPT
Table 4, below shows the sum-up of impact of assorted factors on the system public presentation. For illustration at RF=1, PR =6 to 66, NPMB = 60, NPB & A ; gt ; 66 and decrease in MST is 26.42 % , when figure of palettes is increased from 6 to 60.
Table 3: Impact of MST on RF and NP ( MWTQ/MBPT )
Degree of Routing Flexibility
Lead
NPMB
NPB
Max. % Decrease in MST
0
6-60
36
& A ; gt ; 60
24.35
1
6-66
60
& A ; gt ; 66
26.42
2
6-66
60
& A ; gt ; 66
14.15
3
6-66
36
& A ; gt ; 66
09.59
4
6-66
48
& A ; gt ; 66
04.69
5
6-66
30
& A ; gt ; 66
00.21
Table 5 shows the comparing of public presentation of the system with MWTQ/MBPT and MWTQ/SPT as the combination of sequencing and despatching regulations. It is observed from Table 4 that different combination of despatching and sequencing regulations gives different degree of public presentation. The maximal betterment in the system public presentation depends on the degree of routing flexibleness, figure of palettes and control schemes. With MWTQ/MBPT, the maximal benefit ( 26.42 % ) is obtained at RF=1, and NPMB =60. With MWTQ/SPT, the maximal benefit ( 26.02 % ) is obtained at RF=1, and NPMB =48. It is seen that simply increasing the figure of palettes in the system does non needfully better system public presentation.
Table 4: Comparison of impact of MST on NP, RF and DR/SR
DR/SR
Releasing factor
Praseodymium
NPMB
NPB
% Reduction in MST
MWTQ/MBPT
0
6-60
36
& A ; gt ; 60
24.35
1
6-66
60
& A ; gt ; 66
26.42
2
6-66
60
& A ; gt ; 66
14.15
3
6-66
36
& A ; gt ; 66
09.59
4
6-66
48
& A ; gt ; 66
04.69
5
6-66
30
& A ; gt ; 66
00.21
MWTQ/SPT
0
6-60
12
& A ; gt ; 60
07.24
1
6-66
48
& A ; gt ; 66
26.01
2
6-66
30
& A ; gt ; 66
14.13
3
6-60
54
& A ; gt ; 60
09.48
4
6-66
60
& A ; gt ; 66
04.51
5
6-66
36
& A ; gt ; 66
00.37
5
6-66
36
& A ; gt ; 66
00.26
4.2 Impact of DT for storage and retrieval of parts from CB
In the above subdivisions, the impact of routing flexibleness and figure of palettes on the system public presentation was investigated. The survey was conducted by presuming zero hold clip in hive awaying and recovering the parts from CB. In this subdivision some hold clip for storage and retrieval of parts from the CB is considered. It is of import for FMS interior decorators and accountants to hold cognition of the impact of these holds on the public presentation of the fabricating systems. This cognition will assist interior decorators and accountants to make up one’s mind on the degree of mechanization that will be good to them. With delay manner we try to undertake the undermentioned issues:
Impact of DT: Performance of RF
It has been reported by the survey on FMS with existent clip capablenesss that the addition in flexibleness consequences in a better public presentation. It is interesting to analyze whether this besides holds true for system holding CB holding finite capacity and hold being incurred for storage and retrieval of parts from it. This hold clip is added in the processing clip of the parts whenever it arrives in CB. Further, how these holds affect system public presentation with addition in degrees of routing flexibleness is besides rather interesting. Figure 4 shows the fluctuation of MST with alteration in hold clip on the public presentation of system at assorted degrees of routing flexibleness. The impact of hold clip is being investigated at all the degrees of routing flexibleness ( i.e. , from RF=0 to RF=5 ) with MINQ/SPT as the combination of despatching and sequencing regulations. Figure 4 shows that there is uninterrupted decrease in MST with addition in the degrees of routing flexibleness when DT & A ; gt ; 0. It is besides seen that when the degree of routing flexibleness is increased, the variableness in MST due to detain clip reduces. This is due to the fact that as the degrees of routing flexibleness are increased there is better distribution of parts among different machines. This leads to less parts being routed to CB, hence decrease in the variableness of MST with increased degrees of routing flexibleness. At RF=5, the impact of hold clip is undistinguished. This is due to the fact that at this degree of routing flexibleness fewer parts are moved to CB hence the less impact due to detain clip.
At DT=0, with the addition in the degrees of RF there is lessening in MST boulder clay RF=1. There after there is little impairment in the system public presentation. When RF degrees are increased from 0 to 1, and DT is increased, there is lessening in per centum decrease in the MST. This is because when RF degree is increased from 0 to 1, there is merely one alternate pick of the machines on which the portion can be processed. At the given figure of palettes in the system and the capacity of CB, parts non happening the possible machine are moved to the CB, incurring DT which increases the processing clip of the parts and finally the MST. This leads to per centum lessening in MST with addition in DT. However with the addition in RF from 1, and increase in DT there is addition in per centum decrease in MST. This is because with addition in RF degrees there is more option to parts to choose the possible machines. These consequences in less chance that the parts are moved to CB, therefore less opportunity of incurring DT thereby bettering system public presentation. From this survey we conclude, that practicians can see some hold clip for storage and retrieval of parts from CB and still acquire good public presentation. As we are cognizant that the maximal decrease in MST occurs when routing flexibleness is increased from 0 to 1, the impact of hold clip to some extend at this degree of routing flexibleness is non really much. Hence practicians can see delay clip and still acquire about same sum of benefit when hold is non used. The impact of routing flexibleness on the system public presentation depends on the sum of hold incurred in hive awaying and recovering the parts from CB.
Figure 4: Impact of MST on RF at different degrees of DT ( MINQ/SPT )
5. Decision
The survey in this paper was carried with flexible system of incorporate system holding centralized buffer. First we analyze the impact of design and control factors on the make-span public presentation of the system. We see that with system constellations, it can run satisfactorily with 60 palettes at all the degrees of routing flexibleness. However simulation consequences indicate that, increase in routing flexibleness and addition in figure of palettes is non ever good. There is a suited flexibleness and palette degree, beyond which system public presentation deteriorates, as judged by the make-span step of public presentation. It is observed in all the experiments that increasing the figure of palettes beyond 60 or 66 lead to the blocking of the system. For different degrees of routing flexibleness, the system blocks, when the figure of palettes is increased beyond 60 or 66, as the instance may be. The scope of palettes for all the degree of routing flexibleness, at which the system performs satisfactorily is 6 to 60 or 6 to 66. Hence we conclude from the experiments, that simply increasing the figure of palettes in the system does non needfully better public presentation. We have besides observed that the maximal decrease in MST occurs when the degree of routing flexibleness is increased from 0 to 1. There after addition in routing flexibleness proves to be undistinguished. Besides there is some impact of control scheme on the system public presentation. Besides there is impact of hold clip for storage and retrieval of parts from the CB. We observe that the system performs satisfactorily even in the presence of hold clip at all the degree of routing flexibleness. There is uninterrupted decrease in MST with addition in routing flexibleness at a fixed degree of hold clip. When routing flexibleness is further increased, the variableness in MST due to detain clip reduces. This is due to the fact, that at higher degrees of routing flexibleness, fewer parts are moved to CB, therefore less impact of hold clip. Different control regulations perform otherwise at different degree of routing flexibleness and hold clip. Relative public presentation of all the control regulations is influenced by the hold clip that is incurred in hive awaying and recovering the parts in CB. Hence, it is necessary to make up one’s mind the best design, and control schemes to acquire maximal benefit out of the proposed constellation of the system.
