Maritime University of Szczecin
Akademia Morska w Szczecinie
2010, 24(96) pp. 41–47 2010, 24(96) s. 41–47
Implementation of Total Productive Maintenance – TPM
in an enterprise
Wdrażanie TPM (Kompleksowe Utrzymanie Maszyn)
w przedsiębiorstwie
Edward Michlowicz, Bolesław Karwat
University of Science and Technology, Department of Production Systems Akademia Górniczo-Hutnicza, Katedra Systemów Wytwarzania
30-059 Kraków, al. Mickiewicza 30, e-mail: michlowi@agh.edu.pl, karwat@agh.edu.pl
Key words: lean management, methods to improve, quality indicators Abstract
Most of modern companies implement to the management principles known as “lean”. One of the methods proposed by Lean Management is a TPM (Total Productive Maintenance). There are applications of this method in relation to production systems. TPM can also be used to improve the quality of internal transport systems. The article presents the basic principles of TPM used in the method, as well as its use in stock products ready for distribution and in division of the car wipers.
Słowa kluczowe: szczupłe zarządzanie, metody poprawy, wskaźniki jakości Abstrakt
Większość nowoczesnych przedsiębiorstw wprowadza do zarządzania zasady znane jako chude, wyszczuplo-ne (lean). Jedną z metod proponowanych przez Lean Management jest Kompleksowe Utrzymanie Maszyn – TPM. Znane są aplikacje tej metody w odniesieniu do systemów produkcyjnych. TPM można także wyko-rzystać do poprawy jakości działania systemów transportu wewnętrznego. W artykule przedstawiono podej-ście stosowane w metodzie TPM. Wskazano możliwości jej wykorzystania w magazynie wyrobów FMCG przygotowanych do dystrybucji i w dziale produkcji wycieraczek samochodowych.
The essence of the TPM method
The continuous search of methods improving effects of carried out activity has been characteristic feature for enterprise management in recent years. Currently the following ways are recommended more and more often: lean approach and lean thinking as a countermeasure to eliminate wastage (muda) by creating value stream in an enterprise [1]. The essence of lean approach is transformation of wastage (muda) into a value, thus determination of value is the first step during lean approach implementation.
The basic tool of lean management is:
• VSM – Value Stream Mapping – which involves analysis of all actions at production stage, or other process (e.g. transport) and its environment [2],
whereas, tools supporting the lean concept include: • The Five Pillars Method – 5S – work organisa-tion method for all processes, which involves increasing quality and productivity by eliminating losses resulting from lack of order at a workplace. As a rule, enterprises implementing lean manage-ment start the process from implemanage-menting the 5S [3].
The five pillars are:
Pillar 1. Sorting (Seri) – removing from work area all objects unnecessary for current actions.
Pillar 2. Straightening / Setting in order (Seiton) – arranging all objects necessary to operate to facili-tate their use.
Pillar 3. Sweeping (Seiso) – workplace tidying up, cleaning.
Pillar 4. Standardising, Neatness (Seiketsu) – method employed to adhere to the first three pillars; good organisation of one’s own workplace.
Pillar 5. Sustaining the discipline (Shitsuke) – maintaining the custom of continuous observance of proper procedures.
• SMED method – that is Single Minute Exchange of Die.
These are actions aimed to reduce time required for die exchange in equipment (where it is possible) to number of minutes expressed by a single digit, that is less than 10 minutes. In production systems die exchange includes all actions required to carry out product type change at a given machine, line or device. For this purpose, the so-called external ex-change of die is introduced, which includes opera-tions carried out beyond the machine, and inside exchange of die that covers operations carried out while the machine is halted. Whereas, in internal transport processes, especially in distribution ware-houses, the SMED separates logistic process into two parts: external and internal operations. The logistic process runs in the following stages: order acceptance, selection of proper transport
facilities and route (external operation),
preparation of transport documents (external operation),
preparation of shipping units, e.g. in pallets – according to documentation (external operation), embarkation/loading (internal operation). • The 5W and 1H Method (5 why and 1 how) involving repetition of a specific question why? five times. The first question concerns the cause of fai-lure (or an incident). Next questions are asked to elaborate on responses and to get to know the rea-son of the ensuing problem more thoroughly. After five questions why it is possible to answer how to solve the ensuing problem (how?).
• The Pareto principle,
also called the 80/20 rule because it assumes that 80% of results come from 20% of reasons. Carried out observations, and collection and analysis of results allow to get relationships used to improve the impact of adverse reasons on specific action results.
• TPM Method – Total Productive Maintenance. The purpose of the TPM is to strive after main-taining continuous work of devices and machines executing specific tasks, which at the same time shows improvement of their functioning effective-ness. Until recently, the TPM was used mainly in production and repair processes. Currently, it is also
used in internal transport departments. The method is based on using human resources to analyse reasons for wastage and losses (muda) occurring in processes. Moreover, it requires systemic solving of problems constituting the reasons for machinery and equipment downtime [4].
Basic objectives for implementing the TPM method are:
reduction in the number of equipment failures, acceleration of repair time (restoration of good
working order) for a device or line, elimination of micro-downtime, losses reduction.
Indexes allowing to analyse losses, used in the TPM method
The TPM method most often uses three indexes: MTTR, MTBF, and the most characteristic – OEE.
MTTR (Mean Time to Repair) is an index speci-fying mean time needed to carry out a repair of device (line equipment).
repairs of number repairs of durations MTTR
(1)MTBF (Mean Time Between Failures) is an index specifying mean time separating occurrence of two failures or micro-downtimes.
s occurrence operation correct of number operation correct of durations MTBF
(2)The OEE (Overall Equipment Effectiveness) index is the primary measure for the TPM imple-mentation effects. The OEE is either overall equip-ment effectiveness or general equipequip-ment efficiency (machines, devices). This index shows what percent value of theoretically obtainable efficiency is cha-racteristic for an examined device or line.
The TPM identifies 6 main losses (in three sub-groups):
• Time losses (availability): 1. Losses due to failure.
2. Losses for exchanges of die and adjustments. • Efficiency losses (efficiency):
3. Losses for dead time and micro-downtime. 4. Losses due to process speed drop.
• Losses due to defects (quality):
5. Losses due to occurrence of rejects and cor-rections.
6. Start-up losses.
Figure 1 presents a diagram showing compo-nents that allow to practically determine
effective-ness (efficiency) evaluation index for machine or line used to carry out specific process.
Fig. 1. Components of the OEE index (own work as per [4]) Rys. 1. Składniki wskaźnika OEE (oprac. własne wg [4])
The OEE index is most often computed using simple formula:
OEE effectiveness index =
= availability efficiency quality 100 [%]
OEE = D W J 100 [%] (3)
where: D – availability: practical availability, avail-ability ratio; W – efficiency: efficiency of perfor-mance, efficiency ratio; J – quality: quality factor.
Using description provided in figure 1, indivi-dual product factors may be determined as follows:
time) (possessed time operating net stops) planned time operating (net time work 1 2 D D D (4) production target production real 1 2 W W W (5) production real products) good of (number production good 1 2 J J J (6) Analysis of losses initiates the whole process in-volving introduction of modifications. The analysis provides grounds to identify the problem and assess the impact of individual components (D, W, J) on tested object functioning. Data concerning losses is
used to determine operation priorities and to estab-lish plan of actions.
Implementation of the TPM method in production company transport department
The implementation of the TPM method in one of the FMCG sector plants required complex approach to the company activity. Thus, specific TPM structure was accepted, consisting of eight pillars (8 Units), including:
1. Planned repair management pillar – PM. 2. Quality improvement pillar – PQ. 3. Training and education pillar – T&E. 4. Lean flow pillar – LF.
The LF (Lean Flow) pillar was established in company Logistics Department in order to reach lean flow of materials in delivery chain. The pillar consisted of units facilitating activities and mini-mising main losses (7 Muda) in flow of materials since ordering until finished product delivery to consumer – the TPM units from the areas of plan-ning, supply, storage, and transport.
Transport Department (DT) belongs to company logistic structure and its task is to organise product transport from Finished Product Store (MWG) to external consumers. The transport service is outsourced to a freight forwarding company. For-warding is responsible for the whole process of organising operations involving the selection of an appropriate transport facility, carriage and product delivery according to the documentation.
Carrier is the entity responsible for delivering transport service according to waybill issued by Transport Department. The waybill is the document confirming acceptance of goods by carrier for transport. As soon as the delivery process to desig-nated buyer is complete, the waybill becomes the basis for making payment for the service.
Selected results of the TPM unit operations – transport
The historical data analysis allowed to state that mean time of no cars for embarkation for 3-month period (January through March 2009) was 204 minutes per day (MTTR – mean for two embar-kation changes). During that period 2409 cars were loaded, and Finished Product Store (MWG) ob-served 557 rests resulting from the fact that no cars were present. Thus, the main objective of the unit was to reduce that time to 160 minutes. The second objective was to analyse reasons of no cars for embarkation. The first stage of TPM implementa-tion, analysis of results, introduction of innovations Total (operating) time of work
Net (operating) time of work Work time
Target production (valuably) Real production Real production Good production Planned down-times Shut-down losses Speed losses Reject losses D1 D2 W1 W2 J1 J2 D – A va ila bi lit y W – Ef fi ci en cy J – Q ua lit y
and unit work effects, covered the period from July to November 2009.
The operations were started by implementing the Five Pillars 5S (therefore, much the same as in most companies).
Results of these operations included:
• accurate determination of outline for individual positions (lines on the floor);
• setting out passage road, pedestrian crossing and passage across vehicle circulation area;
• placing information boards concerning driver’s operations at individual positions;
• placing road signs informing about traffic or-ganisation within vehicle circulation area – with priority for forklift trucks.
The method of 5W and 1H questions was em-ployed to analyse primary causes (no car). Table 1 presents examples for using the method.
The reasons for rest in embarkations were ana-lysed using the Pareto principle. The analyses al-lowed to establish the main reason for rests in em-barkations, constituting 80% of all cases of this type.
Table 2 shows example results obtained before implementing modifications. They prove that the main reason for rests in embarkations was faulty planning of embarkation time by dispatchers (over 80% of all cases).
Table 2. The quantities of the rest in embarkations according to DT data (for 3 months)
Tabela 2. Ilości przerw w załadunkach wg danych DT (za 3 miesiące)
Item Reason for rest Quantity of rests Share [%] 1 Improper planning – by dispatcher 458 82.23 2 Driver’s late arrival (to the store) 51 9.15
3 System breakdown 25 4.49
4 No products for embarkation 23 4.13
Total: 557 100.00
Table 3 presents results of corrective actions that involve planning system change. Faulty dispatcher’s planning dropped from 80% to less than 2%. Late arrivals of drivers proved to be the main reason of rests after modifications (over 80%). Thus, further actions were aimed to reduce this loss.
Table 3. The quantities of the rest in embarkations after changes
Tabela 3. Ilości przerw w załadunkach po zmianach
Item Reason for rest Quantity of rests Share [%] 1 Improper planning – by dispatcher 1 1.92 2 Driver’s late arrival (to the store) 42 80.77
3 System breakdown 4 7.69
4 No products for embarkation 5 9.62
Total: 52 100.00
In order to assess effectiveness of all introduced changes, the TPM Unit applied indexes used at all plants of the FMCG manufacturer’s group (possi-bility to compare). These are:
1. Internal transport productivity index (W – effi-ciency).
2. Index representing duration of car stay within a plant (D – availability).
3. Index showing promptness of deliveries to a client (J – quality).
Figure 2 presents an example diagram of pro-ductivity change. All results obtained during TPM implementation are shown in form of tables and charts.
Internal transport productivity index (W)
The number of pallets with goods loaded in a car during one hour was taken as the measure of inter-nal transport productivity. Chart shown in figure 2 shows that the assumed productivity plan has not been reached. The plan provided for loading 26
Table 1. Examples of the use of method 5W and 1H – no car
Tabela 1. Przykładowe wykorzystanie metody 5W i 1H – brak samochodu
Potential reasons – why Measures taken – how
Why (1) Why (2) Why (3) Why (4) Why (5) Preventive measures Corrective measures driver has not
accepted an order because he/she is unreliable – – – independent rea-sons; no further questions none faulty trans-port company planning
few orders for short courses during one day
aiming at max. car use no means of transport; all “en route”
unpredictable dates for bringing means of trans-port for embarkation
correction of contracts with forwarding imposing disci-pline on drivers and forwarding
pallets per one hour of operator’s work on average, and in fact 23 pallets per hour were reached.
W = 23/26 = 0.885
Index representing duration of car stay within a plant (D)
The duration of the car stay within a plant (spe-cified in minutes) was calculated as the difference between the instants of vehicle arrival to the plant and its departure from the plant. Mean time for 2009 was 49 minutes – less than planned 50 mi-nutes.
D = 49/50 = 0.980
Index showing promptness of deliveries to a consumer (J)
The index showing promptness of deliveries to a consumer is a percent measure for punctuality of merchandise delivery to a client. It was calculated as the quotient of prompt deliveries and the number of all shipments per month. Result obtained for 2009 reached 99.5% of prompt deliveries, exceed-ing planned 99%.
J = 99/99.5 = 0.995
And thus Overall Equipment Effectiveness (OEE) is:
OEE = W D J = 0.863100% = 86.3% It is worth observing that productivity index improvement from 23 pallets/hour to 25 pallets / hour will result in W index value change from W = 0.885 to W = 25/26 = 0.962, which will also improve overall index OEE from OEE = 86.3 % to OEE = 93.8 %.
Implementation of the TPM method in windscreen wiper production department
Assembly line for windscreen wiper mecha-nisms is the object in which the TPM has been implemented. It consists of three stations. The first one is press that crimps pipes with articulated joints and couplers. The second station allows to install sleeves with absorbing rings, which are used to mount mechanism in a car, and then the motor is screwed down. Final mechanism assembly is car-ried out at the third station. This process involves 0,0 5,0 10,0 15,0 20,0 25,0 30,0 35,0 on average Months P all ets / ho ur
Plan Implementation Linear plan I II III IV V VI VII VIII IX X XI XII
Fig. 2. Productivity of internal transport Rys. 2. Produktywność transportu wewnętrznego
0 50 100 150 200 250 300 49 50 51 52 1 2 3 4 5 6 7 8 Week number S um o f bre ak do wn s [m in ] L11 Production unit Fig. 3. Comparison of failure times for line L11 and the production unit Rys. 3. Porównanie czasów awarii linii L11 i jednostki produkcyjnej
fixing articulated joint arms to the motor with cou-plers, and fitting gaskets in each of these joints. Each of the stations has exchangeable tooling that allows to carry out production of 12 different mechanisms in the line.
The discussed line (marked L11) used to be among few most frequently breaking down lines in the plant (out of tens of lines operated in the plant). The difference in total breakdown duration between line L11 and average for production unit, in which considerable portion of lines was characterised by much the same complexity level, was almost threefold. Additionally, among operators it had the opinion of most troublesome, causing minor problems including: locking, stops during cycle, or releasing products requiring corrections.
Figure 3 presents diagrams of changes in line L11 breakdown durations and mean breakdown time for all other lines during 12 weeks of operation (data from base contained in SAP).
Selected results of the TPM unit activities
The unit had the following objectives:
change of the MTBF value for correct operation between breakdowns from 8 minutes up to 40 minutes,
reduction of the MTTR index value for total line L11 downtime duration during a week from 200 minutes down to 100 minutes.
The first stage of works involved implementing the 5S and SMED methods. Examples of imple-mented improvements – Five Pillars 5S:
1. Preparation of line cleaning instructions accord-ing to the data from sheets prepared duraccord-ing thor-ough cleanup.
2. Change and update of instructions for preventive inspections in order to increase their effective-ness and reduce time required to carry them out. 3. Marking of lubricating points on the machine
using appropriate pictograms.
4. Making of new description plates for control pushbuttons in Polish.
5. Providing operators with sets of basic tools al-lowing efficient carrying out of exchange of die and adjustment.
Next steps involved looking for the reasons of micro-downtimes and breakdowns. Pareto diagrams were used to analyse the reasons.
Figure 4 presents diagram of changes in the MTTR index for line L11 while carrying out works involving improvement of production and assembly processes. Similar relationships, also tabulated, were developed for the MTBF index.
Summary
Effects of work for both units are both economic and mental in nature. They change thinking and engagement of each employee in the process of plant functioning improvement.
The objective of transport unit, that is reduction of rest time during embarkation, has been achieved. After having introduced corrective measures, in final month of changes the time reached 123 minu-tes compared to 160 minuminu-tes set by the unit as the target value. Comparing this time to the value of 204 minutes before introducing changes, the team efforts shall be deemed considerable success.
In case of production unit, both assumed objec-tives were achieved, however in each case dif-ferently. As a result of systematic elimination of breakdown sources, MTTR – total downtime for
0 50 100 150 200 250 300 49 50 51 52 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Number of week S um o f bre ak do wn s [m in ]
Fig. 4. Chart showing duration of failures in individual weeks after changes Rys. 4. Wykres czasu trwania awarii w poszczególnych tygodniach po zmianach
line L11, was gradually decreasing almost from the beginning of implementation process, to reach less than 50 minutes after 26 weeks – much less than assumed 100 minutes. In case of eliminating micro-downtimes significantly affecting the MTBF, effects were invisible at initial stage. This was due to the fact that, in contrary to breakdown sources, the reasons for micro-downtimes proved to be not easy to identify. In order to determine them it was necessary to analyse the details of line L11 func-tioning, and production and assembly. In connec-tion with that few problems were examined at the same time and their solutions coincided in time and gave synergic increase of mean work time between downtimes. As a result, after 21 weeks the MTBF index increased from 8 minutes up to 80 minutes, thus exceeding twice the assumed value of 40 mi-nutes.
Results achieved in both discussed examples are very optimistic. They prove high versatility of the TPM method, which may be successfully used both in production and assembly processes, and in inter-nal transport processes.
References
1. WOMACK J.P., JONES D.T.: Lean Thinking. Published by ProdPress.com, Wrocław 2009.
2. ROTHER M.,SHOOK J. (translated by Koch T.): Learn to See. Wrocław Technology Transfer Centre, Politechnika Wrocławska (Wrocław University of Technology), Wrocław 2003.
3. KORNICKI L., KUBIK SZ.: 5S for Operators. 5 Pillars of Workplace Visualisation. Published by ProdPress.com, Wrocław 2008.
4. KORNICKI L., KUBIK SZ.: OEE for Operators. Overall
Equipment Effectiveness. Published by ProdPress.com, Wrocław 2009.
Work financed from resources of the NN504 407 235 research project
Recenzent: dr hab. inż. Zofia Jóźwiak, prof. AM Akademia Morska w Szczecinie
