Reduction of inventory waiting time in machine component manufacturing unit by using lean tools

 

Sankaranarayanan. B¹*, Vijaya Kumar S²

¹Student, Department of Management and Commerce, M S Ramaiah University of Applied Sciences, Banglore, India

²Asst.Professor., Department of Management and Commerce, M S Ramaiah University of Applied Sciences, Banglore, India

 

ABSTRACT:

In current competitive world, manufacturing industries are gaining an advantage by constant elimination of Non-Value-Added activities in their process in order to increase productivity, reducing inventory waiting time, operating cost and lead time to meet a customer demand and satisfaction. Industries with higher inventory waiting time leads to lead time of a product. Work aimed for the individual project is Reducing an inventory waiting time of Tool Magazine Bracket for 10% by using lean tools.

In this study inventory waiting time of Tool Magazine Bracket (Product) was reduce by focusing on VMC machine. For reducing inventory waiting time, current process and it’s timing are measured to identify a problem using lean tools. These problem would be neglected or reduced in order to decrease total inventory waiting time. For resolving this project various tools, methods and methodology are used like Gemba visit, Value Stream Mapping, Single Minute Exchange of Die (SMED) and Standard Operating Procedure.

By drawing a current value stream mapping, the current job is measured and identified a processing time and inventory waiting time. SMED technique was used here to reduce a changeover time of VMC machine from 342Sec to 197Sec, by this inventory waiting time is reduced to 11.12%. With the reduction of inventory waiting time, lead time is also reduced by 4.08%.

 

 

 

1. INTRODUCTION:

Lean adoption in manufacturing unit will increase productivity by reducing a seven types of waste which are over production, defects, inventory, transportation, waiting, motion and over processing. These seven wastes are known as non-value added activity and it should be reduced in order to productivity and meet the customer demand on more efficient way.

 

The company that has taken for study is "M/s Nidhin Engineering Works" located at Banglore, Karnataka. The company runs its business for past 14 years. The current annual turnover of company is 1.7 crores. This company is purely based on job work by customers. The core activity of this company are plano milling, jig boring, machining  and scrapping. The major customers are BFW and Kenna metals. The company employees 18 people out of which 11 are skilled, 4 are semi skilled and 3 are unskilled labour.

 

2. AIM:

Reduction of inventory waiting time by 10% in a processing time of manufacturing tool magazine bracket

3. OBJECTIVE:

1.     To study and collect data on existing inventory waiting time  in a machine component manufacturing unit

2.     To identifying different problems with higher inventory waiting time

3.     To analyse and generate solution to reduce the inventory waiting time

4.     To validate and standardize the developed solution

 

4. LITERATURE REVIEW:

Vipulesh Shardeo (2015) Inventory generate a large cost of investment to the firm. This paper Investigated relationship between inventory turnover ratio and profitability of three companies M/STATA steel, M/S SAIL and M/S JSW steel by using pearson correlation. The data used in this paper are secondary data been collected from different sources like money control, journals and books. This shows a positive correlation for M/S. SAIL and M/S. JSW steels and Moderate correlation for TATA steels. By this analysis, he concluded that inventory turnover ratio is correlated with the net profit of the companies and companies need to adopt some inventory management practices to enhance their efficiency.

 

Anna Karwasz Przemyslaw Chabowski (2016) This paper focus on reducing a changeover time of machine which produce non-ferrous metals and steel which involve chemical and mechanical action. SMED technique is used in order to reduce changeover time. Internal and external activities are categorized so that it is easy to change internal activities to external activities. This shows that total changeover time is about 148min. The major part of changeover time is due to a installation of tool in tool candy. Tools on a tables are not organized properly which also leads to increase changeover time. By implementing Kanban and 5S changeover time is reduced by 50%. Reduction in changeover time will simultaneously increase productivity.

 

Praveen saraswat., Deepak kumar (2015) Value stream mapping shows a activities on production line from initial supply of raw material to final product. This technique shows all processing step in single diagram. This is used to observe a waste on different step and can be eliminated. By collecting a respective data from company, current state of value stream mapping been drawn and calculated the tack time. A new value stream mapping is drawn by neglecting some waste which reduces a total lead time and production lead time by 3.5 days and 65Sec respectively.

 

K.Eswaramurthi,  P.V.Mohanram (2014) The main focus of this case study is to classify value and non-value added activities for a process of inspection in manufacturing industries. The process involves moving a product from production line to inspection cell for quality check and again moving to production line for further process. By identifying NVA activities in this process transportation time is drastically reduced. Total inspection time is reduced by 30% and NVA activities are reduced by 77% which of 137 min to 32min.

 

Santosh B. Dighe, Abhay Kakirde (2014) This paper focused on reducing a lead time specific product family. To identify a specific product pareto chart is used based on sales. For this value stream mapping is used to measure a activities of current job. By analyzing current state map problems are identified with respect to product changeover time, cycle time and inventory which leads increase a product lead time. By implementing supermarket racking system and single piece flow model lead time is reduced from 54 days to 36.5 days.

 

5. METHODS AND METHODOLOGY:

Current Value Stream Mapping:

The current manufacturing process of tool magazine bracket and its efficiency was analyzed by the value stream mapping. Based on the process observation value stream mapping is prepared. By current VSM processing time, Lead time and Inventory waiting time are identified. Process of tool magazine bracket involves 3 skilled labour for fabrication, VMC machining and Inspection, where grinding and painting are carried out by unskilled labour. Current VSM of tool magazine was done for a single batch of 39 units.

 

 

Fig. 1: Current value stream mapping for tool magazine bracket

Lean metrics:

Table 1: Overall metrics for manufacturing tool magazine bracket

Metrics	Time taken
Processing lead time	4720 Min
Total cycle time	3900 Min
Total change over time	344 Min
Inventory waiting time	820 Min

 

The bottleneck activities:

·       Higher change over time in VMC machining

·       Higher inventory waiting time between grinding and VMC machining due to higher processing time of VMC machining.

 

Reduction of inventory waiting time is depend on change over time of VMC machine. If change over time of VMC machine is reduced then total inventory waiting is also reduced. Single Minute Exchange of Die (SMED) is used reduce change over time, with reduction of change over time production time is also increased.

 

Single Minute Exchange of Die:

SMED is a technique which dramatically reduce a time taken to complete changeover time by eliminating waste. The major focus of SMED is to convert internal activity (activities which are take place while machine are in stop condition) to external activity (activities which are take place while machine are in operating condition) or reduce a time taken for internal activity so that total change over time will be eventually reduced. All current change over activities of VMC machine was done as internal activities.

 

Improvement actions:

Combining of unskilled labour with VMC operator:

For reducing a changeover time, a unskilled labour is assigned to work from step-4 to step-11. Here unskilled labour should be trained to remove and tightening a bolts and clamps while replacing a product. There is no need of recruiting a new unskilled labour to company, because in current manufacturing process of tool magazine bracket grinding and painting are take place by unskilled labour and those activities have very less cycle time and which does not increase a total processing time or lead time. By adding a unskilled labour changeover time is reduced to 128 seconds.

 

Table 2: Current change over process for VMC machine

S.No	Activity/Process	Time Taken Before SMED	Initial Situation
1	Opening a door	4 Sec	Internal
2	Removing a scrap material in a driller and over a product	15 Sec	Internal
3	Cleaning a product with air blower gun	9 Sec	Internal
4	Opening a nut and bolt to remove a product	82 Sec	Internal
5	Again cleaning a product with air blower gun	12 Sec	Internal
6	Removing a lubricant which are stuck inside a product	14 Sec	Internal
7	Replacing a product with another product (helper)	36 Sec	Internal
8	Tighten a nut and bolt to fit a product in machine	139 Sec	Internal
9	Checking whether all bolts are tight enough	15Sec	Internal
10	Cleaning the inside portion of glass door for proper visibility of process	9 Sec	Internal
11	Closing a door to start next process	7 Sec	internal
Total		342 Sec

 

Reduction of Internal time:

In step7 (I.e) replacing a product with another product, there is small changes in steps which leads to reduce a 17sec in changeover time. In initial stage replacing a product takes 8m of travel (i.e) once the VMC machining process is finished, the finished product from VMC should be move to semi finished area which takes 3m of travel and grinded product will be placed in VMC machine, this activity takes a travel of 5m. These all activity are occurred as internal activity.

 

Table. 3: Change over  process and its timing after improved actions

Steps	Internal Activity	Time taken before  SMED	Steps taken for reduction	Time taken after SMED
1	Opening the door of VMC Machine	4sec	-	4sec
2	Removing  scrap material in the  driller and over the  product	15sec	-	15sec
3	Cleaning the  product with air blower gun	9sec	-	9sec
4	Opening a nut and bolt to remove a product	82sec	Adding additional unskilled labor with  operator	41sec
5	Again cleaning a product with air blower gun	12sec	_	12sec
6	Removing a lubricant which are stuck insider a product	14sec	Adding additional helper to operator	7sec
7	Replacing a product with another product (helper)	36sec	Layout change	19sec
8	Tighten a nut and bolt to fit a product in machine	139sec	Adding additional helper to operator	70sec
9	Checking whether all bolts are tight enough	15sec	Adding additional helper to operator	8sec
10	Cleaning the inside portion of glass door for proper visibility of process	9sec	Adding additional helper to operator	5sec
11	Closing a door to start next process	7sec	-	7sec
	Total	342sec		197sec
	Total time reduced	145 Sec

 

 

Fig. 2: Internal motion distance before and after SMED

 

Once a VMC machine is start to processing, operator and helper should carry a grinded product near to VMC machine which will reduces internal motion distance from 5m to 1m. The finished product from VMC should keep near to VMC machine instead of semi finished area. once a VMC machine starts VMC product should be move to semi finished area which will reduce internal motion distance from 3m to 1m. By this changes total internal motion distance is reduced from 8m to 2m which leads to reduce a changeover time by 17Sec.

Impact of SMED implementation:

By implementing a SMED in changeover time of VMC machine provide a good reduction of change over time. The change over time was reduced from 222.15 Min to 128.05 Min.  Due to the reduction of changeover time waiting time and processing time is also gradually reduced.

 

Future state value stream mapping:

With the current state map it is observed and analysed some major problem for high waiting time of inventory between the processes. It is observed that major waiting time is cause due to VMC machine and hence SMED technique is used to reduce a changeover time of VMC machine and it eventually reduces a waiting time. Red star represents reduction changes comparing with current state map.

 

 

 

Fig. 3:  Future State Map for Tool Magazine Bracket

 

Table 4: Time Line Comparison

Time Reduction (min)			Reduction Rate
Metrics	Current State Map	Future State Map	Minutes	Percentage
Inventory waiting time	820 Min	723.29 Min	96.1 Min	11.71%
C/O of VMC Machine	223 Min	126.9 Min	96.1 Min	43.09 %
Processing lead time	4798 Min	4605.8 Min	96.1 Min	4.08%
TAKT time	130.257 Min	123.70 Min	4.93 Min	4.08%

 

 

Fig. 4: Comparison of inventory waiting time

 

 

Fig. 5: Compression of changeover time of VMC machine

 

6. COST BENIFIT ANALYSIS:

To reduce the inventory waiting time, changeover time of VMC machine is analysed and reduced. For this there is no additional resource are added. Only current procedure of changeover activities are been changed. By reducing inventory waiting time by 11.07%, productivity time of VMC machine while manufacturing tool magazine bracket is gained by 4.55%

 

Table. 5: Economic impact of inventory waiting time reduction in productivity:

Average initial change over time	342Sec
Average final change over time	197Sec
Gain per Change over time	145Sec
Average No of daily change over	12units
production time gain per day	29Min
Working days per month	25Days
Production time gains per month	725Min
Production time gains per month	12.09Hr
Cost per hour of the VMC machine	Rs 860
Total cost for gained production time per month	Rs 10,337.2
Total labor cost gained per month	620Rs

 

Total cost gained per month   =  Gained production cost + Gained labour cost

                                                 =  10,337.2 + 620

                                                 =  10,957.2Rs

 

7. CONCLUSION:

This thesis shows that the SMED technique could be effectively applied to reduce changeover and setup time. With the combination of  using Lean tool (Value Stream Mapping) this method was highly useful to understand a process and identifying of wastes in lead time. Reduction in change over time will results in increasing of productivity. Systematic changeover will eradicate a waste and increase processing time in workstation. For the technique of SMED implementation employees should be trained and informed about the cause of changes and motivate them to do the systemize work with more accurately and efficiently. 

 

 

The major goal of this thesis is to reduce a waiting time by 10% in processing time of manufacturing tool magazine bracket. The higher waiting time is occurring due to the changeover time of VMC machine. With the implementation of SMED it is expected to reduce 11% percent of total waiting time which leads to reduce a processing time and lead time of tool magazine bracket, that reflects a potential raise in productivity of VMC machine for 12hrs per month due to the reduction of waiting time of 10%.

 

8. SCOPE FOR FUTURE WORK:

Current approach of reducing inventory waiting time and benefits in productivity are applicable for production of tool magazine product. The current process for tool magazine bracket is same for other four product spindle motor MTG Bracket, TC24 MAG MTG Bracket, TC25 MAG MTG Bracket and compound slide bracket. The current approach of tool magazine bracket can be applied to other four products in order to reduce inventory waiting time and increase productivity.

 

9. REFERENCES:

1.      Anna karwasz., Przemyslaw Chabowisi. Productivity Increase Through Reduced Changeover Time. Journal of Machine Engineerin. 2016; Vol. 1: No. 2: pp. 61-70.

2.      Praveen Saraswat, Deepak Kumar, Manoj Kumar Sain. Reduction of Work in Process Inventory and Production Lead Time in a Bearing Industry using Value Stream Mapping Tool.International Journal of Managing Value and Supply Chains. 2015; Vol. 6: No. 2: pp. 27-35.

3.      Santosh Dighe B, Abhay Kakirde G. Lean Manufacturing Implementation Using Value Stream Mapping: A Case study of Pumps Manufacturing Company. International Journal of Science and Research. 2014; Vol. 3: pp. 2492-2498.

4.      Eswaramurthi K, Mohanram P V. Value And Non- Value Added (VA / NVA) Activities Analysis Of A Inspection Process – A Case Study. International Journal of Engineering Research & Technology (IJERT). 2015; Vol. 2: pp. 1-5.

5.      Vipulesh Shardeo. Impact of Inventory Management on the Financial Performance of the firm. Journal of Business and Management. 2015; Vol.1: pp. 01-12.

 

 

 

Received on 22.08.2019            Modified on 21.09.2019

Accepted on 15.10.2019           ©A&V Publications All right reserved