Khalandar S

For tracking the delivery time of each order in Domino's, it is recommended to use Z MR chart to check the process stability. For better Understanding, let’s have a quick look on the I MR & Z MR charts.
 
 I MR Chart:
When you have Single run process (Ex: Mass Production, High Volume - Low Mix Manufacturing process etc.)
When you have good amount of data and more than 25 Data points
Its suitable for long run process
 Z MR Chart:
When you have different runs in a Process (Ex: Batch production, E Commerce, Telecom Service, High Mix & low Volume etc.,)'
It is used for short run processes (Each run has its own process paraments - Process Mean & Standard deviation)
When you have limited data (Short run processes do not have good amount of data for the good estimation of Process parameters)
Like I_MR chart, Z_MR chart has 2 charts, namely Z chart & MR Chart.
 
In Z Chart, the distribution consists of Observation in X Axis & Standardized Individual Observations (Z values) in Y Axis (Standardized "Z' is nothing but the Z value of each run & the formula of Z = (X  - X bar)/ Std Deviation of each run). The above calculation leads to Z distribution, plots over Process mean (X bar=0) and Process standard deviation (Sigma=1)
 
On other hand, MR Chart consists Observation data points on X axis and Moving range of Z values on Y Axis. It monitors the variation between consecutive Standardized Individual Observations (Z Values) of the process which has different runs.
 
The control limits of Z Chart are Straight forward. The Process mean is O & control limits are -3 & 3 
 
The MR chart has always had UCL = 3.686 (D4*1.128) and LCL =0 and Average Moving Average (MR)= 1.128 because data are standardized in Z chart.
 
To plot the Z-MR chart in Minitab, Choose - Stat - Control Charts - Variable charts for Individual - Z MR chart

SMED technique is one of the powerful lean tools which is widely used for Reducing changeover within 10 min both in Manufacturing or non-manufacturing. It helps to enhance the available time of the machine thereby increase OEE significantly. The following are the key steps involved in SMED
 
1. Conduct video workshop( select & record the changeover time which is taking more time) - Conduct time study for at least 5 changeovers for accurate changeover data.
 
If Changeover time is taking product A to product B is X hrs. but the frequency is 2 times/ shift & Product B to Product C it is consuming X+ hrs. & frequency is 3 times/ week. It is better to select the former one(A to B)since the frequency of changeover is high compared to latter.
 
2.  Carry out video analysis to separate internal & external activities ) Internal activities are which to be carrying out when the machine is stopped & external activities are those which can be carried out when the machine is running. This helps to analyze the loss of productive time which is also termed as Loss analysis.
Some of the examples of internal activities are Removing old die & fixing new die, resetting machine parameters like speed, feed etc & some of the examples of external activities are preparation of jigs & fixtures ready with suitable product material, keeping ready tools &tackles to eliminate search & find( some ineffective therbligs during changeover)
 
3. Convert internal activities into External activities as much as possible through ECRS (Eliminate, combine, Rearrange & Simplify) analysis to reduce the internal setup time& thereby reduce the work while machine stoppage
 
4. Eliminate/ reduce internal setup time. By taking the support of updating technology, we can eliminate/ reduce internal setup time like reducing screw fixing by tool by wing nut etc. & eliminating manual conveyor adjustments by automated adjustable conveyors etc.)
 
5. Eliminate/ reduce external setup. Whatever the activities are performing while the machine is stopped, that should be reduced which indirectly effect in reducing internal setup time. Getting material during the changeover (even though short notice demand), 2 S practice( A place for everything & Everything in its place)  for every changeover.
 
6. Streamlining the activities by updating method instructions, providing awareness training on F1 culture followed by SMED workshop on new tool & tackles to each & every operators.
 
7. Carryout Cost-effective analysis to obtain actual benefits by eliminating changeover. For this, it is mandated to prepare Kaizen sheet for each & every improvement(both tangible & intangible) & it should be verified by CFT team( Maintenance, Quality & other related departments) & approved by plant head as well as Finance head. The kaizen sheets should be converted into OPL(one point lesson) & display at the machine for deskilling management. Visual controls can be useful to give an entire idea to operators/ supervisors about implemented kaizens.
 
Sometimes, it will require customer approval of every kaizen to see the impact of quality on the final product.
 
The three analysis namely Loss analysis, ECRS analysis & cost-benefit analysis are mandated & it gives you clear scope & target to fix future target to reduce changeover from SMED to OTED(One touch exchange of die-  reduction of changeover time by 100sec)