Why Not Chase the Rabbit?

This is a question I have most often heard from European engineers, or from people in other countries who are working with extremely high volume light assembly operations, usually following some teaching about just in time production or Standard Work:

I don’t like the rabbit chase system at all. I would rather have people try the rabbit system, as well as Standard Work in u-cells or straight lines, whichever made sense, and compare the results. But if asked, I will explain that the rabbit chase does not seem Lean to me at all.

The rabbit chase system, first of all, involves each worker doing all operations in a cell from beginning to end, “chasing” each other around and around as they work in the same cell. I don’t know where the “rabbit” piece comes from.

The advantages stated for the rabbit chase are that it is easy to add or subtract people from the line to increase output, and that you do not need to balance the line because people self-balance as they develop a pace. In addition, each person could gain a sense of satisfaction from learning how to operate each process.

One of the main reasons that I have seen the rabbit chase performed is that the line speed or takt time for that cell is much too fast to do anything other than race to keep up. In some cases there would be more time waste in hand-offs and than in actual value added work done. But in these cases the design of the equipment and the pacing of work itself needs to be reconsidered, and slowed down through duplication of cells and low cost equipment.

The hand-off approach that is the typical flow line or u-cell involves balancing cycle time between workers, and a clear definition of work sequence. Some raise the issue of timing of the hand-off but this is a non-issue if you allow one piece of Standard WIP.

In the rabbit chase full training needs to be done for entire process for each person, which is a good thing if you can do it, but more practically the u-cell allows you to cross train step by step.

In the rabbit chase each person must check their own quality, or perhaps rely on an end-of-line inspection, while in Standard Work the quality is built-in through in-process checks by the person doing the work as well as verification and feedback by the downstream person upon hand-off.

In the case of the rabbit chase it would seem like there is the possibility of interference between one person and the next, if the speed difference between workers stacked up over time.
Standard Work forces you to document a repeatable work sequence for each person that is based on takt time and while this is not always easy, it is an important discipline and the foundation of kaizen through the removal of variations in cycle time, making the work easier, low cost automation, etc.

No doubt I am understating the benefits of the rabbit chase system, since I have undone far more of them than I have implemented. Feel free to comment in defense of the rabbit chase, as I could use the education.

Whichever way you prefer, do an experiment to try it the other way. If you don’t like the results keep trying until you get the results you need. Just don’t say “I told you it wouldn’t work” and revert back to today’s proven method, which you need to think of as the “worst ever”. That’s kaizen way.

Ron
January 18, 2007 - 6:49 am
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Hi Jon, to me the biggest advantage to properly designed u shaped cells is the pacing factor. One operator is able to work the entrance and exit of the cell which is an excellent pacing mechanism. Rabbit chasing is great for designing the cell though since a cell should be created such that one person can easily do all steps sequentially. But then once this is done the rabbits must leave! Just my two cents.
Thomas
January 18, 2007 - 12:41 pm
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Jon,
I don’t see the two approaches as opposed to each other, quite the contrary actually. I have implemented various “rabbit” lines when working for a (yes, european…) automotive supplier, all with a 45-60s takt. Here is how we overcame most of the issues you mention, except maybe cycle time variation which was not always easy to spot:
First example: A 5 or 6 station U-shape of low cost machinery (spot welding, rivetting, manual assembly and functional check), manned with 2 or 3 workers according to takt–this ratio is crucial to avoid interference. All stations included extensive poka-yoke, SMED, manual load and automatic unload. When the workers arrived at a given station, they’d find the previous operator’s part unloaded (when OK) or blocked (NOK) and would either load the station with fresh parts, start the process and carry the previous OK part with them to the next station–or pull the cord. Standard WIP = 1. Changeover was performed by a team leader who entered the cell between two workers and followed them from station to station while changing the fixtures in less than historic minimum takt, so the line didn’t even have to stop.
Second example: Low cost O-shaped moving lines with 5 to 7 pallets with some 7ft between workers, extensive integrated poka-yokes and one off-line functional check station, and flow racks from the outside. One lap corresponds to one assembly cycle, line speed and/or number of workers vary according to takt. Every worker assembles one complete process. Standard WIP = 0.
Both systems used standard work (although it went by a different name), enforced a repeatable work sequence, were based on takt–and worked best when each worker performed a full cycle. We tried both ways.
Jon Miller
January 18, 2007 - 10:52 pm
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Thanks Thomas. You tried both ways. That’s great. Why did you find one method better than the other?
Thomas
January 22, 2007 - 11:36 am
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Jon,
In the first example we encountered a serious balancing problem when operating the line with the number of operators necessary most of the time (product specific issue). In the second example we planned like this from the start, the operators (some of them came from the first example line) initially were reluctant because of “the endless miles we’ll have to walk”. They wanted to try it the other way and finally liked “full circle” better, mainly for ergonomic reasons. HTH.
Jorge Luis Angeles
November 20, 2008 - 3:33 pm
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Jon,
I’ve been working with “Rabbit Chase” System (Cell in Motion) for 8 years, and I’m absolutely convinced that is a powerful system.
I discovered the system being Production Supervisor and I profited a lot of it.
I have done some applications in a French Automotive company in Europe and Mexico. Since 6 months I’m deploying the concept in an American Electrical company in Mexico with great results (100% Lean).
Here you are some benefits that I found:
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+ Avoiding impact of repeatable operations (vg. on the hands or arms).
+ Better blood circulation on the body (Compared with stand up or seated -especially women are facing problems on the legs-).
+ The “value” of operators is clearer, because they are building a complete product (100% of flexibility), “stronger” operators.
+ Team work becomes natural due to good communications in case of troubles.
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+ Auto-Quality: each operator is responsible for quality of complete product, if a quality problem appears during the process; each one is responsible for that!
+ Stopping the line at first defect and everybody is immediately concerned and looking for solution (Quick response).
+ Avoiding impact of variability on the process, because each operator is performing always the same job, no matter the quantity of operators on the line.
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+ One-Piece-Flow at 100%
+ Changeover activities are deployed in team (Is the only way!).
+ Adaptability 100% to Takt Time (From 1 operator on the line, to the maximum defined).
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+ With operator fixed; the peace is given by the bottle neck (any improvement on other workstations is useless, no impact on the rate), operators are waiting or doing over-production. With Cell in Motion; the pace is given by the operators according to the standard (any improvement on any workstation will improve the total time), the bottle neck will determinate the maximum quantity of operators on the line at the same time.
+ Avoiding waiting time due to unbalancing on the line (time that is of course paid!), usually we lost more than 15% for this reason with fixed operator.
+ Can adapt resources to the takt time on real time without big efforts to make new balancing every time and having a cost of ramp-up every change.
+ Saving time if we have semi-automatic machines like press, using auto-eject concept and launching the cycle without an operator waiting in front of the machine.
+ No impact in case of absenteeism from the productivity point of view.
+ With Cell in Motion MUDA is more evident.
It works like the races on the Formula 1.
This system is applied with kanban, in order to follow exactly the customer demand (Automatic pilot).
BENEFITS
 Better Ergonomics (reducing repeatability)
 Sense of Auto-Quality and Quick Response
 One-Piece-Flow
 Zero Inventories
 100% adaptability to Customer demand (Takt Time)
 Elimination of unbalancing (PPH Increase)
 No Variability in the Line
 Part Travel and Area Reduction
 MUDA is more evident
Mariappan
June 30, 2009 - 2:29 am
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Dear Jorge,
Your words are expressing good results, but at the same time if we are going for RC, the following problems are facing:
1.If we take a manual assembly cell with 5 manpower (4 operators &1 final inspector), if we engage all the 5 in RC, they have to undergo all the stations. If the assembly is having 25 parts to be assembled,
1. Difficult to train all the operators in all the stations
2. No operators will have same mind capacity to take over the job at all stations
3.With walking around the cell is more fatigue than Standing
4.Operator need to walk more than 50% than earlier
5.In India / China no company is employing 100% operators as employee (present ratio in leading companies is 30%(company employee):70% Causal labour
6. So training is very difficult to provide to all the new CL
7. No CL will work with 100% involvement
8. Because cost given to him/her is lower than permanent employee
9. Ok, by technically speaking throughput time is not deciding the output of a manufacturing cell, but bottle neck time only deciding the output.
These are all my experience with RC.
So kindly tell me how is (RC) this possible to implement & how is it giving savings & benefits?
Thanks & regards,
M.Mariappan
Visiocorp Motherson Ltd, Chennai
+919941535540
Ashish
December 20, 2010 - 7:45 am
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Mr. M.Mariappan
I have recently successfully implemented RC in high volume production system at Hero Honda Motors Ltd in Welding line.I faced the similiar issue which you are talking about. In my views
1. We can break complete line (15 to 20 Station ) into 3/4 Cells based on the component. This is little difficult but once done can solve major training issue. In my case i breaked the complete line into three cells without compromising the overall flow of line.
2. As Standard Industrial practice we take 10 to 15 % efficiency factor which covers the learning & speed gap of different operator.Also in my views once proper training of operators are completed with right mechanism, operator find RC better as they feel more engaged.
3. If correct Ergonomic principals are applied, RC is infact able to reduce waste work content like loading/ unloading parts in bins.Also in assembly line not all stations are of similiar nature. Some are difficult then another. But with RC, Work get distributed equally amoung all operator so no easy/ tough station issue. Infact I have experienced that it become easy to handle Industrial relations with operators.
4. CL issue is little tricky to handle & require management involvement. With RC you can increase your productivity or decrease manpower requirement by min 30 to 40 %. So potentially you require less CL. Also RC gives you flexibility as far as manpower deployement is concerned. You need to analyse al these benefits.
I guess you may find some answers.
Thanks
Ashish Gupta