How digi­tal tools can redu­ce was­te and over­load in your manufacturing!

The three Mu are used in the Toyo­ta Pro­duc­tion Sys­tem (TPS) to descri­be los­ses within a pro­duc­tion pro­cess. The first “M” stands for the Japa­ne­se term muda and descri­bes was­te within a pro­duc­tion pro­cess. The second “M” stands for Mura and descri­bes the imba­lan­ce of pro­duc­tion pro­ces­ses. Muri, the third “M” descri­bes the los­ses that occur due to over­stres­sing within the pro­duc­tion pro­cess. The three Mu ser­ve as a start­ing point for the iden­ti­fi­ca­ti­on of was­te and thus as a basis for cor­re­spon­ding impro­ve­ments of pro­ces­ses, mate­ri­al, work sta­ti­ons or machi­nes. In this way, the three terms sup­port the con­ti­nuous impro­ve­ment pro­cess (CIP) or KAIZEN, as poten­ti­al for impro­ve­ment is con­stant­ly sought here. Through the sys­te­ma­tiza­ti­on into the three terms Muda, Mura and Mudi, the employees have a clue what to look for in the pro­ces­ses. This is then the start­ing point for employee enga­ge­ment and creativity.

In this blog post, we want to explain the­se three mu and give you gui­dance on how digi­tal tools in manu­fac­tu­ring can help iden­ti­fy and then eli­mi­na­te the­se types of inefficiencies.

Muda — The eight types of waste

A was­te of resour­ces is the most obvious cau­se of los­ses and thus inef­fi­ci­en­ci­es in pro­duc­tion pro­ces­ses. Resour­ces in manu­fac­tu­ring can be divi­ded into two cate­go­ries: Value-added resour­ces (e.g., machi­ning times of a pro­duct) and, on the other hand, was­ted resour­ces (e.g., long set­up times). The sum of value-added and was­teful com­pon­ents of a manu­fac­tu­ring pro­cess descri­bes the effi­ci­en­cy of that pro­cess. Muda — Japa­ne­se for was­te — descri­bes pre­cis­e­ly the­se non-value-adding com­pon­ents of pro­duc­tion pro­ces­ses and sys­te­ma­ti­zes the­se was­tes into eight types of was­te. The­se can be easi­ly remem­be­red by the Eng­lish term “DOWNTIME”:



Defects are defi­ci­en­ci­es that occur during the manu­fac­tu­re of a pro­duct. The­se can be, for exam­p­le, qua­li­ty defects that lead to rejects or cus­to­mer complaints.



Over­pro­duc­tion often occurs when manu­fac­tu­ring is based on the push prin­ci­ple and the indi­vi­du­al employees do not have an over­view of the over­all pro­cess. Inter­me­dia­te warehou­ses can then quick­ly fill up and the mate­ri­al stock in work-in-pro­gress increa­ses steadily.



Wai­ting times can be cau­sed by a lack of mate­ri­al stock or mal­func­tions at the work­sta­tions or machi­nes and are basi­cal­ly not value-adding.


Non-Uti­li­sing Person

Insuf­fi­ci­ent­ly trai­ned or infor­med employees in manu­fac­tu­ring lead to many defects, a decrease in employee moti­va­ti­on and many other pro­blems. The­r­e­fo­re, ina­de­qua­te trai­ning of employees is also a type of waste.



If trans­port rou­tes are not well plan­ned, this can lead to employee wai­ting times and thus inef­fi­ci­en­ci­es. Incor­rect con­vey­ors, which can poten­ti­al­ly dama­ge pro­ducts, lead to fur­ther types of was­te (defect, waiting).



Unneces­s­a­ri­ly high mate­ri­al stocks tie up a lot of capi­tal and are the­r­e­fo­re fun­da­men­tal­ly inef­fi­ci­ent. Howe­ver, it should be noted that a midd­le ground must be found bet­ween low capi­tal com­mit­ment and suf­fi­ci­ent­ly high safe­ty stocks!



Moti­on descri­bes the non-value-adding (i.e. super­fluous) move­ments within the manu­fac­tu­ring pro­cess. Unneces­sa­ry wal­king and move­ment by employees should be avo­ided, for exam­p­le, through good work­place design.


Extra Pro­cess

Ope­ra­ti­ons should not be dupli­ca­ted. This includes loo­king at unneces­sa­ry docu­men­ta­ti­on or dupli­ca­te pro­cess steps at indi­vi­du­al work­sta­tions. For exam­p­le, sur­face dama­ge should only be che­cked at the last work sta­ti­on and not at each of the stations.

How can Muda be minimized?

Not all was­te can be com­ple­te­ly eli­mi­na­ted. Howe­ver, the­re are many ways to mini­mi­ze dif­fe­rent types of was­te. In our blog post “The eight types of was­te”, we look at each type of was­te and show you ways to iden­ti­fy and fix them using digi­tal tools.

Mura — The imba­lan­ce of manu­fac­tu­ring processes

The Japa­ne­se term mura stands for an imba­lan­ce. This expres­ses a lack of har­mo­niza­ti­on of pro­ces­ses, working methods or capa­ci­ties in gene­ral. One sym­ptom of imba­lan­ce is los­ses due to “queu­ing” in front of work sta­ti­ons or in the inter­me­dia­te sto­rage are­as bet­ween the­se sta­ti­ons. this results in a high mate­ri­al inven­to­ry and thus a high capi­tal com­mit­ment in work-in-pro­gress. Machi­nes or equip­ment that are not opti­mal­ly uti­li­zed, and thus idle time, are also often a sym­ptom of mura.

The imba­lan­ce is respon­si­ble for some resour­ces being over­ex­ten­ded In the case of an assem­bly line, this can be expres­sed in the fact that indi­vi­du­al assem­bly sta­ti­ons often remain far below the spe­ci­fied cycle time, while cycle time over­runs occur at other work sta­ti­ons. In the case of a line cycle wit­hout inter­me­dia­te sto­rage, this results in wai­ting times at indi­vi­du­al work sta­ti­ons. In a line with sta­ti­on-based takt (i.e. with mate­ri­al sto­rage bet­ween the sta­ti­ons), the imba­lan­ce can lead to high stock levels.

The three cau­ses of imbalance

Mura, i.e. imba­lan­ce, can occur in pro­duc­tion, but also in the pro­vi­si­on of ser­vices or in the pro­ces­sing of an ope­ra­ti­on. The loss due to mura can occur at three levels:

  • At the pro­cess level: Pro­duc­tion equip­ment, machi­nes or sys­tems that are not coor­di­na­ted with each other, or pro­ces­ses that are not opti­mal­ly dove­tail­ed, can lead to dif­fe­rent pro­ces­sing times at the indi­vi­du­al pro­duc­tion sta­ti­ons. This can bring the pro­duc­tion flow to a standstill or cau­se employees to wait. This lack of pro­cess opti­miza­ti­on then leads to los­ses (muda) and/or over­load (muri).
  • At the level of the per­son­nel: Dif­fe­rent, indi­vi­du­al working methods of the indi­vi­du­al employees can lead to imba­lan­ces in the pro­ces­sing times. Dif­fe­ren­ces in moti­va­ti­on or skills must also be taken into account for a sen­si­ble syn­chro­niza­ti­on of assem­bly lines and make this more dif­fi­cult. Alt­hough an attempt can be made to level this out by spe­ci­fy­ing tar­get cycle times, this can lead to over­load (Muri) for indi­vi­du­al employees and thus to a was­te of per­son­nel resources.
  • At the pro­duct level: Fre­quent­ly chan­ging cus­to­mer requi­re­ments for a pro­duct can also be cau­ses of imba­lan­ce. Due to an incre­asing num­ber of vari­ants with dif­fe­rent work steps (and thus also lead times), it is very dif­fi­cult to balan­ce assem­bly lines. The JIS (just-in-sequence) deli­very prin­ci­ple is a good exam­p­le of this. Here, work is done accor­ding to the pull prin­ci­ple and the­re are many dif­fe­rent vari­ants. All vari­ants have dif­fe­rent lead times, so that depen­ding on the vari­ant, the indi­vi­du­al work­sta­tions (with a low level of com­ple­xi­ty of the cur­rent vari­ant) have to wait. In the mean­ti­me, other work­sta­tions are busy pro­ces­sing a more com­plex vari­ant in the same cycle and are the­r­e­fo­re overloaded.

How to redu­ce the imbalance

With the num­ber of pro­cess steps and vari­ants in a pro­duc­tion pro­cess, the degree of imba­lan­ce increa­ses. The fewer stages or assem­bly sta­ti­ons a pro­duc­tion pro­cess has, the easier it is to coor­di­na­te them. The more vari­ants of a pro­duct are manu­fac­tu­red on the same line, the more com­ple­xi­ty increa­ses and it beco­mes more dif­fi­cult to coor­di­na­te indi­vi­du­al pro­ces­sing steps. In prin­ci­ple, the­r­e­fo­re, Mura should be coun­te­red by redu­cing com­ple­xi­ty. Howe­ver, it should be noted that a cer­tain degree of imba­lan­ce remains in every pro­cess. The big goal is to ste­ady manu­fac­tu­ring pro­ces­ses in order to make the best pos­si­ble use of exis­ting capa­ci­ties and to avo­id was­te, espe­ci­al­ly due to down­ti­mes or wai­ting times.

Methods such as Hei­jun­ka (har­mo­niza­ti­on of the pro­duc­tion flow through quan­ti­ty-based balan­cing) or One-Pie­ce-Flow are sui­ta­ble for this pur­po­se. Howe­ver, it is first important to unco­ver the imba­lan­ce and iden­ti­fy which of the assem­bly sta­ti­ons is the bot­t­len­eck. This can be achie­ved through a worker assis­tance sys­tem. This can be used to record the indi­vi­du­al work steps and the dura­ti­ons of the­se steps. In a second step, it is then easy to iden­ti­fy which sta­ti­ons have too much work and which are per­ma­nent­ly under­loa­ded. This makes it pos­si­ble to balan­ce work sta­ti­ons. Ano­ther advan­ta­ge of worker assis­tance sys­tems is the leve­ling of employee know­ledge. All employees at the work­sta­tions have access to com­pre­hen­si­ve infor­ma­ti­on on the assem­bly steps. Digi­tal aler­ting tools can be used to call for help quick­ly in the event of ambi­gui­ties or impen­ding mal­func­tions. All the­se mea­su­res lead to a bet­ter balan­ce of the manu­fac­tu­ring processes.

Muri: The over­loa­ding of manu­fac­tu­ring resources

Over­loa­ding of resour­ces is descri­bed in the Toyo­ta Pro­duc­tion Sys­tem as muri (Japa­ne­se for over­load). This can affect human labor as well as occur on machi­nery and equipment.

Over­loa­ding of per­son­nel results from con­ti­nuous ove­r­use or misu­se. A distinc­tion must be made as to whe­ther the over­load ari­ses phy­sio­lo­gi­cal­ly (i.e., affec­ting the body) or whe­ther it is psychological.

Psy­cho­lo­gi­cal over­load can be cau­sed, for exam­p­le, by exces­si­ve time pres­su­re or a lack of know­ledge about indi­vi­du­al work steps. The con­se­quen­ces of this, in addi­ti­on to the effect on work results, are a drop in moti­va­ti­on among indi­vi­du­al employees and a poor working atmosphere.

Phy­si­cal over­load occurs when employees are expo­sed to unfa­vorable envi­ron­men­tal con­di­ti­ons. This can be due to noi­se, vibra­ti­ons, high or low tem­pe­ra­tures, unfa­vorable light­ing con­di­ti­ons, strong odors and much more. Very phy­si­cal­ly deman­ding work (e.g. lif­ting hea­vy objects) can also lead to phy­sio­lo­gi­cal overload.

Effects of over­loa­ding per­son­nel and machinery

Over­load occurs, for exam­p­le, when peo­p­le have to absorb the uncoor­di­na­ted work pro­ces­ses (mura) and the resul­ting was­te due to unfa­vorable fac­to­ry design or avo­ida­ble trans­port and long distances (muda). In many cases, this leads to extra work or a fas­ter through­put of work pro­ces­ses. This leads to time and per­for­mance pres­su­res. Increased pres­su­re leads to a hig­her fail­ure rate among tho­se invol­ved and redu­ces the qua­li­ty of the results. Ulti­m­ate­ly, the result is not only more was­te, but also men­tal and phy­si­cal stress and over­work. This can lead to fati­gue, stress, depres­si­on and other sick lea­ve, but it can also affect the work environment.


Machi­nes and equip­ment can also “suf­fer” from over­load. If they are con­stant­ly run at bor­der­line capa­ci­ty, high wear and tear is to be expec­ted. The qua­li­ty of the pro­ducts can also suf­fer from such a machi­ne. In addi­ti­on to grea­ter wear and the need for increased main­ten­an­ce, the life of the machi­ne or sys­tem also decrea­ses. Ulti­m­ate­ly, the con­ti­nuous load leads to high down­ti­mes of the machi­nery and thus to mani­fold losses.

How to mini­mi­ze overload

The most sus­tainable mea­su­re to pre­vent over­loa­ding is good plan­ning of the assem­bly line. The reason for this is that the work­place design can be opti­mal­ly adapt­ed to the pro­duc­tion and its needs and desi­gned ergo­no­mic­al­ly. At the same time, many other types of was­te (muda) are thus mini­mi­zed. It is the­r­e­fo­re wort­hwhile to plan ahead in order to impro­ve pro­duc­tion pro­ces­ses and other acti­vi­ties in a long-term and sus­tainable manner.

When opti­mi­zing exis­ting pro­ces­ses, it is usual­ly neces­sa­ry to redu­ce the num­ber of pro­cess steps in order to make the pro­cess clea­rer and simp­ler. In this way, employees can moni­tor not only their own actions, but also tho­se of others. This can be sup­port­ed by other mea­su­res to redu­ce noi­se and increase staff aut­ho­ri­ty and respon­si­bi­li­ty. The­se include, for example

  • Stan­dar­diza­ti­on of work through the use of com­mon docu­men­ta­ti­on in worker assis­tance systems
  • Kan­ban or andon as a com­mu­ni­ca­ti­on and con­trol tool
  • The 6S con­cept for various acti­vi­ties (sei­ri: clas­si­fi­ca­ti­on, sei­ton: clea­ning, seisô: cle­an­li­ne­ss, sei­ketsu: main­ten­an­ce, shit­suke: self-disci­pli­ne, shû­kan: automation)

Mana­gers can sup­port the imple­men­ta­ti­on of the­se mea­su­res by trai­ning and moti­vat­ing employees and app­ly­ing the prin­ci­ples of lean management.

Curious now? Cont­act us, we will be hap­py to advi­se you!