Level-loading Heijunka Cycle

Heijunka, also known as level-loading, production-leveling or production-smoothing, is a foundational element of the Toyota Production System. It facilitates system stability by addressing workload unevenness (mura) through the leveling of both volume and mix over time, see Figure 1. Heijunka also serves as a pacing mechanism for operations, often reflected in the use of heijunka, leveling, or schedule boxes, which are typically designed using pitch intervals, see separate pitch post. Successful heijunka reduces lead time, inventory, and worker physical and psychological stress that can accompany fluctuating workloads. Some prerequisites include quick changeovers, capable processes, standardized work (or at least defined work content), good visual management, and a solid understanding of customer demand – volume, mix, and variation, see separate demand segmentation graph post.

heijunka graph Figure 1. Example of volume and mix leveling

 

The heijunka cycle (Ch) represents a regular, repeatable production sequence to facilitate the leveling of mix. The lean practitioner can readily calculate it using a simple spreadsheet and one or more illustration iterations of the proposed cycle, followed by some real PDCA at the gemba. See Figures 2 and 3, as well as the related formulas. As with the concept of takt time, consider Ch more as a design parameter, than a precise and rigid blueprint for developing the heijunka system.

Ch Calc- Figure 2.Example heijunka cycle calculation

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See the Resources>Templates menu options for a downloadable example Excel heijunka cycle calculation spreadsheet.

    

heijunka sequence Figure 3. Heijunka cycle illustrated

 

heijunka text1heijunka text2It bears repeating, don’t sweat the math if the ratios aren’t perfect whole numbers (that only happens in the examples provided by teachers and consultants). Pragmatically round when appropriate and remember that mix is often a dynamic thing. Good, simple and visual heijunka standard work will cover for real-life variation.

 

There are 65 Comments

Jeremy Svoboda's picture

Hi Mark,

Very interesting, any possibility of sharing the spreadsheet?

Kind regards,
Jeremy

MarkRHamel's picture

Hi Jeremy,

I just sent you the spreadsheet.

Best regards,
Mark

MarkRHamel's picture

Hi Reggie,

I just sent the spreadsheet your way.

Best regards,
Mark

MarkRHamel's picture

Hi Ger,

I just emailed the spreadsheet to you. Hopefully, it makes sense. Of course, there is always the possibility that my spreadsheet math is wrong. Please let me know how it turns out.

Best regards,
Mark

Ger de Waard's picture

Hi Mark, good piece of work.... to make sure I really understand it, i tried to recreate the excel sheet based upon your formulaes, calcs and pictures, but i have troubles with the bits around Ch adjustments and the n/a ... i can't get to the right numbers. Would you be willing to mail me your spreadsheet producing the Ch calculation example so I can see where i am going wrong?

Wayne T's picture

Great article Mark. Can you send me the spreadsheet as well?

MarkRHamel's picture

Hi Wayne,

I just emailed the spreadsheet to you.

Best regards,
Mark

MarkRHamel's picture

Done!

Reggie King's picture

Excellent work. Easily understood!
I too, would like a copy of the spreadsheet, thanks.

Reggie

Mridul's picture

Can you Sen d me the spread sheet mark it was a really tricky and cool method evaluate heijunka constant

MarkRHamel's picture

Mridul,

I just emailed the spreadsheet to you.

Best regards,
Mark

Gintautas's picture

Good job Mark. Can you send me the spreadsheet as well?

Federico Hdz.'s picture

Hi Mark, great work can you send me the spreadsheet to clarify some doubts.

Best regards,

Federico.

MarkRHamel's picture

Hi Federico,

Spreadsheet on the way.

Thanks,
Mark

Devendra Shinde's picture

Hello Mark,

Excellent explanation.

Please can I have the spreadsheet too?

Devendra

MarkRHamel's picture

Hi Devendra,

Spreadsheet has been emailed to you.

Best regards,
Mark

kourosh's picture

Mark Good job
Can I have spreadsheet to have a look at

MarkRHamel's picture

Hi Kourosh,

Spreadsheet emailed to you.

Best regards,
Mark

Kamal's picture

Hi Mark....Excellent work. Pls send me spreadsheet to understand better about ch calculation.

Regards

Kamal

MarkRHamel's picture

Hi Kamal,

Spreadsheet on the way.

Best regards,
Mark

Chris Durre's picture

Hi Mark,
If it's not too much to ask, I'd also like a copy of the spreadsheet. Thanks!

MarkRHamel's picture

Hi Chris,

Just sent you the spreadsheet.

Best regards,
Mark

Adrian Valadez's picture

Hi Mark, excellent work!! can you send me the spreadsheet? thank you so much.

MarkRHamel's picture

Hi Adrian,

Just sent you the spreadsheet.

Best regards,
Mark

Ashok's picture

Mark, In Fig 2 step D, I am unable to calculate the same numbers for product B as it relates to columns "2 cards every x cycle" and "3 cards every x cycle".
For product B & "2 cards every x cycle", calculation is (1/(3.11-3))*2 = 18.
For product C & "2 cards every x cycle", calculation is (1/(2.00-2))*2 = n/a

Please help/ advise where i am making mistake.

MarkRHamel's picture

H Ashok,

We can certainly calculate the number of multi card adjustments for B (for example, a 2 card adjustment every 18 cycles would be the number). However, I was looking for the lowest whole number (or as close to a whole number as possible) - thus every 9 cycles was a good "solution." Accordingly, I used n/a for 2 cards and 3 cards. There is no adjustment for "C" because it is the lowest period demand and is used as the basis for the production ratio. In other words, it is a 1:1 relationship, by definition.

I hope that makes sense.

Best regards,
Mark

MarkRHamel's picture

Hi Marco,

Just sent you the spreadsheet.

Best regards,
Mark

MarkRHamel's picture

Hi Ashok,

You are absolutely correct. It is annual. I had it mislabeled as "Monthly."

Thanks,
Mark

lloucka's picture

Fixed now. Thank you for the reminder.

twardtew's picture

Please feel free to delete my message and your response (and not publish this one), since it no longer adds value now that the error has been corrected. Keep the comments lean, reduce non-value added activity!

MarkRHamel's picture

Hi Shureka,

Just sent you the spreadsheet.

Best regards,
Mark

MarkRHamel's picture

Hi Gabriel,

Just sent you the spreadsheet.

Best regards,
Mark

Shureka Gantt's picture

Hi Mark,

Could I please have a copy of the spreadsheet?

Ashok's picture

Mark, Very detailed explanation! Thanks a lot.
Please help me understand in step C will actual cycle time be a factor to define which calculated production ratio multiple be more practical? I am also assuming the sequence of build is for a mixed model cell, not dedicated product assembly cells. Please confirm.
Also i used 65 working days in a quarter to calculate daily demand. My numbers did not match your table in Fig 2. Please share your calculations for me to check where I made mistake.

Ashok's picture

Mark, I just realized that first column in Fig 2, represents yearly demand, not weekly. Correct?

Gabriel Gómez's picture

Hi Mark Excellent work. Please send me spreadsheet to understand better about ch calculation.

Regards

Gabriel

Albert's picture

Mark,

Best detail explanation I have seen! Thanks so much for sharing. This is very much based on demand and takt time, how do set up time and cycle time get looked at in the schedule? In a cell we are creating, we have cycle times that are above takt time prior to improving it. I would like to pick the optimum batch size for the current cycle and set up time and have it adjusted as we improve setups and cycle times. Please share the spreadsheet with me as well!

Thanks,

Albert

MarkRHamel's picture

Hi Albert,

I just sent you the spreadsheet. Sorry for the slow response.

If you have significant set-up times, then heijunka cycles, as such, probably do not make sense for you. I would consider using a signal kanban for scheduling batch processes. The post, "Pull System Design: Brief Thoughts on Sequence and Math," may be a good start for you.

Let me know if you have any questions.

Best regards,
Mark

Marco di Sanctis's picture

Mark, could you please send me the spreadsheet?

Joe's picture

Hi Mark,

I am also looking to implement Hijunka for one of our production lines. Would you mind sharing the spreadsheet.

Thanks,

Joe Szymanski

lloucka's picture

Please go back to the article and follow the download link there.

Hayden Capps's picture

Hello Mark,

I would love to have a copy of the Excel spread sheet. We are in the process of implementing a level load plan at our small factory.

lloucka's picture

Please go back to the article and follow the download link there.

Alfredo Guzman's picture

Hi Mark, I'm in the process of trying to implement Hijunka for one of our production lines. The information is just what I need. Would you mind sharing the spreadsheet.

Thanks,
Alfredo Guzman

MarkRHamel's picture

Alfredo,

Thanks for the comment. Spreadsheet is sent.

Best regards,
Mark

tony's picture

hi mark,

thanks for your post about heijunka cycles, it is very interesting stuff. I am going through your calculations, would it be possible for you to send me the spreadsheet as well?

many thanks,

Tony

lloucka's picture

Please go back to the article and follow the download link there.

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