Poka Yoke pattern making

Posted by Kathleen Fasanella on Oct 31, 2005 at 3:07 pm / Glossary, Lean Manufacturing, Patterns, Sewing, Tutorial / Trackback

By now, all of my readers know I’m enamored of lean manufacturing and I try to apply it specifically to sewn products manufacturing. One of the things I wrote about extensively in The Entrepreneur’s Guide… was error-proofing your patterns; the lean concept to describe this is called Poka Yoke (pronounced “poh-kah yoh-kay”). An excellent introduction to Poka Yoke can be found here. By the way, check out this site’s management topics sidebar for very nicely written and presented information. Poka yoke comes from two Japanese words – “yokeru” which means “to avoid”, and “poka” which means “inadvertent errors.” So, poka yoke translates to “avoiding inadvertent errors”. This is the best site on the web for Poka Yoke. Please visit; the main page is a riot and thanks to Eric who sent me the link (each of the poka yoke pages are represented by a photo of a different pocket protector -who says geeks don’t have a sense of humor?). Poka Yoke is kind of fun to look for too, you already know lots of examples of it. For example, your coffee grinder. If the cap is not aligned properly, it won’t grind. Similarly, you can’t spill coffee while it’s being ground, saving you the potentiality of a lot of mess. As the mother of a smoothie-making child, I can only hope we’ll soon have a blender that works the same way. Another example of Poka Yoke is a ground plug; you can only get those in one way. Poka Yoke is a great concept because people rarely make errors when they’re focused and “on top of it”; people make mistakes when they’re distracted, tired, irritable, hungry or whatever. Anyway, today’s topic is Poka Yoke pattern making.

Above is a technical sketch of a leather jacket. I realize that the left and right side of the sketch don’t match. I drew it that way to show how it’d look if you sewed it with fringe and hair pipe and the other side without it, so ignore that; that’s not the point of this discussion. Notice the “V” in the sketch below



This “V” is what I want you to notice, it is perfectly matching at center front. Now, if you’ve never made or sewed a pattern like this you’re probably thinking this is no big deal. If you have made or sewn something like this, then you know that the center front pieces are not mirrored; these are not 2 pers. In other words, the upper right front is different from the upper left front. Likewise, the lower right front and lower left front are not the same either. To keep things simple, I’ll be using the lower fronts as a sample since the pieces are small. (see below).

Looking at the pieces in the photo above, you can see that these pieces look so similar as to cause a great deal of confusion and error even if you are paying attention. If you cut the 2 upper and the 2 lower pieces the same, the “V” will never match up. Anyway, there is a poka yoke to prevent the mis-cutting of these pieces.

The first way we prevent the mis-cutting of two nearly identical pieces is to use green backed pattern paper. It’s easy to flip pieces not realizing it if you’re cutting out a jacket like this because there are so many pieces to the coat and it’s easy to lose track. See the photo below for this example. If you accidentally flip your pattern piece, the green side can’t be missed so you quickly turn it to face manila side up. This poka yoke is similarly invaluable if the person cutting doesn’t speak or read English.

Below you can see a comparison; a photo of the left and right pieces laid on top of each other. Since I’ve laid them as “mates”, one side is green. This makes it very easy to prevent the mis-cutting of these pieces. You’ll notice the manila colored piece underneath is not the same shape as the piece above it.

Still, the green back pattern paper is not the only poka yoke in use here. As I mentioned extensively in the production pattern making section of The Entrepreneur’s Guide…, you need to off-set your notches to prevent the wrong pieces from being joined to each other. You should also examine the notches along the top edge in the photo above and you’ll notice the notch on the reversed (green) piece does not align with it’s “mate” underneath. These mis-matched notches are another poka yoke.


For example, in the above photo, I’ve laid the lower front right on top of the upper right front, right sides together in the position they would be if you were sewing it together and you can see that the notches on that sewing edge are perfectly aligned. But let’s say that somehow the pieces were mis-cut anyway -in spite of using the green back paper- and you tried to sew the wrong sides together, in the photo below, you can see the matches will not match up. In real life, your stitchers will stop sewing immediately and start looking for the right pieces because they’ve got the wrong ones in hand.

However, you should notice that each of the lower fronts have a notch off to either the left or right (depending on their position) and each of those notches are exactly aligned because once the upper and lower fronts are joined, they will be sewn to the side fronts. The side fronts are mirrored pieces.

Anyway, these are some pattern making poka yokes. These are the kinds of features that are incorporated into a production quality pattern and unfortunately, books don’t tell you anything about this. Failing to have these kinds of features is usually why there are sewing problems with DE products. Writing posts like this really makes me wish I could just drop everything and write a production pattern making book; it is so needed.

If you’d like an example of the proper labeling and piece ID of the pattern, you’ll find that below.
1. Please note I wrote in all block letters. I used black ink (this is a shell/self piece) and notice the direction of the writing.

2. Please do not -do not!- write on pattern pieces the way many teachers or pattern books tell you to do it (up and down along the grain line).

3. You’ll notice the directional indicator [R] is circled. The words “Face-up” and R.S.U. are a redundancy (Right Side Up). To prevent mistakes, being redundant is good.

4. You should mark the wrong side of the pattern with an “x” which always means “do not use”. Sometimes I also write W.S.U which means Wrong Side Up. Pieces are never cut wrong side up.

5. Lastly, as this is a leather pattern, I’ve marked the direction the nap should be when laying out this piece. You should only use arrows on a pattern piece if it has a nap, and then, only one. Do not use a set of arrows on either end of the grain line like they do in home sewing. You only use arrows to indicate nap and if you’re indicating nap, your one arrow will only point in one direction.

22 Responses to “Poka Yoke pattern making”

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Jinjer Markley
October 31st, 2005
5:31 PM

Oooooh, I’m happy to report that I invented a Poka-Yoke for a designer friend of mine, before even knowing about Poka Yoke (or lean production). She makes hand-felted items, including cute mini-scarves where one end feeds through a slit in the other. To hold the scarf closed, the slit should be a certain length. For good looks, it should be centered and straight. She always “eyeballs” them, and just cuits freehand with the rotary cutter, but asks that we use a ruler if we can’t do that.

Needless to say, the error rate was very high, which was particularly bad because it was the last step in production. I wasn’t the person who did this for her, but one day I was filling in. I made mistakes. She pointed it out, frustrated (more because it happened so often). So, I cut a little jig out of plastic that is easy to line up properly and prevents the rotary cutter from cutting too big a slit even if you wanted to. It took me maybe 20 minutes and cost a portion of a sheet of plastic. aka cheap.

BTW, if anyone in the Bay Area wants to hire me to be part of a lean production sewing team, I would make a great employee. I’m a natural efficiency freak, I color-code everything anyway, and I like things nice and neat (not that MY studio is always sparkling, um….).

Fashion-Incubator
November 1st, 2005
12:26 PM

Piece naming conventions

An aspect of production pattern making that I’ve wanted to discuss for a long time is (pattern) piece naming conventions. Unfortunately, it doesn’t appear that pattern making books itemize this other than through usage. Again, you may think this topic…

Gigi
November 1st, 2005
1:48 PM

Kathleen, are you saying that grainline is marked with a line only? Would they run the length of the pattern piece? I have often wondered why home sewing patterns don’t just put a grainline from one end of the pattern piece to the other because it would be so much more accurate. Those stunted little grainlines they use seem so utterly useless to me.

kathleen
November 1st, 2005
2:59 PM

Kathleen, are you saying that grainline is marked with a line only? Would they run the length of the pattern piece?

Yes, the grainline is marked with a line only. And yes, please draw the line so that it extends the full length (off the edge). If you don’t, the pattern grader will have to do it in order to align it properly on the digitizing table. Or worse, the grader won’t do it, laying the piece down by eye and then it all just becomes a big mess if the orientation is off. If you have the ruler out to draw the grainline, you may as well do it properly. This is why you need really long rulers. You need rulers that are longer than your longest pattern pieces. My longest ruler is 96″.

I have often wondered why home sewing patterns don’t just put a grainline from one end of the pattern piece to the other because it would be so much more accurate. Those stunted little grainlines they use seem so utterly useless to me.

Believe me, I have no idea why they do the things they do. What I see as unfortunate is that due to their dominance in sewing, they provide a skewed “orientation” that becomes a standard for people who don’t know any better (people getting into the business from the homesewing side of things). The mis-orientation can really muck things up.

Tracey
November 2nd, 2005
11:29 PM

Kathleen, pleeeeeeeease write that production patternmaking book!

kathleen
November 8th, 2005
1:29 PM

I cut/pasted the following from an email that I got from someone who bought my book in Japan:

It feels funny to see Japanese words used in English – many of the colloquial or mundane terms seem to be treated as something special elsewhere. It’s really the concepts that matter – but then, maybe e.g. pokayoke (flub-guard) is kinder and maybe more precise than idiot-proofing.
Teijo

Eric H
November 9th, 2005
9:29 AM

Interesting point Teijo. If I told one of my guys to make something idiot-proof, that would seem mundane. If I told him to think of a good poka yoke, he would see that as an intellectual challenge. I think using the “foreign” word for it lends some aura of legitimacy.

That’s one reason law and medicine tend to use arcane phrases.

Si hoc legere scis, nimium eruditionis habes.

On the other hand, they may also use those phrases to maintain their status.

Poka yoke sounds playful to ears accustomed to English, much better than “idiot proof”.

Carol Kimball
December 11th, 2005
1:42 PM

Poka Yoke in Action:

Some time ago, I posted about the “Tall Girls” project. There has been a necessary hiatus while the initial Medium dress shirt prototype was tested (I will mention again what a joy these people are to work with – at our first meeting they immediately bought ENTREPRENEUR’S GUIDE, from the stock I keep on hand).

With the measurements refined, building another shirt is necessary. I made notes while developing the original garment and incorporated poka yoke techniques wherever possible (although Kathleen wasn’t calling them this when I got her book).

The easiest way to construct anything is with an earlier version at hand, and I didn’t have the first shirt to look at. All the poka yoke not so much kept me from making mistakes, but speeded up the construction enormously. There was constant reassurance that I was on track.

final fashion
December 17th, 2005
7:24 AM

light bulbs ding ding! Of course you only need the arrows if you’re using a nap! Yet another case where my school taught me an unsubstantiated convention… think of all that time I spent drawing little unnecessary arrowheads pointing both ways. Hm. And I promise to stop labelling along the grainline, too.

Yes, please write a book on production pattern making!

Shauna Smith
August 17th, 2006
4:25 PM

Where in the world do you find “green backed pattern paper”? I found a roll in Canada, but the shipping doubled the cost. I thought I found a roll in NYC, but they shipped me the plain manila.

Andrea Frost
December 8th, 2006
10:28 PM

I LOVE your blog. Already it has been so helpful with all the pattern maker recommendations. Thanks Kathleen!

Trish
November 2nd, 2010
8:06 PM

Kathleen… help!! I was taught from industry patternmakers to annotate (write) on (not the grain) but a straight line on the pattern. Why is this not a good idea?

Also, the same company taught me that we would always use an arrow, but only pointing to the bottom of the piece. Would this not be important for one-way and directional prints?

Finally, another thing the same company taught me is that each grain line should go from top to bottom of the entire pattern piece and that they should align for pieces that are attached during sewing.

Just curious about the location of annotation, if you happen to see this.. thanks, Trish

[…] response to the entry on preventing sewing mistakes through proper pattern marking, Trish wrote: I was taught to write along the grain line. Why is this not a good […]

Lily Yang
May 29th, 2011
11:43 PM

I really love your website. It’s been very very helpful. Here are some question for you,if you happen see it:
If the pattern need to use both side, how do you mark it on the pattern to indicate that turn over other side to cut. For example shirt’s cuff(upper cuff and under cuff but normally you only make one cuff and write cut 4 self on the pattern.) Also what about with contrast fabric for under cuff,how to mark it?

I’ve see pattern wrote done more details like company name,type of garment(ex,men’s shirt button up)style number,size and number of cut.However from the photo you showed,I only see the style number,part of garment,size, nap direction and side of notice.IS that what you usually use for the production?

Kathleen
May 30th, 2011
12:13 PM

Hi Lily. It is assumed one would flip the pattern depending on the number to cut so it would not need a marking to tell someone to flip it.

If a cuff were a total 4 per to cut but two of them were contrast, you would write:
cut 2 per (black ink for shell)
cut 2 per (green or purple ink for contrast)
the specifications of the pieces to cut and of which fabric would be repeated on the pattern card and cutter’s must. The latter are a parts list of pieces to cut to complete the style.

Re: more details on patterns (ie company name etc). I suspect this would be more typical of a package service that provides pattern services along with production. It is not wrong to do it like this (and it’s not wrong not to either). Every service provider has internal means to track each client’s work. I do it by the job. I’m not a large firm so it is not difficult. I track each customer’s job with the pattern card; that has the company’s name on it etc.

Lily Yang
May 30th, 2011
2:11 PM

Hi Kathleen,
Thank you very much for responding the post. Just wanted to understand about the information on the pattern cart and cuter mast. You state that “the specifications of the pieces to cut and of which fabric would be repeated on the pattern card and cutter’s must.”
Pattern card
When I write my pattern card I tend to write in total of the pattern of each piece for one style pattern,ie., cuff / 4 Qty. and with a note:contrast(in purple ink to match my note written on the pattern:cut 2 self(black ink ) /cut 2 contrast(purple ink ) ):cuff,collar stand….
Do you think it will be better if I do other way like:#7 upper cuff /2 Qty. under cuff /2Qty. even thought I only have one pattern for cuff.
Do you write date on the pattern?

Cutter mast
If so the cutter mast is operated base on the fabric that should be cut but not by the number of pattern piece. Therefore, we should write self on one card ,interfacing on one card and contrast fabric on one card for one style pattern. Is that what you mean?
Do you write fabric information to the cutter mast such as fabric width,color,fiber content and illustration (flat)?

Thank you,

RoseAngela W.
November 8th, 2011
5:14 AM

Hi Kathleen,

I am trying to contain my joy here …. My two cents: I am glad you are thinking about writing a book on patternmaking

Ditto on final fashion’s comments exactly. My school, so far (Fashion Design I), instructs us to do the same on our patterns. I will keep my eyes peeled for ‘upgraded’ info as we progress. (AAU tends to give more info as we graduate up the levels of FD).

Your instructions make sense to me …. I am understanding in industry, clarification in communication is key. Symbols and coding that everyone can understand in more important.

Regarding home sewing pattern instructions, I remember reading that market assumes that the sewer already ‘knows’ how to sew and that the home sewer is taking command of their system of organization with their sewing plan so they leave all organization details to the discretion of the home sewer. They are only giving a guide to pattern layout and cutting and sewing. The rest is not their concern. They are only in the business of selling patterns.

I have also shopped at V Brothers, they are pretty good at customer service.
You can also find green backed pattern paper for $4.50/yard. Sold by yard or 120 yard rolls at:

http://sewtrue.com/Store/Tagboard-Pattern-Paper-P231.html

Kathleen
November 8th, 2011
2:12 PM

Wow! $4.50 per yard? That is crazy. Southstar sells oaktag for what amounts to $1.50 per yard (@$100 for a 200 foot roll). It’s not greenback but it isn’t worth the $3 extra per yard to me. Good to know tho, thanks for dropping that link. Someone had been asking about greenback in the forum awhile back.

The patternmaking book is not like anyone else’s, it’s not how to make X styles. It’s all the stuff that pattern books never mention along with sewing it up etc. You know, production stuff. Like how to correct the overlap on a V so the two points line up.

RoseAngela W.
November 9th, 2011
3:10 AM

Your book’s perspective is just what I thought you were aiming for, and just what is needed! Do it Kathleen…. you will be blessing all of us!

anything I can do to help as a student, ….!

Kathleen
December 19th, 2011
12:59 PM

Yay! I found a source for greenback pattern paper in Dallas that is reasonably priced. Here are the details:
2X, 9″ diameter, 48″ wide, $139.
Sunny Sewing, Dallas TX

RoseAngela W.
December 27th, 2011
5:58 AM

perfect! Adding this one to my sewing repertoire. Thanks Kathleen!

Chris J.
May 9th, 2012
10:58 PM

I am studying industrial engineering in school, and while I work with a battery company at the moment I write this, I still find many of the same lean methodologies apply at a very basic levels here! It’s so exciting to have found someone like you whom talks about manufacturability and standard practices in clothing, rather than just parroting vanilla stuff and blabbing about seasonal aesthetic choices. (and while I can relate to that too, I prefer to focus on the solid engineering parts)

Either way, I’ve felt inspired to explore the sewn product industry to learn the ropes/standard practices and further test out my understanding of its processes. Until then, I’ll definitely be buying/reading your book and will be continuing to read your blog!

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