From Grading

Grading stretch knit patterns

Returning to the list of topics from the reader's poll, stretch knit pattern grading is next so that's what we'll do today. To refresh your memory, I'd said, knit pattern grading the way that Stuart does it which is very different from how we do it in North America. To discuss the dichotomy of Stuart's approach requires that you already understand grading to see why his method is a departure from what we typically do and we can discuss why it may be better and easier. My role is best described as a facilitator of this discussion because my experience with his method is very limited, albeit successful. And by the way, I refer to Stuart Anderson whose website is better known as Pattern School. Pattern School is offline for now but you can easily access it via the WayBack Machine and all links I'll use will direct there. Ready? Okey dokey.

Stuart says there are two types of grading, incremental and proportional. Traditionally, we use incremental which means we attach a value to grow or shrink a given point according to X or Y coordinates. [At right is an illustration of rules applied to a pattern the traditional way.] Stuart uses another way, namely proportional. This requires calculating the degree of stretch in the fabric and using a feature common to CAD programs, stretch the pattern pieces in accordance with the stretch properties. Doing it this way can be easier, faster and more accurate than grading via XY coordinates.

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Day 6 Giveaway: Grading Workbook

CC_grading_workbook_coverBefore getting into this review, you can still enter to win the pattern book until late tomorrow afternoon. A winner for the Stylish dress book will be selected on Wednesday. Moving on.

Today's giveaway features the second edition of Connie Crawford's Grading Workbook. I have the hard copy, spiral bound edition, 136 pages. It is nicely formatted and illustrated, similar to the drafting book. I do think it is a low cost option to learn grading from -all explained in a clear manner as possible but there are a few issues to be aware of. Before I forget, if you're not sure of all the technical terms I'm using, you might consider perusing the grading posts on this site, they are extensive and detailed.

No matter how dedicated and disciplined an author, discrepancies will creep in. For example, the grade stack of the neck point at the bottom of pg 35 is correct but in a later section on page 54, it is not. That said, scale is everything. My disputation amounts to something on the order of 1/32nd to 1/64th of an inch -something only professional graders will fuss about (and fuss we do). I only bring it up in the event that you follow the instructions step by step and your result doesn't look exactly like the illustration on page 54. If it looks like the one on pg 35 instead, you're doing fine.

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Life in the trenches from the real world of a technical designer

Edited July 1, 2012 the server this site is hosted on has been undergoing sustained hack attacks. Please disregard any unpleasantries, I’ll deal with it in an expedited fashion when I return on Tuesday. I appreciate your patience.

The alternative title of this entry is How to check the accuracy of graded patterns pt.4.

In part three I had mentioned I would publish an email from an esteemed colleague who wishes his company did sew samples in all sizes (if you need to catch up, see parts one, two and three). This email is very telling -it says much more than on the face of it. It is a very candid and telling portrait of what goes on in many larger offshore companies. If you read between the lines, it is a message of either hope or doom. It is hopeful if you’re a small company committed to staking a future in this business because there is definitely room for you if you’re doing things right; your time is coming so stick it out. It is also doom because the old (old as in from 1990-today) ways aren’t working so well anymore so if this is your model or the model you aspire to adopt, it is only a matter of time. It will become increasingly difficult to make headway with price being the only point of differentiation -ultimately a race to the bottom. Anyway, this email indirectly shows why I think the market is still ripe with opportunity for people who don’t fall into these traps.
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Hi Kathleen, I just had to comment on your grading articles–they were so timely.

The company I work for has no technical background in their staffing. They have always left everything up to their vendors. In late August of last year they hired me -someone with almost 40 years in the industry as a designer, patternmaker, merchandiser, sourcing manager, Design Director and Sr. Technical Designer. I have worked with factories in almost every country in the world or have done trend research in the balance of the rest.

It has been a long and hard battle where I am working– to do things properly that will result in better quality goods. Management has been focused on getting new product into the stores every month. They have never checked the goods delivered from China. The goods were not checked at the factory nor were they checked in the DC [distribution center] upon arrival. I got them to hire an inspector for one of our bigger vendors in northern China/Shanghai area, but the work load has become too difficult for one person to do a 4.0 AQL on every style. He has no time to go back and recheck to make sure that they have corrected the callouts. Read more

How to check the accuracy of graded patterns pt.3

Sorry for the delay in the continuation of this (by all accounts) most popular series ever (not) but as I mentioned, there was a bit of hacking in the interim. Hopefully by now no one is receiving an error message of a phishing attack when they load the site.

If you need to catch up, see parts one and two; today I’ll post three and four. Part three includes reasons why I don’t think you should sew sample size sets (and what to do instead) and part four is an email from a colleague who wishes his company did sew samples in all sizes. That entry is titled: Life in the trenches from the real world of a technical designer
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The original question Mary asked was how to check a grade. Left for discussion was whether one should sew a sample in each size to test the grade. I don’t think you should. Mostly. I should qualify that.

Whether you should sew samples for each size depends on where you are in the gestation of your line. If you are new and perhaps tentative and uncertain that your sizing meets targets, you might want to sew samples of each size to test fit to your target customer. If you do this (and you should, but not routinely), pick one style that is representative of your basic body, aka whatever is closest to a block that you may have. The trick will be to find various bodies to try them on.

The danger of sewing full size sets and test fitting them can be endless iteration cycles. I’m not saying you should put out crap. I’m saying it is difficult to find one fit model that embodies your prototypical customer much less a whole size run of bodies that will. The problem is that you may end up using the fitting results of an outlying size body that is available to you, to adjust the other sizes (because grading cannot change shape, it only makes things bigger or smaller). Once you do that and re-cut another size set, the new pattern won’t fit the middle of the size run so you have to redo it again …see my point about endless iteration cycles? Read more

How to check the accuracy of graded patterns pt.2

Picking up where we left off in part one, someone I'll call Mary asks:

At this point I'm not 100% sure what the procedure is, hopefully you can confirm. Once I get the nest I will test it by sewing one sample? or should I sew every size?

The short answer is no, kind of. The real answer is that it depends. I'll explain still another way to check the grade on the nest without convoluted charts. In part three I'll explain why you mostly shouldn't sew up a set of sizes to check the grade.

Checking the nest:
This presumes you provided the grade or grading guidelines and calculated its division across however many pieces. It also presumes you know where the cardinal points lie (these points are numbered in the Excel grade rule report I showed you in the first entry). What you want to do is measure along the XY grid to see the grade of each point and for each size. I'll show you how to do this for one point; this is the junction of the side seam and under arm.

This first illustration below shows a line drawn perfectly vertical and another horizontal to intersect with the base size cardinal point. Since all of your sizes grow and shrink from the base size, each cardinal point of the base size is effectively the zero point.

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How to check the accuracy of graded patterns

grade_post_seam_measure2Edited 6/23/12
So you had a pattern graded, what do you do next? By way of introduction to what can go amiss if you don't know what to do after you get a pattern graded comes this comment (emphasis is mine, edited for clarity):

In the midst of my first production, I visited the factory today and found out that the sleeves of my dresses were much larger than the armholes they are supposed to fit in to. In some cases, the sleeves were 1" larger on each side, front and back armholes (total 2"). This was across the board, 5 styles in 5 graded sizes. Result: waste of fabric and sewing time trying to correct the problem. The sample pattern was checked against the sample size in the marker. Don't graders have the ability to check seam lengths on graded sizes? Has this happened to anyone?

The short answer is yes, graders have a tool to check grades which I will show you and then I will describe the process to follow after having a pattern graded to prevent this sort of thing. Before proceeding, one off topic mention: Sleeve and armhole seams should match evenly; see Sleeve cap ease is bogus. Additionally, it bears reminding that a grader might not be at fault if the pattern was wonky before it got to them and no, they're not responsible for checking it unless you pay for it. Which is why a lot of pattern people don't want to grade patterns they didn't make because patterns must be checked for accuracy (see how to do it yourself) before grading to prevent cumulative error.

Using my CAD program (StyleCAD), I can display seam measures in a variety of ways. This first one (top right) shows seam lengths (the key is F7 if you have this software) from notch to notch. In the above example I'm showing two adjoining pieces. From the left corner to the notch, the seam is 3 63/64ths on both sides. From the notch to the right corner, the seam length is 2". In this way I'm checking not only total seam length but that the notches are exact on the two pieces that will be sewn together.

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Pop Quiz: grading necklines pt.2

Following up from the first entry and the side jaunt (what does a 1" grade mean?), I'm not sure we have a clear explanation for the apparent contradiction. Specifically the contradiction is:
If we only grade the neckline a total of .5" for a 1" grade, how come we don't grade the neckline an inch for a 2" grade? [Informal (unscientific) polling shows we usually grade the neck 3/4" for a 2" grade, 1/2" for a 1" grade.]

Some suggested ideas were as follows (mostly paraphrased, please correct me if I misquote, mis-attribute or misinterpret what you said):

Theresa said 3/4" is used for a wider demographic because one is using SML instead of 6-16 etc. You know, there is some validity here. I take this to mean this is a way of refining the grade, to tweak it with a semblance of fit to one's customer rather than an across the board, gross increase. This seems just as likely as any other theory.

Katyrenee said it amounted to "just because", that we do it this way because it works (for whatever reason) instead of blindly following a rule. I like this too, another good theory.

Brina said the neck increase should be relative, not absolute -using the example of grading from a M to an XL. At first I wasn't sure what she meant as the amount of grade applied to an area is relative (explained in the second post) but I think I get it now.

It brought to mind an ongoing argument I've been having with Cooklin's grading book -yes, I argue with inanimate objects since Cooklin is now deceased and couldn't be compelled to leave the piano (and wine and women) long enough to discuss it with me and for which I do not blame him, my being generally quarrelsome. Pg 25 of my copy has scrabbled sketches with a lot of notation to include exclamation! points! such as "F&G do not equal D!" , "D-(F+G)=8%!"and "D=25%, F+G=17%, E=12.5%!" This of course is totally aside from the fact that I am in complete agreement with him that the front should get 62.5% of the grade and the back 37.5% of it but I don't know anybody who grades like that (anymore). Which is because your front is bigger than your back (yes it is, yes.it.is). Which is in sum, kind of sort of what Brina was saying drawn out to its logical conclusion. I think. Either that or I am too liberal in my attempts to inject a little fun into a normally dry discussion.

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What does a 1″ or 2″ grade mean?

A funny thing happened on the way to writing a follow up post to Pop Quiz: grading necklines -and as it has come up before, I thought to dispense with it for once and all time. Namely, what do we mean when we say we have a 1 or 2 inch grade (or however much)? This is not so easily summarized because it seems ambiguous if one doesn't understand the underlying references. I'll try to explain the primary tenets of grades which are:

  1. A grade describes sizing changes for the major fitting attribute only.
  2. Application of the grade is proportionate.
  3. Grading is a logarithmic scale. Or should be.

Defines major fitting attribute: Generally, when we say something has a 1" grade, we mean that the major or defining attribute of the garment will grow or shrink that amount. If the item is a blouse, it is understood that the bust measure will grow or shrink 1". If the item is a pant, it is understood that either waist or hip is the primary fitting attribute. It is also possible they both are, it depends on the company.

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Pop Quiz: Grading necklines

This amounts to an informal survey, it would be great if you could provide a bit of insight.

I had a conversation last week with someone who wanted to know why we grade necklines like we do -this refers to adult apparel. I'll number these so you can respond easier.

1. When we use a 1" grade, we typically grade the neckline a total of 1/2". Do you or don't you?

2. However, when we grade with a 2" grade, informal feedback says we grade the neckline only 3/4". Do you or don't you?

3. With respect to #2, why aren't we grading the neckline a full inch? If a 1" grade takes a half inch increase in the neck, it only stands to reason that a 2" grade would be double that.

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Why larger sizes cost more or Size is nothing but a number

Inspired by a recent comment:

Please explain to me why lines that sell the exact same clothes in a 6 to a 20 charge more for the 16-20. In my example it is the exact same style and brand (pinup style clothing which tend to fit plus sizes well). PLEASE help me understand as I find it entirely perplexing!

The answer to this question may seem intuitive but the context is that she read Why existing manufacturers don't add plus sizes in which we said the costs of adding on a plus size line were considerable, on the order of adding another division. Since the manufacturer she mentions already tacks on larger sizes to the standard sizes they offer, I can see she has a point.

It goes without saying that Lisa is new in these parts because she has not learned I cannot tell you the time without also explaining how to build the clock. Thus opens this discussion circuitously in which I explain that size is nothing but a number.

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