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.

Once the pattern is graded, I can compare all of the lengths easily, even per size.  The illustration below is another seam (not the same as above).  The piece names are SFRT and FRT, this is found under “pattern” on the left side of the chart with the graded sizes (10-18) listed beneath. [The base size is 14 which is why the chart shows zeros for that size.]

grade_post_seam_measure1

The perimeter column lists seam lengths of each size. The increment column shows how much the seam (red dashed line) changes per size. In this case, the seam lengths are changing plus or minus 3/16ths per size.  In all cases but size 10, we have an exact match in seam length. The size 10 SFRT is 1/64th shorter. By the way, if you are wondering why the pieces have such strange names, this will help.

The grader should check their work (the uniformity of the grade) before sending you the nest. This means that the column labeled “increment” should be uniform (usually logarithmic). However, it doesn’t necessarily hold that the perimeter column will be a match like mine is unless you hired the grader to walk the pattern to verify seam lengths. A lot of designers are certain their patterns are perfect because it was tested with a sewn sample but this isn’t the same thing because people make adjustments during sewing of one-offs and think nothing of it.

But I digress. It isn’t possible for a grader to export charts such that I’ve shown you so you can check more easily. This means you have to do something else.

There are two ways for you to check the grade. One is to request that the grader export the grading chart to Excel, any industrial program should do this. I don’t know what the output looks like for other CAD systems but I really like how StyleCAD sets theirs up. Below is an image sample of one piece.

grade_post_rul_lib_chart

Analyzing one of these Excel spreadsheets is rather mind numbing (just my opinion) because you have to compare the grade of points 1-2 of FRT to points 4-6 of SFRT. Those point numbers are just examples but you have to jump around in the spreadsheet a lot. I would much prefer to do this visually but if you don’t have a CAD system, it is a bit difficult to do it. So what can you do?

When you have a pattern graded, it needs to be approved and the person doing the approving is usually you. In anticipation of that, the grader will send you a nested pattern (all of this is described in much more detail in my book so if you are confused about any of this, reading it is the first step). The nest will have all of the pieces laid inside each other. The usual process of checking the grade is with a ruler. You measure seam lengths of various adjoining seams to make certain they will sew together. It is critical this be done well because once you approve it, if anything goes wrong with it after that, whomever proceeded you is technically off the hook. With approval, you “had it last”. In real life though, unless you’re working with a total jerk, an error discovered after the fact should be repaired at no cost to you provided you or somebody else didn’t fiddle with it. I think it is a good practice for you to save the nest and for the pattern grader to save that version with a unique file name.

However, these days since so many people don’t feel qualified to approve the grade, I suppose you could ask the grader to sign off on it. You need to make it clear so they save a version of this file independent of any later changes. Depending on the complexity, it may take time for the grader to highlight anomalies. For example, in the image I showed you measuring perimeters with the chart, the size 10 was 1/64th off. Sometimes -depending on the grade you requested- a small variation like this may be unavoidable. In this particular case, the designer wanted a companion piece (not shown, a sleeve) to grow a non-standard length so this affected the grow of this piece. [1/64th is not much of a problem but it does bring to bear my constant preaching that your base pattern must be perfect. If it were not, the differences magnify, errors are cumulative when it comes to grading apparel.] Personally I don’t think it is out of line for a grader to charge for the time it takes to explain these things to you because this is the responsibility of design and it would take you time to do it yourself. Once you understood (learning as you went along), you wouldn’t need so much hand holding so it would cost less.

To be certain there are still other ways to check the grade but they are much more laborious and costly in terms of materials. By way of example comes this query:

Once I get the nest, do I test it by sewing one sample? Or should I sew every size?

Perish the thought! I will answer this in my next post. Til soon~

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