3D knitting of shoes, can save 50%+ production time?
We were told recently, by a very popular factory in China that knitting to shape is not efficient and costs too much to produce. We proved that knitting to shape is much more cost effective.
Given that the machines are about the same, (slightly less expensive in China, due to high volume machine sales), and that one person can run 8 to 10 machines, the labor and machine cost, are negligible in cost sheets. Material is about 50 to 75 grams per shoe when knitting to shape. It can be 3 times that wastage when knitting rectangles and die cutting. All that fabric that the machine spent valuable time, utilities, and maintenance knitting is trash. All the yarn which the yarn supplier spent time, materials, and dye making, is thrown away. Where does all this production trash go, but into the landfills, and water supply.
Here are the differences by time and waste made on Stoll 530 machine (not ‘High Performance’ HP)
26 minutes: die cut 60% waste 21.5 minutes: die cut 30% waste 15.5 minutes: no cut >1% waste
Above are examples of 2D shoe applications. An HP or High-performance machine typically increases the savings an additional 12% or more. An ADF usually increases savings additionally, over the HP.
So why aren’t more products, including other knitted shoes made this way? There are a couple of reasons why companies don't knit to shape.
- The most prevalent reason we’ve come across as to why knitting to shape is dismissed, especially those in the 5 countries that do the lion’s share of production, is that it is easier for companies with unskilled labor to enter the market making rectangles, cut and sew.
It is far easier for machine builders to sell machines to companies getting into knitting and with limited machine knowledge, by starting with how to make rectangles of fabric. It is also simpler for anyone wanting to get into the knitted shoe trend, to take rectangles of knitted fabric, regardless of what machine they are knit on, (warp, flat, circular), die cut the 2D fabric, send the cut pieces to a shoe factory and send to the landfill, the 60%, of the material in that rectangle that is left. The shoe factory then pulls, tug, and ease the fabric into a shoe for multiple sizes. The result is that the 2D fabric doesn't fit properly. The fabric then needs a lot of extra support of PU, foam, felts and liners. The knit fabric is then just the exterior and treated like a component, that mimics a genuine knit shoe, but is completely a different product. The addition of all the other components, which are not of the same fiber content, means that the shoes WILL go to the landfill, rather than being recycled.
Because these new factories have been taught to make 2D rectangles in cut and paste modules by the machine builders, this is the easiest way for them to make a significant volume of product as fast as possible. But, if you look closely at any graphics or stripes, the right and left shoes never match. Most times the rectangle is not graded for sizes, and the same graphic fits from a 6 ½ to a 13, and more. This means that you will see a lot of solids, gradients, and simple designs, while also seeing a lot of additional support materials added. How many shoes’ toe areas collapse so much that fabric takes the shape of the wearer’s toes in all their twisted and hammered glory. Is this good enough to sell the product? For low end sales around the globe, the answer is yes. Due to little government oversighte in those 5 countries, the tremendous amount of waste generated in production, with no exit strategy other than the fate of a landfill, is not an issue. Nor is the fate of now having to landfill the product when its usefulness is over.
What they are not understanding is that cutting and pasting into 2D knit to shape can be done just as easily, and should save almost half the production time, depending on the style.
Knitting to shape guarantees that any graphic will fall into the same place on every single pair. Mirroring gives the exact reverse for the opposite foot of that style. The graphic needs to be graded for sizes. We have seen factories uses these templates to make many variations of the same style (same upper pattern), for multiple styles.
Yes, there is a little more preparation in the up-front programming for each type of fabric in knitting to 2D shape, but the knitting is faster, nearly 50% more efficient. There is nearly zero waste in production, and each upper fits precisely into the upper shape pattern needed at the shoe factory, and if it is done in 3D it also fits better. The prep time for the first 2D or even 3D shoe in then amortized into all the styles ever made. By then the programming time is negligible. What is more is the fully integrated 2D or 3D product is all of one fiber and can have an exit strategy of being recycled into something else. It is hyper-sustainable because it can be multiple loops of different products. We think of new recycled products like sourdough bread. They always have a part of the first mother product in them. If you want to read more on why sustainability important to both finances and production, read here.
Personal example of building a 3D shoe with an 'exit strategy': “Exemplifying Sustainability”
In 2008, Stoll asked us at Fabdesigns to do a favor. The favor was to see if we could help one of their potential clients. After the introduction, asked if we could help them build a product. We’ve done slippers and medical footwear, so why not?
Our contact at the client asked us to make five pieces that could be semi-finished, clipped, and stitched together like a regular shoe upper is made. We asked, ‘why do you want to use five pieces?’ We told him there was, ‘so much time and waste in individual components.’ We invited him to look thought our studio in North Hollywood in January 2008. After he spent half a day with us, looking through our entire library of thousands of 2D and 3D knit swatches, we suggested to him to instead make a shoe all in one piece. He said he’d get back to us. About a month or two later he did.
He could not believe that a shoe upper could be made all in one piece. He said they’d been trying to make a shoe for 10 years and all they had was a sock shoe. He challenged us to prove that not only could we make a 3D shoe on a flat knitting machine, but added another challenge, that this shoe would stand on its own and not collapse under its own weight. With decades of 3D knitting, we weren’t daunted.
This technology we have been building since the CMS debuted in 1987, is our 'textiles on steroids' version of a textile manufacturing format that precisely engineers yarns and fabric variations solely where they are needed. By doing this far more efficiently than WYSIWYG CAD software, we can create fabric structures and or functional variations for load or performance, which are mapped into the resulting products, any product, with anatomical correctness and a virtually seamless fit. The knits’ structures are specially engineered for performance to create light weight designs that minimize excess materials and feature only the essentials. There is nearly zero waste. Yes, it takes some time to figure all this out. We started as we start with any project from the fiber up, using yarns from our studio. We tested structures next, then integrated many types of techniques into different zones, while also using a fusible yarn we used in apparel for stiffening specific areas.
We showed the client that we can make rigid areas and stretchy areas, holes for ventilation, padding, all in one piece, making the fabric do more than a single fabric structure. The entire 3D shoe was built of 100% polyester from our studio, on our own feet for size.
The additional bonus idea we demonstrated, was the built-in exit strategy. By using only one polymer the upper could then be again recycled into something else – cradle to cradle. We made the first prototype of a 3D shoe in 2 weeks in the late spring of 2008. In two months, we made 14 prototypes to prove that not only was make a 3D shoe completely finished off the machine possible, including the tongue. but it was also hyper efficient, repeatable, and scalable to mass production.
At right is an example of 3D knit to shape integrated shoe upper that takes
10 minutes and 38 seconds on a CMS 502
At this very same time in 2008, it was reported in Fortune Magazine that post production waste for footwear alone from one company was $800 million dollars. $800 million of scrap that is thrown away. At that time, the company was a $18.6 billion-dollar company.
This project was supposed to be only 3 months, and we expected to go back to our own highly efficient sustainable knitting factory in North Hollywood, but the client was excited. The rest is history and complicated, but we will focus on the positive here. To date, as noted by the UN, this technology we brought to the client, has saved 3.5 million pounds of scrap in post-production 2012 to May 2016 from entering landfills.
This process of knitting to shape, or knitting in dimensions is not new, Cashmere in Hawick, Scotland has been knitted to shape since 1883, and Johnston’s of Elgin since 1797.
The process we built on the CMS, by integrating multiple fibers and zones of structure, also eliminates cutting, the department where the most serious industrial accidents happen in the apparel industry. Modern flat knitting machinery makes these pieces so much faster and more precise than past generations of equipment.
Our techniques which we have used for years before meeting the client, allowed a savings of over two minutes knitting time alone in the waste section over the machine builder’s standards. Multiply that by millions of pairs of shoes, and that is serious savings in money, time, and machinery.
The client has published that this technology in make 3D knitted uppers saves 90% of cost of materials and energy that goes into making a shoe.
These savings came from just one product using this technology. In 2013 MIT quantified the amount of carbon in making shoes. In 2013 The client ’s meeting was full of this knit technology we brought and taught. Today, the client is worth 27.8 billion in revenue. And, they promote that knitted shoe and the manufacturing system we taught them as 'exemplifying sustainability.'
1. No cutting
2. Minimal sewing and negligible waste
3. Ready to finish, pack and ship
4. Far more efficient in production
5. Consumer perceived quality does not justify high price
6. No unraveling edges (eye stays, heels, toe)
7. Right and left match in jacquards
1. Takes extra prep time to prepare a 3D program, 2D just a little extra time (minutes)
2. Must grade or group grade sizes
3. Program is specific to yarn used
4. Need more programming skills / training
2. Price point
4. Building the quality of knit technicians' knowledge
Connie Huffa – Fabdesigns, Inc.
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