I’ve already posted about hacking a knitting machine to accept multi-colour patterns. Today I’d like to expand on that with some work I’ve done recently to improve the multi-colour algorithm.
When I knit in multi-colour I use a method called Double Jacquard. This involves the Brother KM-950i, ribber KR-850 and colour changer KC-900.
The result is a multi-coloured pattern on the front and a simple pattern called Birds Eye to tie all the loose yarn together on the back.
But we can do better than this.
There are several complexities to be aware of with this setup. For each row of knitting in the fabric the carriage has to pass over the knitting twice for each colour. Once to go to the right edge of the knitting machine and again to get back to the left to change colours.
That means for a three coloured pattern, there’s six passes of the carriage to knit one row in the fabric. It’s a lot of work!
In the interest of keeping the process as simple and stress-free as possible, I try to use the same sequence of colours all the time (1,2,3,1,2,3,1,2,3) and never change the ribber settings as I knit (although there are some fantastic variations you can try if you’re so inclined).
My first multi-colour hack created patterns that incorporated these ideas, but it only works by doubling the height of the pattern (using pattern variation switch 4 on the knitting machine) to enable the carriage to return to the colour changer.
Obviously, this isn’t ideal as it means there are two knits for every pixel in the original image. Four knits if you want square pixels using the double width as well (pattern variation switch 3). The results get very pixelated!
Alessandrina also posted about this issue a few years ago to help punch card knitters plan their multi-colour work by hand. Unfortunately, she didn’t provide any workable solutions aside from my double height method.
Thing is, I KNOW for a fact multi-coloured double jacquard can be done using one knit per pixel. I know because other very talented machine knitters such as Woolly Wallaby have shown me it can be done. The fancy Passap E6000 can do it (clearly using some kind of dark magic). Sadly I don’t have access to such clever machines to understand how they do it.
Phew, that’s an awful lot of typing and I’ve only just introduced to you the basic premise of what I’ve been up to.
So what HAVE I been up to? Theoretical knitting of course! I’ve been theorizing how machines like the Passap E6000 might generate multi-colour patterns with one knit per pixel. And with a single colour changer on one side no less. Excitingly, I’ve come up with a benchmark of a few possible algorithms! It nearly did my head. Here are the results.
1. Double width, double height method
This is the original method I described above, knitted here to benchmark against the theoretical methods. It’s just a standard pattern which works with the double height pattern variation switch so the carriage can return to the colour changer after each pass. Double width to get square pixels.
1.5 rows of birds eye knitting in the back for every row in the front so overall elongation of the work is kept to a minimum. 456 total rows of knitting this test pattern.
2. Offset every first and last colour method
This method offsets each line just like the KRC pattern variation switch. This means it knits the last colour in the previous row and returns by knitting the first colour of the next row. The only way I could work out how to knit a third colour into this method is to return with a blank row, although dithered would probably work as well.
2 rows of birds eye knitting in the back for every row in the front causing some elongation. 283 total rows of knitting this test pattern.
3. Blank second pass method
3 rows of birds eye knitting in the back for every row in the front causes worse elongation. 456 total rows of knitting this test pattern.
4. Dithered method
3 rows of birds eye knitting in the back for every row in the front. Oddly the elongation is worse than the blank second pass method. 456 total rows of knitting this test pattern.
The double width, double height method has its charms but the clear winner here is the offset method. It has a negligible amount of elongation, the least number of passes overall and is able to achieve the one knit per pixel goal.
I’ve released an update to the multi-colour hack so you can choose which algorithm you want to use. If you don’t define an algorithm it’ll use offset by default. Enjoy!
If you have a fancy knitting machine like the Passap E6000 or know how they calculate multi-colour patterns PLEASE GET IN TOUCH! I’d love to know if any of this work even comes close to how they do it.
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