Converting a Cheap Knitting Machine to an Automatic Multi-Color Monster

You can, of course, knit scarfs or socks by hand. But if you’re going to do a lot of knitting, you might consider one of those inexpensive manually operated knitting machines you can find on the rain forest website. They do the looping and weaving, so all you have to do is rotate the crank to get a tubular textile. However, they’re only made for knitting in a single color and that can be very limiting. YouTuber Martin Makes Things addressed that shortcoming by automating an affordable Addi knitting machine so that it can make custom multi-color patterns.

The Addi knitting machines (and others like it) start at less than $100 and even the large models are less than $200. They have a circular arrangement of needles rotated by a crank, with a mechanism that pulls the loop of each needle as it passes. They let the operator knit tubes pretty much as fast as they can turn the crank.

A popular modification is the addition of a crank motor, which can be as simple as cordless drill. But Martin took it several steps further with CNC control of the crank, as well as a clever mechanism for swapping between three different strands of yarn. That allows for two-color knitted patterns, as one strand is for the backing structure and will match one of the primary colors in most cases.

Like the crank, a stepper motor actuates the yarn-swapping mechanism. It is a clever 3D-printed apparatus that moves one strand or the other (of the two primary colors) in front of the needles. An infrared break beam sensor tells the machine when there is a gap in the needles to make a switch and two additional infrared sensors provide feedback on the positions of the mechanism’s arms.

To prevent problems that would arise from loose yarn or the end of a strand, Martin also implemented a mechanical tensioning system. That, too, has a sensor to detect the end of a strand and it works a lot like a filament runout sensor on a 3D printer. When the yarn runs out, it removes tension on the mechanism and causes an arm to move up in front of an infrared sensor.

This seems to work very well and Martin is able to create any arbitrary pattern, including pixelated two-tone images, using custom software he wrote to output g-code to the machine’s control board. That appears to be a RAMPS 1.4 control board, like the kind often used on DIY 3D printers.

Now Martinn has a fully automated knitting machine that can churn out complex patterns.