This is development of a robotic quilting machine, QuiltBot.
It is a collection of tools and methods that allow the machine to sew a 48-inch square under computer control. It is conceptually related to the ‘TrolCat project and shares many components.
An Arduino runs GRBL, a G-Code interpretor. GRBL is the mother of all 3D printers; its core routines have been transplanted into most of the special printer boards on the market. I chose to go to the source, and use pared-down hardware/software to simplify development.
X and Y axes are belt drives from Festo. These are well-designed units, expensive but easy to work with/on. They’re deployed in pairs connected by a drive shaft so the two end of an axis are always syncronized.
X and Y are driven by ClearPath SD motors. These little gems take step/direction like a stepper, but have a built-in closed-loop servo controller. That means they win over steppers in three areas: speed, accuracy, and power. And they can be digitally tuned to the application. All the Arduino needs to do is turn them on and send pulses.
Z1 and Z2 are ClearPath MC motors. The MC family takes a pulse and translates it into motion. In this case, I have defined 1 pulse=1 stitch. The MC will take that one pulse and move the motor one revolution (4000 pulses). Both Z motors get the same pulse and will move in unison. This offloads a lot of work from the Arduino, and it performs the same sync function as the drive shaft on X and Y.
That’s most of the hardware. There is a box full of power supplies - 85V and 12V. There is a box full of controls - GRBL and some switches. There is a box full of computer - I will use an MacBook for now. Notice the absence of wires, thanks to the ClearPath technology. Especially note the lack of limit switches. All Teknic motors can use torque sensing to know that they’ve reached a hard stop. Festo linear actuators anticipate this, and so I exploit it.
This project started in 2010, and has been patiently waiting for technology to catch up. To achieve the desired result, motors had to evolve (from Sst1500/M23XX combos to ClearPath), controllers had to gain capability (from CTC 2600 PLCs to Arduinos), the tooling had to be built (local capability with lasers and 3D printing). The user interface is also evolving, from a proprietary controller (MQR) to an open-source scheme based on G-Codes. And the community had to change; gone are the days of a lone inventor locked in a garage. Make717 enables thought and action by bringing creatives together in the presence of tools.
10 August 16
Most of the machine is finished. There are a few mechanical mods that await attention - the Y axis needs a gearbox to reduce reflected torque, and the throat plate needs a sightly larger hole for the needle. Leveling and alignment are also on the to-do list. Electrically, the machine needs to be wired to a GRBL controller and its power supply needs to be boxed. Since this machine is closely related to 'TrolCat, it waits for the Cat to be finished so that lessons learned from that project can be applied.