_Index on Open Knitting Motor Project

Operation manual

Mon, 18 Mar 2024 00:00:00 +0000

Open Knitting Motor Project - Operation manual

0. TL;DR

You like videos more? See every menu function of the control box described in detail in this video:
Open Knitting Motor Control box in detail

But you should definitely come back and read about how to operate the whole system on a daily basis.

1. System startup

After powering on the control box, you will have to reset (aka homing) the knitting carriage once by pressing the SELECT button.

Parts list

Mon, 18 Mar 2024 00:00:00 +0000

This document hopefully lists all the needed parts to build the open knitting motor.

3D printed parts

If you have a Bambulab X1C printer and use BambuStudio as your preferred slicer, print all of the parts you find in the Open knitting motor.3mfwithout any further modifications. I positioned every item the same way I printed them myself.

If you have to use the single STL files, then, as a rule of thumb,

Component assembly

Mon, 18 Mar 2024 00:00:00 +0000

What you’ll find here and what not…

This assembly guide is not the “a) connect this to that b) now screw together blabla” type of guide, but more an overview of how things go together in general. I.e. I will not give an exact type, length or amount of screws, nuts and bolts for most of the parts, especially because sizes are not that critical in most cases or because, for some people, metric hardware won’t be easily available in some countries.

Firmware

Thu, 04 Apr 2024 00:00:00 +0000

The project is being developed under Visual Studio Code with the PlatformIO plugin. If you use the same IDE, you should not have any problems compiling and flashing the firmware to the Arduino, as all necessary external libraries will be configured via platformio.ini.

1. Pre-built firmware download

The firmware is (theoretically) available in two different versions:

Arduino R4 support (r4wifiv2 branch)
(Arduino R3 support (master branch) - OLD - NOT SUPPORTED ANYMORE - ONLY FOR REFERENCE - DONT USE!)

-> Always get latest firmware release here!

Wiring

Tue, 30 Apr 2024 00:00:00 +0000

How to wire all parts?

I try to describe how I wired everything together the best I can. Sorry, no schematic available atm, but it should not be too complicated. If I find the time I will try to add schematics.

PIN defaults

See include\HardwareConfig.h for the pin assignment defaults.

The minimum sensor (aka switch) pins you have to use are:

home endstop
max endstop
foot switch

Regarding yarn sensor / overload sensor pins: You HAVE to assign valid pin numbers, even though you do not have to use the sensors as of the current firmware implementation.

ChangeLog

Thu, 04 Apr 2024 00:00:00 +0000

FW Version	Gitlab branch	Comment
v0.4.6+138	r4wifiv2	main branch, don’t use `master` branch anymore, dropped Arduino UNO R3 support
v0.4.6+78	r4wifiv2	featurewise same as v0.4.6+65, but for Arduino UNO R4 (only!) support
v0.4.6+65	master	features ready (Arduino UNO R3 only!)
v0.4.2-prod	master	first public release

As I find it too tedious to list every change in the changelog here, I will only sum up milestones more or less. You can find more detailed version information via git log.

Roadmap

Fri, 19 Apr 2024 00:00:00 +0000

Things could get better over time…

Although I am quite happy with how the system is working today, things can always be improved.

Control box

Optimize display performance of control box in case of an error
In case one of the sensors (yarn, overload, endstop) got hit it can happen, that the display will begin to flicker or at least need some time until the error message is clearly blinking on the screen. It does not happen all the time and I am not quite sure atm why it does that. Might have to do with how the main firmware loop is working. Has to be investigated further.
Poweroff stepper motor while the carriage is not running
At the moment, when the carriage is not running, the stepper motor is still powered by the driver, so that the control box does not loose track of its position in relation to the knitting bed. This has the sideeffect that you cannot move the carriage by hand while it is being coupled to the carriage mover. As the system already has a rotary encoder attached to it, it should be possible to poweroff the stepper motor and correct its internal position from any manually introduced positional deviance based on encoder position calculations. This would make moving the carriage by hand possible without disconnecting the coupling bolt and also save some power.

Technical background:
The stepper needs 1600 steps/rev and the rotary encoder delivers 2400 pulses/rev, so we can say that moving the stepper to any direction manually changes the current positional step value by [0.6̅ x no. pulses = Δ steps].
I already made some tests regarding the positional error between the stepper motor steps, which is controled by the driver, and the pulses the rotary encoder returns while the motor is turning: I get about 20 pulses difference while the motor is running, and about 5 pulses when it is not moving. As the rotary encoder returns 2400 pulses/rev I think its preciseness should be enough and we can ignore the pulse errors here. Otherwise we would have to introdice some kind of error map based correction which can get reeeaallyyy tricky!

3D printed parts

The sensor mount for the overload sensor is currently mounted towards the front end of the spring lever near the spring. This is not the best for real fine adjustment of the sensor as the lever’s movements naturally are much bigger at its front end than on its back end. I plan to reposition it to the back of the lever near the bolt so that smaller adjustments of the sensor mounting plate are necessary to cover a wider (and so logically more precise) adjustment range.
Done. See mover_plate_v2.stl and additional chapter in the assembly documentation.
Due to feedback of the community (Thanks, Klaus!) I might think of offering the possibility to replace the endstop switches with reed switches or even hall effect sensors for contact-less switching. Reed switches could even be placed inside the groove of the aluminium extrusion which would literally make them disappear from the outside frame structure, what I’d prefer here. Have to think about it…

License

Mon, 18 Mar 2024 00:00:00 +0000

Attribution-NonCommercial-ShareAlike 4.0 International

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Fri, 05 Apr 2024 00:00:00 +0000

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