What is the backpack?
The backpack is a low budget 3D delta printer. He uses the favorable 28BYJ-48 step motors and fits in a backpack as well. The idea for the backpack arose when there was a gap between the Low Budget 3D printer and The Sparkcube v1.1. The 28BYJ-48 stepper motors fill the gap between stepping motors from CD drives and Nema17 motors. From this gap, the following requirements were formed.
In this project several hundred hours have passed. From the idea, to the design to the prototype, it took a lot of sweat and effort, not to forget the investment in several components and several prototypes. For this reason, I would like to draw attention to the possibility in the form of a PayPal donation.

Requirements:
Low budget
As quietly as possible
28BYJ-48 stepping motors
Mini 3D printer for the desk
Simple construction
No special tools required
Each (with a 3D printer) is able to build a backpack by itself. However, the backpack should be built with basic knowledge about 3D printers.
Links
Project…

Nano delta is a tiny and simple delta 3d printer designed for people who are new to 3d printing or interested in delta mechanism.
The printing quality is not so great and it is slow, but it can surely demonstrate the mechanism and common characteristics of delta 3d printer.
For me, total cost of this project was about 80$ and more than half of this cost was used for electronic parts (ramp,mega2560,a4988,lcd2004,hotend,endstop) which can be disassembled to make a new better printer.

Simple
Only 9 printed parts are needed to make this printer so the assembly is very easy

Cheap
It uses 28BYJ-48 stepper motor with bipolar hack which is very cheap
You don't need anything more than a cheap masking tape on the bed to print pla or petg
The print volume is 64mm in diameter, 150mm in z axis.
I used these settings for printing speed.
printing speed 30mm/s
accel 300mm/s^2
jerk 5
I didn't tested anything higher than this since the motor is quite small and weak.
Rest of the settings are in the firmware.
I really wanted…

This will be a tiny Delta Rotational utility robot framework using those inexpensive 28BYJ-48 steppers. I am experimenting with them even though I am conscious that these steppers seem to have some backlash in the gearing, and that even appears to get less when the second pivot point is added like in this design. There is a planned place for a spring or rubber band to along with gravity 'default' that backlash. I am not sure how valuable the result will be but at any rate it is a interesting use of those motors and could be very accessible and inexpensive... Especially exciting is that this seems to be the first and only rotational delta experimentation platform so far on Thingiverse! However there are the FirePick and IcePick projects which are bigger open source rotational deltas.
Now that I just finished the last components and assembled them I am surprised, the operating range might reach beyond 10cm diameter and quiet a few cm height too. There are some errors still and some missing positions for end stop…