Movement Settings:
Axis steps per unit: These values were changed based on the Stepper motor used. #define DEFAULT_AXIS_STEPS_PER_UNIT { 80, 80, 80, 96 } set to #define DEFAULT_AXIS_STEPS_PER_UNIT { 80, 80, 80,200 }
Maximum/Default/Retraction/Travel Acceleration: All movement related script was changed to reduce the speed of the various movements during printing.
#define DEFAULT_MAX_ACCELERATION { 3000, 3000, 3000, 3000 } set to #define DEFAULT_MAX_ACCELERATION { 1000, 1000, 1000, 1000 } #define DEFAULT_ACCELERATION 2000 set to #define DEFAULT_ACCELERATION 1000#define DEFAULT_RETRACT_ACCELERATION 2000 set to #define DEFAULT_RETRACT_ACCELERATION 1000#define DEFAULT_TRAVEL_ACCELERATION 2000 set to #define DEFAULT_TRAVEL_ACCELERATION 1000
Default E-Jerk: The E Jerk value is the minimum speed change that requires acceleration. This was reduced in order to create smoother print movements whilst printing smaller and finer constructs.
#define DEFAULT_EJERK 5.0 set to #define DEFAULT_EJERK1.0
Bill of Materials
The complete bill of materials for the final Bioprinter manufactured is listed in Table 1. The original 3D Delta printer used for modification was assembled according to manufacturer’s instruction and all parts used in the final bioprinter model were from the original 3d printer, unless mentioned in the Bill of materials Table 1.
Build Instructions
Assembly of commercially available ANYCUBIC Kossel Delta 3D printer
For ease of access to build materials, an Anycubic Kossel Linear Plus Delta 3D printer was purchased from DIYelectronics (Durban, South Africa). All parts were provided within the build kit and assembly of the printer was done as per supplier’s instructions. The printer technical specifications are outlined in Table 2.
Firmware Flashing
The Tri-gorilla control board (integrated with the function of the Mega2560+ramps 1.4; main control chip: ATMEGA256016AU), on the assembled delta printer, required installing (i.e. flashing) software (firmware) specifically written for controlling and monitoring the 3D printer. Open-source Marlin Firmware (v.1.1.0) was first used for flashing the board; available on the manufacturers’ website [L4]. Firmware installation was performed through the Arduino Integrated Development Environment (IDE) desktop software (v.1.8.1.0, [L5]). The printer was first connected to a PC using a USB cable (USB 2.0-A Male to USB-B Male cable), the Arduino.ino file was then opened using the Arduino software environment. In the Arduino environment, Tools > Board > Arduino MEGA 2560 serial connection was selected. The Firmware was subjected to several changes as described in detail in section 1.1. Within the Arduino environment, the Configuration.htab was used for the software modifications. The “upload” option was then selected to flash the Tri-gorilla board. The final modified firmware is available at https://doi.org/10.17605/OSF.IO/7TQKB.
Hardware modification
Based on the criteria for bioprinting, the delta printer was modified to accommodate for tissue engineering application purposes. The methods of modifications to the hardware are explained throughout the following sub-sections.
Enclosure of the printer
The printer was encased to maintain sterility during future bioprinting. All parts used were designed using CAD software and manufactured in PLA (corners), Perspex (sides) or Glass (lid). Assembly was as follows;
Corners:
1) Printed corners were pushed onto the aluminium frame.
Sides and door:
1) Each frame was secured to the aluminium extrusions of the printer using six M3 x 10mm cap-head screws, six M3 T-nuts and twelve M3 washers.
2) The windows, for the two sides of the printer, were secured onto the newly attached frames using four M3 x 8mm cap-head screws, four M3 nuts and eight M3 washers.
3) The door handle was fitted onto the door without the need for fasteners.
4) The door was assembled onto the frame of the front facing side of the printer using two hinges, ten M3 x 10mm cap-head screws, ten M3 nuts and twenty M3 washers.
Lid:
  1. Additional aluminum extrusions were secured to each existing extrusion using 3D printed parts and twelve M4 x 5mm screws and twelve M4 T-nuts.
  2. Glass was secured onto the top of the new extrusions using six M4 x 5 mm screws and six M4 T-nuts.
  3. The finishing pieces were added simply by sliding into the new extrusion grooves.
  4. Electronic board box
The Tri-gorilla electronic board (assembled according to manufacturer’s instruction) was moved to outside the printer. A board box was designed and manufactured in PLA using a standard Delta 3D printer. The designed and printed board box consists of two separate pieces: the box and the lid. Assembly was as follows;
1) All wires were disconnected from the Tri-gorilla electronic board and the board removed from its original fixture (under the print bed).
2) The board was secured onto the newly designed and printed board box using two M3 x 10mm cap-head screws.
3) The board box was secured onto the aluminium extrusions of the correct side of the printer using two M4 x 5mm cap-head screws and two M4 T-nuts.
4) All wires were fed through the aluminium extrusions (from within the printer) into the board box and reconnected in their respective places.
Bed platform
A print bed platform was designed and printed using a standard Delta 3D printer using PLA as extrusion material. The platform consists of six separate pieces; designed to hold two 220 mm diameter glass plates, with the top plate designed to hold a standard size petri dish. The printed pieces were secured onto the printers aluminium extrusions using two M3 x 25mm cap-head screws and two M3 T-nuts per piece.
Extruder
The original thermoplastic extruder was removed from the effector plate and replaced with a newly designed syringe-based extruder. Assembly of the syringe-based extruder was carried out exactly as described online [L6]. Instructions up until attachment of the power-supply mounting bracket were followed exactly as described. The following changes were made from there;
Assembly onto mounting bracket and printer
1) The assembled drive block was attached to the mounting bracket using four M3 x 35mm cap-head screws and four M3 nuts.
2) The mounting bracket with attached drive block was attached to the printer frame aluminium extrusions using two M4 x 15mm screws with four M4 T-nuts.
3) The NEMA17 stepping motor was connected to the E0 port of the Tri-gorilla electronic board using a standard 4-pin extruder cable.
Assembly of Luer-lock effector plate adaptor
A “nozzle” was designed for the extrusion of biomaterials using the syringe-based extruder system. It was designed to attach to the original effector plate provided with the Delta printer. The nozzle was designed to incorporate a male Luer-lock connection fitting and a Bowden tube connection fitting. Assembly went as follows;
1) The printed adaptor piece was secured onto the effector plate using four M3 x 8mm cap-head screws and four M3 nuts.
2) The bowden tube was pushed into the bowden tube connection fitting and secured into place using insulating tape and silicone paste.
3) A Luer-lock syringe needle was then fastened into place using the male Luer-lock connection fitting part of the adaptor piece.
Addition of syringe, top strengthener and tubing
1) A 5 ml Luer-lock syringe was added to the assembled and mounted syringe extruder.
2) The printed top strengthener was fitted onto the mounted syringe extruder using the threaded bar used to secure the motor to the frame and the two M3 x 35mm cap-head screws positioned on the other end of the frame.
3) The bowden tube was attached to the syringe using a Luer-lock adaptor, silicone sealant and insulating tape. The other end of the tubing was attached to the Luer-lock nozzle piece.
Operation Instructions
Software requirements