Software Open Access

symbiolab/Vitaprint_extruder: Vitaprint extruder

Luka Banovic; bostjanvihar

Vitaprint extruder 1.0 Table of contents

Bill of materials <a id="billmat"></a> Housing: <a id="house"></a>
  • Aluminium plates (300mm x 400mm x 5mm)
  • Aluminium blocks:
    • SYRINGE MOUNT: block 35mm x 45mm x 70mm (minimum)
    • FRONT CAP: block 40mm x 12mm x 60mm (minimum)
    • 24BYJ48 NUT: block 15mm x 25mm x 30mm (minimum)
  • M3x12 DIN965 philips screw 10 pcs
  • M3x12 BN6404 torx sxrew 20pcs
  • 2 x fi3 stainless steel rod (L = 110mm)
  • 40mm x 8mm x 2mm rubber sheet
Movement <a id="mov"></a> Thermoregulation <a id="thermo"></a>
  • Thermistor (read how to calibrate your own thermistor in the Calibration section)
  • 40W ceramic heater for 3D printers
  • 24V DC power supply
  • In our iteration we used PID thermoregulation algorithm (parameters need to be tuned by the user, depending on the control setup). Other temperature control systems can also be applied with this given hardware (relay switchin etc.).
Manufacturing and Assembly <a id="manuass"></a> 1 Overview and Toolset <a id="OVER"></a>

Here you can find manufacturing and assembly details for one Vitaprint unit. In this repository you can find STEP files for the Vitaprint unit in both orientations - Left and Right. The procedure is the same for both orientations (the final product is only mirrored) therefore you will find details for assembly for one unit in this repository.

1.1 General
  • Manufacturing time: approximately 8h
  • Assembly time: 30 min

NOTE: manufacturing and assembly time estimates assume well-skilled user and presence of all the tools listed below

1.2 Tool List and Skills Required
  • 3D printer (ABS)
  • CNC mill
  • CNC router
  • band saw
  • lathe
  • HAND TOOLS:
    • torx srewdriver
    • phillips screwdriver
    • super glue
    • two-sided tape
    • scalpel
1.3 Necessary Steps
  • purchase of raw materials and components
  • manufacturing of parts
  • assembly
  • calibration
2 Part Manufacturing <a id="MANUFACTURING"></a>

<img src="https://cloud.githubusercontent.com/assets/14543226/24997531/3aaafcba-2037-11e7-8800-1aba4ec7eacb.png" alt="bubble" width="450" height="400">

<img src="https://cloud.githubusercontent.com/assets/14543226/24997449/fa3d8c7e-2036-11e7-8a56-a97ed070c891.png" alt="table" width="500" height="600">

3 Assembly Details <a id="ASSEMBLY"></a>
  • Use philips DIN965 screws wherever you see the hole chamfers, use torx BN6404 screws elsewhere
  • for the following steps gently apply hammer:
    • sliding the ball bearing into the rod holder
    • sliding the M5 threaded rod into the coupler
    • sliding the fi3 stainless steel rod into rod holder at the bottom and N11 motor plate at the top
4 Arduino: Temperature Regulation <a id="CODE"></a>

To download Arduino firmware for temperature regulation please visit vitaprint_heat_regulator. This is an external temperature control system and can be replaced by any system you may have available.

Extruder calibration <a id="extcal"></a>

To ensure the stepper movement translates into the piston movement accordingly to the g-code, it needs to be calibrated properly.

Calibration set-up <a id="calset"></a>

In principle, the calibration set-up requires:

  • CNC control of the piston powering motor (we use Nema 11 with a planetary reductor)
  • the assembled extruder (at least the moving parts)
  • a precise displacement measurement device (calipers, etc., high precision indicators are preferrable)

The calibration protocol requires a set-up, where the piston translation, can be precisely measured in the axis of extrusion. For this purpose, the measurement device is fixed on the extruder in a way, that the extruder movement is translated directly into the measurement.

Calibration procedure <a id="calpro"></a>
  1. adjust the steps/unit value of the motor settings in the cnc control software (or use default values)
  2. command piston movement for an exact distance
  3. measure the real movement distance and compare
  4. repeat steps 1-3, until the g-code value coincides with the measured value

For a Nema 11 motor (with a planetary reductor) + an M5 spindle (0.5mm pitch/rotation), the default STEPS/UNIT value is 37914.30.

Thermistor calibration <a id="thermcal"></a>

Every thermistor analog output values have to be mapped to actual temperature values via an equation. Every thermistor needs to be calibrated as described in this section.

EQUIPMENT: thermo block/plate (heat source), alcochol thermometer, thermistor, setup for reading analog signal from the thermistor, oil, glass.

  1. pour a small glass of oil (50mL or so)
  2. place the glass on the heat source
  3. fit a thermistor to the alcochol thermometer
  4. sink the thermistor - thermometer setup into the glass with oil
  5. prepare the system to read analog values
  6. turn on the heat source and record sensor analog output at every 1°C increment
  7. plot data (x - axis: analog output, y-axis: real temperature)
  8. fit the best trendline to the data obtained (MATLAB or EXCEL are good tools for completing this task but there are also others)
  9. software will yield a fit line equation which then has to be transcribed into microcontroller firmware (we used Arduino Mega)

Now your thermistor will give out the right temperature values.

step_vitaprint.zip

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