Gina

Designed and been printing links for a cable chain.

Rough bed levelling is achieved with guitar pegs in the bed corners.  Precise bed levelling is assigned to the automatic bed level compensation in the control board.

This first photo shows the main framework of the printer plus print bed Z carriage frame and XYZ drive systems. The external dimensions are 750mm x 660mm x 1000mm. The frame parts are 20mm x 20mm aluminium extrusion designed for wheels to run on. The X rail is wider at 40mm x 20mm for extra precision. The printing capacity will be 490mm x 470mm x 650mm (or maybe slightly more).  Most printed parts are PETG with the exception of the Z drive gears which are PLA for the large gear and TPU for the motor pinion.  Also, the parts cooler air duct is in ABS for that ability to "solvent weld" it in parts.

This printer is different in some ways from most 3D printers. The X and Y drives are combined in an arrangement called CoreXY where one stepper motor provides X+Y motion and the other X-Y motion. The drive is by standard timing belts and pulleys.  The Z drive is different - it uses fishing line braided cord which is very strong, with negligible stretch. Cords are attached to the 4 corners of the bed frame, go up over pulleys and onto a horizontal aluminium tube that acts as an axle/drum where the cord is wound up to lift the bed. This is driven by gearing with a 10:1 ratio from the Z stepper motor.

Think I'll start a new blog as the upgrade make this printer quite different.  GinaRep Giant Mk.3.

Bed corner blocks completed and installed plus all four suspension cords connected to the adjusters.  Z drive pinion printed, pushed onto motor shaft and motor mounted on main printer frame.  On testing by hand it was found that the Z carriage frame collided with the left hand XY motor so a new motor mounting was required.  Since the standard NEMA17 bracket wouldn't fit, a 3D printed motor bracket was designed and printed in PETG.   With all drive mechanics completed, the printing capacity was measured - 470mm x 490mm x 650mm (XYZ).

Still to do :-

1. Decide location and mount control box and hotend cooling water reservoir.
2. Wiring and water tubing.
3. Umbilical support cable chain.
4. Filament reel support.

Printing blocks for the corners of the Z carriage/bed.  These have three functions :-

1. Hold the Z carriage frame members together, square and level.
2. Hold the wheels that hold the bed in the right position horizontally.
3. Provide brackets for the bed level adjusters (guitar pegs).

Looking at This Cable Chain.  Think I'll design my own...

Calculate the Z drive parameters :-

1. Shaft diameter = 25.4 mm giving circumference of 25.4 x π = 79.8mm.
2. Motor does 200 x 16 = 3200 µsteps per revolution.
3. µsteps/mm therefore = 3200 x 10 / 79.8 = 401.02.

401 µsteps/mm seems pretty reasonable.  That's if I've got the calculation right ?

Rear pulley blocks designed and printed in ABS and checked for fit.  Final blocks will be printed in PETG.

Now working on the Z drive.  A horizontal aluminium tube, 1" (25.4mm) OD will go across the top from side to side and centred front to back.  This will be driven by a pair of spur gears from a NEMA17 stepper motor.  Cords from the corners of the bed will go up over pulleys and be wound up on the tube.  There will be approximately 9 turns to raise the bed from bottom (Z = 700mm) to top (Z = 0).  With a cord diameter of 0.4mm these turns will take up just under 4mm for each cord.  Approximate bed levelling will be achieved with guitar pegs attached to the bed frame - accurate bed levelling will rely on the auto-bed-level-compensation of the controller electronics.

Finished the stripping down and now re-building.  Y rails sorted out and in place.  Y carriages (with X rail) run very smoothly.  Also, have XY motors attached with brackets.

I'm currently almost rebuilding this printer as I'm dissatisfied with certain aspects of it.

1. The Z drive with the 4 threaded rods is very noisy and slow.
2. The brackets for the bed failed to hold it when printing with a high bed temperature so I had it supported on pieces of wood on the floor.
3. In spite of the bungy cords to lift it, the umbilical tended to catch at high level printing.
4. The arrangement of Z drive and XY carriage limited the printing area.

To overcome these problems I'm changing from moving the XY plane for Z axis to the more standard moving print bed, replacing the 5mm thick aluminium bed with a 2mm aluminium sheet supported on aluminium extrusion, parts of which will form the Z carriage.

The threaded rod Z drive will be replaced with cord support on the four corners as I have in one of my other printers. The cords will be taken over pulleys to a crosswise bar on which they will be wound up to lift the bed, with the bar driven by reduction spur gears (3D printed) from a stepper motor.

A TMC2100 works well.  The motor is quiet.

No joy with TMC2208 driver so ordered TMC2100 which are known to work silently in 3D printers.

Got motor unit working but the motor is very noisy so I've ordered a couple of TMC2208 driver modules (one spare or for other clock) to replace the A4988 driver to stop the noise.

Finished clock except for the motor drive unit - tested with a DC motor-gearbox.  Arduino Nano arriving tomorrow.  The one I had was faulty.

The layout diagram was done in LibreOffice Draw and the Arduino sketch (code) in the Arduino IDE.

Working on the drive unit now.  This is the layout of the stripboard and components.  The RTC (Real Time Clock) is accurate to a minute or two a year.  The stepper motor is a NEMA14.

And the Arduino sketch

// Filename :- Giant_Wall_Clock_v1_2018-11-12
// Software timing from RTC on pin 2 using polling
//
#include <DS3232RTC.h>    //http://github.com/JChristensen/DS3232RTC
#include <Time.h>         //http://www.arduino.cc/playground/Code/Time  
#include <Wire.h>         //http://arduino.cc/en/Reference/Wire (included with Arduino IDE)
//
String VerString = " Giant_Wall_Clock_v1_2018-11-08";
boolean lastSqWave = 0; 
boolean ledON = 0; 
int count = 0;  // Used to flash LED
int sqwPin = A6;
int dirPin = 5;  // DIRECTION pin
int stepPin = 6; // STEP pin
int slpPin = 7;   // Sleep pin
int rstPin = 8;  // Reset pin
int ms3Pin = 9;  // Microstepping pin
int ms2Pin = 10;  // Microstepping pin
int ms1Pin = 11;  // Microstepping pin
int enPin = 12;  // Enable pin
int ledPin = 13;  // Internal LED pin
//
void setup() {
  Serial.begin (9600);     // Enable Serial Monitor via USB
  pinMode(dirPin, OUTPUT);
  pinMode(stepPin, OUTPUT);
  pinMode(slpPin, OUTPUT);
  pinMode(rstPin, OUTPUT);
  pinMode(enPin, OUTPUT);
  pinMode(ms1Pin, OUTPUT);
  pinMode(ms2Pin, OUTPUT);
  pinMode(ms3Pin, OUTPUT);
  pinMode(ledPin, OUTPUT);
  digitalWrite(ms1Pin, 0);  //  full-step mode
  digitalWrite(ms2Pin, 0);  //  full-step mode
  digitalWrite(ms3Pin, 0);  //  full-step mode
  digitalWrite(enPin, 0);   //  enable
  digitalWrite(rstPin, 1);  //  not reset
  digitalWrite(slpPin, 1);  //  not sleep
  digitalWrite(dirPin, 1);  //  set on test
  pinMode(sqwPin,INPUT_PULLUP);   //  RTC timing pin
  Serial.println(VerString);
  setSyncProvider(RTC.get);  // the function to get the time from the RTC
  if(timeStatus() != timeSet) 
      Serial.println(" Unable to sync with the RTC");
  else
      Serial.println(" RTC has set the system time");
  RTC.squareWave(SQWAVE_1_HZ);    // 1Hz square wave            
}
//
void runClock(void){
  for (int i = 199; i >= 0; i--) { 
    digitalWrite(stepPin, 1);
    delayMicroseconds(10);     // Make STEP pulse 10μs long
    digitalWrite(stepPin, 0); 
    delayMicroseconds(30); }     //
  ledON = !ledON; digitalWrite(ledPin, ledON); }  //  flash LED 1s on 1s off

//
void loop(){
  boolean sqUp = ((analogRead(sqwPin) > 500));  // read logic level of 1Hz square wave
  if (sqUp != lastSqWave)  { lastSqWave = sqUp; if (sqUp); { runClock(); } }  //  Call runClock on rising edge of RTC square wave
}
// End

Here the latest build.  The dial looked overpowering so I've streamlined it.

Almost ready...

Dial on wall.

Part of clock hung on the wall.

Shortened the hour hand and thickened the number 3 to match the others.

Minute Hand.

Hour hand printed.

Real clock on floor.  The long threaded rod with the yellow sleeve will be replaced with a bolt when I get one.