How to calibrate the build head

Intro

Correct calibration of the build head is key to a successful print on Ember. This tutorial will walk you through the build head calibration process in detail.

This video provides a quick overview of the process:

 

Objective of Calibration

The objective of build head calibration is to align the build head parallel and flush with the PDMS surface.

This is important for several reasons:

  1. To ensure that the first layer sticks onto the build head
  2. To prevent jamming when the resin tray rotates
  3. To ensure an even thickness of the first layer

Main components: 

  1. Build Head
  2. PDMS (i.e., the silicone window of the resin tray) 

The first step of calibration is to become familiar with parts of Ember used in the process. They are;

  1. the Build Arm;
  2. the Build Head and;
  3. the Resin Tray.


If you're already familiar with Ember, skip to calibrating the build head.

About the Build Arm

The build arm connects the build head to the Z-axis. It is made up of the following elements.

  1. Ball joint
  2. Locking lever
  3. Calibration bolt
  4. Calibration hex key
  5. Kinematic coupling


Ball joint

The ball joint allows the build head to be adjust in pitch, yaw, roll and Z. This allows the build head to be aligned parallel to the surface of the PDMS.

Locking lever

The locking lever locks the build head securely in place.

  1. Turn clockwise to lock
  2. Turn counter-clockwise to release

Calibration bolt

The calibration bolt locks the ball joint in position; securing the build head position relative to the PDMS.

Calibration Hex Key

The calibration hex key is used to loosen and tighen the calibraton bolt. When not in use it is stored in the build arm.

Kinematic coupling

The kinematic coupling is the interface between the build head and the build arm. It keeps the the two aligned together with a high degree of precision and accuracy.

In addition, it contains magnets to hold the build head in position when the locking lever is released.

About the Build Head

Parts are printed onto the build head. The build head is made of the following elements.

  1. Build head housing
  2. Build plate
  3. Kinematic balls
  4. Magnets


Build head housing

This is the structure of the build head and has been designed to be easily gripped in one hand.

Build plate

This is the element on to which parts are printed.

Kinematic balls

The kinematic balls interface with the coupling on the build arm.

Magnets

The magnets interface with the coupling in the build arm.

About the Resin tray

The resin tray is made up of the following components

  1. Resin tray
  2. PDMS window
  3. Glass window
  4. Gasket

Resin Tray

The resin tray is made from amber polycarbonate. The amber color blocks blue light and prevents the resin from curing.

PDMS Window

The PDMS window is where each layer is formed. PDMS stands for Polydimethylsiloxane and it is a member of the silicone family.

Glass Window

The glass window is the substrate that the PDMS window is stuck to, it provides rigidity to the PDMS window assembly.

Gasket

The gasket is used to create a watertight seal between the glass window and the resin tray.

 

Tip:

Check out Resin Tray Care for more information on how to maintain the resin tray.

Preparing for Calibration

The process of calibrating the build head will only take a few minutes. 

WARNING When handling resin, always wear protective gloves and clothing, as well as safety glasses.

Before starting check that:

  1. Ember is powered on
  2. The build head is clear of any previous print
  3. The build head is securely locked to the build arm (see install build head instructions)

    Locking lever (1) shown in locked position

  4. There is no cured resin stuck to the PDMS (see resin tray care instructions)
  5. There is resin in the resin tray (see install the resin tray instructions)
  6. The resin tray is properly attached to the rotating plate (and that the three tabs at at the base of the resin tray are securely locked in place). 

Calibrating the Build Head 

 

WARNING

Whenever handling resin, always wear protective gloves and clothing, as well as safety glasses.

 

  1. For Ember firmware version 1.2 and later, Ember will automatically go into calibration mode at the beginning of every print. [If you wish, you can skip this by pressing the according button on Ember's control panel after starting your print.] NOTE: If you're using an older firmware version, you will need to manually trigger calibration mode by holding the right hand button on the UI panel down for 5 seconds. 
  2. Open the amber access door, loosen the calibration bolt (1) with the calibration hex key (2). The build head should be free to rotate in all directions and move up and down
  3. Gently push the build head up to the top of its travel
  4. While holding the build head in position with one hand, tighten the calibration bolt to secure the build head
  5. Close the amber access door and click "Next" on the UI panel, the build head will move to the calibration position
  6. Once the build head is at the calibration position, open the amber access door
  7. Loosen the calibration bolt so that the build head is free to rotate in all directions and move down
  8. Let the build head fall under its own weight into the resin tray so that it is flush with the PDMS surface
  9. Rotate the build head so that it is square with the PDMS and allow it to settle in place
  10. Tighten the calibration bolt and return the calibration hex key to its pocket
  11. Close the amber access door and hit "Done" on the UI panel


You can tell if you have successfully calibrated by the build head if all the following apply:

  1. As the resin tray rotates, the build head pushes all but a very thin film of resin off the PDMS. The PDMS should look almost dry



  2. The resin tray rotates without any jamming or skipping of steps

 

NOTE: 

As of Ember's firmware 1.2 update (released on 4/23/15), the calibration routine is now automatically inserted in front of each print job. To skip calibration and immediately start printing, press the button indicated on Ember's UI panel after pressing Start. If you do not skip the calibration routine, your Ember will go into Calibration Mode and wait for you to complete the calibration process.

 

Continue on to Managing Print Jobs & Printers... 

 

 

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