Auto Bed Leveling - Technical Update
Several backers have asked for some more technical details on the DeltaMaker to help them better understand how this printer is different from other printers. Below are some technical details regarding our auto calibration approach, and our Wi-Fi support.
In February we announced that every DeltaMaker 3D printer would include auto calibration and bed leveling. In this update, we would like to share more details regarding how our auto calibration is implemented.
Consistently printing high-quality 3D objects requires the build platform to be exactly where the printer thinks it is. Automatic bed leveling is the fastest way to calibrate the printer’s build platform. There are several approaches to auto bed leveling; most involve the use of a “touch probe” which is attached near the extruder nozzle.
As the touch probe is moved over the build platform, a sensor is used to detect when the probe is in contact with the build surface.
DeltaMaker Touch Probe and Sensor
To allow for a fully automatic bed leveling feature, the touch probe that is used to “feel” the location of the bed must be retractable to permit it to get out of the way while the printer is printing. The are many different ways to build a retractable touch probe; some use springs, some use magnets, and some touch probes do not retract automatically; they must be manually retracted by the user. For the DeltaMaker, we want a fully automatic touch probe that is small enough to mount next to the extruder nozzle. Our probe is constructed from a small solenoid that is mounted in such a way that when that solenoid is not engaged, the probe is higher than the extruder nozzle. The probe is normally in this retracted position, and it does not get in the way while printing. During the auto bed leveling function, the solenoid is engaged, which lowers the probe below the tip of the extruder nozzle. This allows the probe to make contact with the build platform, which allows the DeltaMaker to measure the height of the build platform at various locations around the build surface.
To measure the height of the build platform at a specific location, a sensor is used to detect when the touch probe is in contact with the build surface. The most common sensor to use with the touch probe is a micro switch (like the end-stop switches used when “homing” the printer). Switches are fine, but for the DeltaMaker we have selected a different sensor for our touch probe. We wanted to select a sensor that would be used for more than just auto calibration. Our sensor is also in use while the DeltaMaker is printing a 3D object.
In addition to sensing the location of the build platform, the DeltaMaker can also sense when the extruder printhead is touched or bumped unexpectedly. This allows the DeltaMaker to respond to various situations that may occur while printing an object -- such as, if the extruder head hits something (or someone) while the printer is operating.
The sensor we used for both the touch probe during auto calibration, and collision detection during printer operation, is a solid-state accelerometer. The accelerometer is mounted on the extruder printhead behind the fan. The accelerometer can detect a variety of events, such as when the touch probe “taps” the build platform, and the extruder collides with something while the DeltaMaker is printing.
The DeltaMaker will ship with built-in Wi-Fi and Ethernet. You may connect your DeltaMaker directly to an Ethernet cable, or add it to your WiFi network. This means that you can send 3D objects to print directly to the DeltaMaker, from any computer on your network. You may also control the printer from your smartphone and other mobile devices. In addition to network support, the DeltaMaker can receive future software upgrades via the Internet. To enable these capabilities, every DeltaMaker includes an embedded Linux computer, such as a Raspberry Pi (raspberrypi.org). The Raspberry Pi may be configured to run a variety of 3D printing apps, such as web-based control panels.
The main app that runs on the embedded Linux computer in the DeltaMaker is the OctoPrint Web-UI app. If you’re not familiar with OctoPrint, please check-out their website (octoprint.org); it is great. We are in contact with the developer of OctoPrint, to discuss adding new features at will be beneficial to the DeltaMaker, and other deltabot 3D printers. Please stay-tuned... Once you begin operating your 3D printer over Wi-Fi, you will not want to go back to the old way of using USB cables and SD cards. Instead of copying 3D objects to print onto an SD card, you simply upload the objects directly to your printer using a web browser.