Archive for July, 2009

Extruder Controller

07/03/2009

I finished soldering the extruder controller, which controls the plastic extruder.

The plastic extruder does two things: it heats, and it pushes using a motor. First it heats; then, when the temperature is right, you feed plastic filament (3mm thick plastic rod) into it and a motor turns, forcing the filament down into the heater. This process is covered in the post on FDM.

The extruder controller is a board with an arduino built into it; it is the brains of the plastic extruder. It handles the signal from the thermistor, which is a temperature sensor built into the plastic extruder. Using the information from the sensor, it is able to regulate the temperature of the extruder very accurately.

extruder controller

Stepper Drivers 2+3

07/03/2009

Solder paste arrived and all of the stepper drivers are done.

stepper drivers, completed

Optical Endstops

07/02/2009

I am waiting on solder paste, but in the meantime I soldered all of the optical endstops because they don’t require the hot plate reflow method.

The printer has a stepper motor for each axis- X Y and Z. Each stepper motor runs along a metal rod. A problem that might arise is this: how does a stepper motor know when it has reached the end of the rod? If it goes too far, it might damage some of the hardware, or maybe even the motor itself.

…Which is where the endstops come in. There is an optical endstop for each end of each axis (two ends per axis times three axes equals six endstops). It works by shooting a beam of light into a light sensor. As long as the light sensor detects the light, everything is fine and it sends a signal equivalent to OK.

However, the printer is constructed in such a way that when a stepper motor reaches the end of the axis, the beam of light is broken. As soon as the light sensor stops detecting the light, it sends a message out. The motherboard interprets this message as STOP.

Pretty clever, right?

endstops, completed

The black component with two rectangular sections (NOT the RJ45 connector) is the sensor. One of the rectangular sections contains a light and the other contains the sensor. Putting anything between those two sections cuts off the beam of light.

Stepper Motor Driver #1

07/02/2009

The first part I constructed was a stepper motor driver. This is a board that controls one stepper motor (there are three stepper motors in the printer). It converts the power to the appropriate voltage and current, and translates the signal from the motherboard into a signal that a stepper motor can understand. As you will see in the pictures, it contains two ethernet (RJ45) jacks. This doesn’t mean the board understands ethernet signal; it is utilizing the ethernet cable because it is more convenient and organized than soldering a bunch of wires individually. The makerbot electronic components all communicate with each other using ethernet cables.

I soldered the first stepper motor driver together. It came like this:

stepper driver unassembled

tiny components

There are a whole bunch of tiny components, which are too small to be soldered using a regular soldering iron. Instead, I used a method called hot plate reflow. A solder paste is first applied to the bare pcb board; it is a thick gray paste which, when heated sufficiently, turns into hard metal. After the paste is applied, tweezers are used to place all the components in the right places.

The board, components in place, goes on a hot plate. Since the solder melts at a lower temperature than the board itself, the hot plate doesn’t damage the board. When the melting point of the solder is reached, it all pops and becomes hard metal, effectively soldering all of the components into place.

hot plate in action

The larger components required a typical soldering iron. Finished:

stepper motor driver #1, complete

Unfortunately the solder paste I used wasn’t the greatest, so I am waiting on some higher quality stuff in the mail. I ran some power through the stepper driver and the appropriate LED lit up, but it remains to be seen whether it is fully functional or not. Fingers crossed…

Makerbot!

07/02/2009

I have received a MakerBot kit.

printer, as shipped

laser cut parts

the electronics come in the form of small bags with heaps of microscopic components:

electronics in bags

…and so I begin.