Episode 285: Super Glue Gun 02: Extruder Motor

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    We're making progress with the Super Glue Gun project, though we've hit a problem and we need your help! To push the glue sticks into the gun, we need motor control. For this we're prototyping with ATTiny24, Arduino, TRIACs, and testing different motors, such as stepper motors. It can be tricky, first the team has to identify how much power they use depending on how much effort it needs to turn, and control them using an Arduino. Unfortunately, there are unforeseen consequences! Let us know if you can help in the comments below.


    Previously Ben took apart the glue gun and learned to control the temperature. Next they’re going to work on the extruder motor. Ben bought a bunch of motors and they’re going to see which one can fit inside a glue gun for one thing and then try to push a glue stick through the hot end using a motor and a gear. So they’re going to be using a DC motor controller, trying to understand how much current that’s going to draw, and what kind of power supply it needs (probably 12 volts). They’ve figured out how to heat it up, next they’re going to figure out how to push it through. Ben opens up a box of motor parts, thermistors, and microcontrollers.  They thought about using one of the 8 pin ATTINYs but they were too small so they got some 14 pin ATTINYs . They also got some 800 mA Triacs. There’s also an ATTINY24.


    Today they’re working on the gear motor extruder so the next thing Ben and Felix look at several different kinds of gear motors.  He’s also got a NEMA 14 Stepper Motor. One challenge they’re facing is they not only have to have a gear motor in there but they also have to have a transformer so they can take the MAINS power and knock it down to 12 and 5 Volts for the motor driver and the control circuitry.  Also in the package are some 3D printer gear heads for moving the 3D prints.  Another challenge that they’re facing is that while most of the DC Motors are 6 millimeter shafts, most of the ones they’re looking at are 5 millimeters. Felix found a little AC/DC  12 Volt power supply and they’re going to see if it can run this motor. They set the multimeter to current so they can see how much current it’s consuming.


    Ben explains what stepper motors can do. Typically one step will be like 1.7 degrees but if you have microstepping which is done by your controller you can step up to a 16th of a single step. So instead of 1.7 degrees it would be 1.7/16 giving you more granularity that way. Microstepping gives you finer movements.  Most 3D printers run their motors at 1/16th microstepping. In the case of a glue gun they can go coarser than that because they’re looking to brute force glue through a gun.  Ben gives a tip on working with a bi-polar stepper motor with 2 windings and 4 wires. Felix finds Ben a supply with AC in and then 12V and 5V DC out. It’s small so they can probably fit it inside their unit.  Ben hooks up several DC gear motor to a multimeter in serial so he can find what the current draw is and if they’re within range.  Ben simulates a custom gear by putting one in the grinder sideways. He also uses the dremel to manually put teeth under the gear.


    Next they wire up a test circuit. There’s a motor driver, a very large current sense resistor, other current sense resistors and capacitors, a 12V input going to the motors, and a logic voltage of 5 V.  Ben salvages parts from an old project and goes back to testing. They connect a power supply to an Arduino microcontroller, the motor driver, and the motor. They’re using a larger motor than they anticipated and a larger motor and motor driver than they anticipated so the power supply couldn’t supply enough current to keep everything running and the microcontroller kept browning out. They switch to a larger power supply and use a motor with a different adapter for extruding the glue stick. Felix switches the wires while Ben goes to work creating a different adapter.