Study Tips on how to Punch Pesky Prints Off The Mattress with The Computerized Print Ejector

The Computerized Print Ejector is made solely from printed components and issues we had laying round within the warehouse of MatterHackers. The printer being victimized is an OpenBeam Kossel Professional.

I began off by rapidly designing some linkages in Solidworks. The holes match some little ball bearings we had laying round. Every little thing is held along with M3 bolts. We had an assortment of various sized bearings, so I needed to design components with a pair completely different gap sizes. All the ones posted on-line are made to suit 9.5mm outer diameter bearings. The holes additionally embody an additional 0.3mm to account for the tolerances of printing.

This was a enjoyable undertaking as a result of most parts took lower than half-hour to print. I may very well be designing the subsequent factor whereas the final piece was printing. There was no ready. In some instances its higher to plan all the pieces out firstly earlier than you construct it, however it may be extra enjoyable to only dive in and determine issues out as you go alongside. That is what I did with this undertaking. I ended up with lots of trashed components, however who cares.

Every little thing was printed in PLA since I used to be not anxious about something getting heat.

Really helpful Print settings:

• 0.2 mm Layers
• 2 Perimeters
• 30% Infill

To be able to actuate the scissor mechanism, I added a gear to the top of one of many linkages. I additionally discovered an previous stepper motor to drive it. I may have used a pastime servo, however the stepper is what we had and its received extra torque in any case. It additionally conveniently had a small gear already on the shaft.

That is the bracket I designed to carry the motor and all the pieces. The plan was that the whole gadget would jut out from the facet of the printer, supported by a size of OpenBeam. As you possibly can see, engineering is an iterative course of.

At this level it grew to become obvious that solely driving one linkage would not work. The whole meeting would simply rotate down as an alternative of extending outward. Each of the top linkages have to be compelled collectively or pulled aside to ensure that the mechanism to work. I added a second gear with inward going through tooth. This fashion it might be pushed in the other way, forcing the linkages collectively.

Because the gears have completely different radiuses, there are barely completely different gear ratios and one linkage strikes barely farther than the opposite. This makes the entire thing rotate downward just a few levels when it extends. Oh effectively. Its adequate.

The boxing glove mannequin was discovered by means of googling and I modified it in Blender with a sq. gap within the backside to attach it to the arm. This glove turned out to be essentially the most troublesome factor to print. Not as a result of it’s a sophisticated form, however purely due to a collection of unlucky coincidental points with the printer (a few of which concerned hearth). When it lastly did print, the help construction beneath the fingers failed, so it would not have fingertips. I made a decision I do not care since you will not see that facet a lot in any case.

That is once I bumped into the subsequent downside. How do you retain the boxing glove horizontal? I designed a fork formed factor that will slide over the bolts within the heart of the linkages. This makes positive that no matter is connected to the top stays parallel to the mechanism.

Final step was to connect the beam to the underside and bolt it onto the facet of the printer.

I needed to design some nook brackets as effectively to be able to join the beam to the printer’s body. The mattress is in the best way so I couldn’t use the official OpenBeam T-Brackets. Thankfully I remembered to place some additional nuts within the beams once I was constructing the printer. As a result of the factor is mounted perpendicularly on one facet, it punches the objects straight into the tower on the alternative facet. Finally I’ll make some 30 diploma / 60 diploma nook brackets so it can punch in the best path.

The 24 cm beam is simply barely lengthy sufficient. The print head narrowly misses the glove whereas doing the auto-calibration routine and bumps into it a little bit bit when printing all the best way out to the sides.

The completed product.

COMPONENT LIST (What you will want)

Wiring was fairly easy. I salvaged an previous Pololu stepper driver from one in all our spare RAMPS boards and used a ribbon cable with feminine headers to wire it as much as the Brainwave. Right here is the the wiring diagram from Pololu:

I used the 12V rail from the Brainwave for VMOT versus the 24V rail from the Kossel’s PSU. Unsure how a lot present the 12V line was supposed for, nevertheless it appears to be doing all proper. The STEP, DIR, and EN traces are hooked as much as OC1B, OC1C, and OC1A, respectively. I did not hassle with microstepping as a result of I wished as a lot torque as potential. A pullup resistor on the EN line may be a good suggestion however I did not embody it. Right here is the pin configuration added to the Brainwave Professional part of pins.h. I needed to dig round in Arduino’s pins_arduino.h to search out the corresponding pin numbers.

#outline PUNCH_STEP_PIN 26     // OC1B
#outline PUNCH_DIR_PIN 27      // OC1C
#outline PUNCH_ENABLE_PIN 25   // OC1A

The motor I discovered already had a connector on the top of it, however once I plugged it in it did not wish to work. I verified the motor connections utilizing an previous trick. If you happen to bounce two of the traces collectively and the motor turns into more durable to show, you already know they’re related to the identical coil. Rearranged the pins on the connector and all the pieces was good.

The programming can also be not sophisticated. I am together with the attention-grabbing components right here however the complete factor is offered on GitHub. The firmware is predicated on the OpenBeam department of Marlin firmware. The adjustments shouldn’t be laborious to patch into every other department of Marlin, although.

I added a brand new G-Code command (G42) that prompts the punching mechanism. It additionally accepts a feedrate (in Hz) so you possibly can inform it how briskly to punch. For instance, “G42 F300”. If you don’t set a velocity, it defaults to 50 steps/s. Right here is the part from the G-Code parser in Marlin_main.cpp:

    case 42: // G42
      if(code_seen('F')) {
        punch(code_value());
      } else {
        punch(50);
    }

That is the precise punching code in pugilism.cpp.

void punch(float velocity)
{
  int delayLength = 1000 / (velocity*2);
  SERIAL_ECHOLN("WHAM!");
  // Allow driver
  digitalWrite(PUNCH_ENABLE_PIN, LOW);
  // Set path
  digitalWrite(PUNCH_DIR_PIN, HIGH);
  // Punch
  // Thought: Ramp up velocity
  for (int i=0; i<150; i++) {
    delay(delayLength);
    digitalWrite(PUNCH_STEP_PIN, HIGH);
    delay(delayLength);
    digitalWrite(PUNCH_STEP_PIN, LOW);
  }
  // Reverse path
  digitalWrite(PUNCH_DIR_PIN, LOW);
  // Retract
  for (int i=0; i<150; i++) {
    delay(10);
    digitalWrite(PUNCH_STEP_PIN, HIGH);
    delay(10);
    digitalWrite(PUNCH_STEP_PIN, LOW);
  }
  // Disable driver
  digitalWrite(PUNCH_ENABLE_PIN, HIGH);
}

Principally it prompts the driving force, sends 150 pulses to the step pin, then reverses and disables the driving force. 150 steps appears to be about the best distance because the stepper motor has 200 steps/revolution and I may inform from transferring the linkage by hand that the gear rotates about 3/4 of a flip.

300 steps/s appears to be the perfect velocity. It’s fast and forceful, however not so quick that it overloads the stepper motor. Generally it skips steps whereas punching however that is effective as a result of it resets its place when it retracts. I had an concept that you would get extra energy by accelerating as an alternative of punching at a continuing velocity. This would not be laborious to implement however I have never carried out it but.

Take a look at the undertaking web page at hackaday.io for future updates to this undertaking.

Completely happy Printing Punching!