Any FDM 3D printer should be capable of making this robot. While the Prusa is a high-quality printer it certainly is not required. The models were designed to have minimal or no supports and work with a large nozzle. These models were printed with a 0.8mm nozzle. Larger nozzles and layer heights dramatically reduce print times, but do reduce the detail in prints. As such, some bolt holes may need to be drilled out depending on your printer settings that may extrude extra filament causing overflow, making the holes smaller than designed. When purchasing larger nozzles, ensure you are buying the correct type for your printer and verify your slicer software has a profile for the nozzle size you are purchasing. The models were designed for fast/large layer heights, however you can print them with your standard nozzle size (usually 0.4mm) and slicer settings.

PLA Filament was used for these prints, but PETG would also be a fine choice. PLA is an easy to print, low cost filament. However PLA lacks the strength and heat tolerance of other filaments. If you plan to travel with your robots in a hot car, you may want to choose PETG to avoid warping due to heat. Other filaments such as ABS or Nylon will offer superior heat and strength tolerance at greater cost. Some more advanced filaments may require printing in an enclosure and suffer from slight shrinkage, which could affect the fit of the parts.

KnightKrawler typically uses the most affordable PLA filaments for projects like this expecting that parts will eventually need to be replaced. We have used a variety of brands and have not seen an issue with any particular brand as long as the filament is new and/or has been kept sealed in a moisture proof bag.

If the square drive peg does not have a snug fit on the motor shaft, use a small piece of a rubber band to create a tight fit. Place the rubber band over the hole, then press shaft into the hole. Make sure to properly align the flat side of the shaft. Push the square drive peg on to the shaft so approximately 1-2mm of space remains between the motor and square drive peg. Trim the rubber band as short as possible after shaft is inserted.

When fastening the bolts on the chassis sides, always place the nuts so they will be under the robot body (towards the motor).

Depending on the settings of the 3D printer or filament being used, the motor may not be as secure as you desire. You can reduce motor movement with hot glue if desired.

Axels can but cut a variety of different ways. A hacksaw with a vice is a solution many robotics teams may have. A more portable solution is to use a Lineman's Pliers. Additionally, cutting axels can leave a sharp end. To round the end to avoid cuts to your skin or snags inside the 3D printed parts, the ends can be sanded with metal sandpaper, or a sharpening stone.

Different print quality can impact the size of axel holes. Axels should slide easily into parts, and wheels should spin freely on the axel. It may be necessary to use a drill and small drill bit to enlarge holes if they are too snug.

If bolts are too long and extend too far into the body of the robot, it may impact mechanisms mounting on the base. You may decide to reverse the bolts, so the extra length of the bolt is towards the outside of the wheel frame, rather than extending into the robot body. Alternatively, the lineman's pliers can be used to trim the bolt length after the nuts are installed.

The geared wheels provide great traction on carpet but can slip on hard surfaces. The wheels are designed to allow for a custom track tread to be designed and 3D printed with extra soft TPE flexible Filament. Unfortunately, flex filament can be difficult or impossible to print on some 3D printers. A wide rubber band can be used as a substitute for a track.

There are extra mounting holes available for the Romi mounting bracket in the event you create mechanisms that would require bolt heads to be in a different location.

Pin headers come in long strips and can be snapped between the pins to obtain the desired pin header length. Pin header jumper caps are an easy way to hold multiple rows of pin headers together when soldering. In this photo, the pin headers for the PWM pins have been connected using 4 jumper caps.

Modeling clay can be used to hold the pin headers in place while placed upside down on the Romi board. When soldering, do not place the solder on the tip of the soldering iron, but rather use the soldering iron to heat the pin and connector on the board. Touch the solder to the pin and board to complete the weld. Electronics solder include a material called flux, which cleans the connection. If solder is placed on the soldering iron, the flux does not do its job of cleaning the parts to be connected. Note: Some modeling clay may melt if too much heat is transferred through the pin into the clay. It may be necessary to use a toothbrush, or other bristle brush, to clean off the header pins if the clay melts to the pins.

The Romi board includes a convenience strip of standard PWM connections for running additional motors or servos for future mechanisms. However the 5v power bus is not connected by default. Use a header jumper cap to connect the 5V pin adjacent to the signal pins, to the middle pins of the PWM connections.

The Romi board should be secured to the Romi mount using screws not bolts. This allows for the board to be removed in the future, without requiring access to the top of the robot base part. The Romi mount includes 4 or 6 spots where a screw lines up with mounting holes on the Romi board.

Attaching the jumper wires requires patience and fine motor skills. 10cm jumper cables are just long enough to complete the connection. Start with the connection on the motor side. It may be easiest to connect the wires one at a time using a needle-nose plyers. Be sure to connect the wires in the same sequence (left to right) between the motor and Romi board.

Carefully slide the wire retention clips in place after the motor wires have been connected. Secure the clips to the Romi mount using M2 screws. With a small zip tie, clamp the clips to the wire ends.

    package frc.robot.subsystems;

    import edu.wpi.first.wpilibj2.command.SubsystemBase;
    import edu.wpi.first.wpilibj.Servo;

    public class IndexerSubSystem extends SubsystemBase {
        private static IndexerSubSystem instance = null;
        private Servo hopperGateServo;
        private Servo shooterGateServo;

        public void openHopperGate() {
            hopperGateServo.setAngle(0);
        }

        public void closeHopperGate() {
            hopperGateServo.setAngle(90);
        }

        public void openShooterGate() {
            shooterGateServo.setAngle(0);
        }

        public void closeShooterGate() {
            shooterGateServo.setAngle(90);
        }

        public static IndexerSubSystem getInstance() {
            if (instance == null)
            {
            instance = new IndexerSubSystem();
            }
            return instance;
        }
        /** Creates a new IntakeMotor. */
        private IndexerSubSystem() {
            hopperGateServo = new Servo(3);
            shooterGateServo = new Servo(2);
            closeHopperGate();
            closeShooterGate();
        }
    }

    package frc.robot.subsystems;
    
    import edu.wpi.first.wpilibj.DigitalOutput;
    import edu.wpi.first.wpilibj2.command.SubsystemBase;
    
    public class HBridgeIntakeSubsystem extends SubsystemBase {
    
        private static HBridgeIntakeSubsystem instance = null;
    
        public static HBridgeIntakeSubsystem getInstance() {
        if (instance == null)
        {
            instance = new HBridgeIntakeSubsystem();
        }
        return instance;
        }
    
        private HBridgeIntakeSubsystem() {}
    
        private DigitalOutput pinFoward = new DigitalOutput(8);
    
        private boolean pinFOut = false;
        
        public void IntakeIn()
        {
        pinFOut = true;
        }
    
        public void Stop()
        {
        pinFOut = false;
        }
    
        @Override
        public void periodic() {
        // This method will be called once per scheduler run
        pinFoward.set(pinFOut);
        }                                    
    }                                    

    package frc.robot.subsystems;
    
    import edu.wpi.first.wpilibj.DigitalOutput;
    import edu.wpi.first.wpilibj2.command.SubsystemBase;
    
    public class HBridgeShooterSubsystem extends SubsystemBase {
    
        private static HBridgeShooterSubsystem instance = null;
    
        public static HBridgeShooterSubsystem getInstance() {
        if (instance == null)
        {
            instance = new HBridgeShooterSubsystem();
        }
        return instance;
        }
    
        private HBridgeShooterSubsystem() {}
    
        private DigitalOutput pinFoward = new DigitalOutput(9);
    
        private boolean pinFOut = false;
        
        public void ShooterForward()
        {
        pinFOut = true;
        }
    
        public void Stop()
        {
        pinFOut = false;
        }
    
        @Override
        public void periodic() {
        // This method will be called once per scheduler run
        pinFoward.set(pinFOut);
        }
    }