Small CNC Reminders

Small CNC Operations

Other Reminders

This is an updated set of reminders for the revised/rebuilt small CNC (thanks Sean!).

Check that the power and USB cables are both plugged in.

Pull out the E-stop (big red button on front left of table).

Login to the small CNC's laptop and run UGS (Universal GCode Sender).

Click the connect button at the top, left corner of the GUI (second icon from the left). It will change from black to orange. The console log will also display some output as UGS connects to the spindle.

You won't be able to do anything in the UGS GUI until you home the spindle. Click the Home button (top left). The spindle will move to the back, right corner of the CNC. This is the home location, the maximum X and Y values.

Note: The zero point is the minimum X and Y location, usually at the front, left of the machine. More on that below.

In the console (bottom center) Command entry line, enter the command: g28

g28 is the "change tool" command. The spindle will move to the front so you can get at it to insert a bit.

Insert the bit you're using. If a bit is already inserted, make sure the chuck is tight.

Note: As a general rule of thumb, you should use the largest bit that your planned cuts will allow. Generally the biggest factor is the minimum diameter of any inside cuts. Larger bits work faster, will wear less, and are less prone to breaking than smaller bits.

In the console enter the command: s12000

This sets the spindle speed to 12000 RPM. 12000 is the maximum spindle speed. You should never set it to anything higher.

In the console enter the command: m3

This starts the spindle rotating in the normal forward direction, aka clockwise direction.

m4 would start the spindle rotating backwards, aka counterclockwise. In normal operation you should always use m3.

m5 stops the spindle from rotating.

Note, the "Overrides" dialog (bottom right), is now active. You can use the buttons there to tweak the various spindle (RPMs), feed, etc values.

Click the Home button (top left) to send the spindle to the home location.

In the console enter the command: m5

This should stop the spindle rotation.

Set Up Your Work Piece

Set up your work piece on the bed of the CNC.

The spoilboard on the CNC as of this writing is 5/8" thick. Measure the thickness of your work piece, do the math, and use appropriate length screws to screw the workpiece to the spoilboard.

Note: If the screws you have to work with are longer than the thickness of both the work piece and the spoilboard, position the screws so they will screw down into the toggle slots.

Secure your workpiece by screwing it down to the spoilboard in at least 3 locations. Make sure the screws are located outside the area you're planning to cut in. If the spindle hits a screw while cutting, it could break the bit and possibly cause physical injury or damage to the machine.

Find the Zero Point

The zero point is the minimum X and Y coordinates.

In the Jog Controller dialog, set the step size value. This controls how much the spindle will move when you click the +X, +Y, -X and -Y buttons.

Use a larger step size value to get near where you want the spindle to go, then set step size to a smaller value to do fine adjustments.

• +X moves the spindle towards the back of the bed.
• +Y moves the spindle to the right.
• -X moves the spindle towards the front of the bed.
• -Y moves the spindle to the left.

Move the spindle as far forward and to your left as it can go while keeping the bit over the work piece and inside the screws you used to secure the work piece.

The goal is to draw a rectangle defined by the two points, home and zero, that includes enough of your work piece to do your cut, while keeping the bit away from the screws you used to secure your work piece.

When you have the spindle where you want the zero point to be, in the 'Controller State dialog (top right) click on the X and Y buttons to set the current location as the zero value.

Zero Out the Z Axis

1. place a sheet of paper under the cutting head
2. lower the spindle using the -Z button in the Jog Controller (bottom left) until the bit touches the paper on the work piece
3. lower the head until you cannot pull the paper out without a little resistance.
4. but NOT so much that the paper tears
5. Click the Z button in the Controller State dialog (top right) to set the current Z value as the zero value.