Tarkin

Tarkin is the new large-format laser cutter in the space. It's a custom-built laser cutter based on an RF CO2 laser and CCM linear rail motion system with a Ruida RDC6445G controller running Lightburn software. It features 225W of power on a 1.6M x 1.0 M (63"x39") cutting bed, powered Z, 8MB alignment camera, and air assist.

It's quite large and capable -- we don't think there's anything like it in central Texas.

A new class will be required for users. The Ruida controller utilizes a workflow that will be common among Asmbly lasers.

Terms (just proposed for now, following documentation needs editing to use these consistently)

Machine bed is the physical machine's actual work area.

Control Panel is the Ruida hardware panel on the physical machine. Small color LCD and membrane keys. Not to be confused with the Lightburn software.

Material is your physical stock- a piece of plywood, acrylic sheet, etc.

Lightburn is the software on the PC for CAD, specifying what to cut and how, and has control for some live interaction with the machine.

Workspace is Lightburn's work area on the PC. This is the same as the machine bed only if you make the workspace size the same as machine bed size and operate in absolute coordinates. Otherwise, where your job is placed on the workspace is not necessarily where the job will be when you go to the machine bed, and your workspace can be declared in a different size than the machine bed.

Job is your content- vector/raster operations you want the laser to do. The location of the job on the machine bed is flexible and can be moved from the control panel, or it can be fixed. Your job exists in two forms- on the workspace (Lightburn software), and on the machine bed (physical machine). In the case of user origin, they may not be in the same place.

User origin is your job's origin. It is not used in absolute coordinate operation. The user origin also has two forms- it is represented on the workspace with a green square, and can move in relation to your job. At the control panel, you will set the user origin to the current head position with the ORIGIN button, which moves your job so that the green square will be at that point.

Origins

Tarkin's origin is commonly set in one of three ways:

1. Absolute coords, using a workspace the size of the machine bed. The location of your job is fixed and the user does not operate the ORIGIN button on the panel, as there is no user origin. The camera may or may not be activated.
2. User origin, where your material is placed anywhere on the bed that is convenient, and the user moves the head to the desired origin point and presses "ORIGIN" to work around that spot. In this case, it is not important where the user places their job on the PC's workspace, or that the workspace be of the size of the laser's bed at all. Lightburn will automatically create a bounding box around all the user's job within the workspace, whether or not it is designated to be sent at that time. The user can specify the work origin to be in the center, any of the 4 corners (top left most common), or 4 sides (uncommon). It is possible to place the origin in a way that the job will eventually run off the machine bed, this will result in "FRAME SLOP ERROR" and will not run. Correct the origin position and use the FRAME button to verify its bounding box. Note that moving your job around the machine bed via the user ORIGIN button does not move your job on the workspace.
3. Camera-placed absolute coords- the material can be placed anywhere visible to the alignment camera, the Lightburn workspace is set to the full machine bed size, the user jogs the gantry out of the line of sight (not obscuring your material), and then Lightburn takes a camera snapshot of the machine bed that shows up as a graphical background for the work on the workspace. The very rear of the machine is not visible to the camera for alignment purposes. The user moves and aligns the vectors/raster job across the workspace so it is over the actual material by moving the job in XY and, if necessary, rotation and resizing may also be done. Lightburn will automatically change to absolute coordinates in camera mode, and the user does not operate the ORIGIN button. This method can also be used for hybrid work- for example, color printing paper graphics that were glued to plywood earlier, this material is then placed and aligned via camera and cut out into desired shapes with the laser, or an existing manufactured object is placed on the bed and the job aligned over it. There is no auto-recognition of printed registration marks, but printed registration marks do make alignment easier and more accurate. Another example might be a unique horizontal slice of a tree can be traced and artwork can flow with that arbitrary shape in size and alignment. So far, the accuracy has been better than 2mm, and may be improved with further calibration.

Lightburn has a database of known-good values for cutting and rastering on Tarkin, listed by material. Feel free to use them, but these can only be created or modified by admin. If you want a new entry, please submit the parameters and if possible a piece of that material and we can include it. Pearl will also have a Lightburn material database after it is converted to that controller, but it will have different values as the beam's power is different.

Current Quirks

X and Y can shift slightly when Z is moved. Be sure to move the Z before placing the origin. This will be corrected soon.

The far side of the Y is not accessible due to a limitation of where the homing sensor could be easily placed. The current available work area is 1600mm x 866 mm. This will be corrected soon.

If the motor drive capabilities are exceeded and a drive fault occurs. the machine will stop immediately, and throw a generic "System Protected" error, the same as if the lid is open. This error might occur if excess rastering speed is demanded (>1000mm/sec?) or crashing the head into the material, clamp, or jig. Of note, the problem axis cannot be jogged with the control panel, even though the panel coordinates increment. The other axis moves normally. This fault is resolved by cycling Main Power on Tarkin and letting it rehome. If this fault occurs due to rastering or any case other than crashing the head, please contact workshop with details about settings and, if possible, a copy of the Lightburn project with the settings that led to the fault.

Maintenance

This tool is owned by Danny Miller and hosted at Asmbly for members to use. Please contact the workshop committee if maintenance is required.