Document Control Dialog
The top part of the dialog remains unchanged from the other GibbsCAM modules, the only difference being the choices in the Machine list. When a MTM Machine is chosen, the second part of this dialog changes significantly. When creating a Multi-Task Machining part an MTM Machine Definition Document (MDD) must be selected. Each MTM MDD is made for a specific machining center's parameters and manufacturer's recommendations - this includes the number of spindles and turrets in each Machining Center. The MDD controls many things in the software, including the quantity, position and display of spindles, the availability of turrets and which spindles they can access and the number of tool positions in a turret, drill cycles and coolant. You will receive an MDD with each post processor for each different machine you have. For more information on MDDs and Multi-Task Machining see the section MDD Support.
Stock & Tool Change
The second part of the Document Control dialog has been modified for the MTM module to accommodate multiple spindles and multiple turrets. The components of the Document Control dialog are described on the following pages.
Spindle Selection: This item is used to select a spindle so its stock size, location and condition may be configured and the tool change position may be set for each spindle. Click one of the blue scroll arrow buttons to cycle forward or backward through the available spindles. The stock size and condition of each spindle in the machine must be defined.
Stock Diagram: The Stock diagram is significantly different for Multi-Task Machining parts. The spindle is represented by the light cylinder around the stock. In addition to the standard Xradius or Xdiameter value and the -Z & +Z values, there is a text box marked Z. This item specifies the distance from the spindle's face to the edge of the stock. If the part is being cut from bar stock and fully sticks out of the spindle this value will be greater than the total length of the part. The value may also be smaller than the total length of the part. This can be true if only the front of the part extends out of the spindle face because the part is to be transferred to a sub spindle to cut the back end of the part. The set up in the Document Control dialog should reflect the actual set up on your machine. The Back of Stock Z (shown as -Z in the following image) is not the part length. This value only controls the length of the displayed stock. The Chuck Face Thickness is an optional item. Enter the Z thickness of the chuck or "0" if no chuck is used.
The orientation of the stock diagram does not change with each spindle, the view is always the "Home" view of the spindle's ZX coordinate system. Basically, all spindles will be shown on the left with the stock extending to the right, regardless of where the spindle really is in the machine. When you are first learning to set up a part file this may not be immediately obvious or helpful. Just imagine that for each spindle you move to the same place relative to the spindle.
Let's look at this another way because setting up your part correctly is critical. Let's use a dual-spindle machine as an example and use a different graphic to explain the elements of the stock diagram. In all likelihood, the stock conditions of the spindles will be different, one spindle will have bar stock and the other will have a partially cut piece of stock that has been transferred to the spindle. The system needs different information for these conditions. Spindles with uncut stock (a spindle designated as having Initial Stock, see this page) is used to define the size of the part and how far it sticks out from the face of the spindle. Spindles that will hold transferred stock (a spindle set with Initial Stock off, see this page) need to have the part's origin and distance from the spindle face designated. The remaining length of the part is assumed to be used for the pick-off and is in the spindle's chuck or collet.
Let's use an example with real numbers. We have a part stock that is 52mm long with 1mm on the Z+ side of the origin. The part sticks out of the spindle by 55mm. We will face off the 1mm, making the part stock 51mm long, sticking out of the spindle by 54mm and the face is now at the origin.
When we transfer the part we will pick-off the part at Z-25mm. That will leave 26mm sticking out of the sub spindle face, 1mm of which will be faced off later, leaving Z0 at the face. The stock diagram for such a part would look like the following image.
If the part is held in a chuck, add the Z-thickness of the chuck to the total part length.
Graphic Part Face Distance: This setting allows you to set the distance of the display of available spindles. This is the graphic distance between the spindles. The actual distance between spindles is fixed by the machine and defined in the MDD. However, for ease of viewing the spindles may be brought closer together. This way when unzoomed, the parts are not difficult to see because of their size. Enter the distance you want between opposing part faces on the screen. This has no effect on the actual program. The setting is a value in part units, inches or millimeters.
Clearance Data: This section of the dialog has two states, with and without Auto Clearance selected. When Auto Clearance is on, the system will calculate positioning moves between operations. The positions will be changed as the part is machined. The value entered is an offset amount from the current part stock that the system will use to always keep an adequate clearance from the material.
When Auto Clearance is off, a fixed clearance position may be entered in the X and Z text boxes for each spindle. The text boxes specify the X and Z location that a tool will rapid to and from during a tool change. This position will also be used when moving from one approach type to another.
X Dimension Style: This selection determines whether X values for the part are input as radii or diameters. Some text boxes in particular dialogs specify that the value entered is either a radius or a diameter value, regardless of the selection made here. X values entered in text boxes are usually based on the radius unless specifically labelled Xd.
Tool Change Position: The Tool change position is generally handled by the MDD. Some MDDs provide text boxes for specifying the X and Z values for the tool change position. In this case, a different value may be entered for each turret. Each available turret is accessed by clicking through the blue scroll arrow buttons. You will need to set all Tool Groups for each spindle the TG can be used on. The values are absolute values from the part origin to the Tool Group/Turret datum. Most MTM MDDs do not have an option of specifying where a tool change is performed. These MDDs will move the Tool Group to a pre-defined, hard-coded position that may not be overridden.
Initial Condition of the Machine When Starting a Program
The starting conditions specify whether stock is or is not loaded into the machine and whether the stock is ready to be machined or has to be fed into position. This is controlled by two checkboxes, Initial Stock and Preloaded.
Initial Stock: This item tells the system which spindle or spindles start with unmachined material in this program. If a part is going to be transferred to the currently active spindle then this item should remain unchecked. When Initial Stock is off, the system expects that the plug will be moved from another spindle to the spindle being defined, (such as from the main spindle to the sub spindle). When Initial Stock is off, the Stock diagram values to be entered are the Z value that specifies the part's distance from the spindle face (the Z value is the length of the part sticking out from the spindle after being picked off) and any material beyond the part origin, such as material to be faced.
Preloaded: This item is only available when there is Initial Stock on a spindle. The Preloaded checkbox specifies how the machine is currently set up. When Preloaded is unchecked the system is told that there is no material in the chuck and a Load Spindle will need to be programmed by the user before machining can be programmed. When checked, the system expects that the first bar feed has been done and that the material is ready to be machined as soon as the program is started. At some point in generating operations a load spindle command will need to be generated, usually after all the operations are made. With Preloaded checked you are telling the system to assume that you will take care of this detail later and to start with the material in place.