CAD Mode Basics.

Hello there,

Today we will see about the CAD mode in WorkNC. 

CAD mode is provided in this software so as to provide the benefits of 3D modelling softwares. But it is in fact a 3D surface modeler. Here we deal with only surfaces of the part not the solid geometry. We can call the surfaces of part as skin. It becomes very useful when we deal with mold design or tool and die design etc. The surfaces of any 3D model are of the prime importance from CAM point of view. 

CAD mode also allows us to import part files from various CAD systems used for designing. WorkNC can import the IGES files and also recognizes the various feature used in that part without even reconstructing its geometry. It can recognize features such as holes, pockets, tapers, groves etc. 

To enter into into CAD mode simply click on New CAD file on left hand panel on the startup screen. The general layout of CAD mode is shown below,

CAD MODE USER INTERFACE

In the user interface of CAD mode you will find,

• On the top of the window you will find the Title Bar, which shows name of current CAD file and also the version of the WorkNC being used.

• Below the title bar there is a Menu Bar which is similar to menu bar in any standard software. It includes commands like File, Edit, Display, Help etc.

• On the left side of the viewing area there is a Management Panel which shows drawing layers by default. But its content changes according to the operations we carry out.

• The main viewing area where we can see the CAD model we are using. At the bottom of the viewing area there is a status bar which displays the co-ordinates information. This area covers most of the screen.

• At the bottom of the window we can find Command Input Panel where we can type the command directly and the execute it instead of selecting it from menus or sub-menus or toolbar on screen. 

• On the right side of command input we can find O-SNAP Panel which basically acts as a filter in any CAD softwares. We can set object snap to midpoints, endpoints, tangent, perpendicular, near etc like any CAD software. Besides O-Snap we can find Rotate Toolbar where we can input value directly to rotate the component in desired direction.

• On the leftmost side of the UI you can find Create & Modify Toolbar. It contains the basic drawing tools such as drawing lines, rectangles, circles, ellipse etc. It also contains basic geometry modifying features such as fillets, chamfers, extend, trim etc. We will see the create toolbar and its sub-menus in next post. 

So this was all about basics of the CAD mode in WorkNC. In the next post we will see in detail info about every toolbar in WorkNC. 

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Lets Start Using The Software WorkNC V21..

Till now i have introduced you to the various type of co-ordinate systems, basic types of offsets required to be considered while setting the work-piece on a CNC machine. I have also provided a light introduction to the type of tools used with CNC machines. That was all for the introductory portion. From today on-wards we are going to start working with the WorkNC software environment step by step from very beginning.

In WorkNC we are going to deal with WorkZone word a lot. So lets see what is meant by a WorkNC WorkZone.

• A WorkNC workzone is the folder in which all the programming data, geometric model, post-possessed output is stored. When we import a geometric model into WorkNc and then we complete all the machining operations required by the work-piece then the output is saved in form of a workzone. The name of the workzone can be customized while saving it. DO not use space between words while renaming the workzone.
• To import any geometric model into WorkNC, first we have to convert that geometric model (like .prt, .sldprt, .catpart etc) into a neutral file format such (.iges, .stp, .stl etc). To do so, if you are using softwares like CATIA, SOLIDWORKS, CREO etc then while saving the file just hit the save as button and in file type select any of the neutral file formats.

WORKNC START SCREEN

The WorkNC start screen is shown in the picture below. It consist of 

1. Menu Bar (Top Left Corner) 
2. New/Open Dialogue Box

STARTUP SCREEN IN WORK-NC

The Menu bar consist of standard functions such as New/Open and Exit.

The New/Open dialogue box consist of big icons on the left hand side which are

1. New Workzone: Used to create a new workzone by selecting a CAD file and setting various parameters related to the workzone
2. Open Workzone: Used to search and open the previously created workzones/ machining sequence and loads them.
3. New CAD File: This button is used to create a new CAD model in WorkNC itself by using CAD editing options.
4. Open CAD File: Click to open the CAD files which are to be used for creating machining sequence. Here CAD files saved in neutral format can only be used.

And on the right side area which is also called as Preview Area there are four tabs as shown above which are,

1. Recent Workzones: This tabs enlist the recently opened and used workzones list. We can easily switch to different workzones from this tab.
2. Recent CAD Files: It shows the preview of the recently used CAD model for creating the machining sequence.
3. Recent Sequences: It shows list of  recently used machining sequence from the various workzones.
4. Search Workzones: It is used to find any workzone by entering its in name in the search box. Before searching we have to set search directory so as to search in a specific location.

So this is how to deal with workzones and importing CAD models in WorkNc. In next post we will see how to set various  workzone parameters, setting default directory for the workzones.
Keep Reading .. :)

Types of tools used with CNC and VMC machines..

There are various types of tools which are used with CNC machines. These tools are differentiated by their method of material removal. Generally there are classified as below,

1. END MILLS: 

• Flat nose mills are used for milling 2D contours and pockets. Ball nose mills are used for 3D milling. Bull noseend mills have a radius corner. They are used to create a fillet on the bottom of a wall. Because they are sturdier than an end mill they are also sometimes used for roughing operations. Chamfer mills have an angled nose used to create a chamfer or to de-burr parts.

Types Of End Mills

• Centre Cutting End Mills : Machine tools are generally centre cutting or non centre cutting. The advantage with centre cutting tools is that they can plung directly into the work-piece where as non centre cutting end mills cannot. In case of centre cutting end mills the flutes of cutting tool are extended upto the centre of the tool as shown in figure below but in non centre cutting end mills the flutes advances to a centre hole.

Centre Cutting & Non Center Cutting End Mills

• No of Flutes: Milling tools usually have either two or four cutting flutes. Two flute cutters provide more chip clearance when milling in close areas. Four flute mills are more rigid, can be fed faster, and are preferred when greater chip clearance is not required, such as when milling an outside contour.

   2. FACE MILLS:

• The face mills consists of "cutting inserts" which can be replaced when worn out. These cutting inserts are mounted on a  central boss. There are used for first roughing operation so as to produce a smooth surface for following machining operations. These may have upto 8 or more cutting edges (inserts) hence making material removal process fast.

Face Mills

   3. SLOT MILLS:

• These types of cutters are used to cutting T-slots or dowtail type of shapes. T slots are very popular in case of machine beds for mounting fixtures or die etc. 

Slot Cutiing Mills

   4. HOLE MAKING TOOLS:

• SPOT / CENTER DRILL - These are used for creating a conic spot on the face of the workpiece so as to facilitate easy entrance of the twist dill at that point. The are short and rigid and provide precise location for a hole. The conic section created by the spot drill avoids wobbling and eccentric rotation of twist drills.

Center Drills

• COUNTERSINK DRILLS - These drills are used to create countersink type of hole profile so as to accommodate countersink screws. Drills having both spot drilling and countersink profiles are also available so as to carry out both operations by using single tool.

• TWIST DRILLS - These comes in various standard sizes according to metric and English standards. Used for drilling standard holes for various purposes. These are made up of High Speed Steel (HSS), carbide or Titanium Nitride (TiN) coated for long life and strength.

Twist Drill Terms

• TAPS & REAMERS - Taps are used to create threads in a pre-drilled hole. These form the materials by shearing away unwanted material. Taps require a hole drilled to the correct size to ensure the thread is formed properly. Most CNC Machines support rigid tapping, which means the tap can be held in a rigid holder. The tap is advanced at a feed rate that matches the thread lead into the hole. The spindle then stops, reverses, and backs out of the hole. Reamers are used to make hole bore of a precise size and excellent surface finish. Reamers give precise holes within 0.0001 mm. 

Images Courtesy : CNC Handbook HSMWorks

Machine and Tool Offsets..

As we know it is difficult to place a vise in the exact same position on the machine each time, the distance from Home to the WCS is usually not known until the vise is set and aligned with the machine. 

Machine set up is best done after the program is completely written, because it is expensive to keep a CNC machine idle waiting for the CNC programming to be done. To complicate matters further, different tools extend out from the machine spindle different lengths, also a value difficult to determine in advance. For example, a Ø20 Ramping Cutter extends further from the spindle face than a stub length a drill or any other milling cutter. 

If the tool wears or breaks and must be replaced, it is almost impossible to set it the exact length out of the tool holder each time. Therefore, there must be some way to relate the Machine C oordinate system to the part WCS and take into account varying tool lengths. This is done using Machine Tool and Fixture Offsets. 

There are many offsets available on CNC machines. Understanding how they work and to correctly use them together is essential for successful CNC machining.

• Fixture Offset XY:

Fixture offsets provide a way for the CNC control to know the distance from the machine home position and the part WCS. In conjunction with Tool Offsets, Fixture Offsets allow programs to be written in relation to the WCS instead of the Machine Coordinates. They make setups easier because the exact location of the part in the machine envelop does not need to be known before the CNC program is written.

As long as the part is positioned where the tool can reach all machining operations it can be located anywhere in the machine envelope. Once the Fixture Offset values are found, entered into the control, and activated by the CNC program, the CNC control works behind the scene to translate program coordinates to WCS coordinates.

Notice in Figure below how Fixture Offsets (+X, -Y) are used to shift the centerline of the machine spindle directly over the WCS.

Fixture Offset

• Tool Length Offset (TLO):

The tools loaded in the ATC (automatic tool changer) unit are of varying length. The length of each tool from the spindle varies according to requirement. Also due to tool wear the length of tool varies hence it becomes nearly impossible to set the tool in same position for each operation. Hence in CNC programming we use Tool Length Offset. It can be found out using following methods.

1. Generally the the TLO can be found out by directly touching the tool tip on the workpiece surface as shown in 1st method in figure below. Here the tool is made to travel from machine home Z-position to the part Z-zero position. In CNC machine controller settings the TLO settings are provided. This value of tool travel length is registered for each tool in that controller register. But during this method as we have to touch the workpiece with tool tip material removal takes place there. Hence this method is not preferable
2. In second method a sample block of some exact standard dimensions is made called as 1-2-3 block whose height is maintained precisely to a predefined value. Here the tool tip is made to touch the block surface and then TLO is calculated..
3. In 3rd method we simply use a Touch Probe which is connected to the machine controller. Here as soon as the tool tip touches the probe it send tool offset distance to the machine controller and the controller automatically registers the corresponding tool offset values.

Ways To Set Tool Offset

So in this module we have seen how to consider fixture offset and tool offsets so as to get precise machining. In next module we will discuss about the types of tools used with CNC machines. 

Images Courtesy : CNC Handbook HSMWorks