Software
This section on the software is about my getting to grips with its use and some of the questions to which I had to get answers to help me understand how to use it. It is not in any particular order and it is not intended as a tutorial!
Starting with the CAD/CAM software. I invested in the level 3 version of the Dolphin Partmaster suit. A luxury, but one of the tasks I intended to have a go at was 3D work, at its simplest a Z profile, and this facility was not available in the lesser versions.
Drawing in the CAD system is relatively straightforward but I found having to remember to use the <shift> key in combination with mouse click or <return> to complete a particular element or task a little frustrating until used to it. Drawing the part point to point is not the way to do it and the "way" to draw is from the use of lines circles and arcs etc. that are put together at the right relative dimensional distances, and apart from circles and arcs which have to have their correct radii or diameters specified the lines can be any length. All of the intersections can then be "split" and the bits of lines or arcs/circles not wanted erased to leave the finished shape. Learning this technique took a little while. There are many features to this software that makes 'fitting' and 'snipping' to achieve the drawing easy, they just require learning and understanding when best to use them.
Screen shot of the CAD software showing a test piece with the contours mapped
There are some NC "canned" cycles included in the CAD program (also in the lower levels too) so it is possible to produce a G code program direct from the CAD software without touching the CAM package. However, these cycles cannot be used if the CAM package is to be used as their code is not transferred to the CAM package. It is easily misinterpreted as at the time of writing there is no instruction on the distinctive difference in the use of these canned cycles within CAD as compared to doing the same required task but in the CAM package. So for example if a series of holes of non uniform centres were required to be drilled there is a canned cycle that will do this in CAD but those holes will not be drawn in the CAM package when the milling module is called up. Instead the non uniform "point" tool has to be used which picks up the hole centres under "snap" and then crosses or bullets will appear in the correct position on the CAM drawing from which the drilling cycle can be set up.
Another issue that bends the mind is the coordinate system. In the CAD CAM and machine tool world there are three basic coordinates; the Geometric coordinates, the NC (Numerical Control) coordinates and the machine coordinates. The Geometric coordinate is established in the CAD drawing and it can be placed anywhere on the drawing relative to the part or parts that are drawn. So it could be arbitrarily placed at the corner or centre of the page or it may be placed at a prominent right angled corner of a part. If more than one part was drawn on the drawing it could be moved around if each part was to be separately transferred to the CAM package.
Screen shot of the CAM software showing the test piece and machining instructions
Likewise the NC coordinate can be placed anywhere, logically within the machine table confines, but not necessarily related to the Geometric coordinate ....... or it can be relative to the Geometry coordinate ...... or it can be the same as the Geometric coordinate ....... by which time wondering where the start point is for a machining activity is getting a bit frantic!
The machine coordinate is the easiest to understand as it is usually the coordinate measured from the "Home" position of the machine's XY and Z travel. X and Y "Home" is typically a corner of the X table and the Z "Home" the top of the head movement on its column. The NC coordinates are usually "offset" from these positions.
1. The machine coordinates for the "HOME" position on the table, logically perhaps bottom left corner and max high Z. All these are set 0,0,0. They are unlikely to change for any reason and will correspond with end stop limit switch settings on the table movement.
2. The position of the work on the table resulting from jogging the table to a position relative to the spindle centre line that aligns a particular feature of the work such as a corner of a blank from which a part is to be cut or the corner of a part on which some machine operation is to be performed. The machine DRO's are then set to 0,0 for X and Y (Assuming Z is unchanged from the home position) and this becomes the NC datum coordinate.
3. The relative position of the Geometric datum of the part to the NC datum. This may be the same as the NC datum if the part has finished edges against which the NC XY datum is established and has also been used as the Geometric datum in the drawing. Or it may be that the part is to be machined out of a blank and the Geometric datum has already been set in the drawing as a defined edge of the blank so jogging the table to the same defined edge of the blank and setting the DRO's to 0,0 will establish the Geometric and NC datum as the same. Or the part Geometric datum can be set up relative to the NC datum in the CAM package if a jigged operation is to occur where the part is always in the same place on the table relative to a known NC coordinate zero position.
What all this boils down to is that when setting the Geometric coordinates on the CAD drawing one has to have in mind how the part is to be machined and how the NC coordinate is to be derived.
.......................to be continued.