Introduction
The word “Cartesian” should be familiar to every machinist. It’s the name of the XY plane that is common to every ordinary machine tool. A point in the plane is expressed as X and Y Cartesian coordinates. But in everyday technical parlance, we usually leave the word “Cartesian” out.
Even the common Digital Readout (DRO) is actually showing you the Cartesian coordinates of the point in the plane that is the tool location relative to the origin. The Cartesian Display takes the concept of the DRO to a new level and shows a graphical depiction of the tool motion and part geometry giving the machinist an unparalleled tactical view of the machining operation.
A circle representing the desired cutter size moves on the screen in realtime response to the hand crank movements by the machinist.
The depiction of the part geometry on the Cartesian Display screen is not just a “picture” of the part; it IS the part since it is derived from the CAD model. The part model file loaded into the Cartesian Display is the exact mathematical model of the part. This allows the machinist to position the tool to exact distances with respect to any geometric entity.
Using RADAR mode, the machinist can monitor the distance from the tool to any surface. When the distance is ZERO, you are exactly on that line and producing whatever dimension that line happens to represent.
This means that the machinist is never burdened with knowing any of the dimensions of the part.
Exceptions to this are cases where tight tolerances are required, in those cases, the machinist may need to take a spring-pass or even adjust the cutter size slightly to take or leave a little more material.
Usually, the only “numbers” the machinist needs to be concerned with is the RADAR distance and DX and DY.
The machinist may continue to use the DRO as usual
In fact, in only very rare cases does the machinist ever need to look at the DRO to know the coordinates of the tool. The Cartesian Display is not "interfaced" with the existing DRO; they only share the same scale signals. The existing DRO is unaware of the Cartesian Display and vice-versa. The only thing they have in common is the geometric origin. Thus, when you find 0,0 using the DRO, you must set 0,0 in the Cartesian Display at the same time; now they are married together but only in terms of the origin they share.
The Cartesian Display is driven by a CAD model of the part
The production of even trivial machined parts takes at least some planning; and more advanced parts require engineering efforts. The driving philosophy behind the Cartesian Display concept is that a master CAD model exists that describes the part to be produced. The need to enter any data on the shop floor is reduced and usually eliminated which helps to reduce human error. Whether you are making parts on a mill in your garage or in a more intense factory setting, any shop can benefit from a master model of a part that has been designed by yourself or an engineer.
Whether you have your CAD workstation out on the shop floor near your machine; or in the engineering department, the process is the same. The geometry that is relevant to a given machining operation is placed on a single layer in the CAD model. Then the model must be saved as a DXF -if it’s not DXF already. Then, using the accompanying Desktop software, the model is prepared for the Cartesian Display and uploaded into the Display. The CAD model, and the relevant layer, are compressed into a compact form that the Cartesian Display accepts. I am glossing over some details here, but they will be presented shortly.
Note that the machinist never enters any dimensional data at the machine. That's the whole point of having a master CAD model, to eliminate this source of error and relieve the machinist from that responsibility. If a dimension must be changed, then the master CAD model must be changed and the part model re-uploaded into the Display.
The Cartesian Display allows non-machinists to produce quality parts
Another benefit of the Cartesian Display is that one need not be an experienced machinist to use it.
Since there is almost never any math and no keying-in of any data, in some cases you can replace the more expensive machinist with a machine operator. Of course the set-up of the operation and tooling could still require some experience, but after it's set up, a machine operator can guide the tool around according to instructions or drill holes, freeing your machinist for other activities.
Another case, one can imagine a part that only needs to be rough machined. You can instruct the operator to simply "stay away from the lines" in a cavity or similar feature. Or more advanced operators could be instructed to use the RADAR to leave a given amount of stock while the finish pass is done later by the machinist or on CNC.
The Cartesian Display can help to fool-proof operations and reduce human error. One can imagine adding a night shift where less experienced operators can be putting the knee-mills to good use doing repetitive machining operations.
When is a Mill outfitted with a Cartesian Display useful ?
The Cartesian Display breathes new life into the humble knee mill. Often, the Bridgeports are demoted to mere drill presses in many shops. Or for doing only the simplest operations. But with the kind of control you now have, coupled with fact that the part model is done in CAD beforehand, possibly by an engineer, you can now legitimately machine parts that you might otherwise only trust to CNC.
The Cartesian Display is most useful for:
One-off parts,
Rough machining parts,
Prototypes,
Short production runs,
Or cases where you can't take a CNC off line to do one or a few parts.
