Zeroing a Prototrak Controlled Manual Mill

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In this instructable, we will learn how to zero the X and Y axis of a manual mill controlled by a Prototrak SMX Controller. This is done to understand where tooling is at when machining, and is common practice in the manufacturing industry. This instructable is aimed toward beginner level machinists, however machining is extremely dangerous if done improperly. With this being said, just because you know how to control the machine and operate the controller, does not mean you have the knowledge to proceed in doing so safely. When learning machining, always operate the machinery in presence of somebody with appropriate experience.

Step 1: Materials List

  • Edge finder (silver round tool)
  • Corresponding diameter R8 Collet
  • Manual Mill with Prototrak SMX Controller (this instructable is made using this machine and controller, however the method is true to any manual mill)
  • Finished stock (the metal you wish to cut)

Step 2: Understanding Axes and Manual Controls

At the beginning of this instructable, we saw the orientation of our axes on the mill. This is important to understand how we are moving the machine and what we are zeroing. Above, we see two round knobs denoted “x” and “y.” These move the table in the x and y direction respectively. The table is moved in the positive x direction by rotating the knob denoted x clockwise. The table is moved in the positive y direction by rotating the knob denoted y counter-clockwise. These knobs are used to move the table manually.

The final two photos display our manual control for the z-axis. Unlike x and y where we can move the full length of the table, we are limited on how much we can move manually in the z-direction. In reality, we want to minimize extending z manually because it leads to a larger amount of tool deflection. However, this is a feature we will use commonly. The large handle with the black knob is the control for the z-axis, and acts similarly to a drill press. The small silver handle above the spindle in these photos locks manual z-axis movement.

Step 3: Moving the Table Using the Controller

Moving the table using the controller is called jogging the machine. To do this, we will select “Jog” as seen on the bottom left of the screen, using the blue triangle directly underneath. When in the Jog command, inputting a number specifies the feed rate in inches per minute (ipm), followed by pressing "ABS SET" for final confirmation of your input. Direction of feed is specified by the sign of the Feed Rate, and can be changed using the "+/-" push button. Upon designation of feed rate and sign, selecting the “X”, “Y”, or “Z” key will lead to movement on that axis and direction. Again, be mindful of the sign of your feed rate.

Step 4: Specifying Spindle Speed

If still in the Jog command, press the blue triangle directly under "Return" at the bottom right of the screen. From the main screen we will select "Spin Speed" as highlighted in the photo above. We will now input our desired RPM, between 1000 and 1500 is normal for an edge finder. After inputting our desired RPM, select "ABS SET" at the top of the number pad to change the spindle speed.

Step 5: Using the Edge Finder

Between jogging and manual controls, move your tool such that you are close to your stock as shown above. Note that you must have stock that is finished to get a useful zero. Also remember to try to minimize manual z extension. We not must turn the spindle on, by turning the switch with the yellow back plate shown to 2. With the spindle on we will MANUALLY move the x-axis toward our stock. I say x-axis because of the orientation in the video example, the process is the same to zero the y-axis. We manually move the x-axis toward our stock until we see the tool "break" as we do in the video. At the instance of the break, we stop moving the table. We've located our edge!

However, the edge finder is a little more complicated that just that, but not much. To zero using an edge finder, we must know the diameter of the tool that comes in contact with the stock. Mine is 0.200". That means, when the edge finder breaks, the center of our tool is a distance equal to the radius of our tool away from center on whichever axis it may be (again x-axis for our video). Because of this, we set our zero offset by 0.100" toward our part.

Step 6: Zeroing With the Controller

I always zero my controller at the instant of break to prevent having to remember a crazy abstract number. It's easy to forget 14.1560, but not so much with -0.100. To set a zero, we must be out of any commands such as spindle speed or jog, so press return if you see it. We next select X, Y or Z, whichever axis is desired to be zeroed. We press "X" (which highlights X as shown above) followed by "ABS SET," and now have a new zero. Next, we have to offset our 0.100" in the appropriate direction, we need the center of our tool to be centered on the stock, as seen above. At that point, we make sure the screen reads +/-0.100 and we zero. It would show the opposite sign if we used the left edge of the stock rather than the right. Upon the second zeroing, we have accurately zeroed the x-axis of the machine. We then must do the same for the y-axis.

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