DRO Programming

Digital readouts that can program contours can save time in longer production runs.

Cutting an arc on a manual milling machine can be a tricky bit of business. If you don’t have the time to use the 1,000-bolt-hole pattern method, and trigonometry is not your strong suit, a digital readout (DRO) with this feature can be a handy addition to the shop.

Without this function, you would need to use this formula to generate each cutter position (offset): multiply the sine of the step angle to the axis by the toolpath radius to get the X position, and multiply the cosine of the step angle by the toolpath radius to get the Y position. Multiply the step angle by the step number before the sine or cosine is taken.

Canadian Industrial Machinery asked Heidenhain Product Specialist Nathan Mathiot to describe how a digital readout system can aid machinists in arc and contour milling.

CIM: What information is needed before programming of contours can be performed on a DRO?

Mathiot: To program contours you need a start point and an end point. If you want to do an arc, you need to know the radius of the arc in addition to the start and end points.

CIM: How is this information entered into the system?

Mathiot: The information is entered into the DRO one item at a time (following a prompt).

CIM: What is shown on the display screen?

Mathiot: The information can be displayed in multiple ways, but probably the most popular is having the program and the graphic up at the same time. This window allows you user to visually confirm that you programmed the right moves or steps when compared to a drawing. Options available on the screen are the features and calculator functions, which can be used to find an unknown dimension on a drawing.

CIM: What kind of time savings can be realized?

Mathiot: The time savings really start to accumulate on a production run because it takes some time to program the DRO. You have the ability to save your programs if you want to create a lot of programs on the DRO.

CIM: How does this affect overall machining effectiveness?

Mathiot: Being able to reuse the program allows the machinist to spend more time on what he is supposed to be doing: machining parts. The tolerance feature on the DRO allows you to program the acceptable tolerances and visually see on the screen whether the tool is within the part tolerances.

CIM: What does the latest generation of DROs add to the process?

Mathiot: The previous version of this caliber of DRO didn’t have as much visual animation or display ability. The visual display allows you to see what you are doing before you cut the part.

CIM: What does a scenario look like for an operator without a DRO to perform this task?

Mathiot: The operator would have to use individual features on the DRO and repeat this process every time he wanted to do the same part. In other words, he would have to reprogram the DRO whenever he decided to change to a different part.  The Heidenhain PT 880 allows the operator to save programs and reuse them by loading the file in the DRO.

CIM: What tips would you offer a manufacturer performing these tasks?

Mathiot: Spend the time to learn how to program the DRO so you don’t waste time or materials trying to figure out how to use the DRO programming capabilities.