Putting the "Read" in Readout

The accuracy and repeatability of the linear encoders prevent the user from making mistakes and requiring additional machining to achieve the desired part. Photo courtesy of Heidenhain Corp.

Using a digital readout (DRO) to save time and improve part quality is nothing new in shops with manual machine tools. However, to get the most out of this technology, shop employees must be able to see and use the readout easily.

Digital readouts, which have been around for many years, allow operators to focus on the machining of parts rather than on how many turns of the dial they have completed to finish a feature.

According to the experts, one of the most important criteria when purchasing a new DRO is a large and easy-to-read screen. Many machine shop floors do not have the best lighting conditions, making screen clarity very important.

Being able to see the screen clearly from any angle gives machinists more mobility when operating the machine.

“A high-resolution screen gives the operator a clear and concise view of the DRO even from dramatic angles, allowing him to work with greater mobility and at greater distances,” said Todd Drane, marketing manager for Fagor Automation.

Screen size and clarity become especially important when the travels of the machine are large, because the operator may not be standing directly in front of the DRO while he is working.

“On lathes the digital readout is mounted either on the headstock or carriage, and the operator is not always directly in front of it. This makes it necessary for a large, easy-to-read screen to be used,” said Drane.

It’s Cycle Time

The screen is the gateway to the productivity-enhancing features of any DRO. And, while the screen and interface are what make the readout easy to use, they are useless without having the cycles and functions that operators need to perform their machining tasks.

Cycles simplify work for the operator. Rather than having to calculate the next move while performing a complex operation, the DRO automatically calculates what that next move is. A DRO’s cycles can reduce cycle time by as much as two or three times.

“The cycles and features within the system allow the user to perform advanced operations with ease that would normally be a little challenging without the aid of a DRO,” explained Nathan Mathiot, product specialist – machine tool marketing for Heidenhain. “Our newest feature within our DROs, for example, is for threading. The thread assist feature allows the user to cut a metric thread with an English lead screw on a lathe.”

Being able to see the digital readout’s screen clearly from any angle gives machinists more mobility when operating the machine. Photo courtesy of Fagor Automation.

Constantly adding new features and cycles to DROs is what’s keeping these tools relevant in today’s CNC world.

“Digital readouts have definitely ‘stolen’ a lot of ideas from CNCs recently,” said Drane.

New on Fagor’s DROs is a cycle enabling constant surface speed (CSS).

This technology maintains the tool at the same speed on the surface of the part regardless of what diameter the operator is cutting.

“This allows for a dramatically smoother surface finish and is easier on the tool and the machine,” said Drane.

This is achieved by an analog output from the DRO that controls the spindle’s speed. Based on the CSS the operator selects at the DRO console, the system will automatically vary the analog output to the spindle to ensure the selected speed is matched. If the spindle speed required to achieve the constant surface speed is in a different RPM range, the DRO will even prompt the operator to change gears.

In addition, spindle speed override is incorporated that allows the operator to override the spindle speed in a range of 50 to 150 percent.

“What operators might find most surprising is the on-screen, guided graphic assist for these cycles,” said Drane. “These cycles are introduced utilizing the graphic screen in a fill-in-the-blank guided design. The operator simply fills in the blank directly off the blueprint onto the screen and the DRO does the rest. The operator can even run the part using solid graphics.”

Digital readouts have a lot of features, but usefulness comes down to quality and ease of use.

“DRO functionality gives the user the ability to start machining faster,” said Mathiot. “Setup is so quick because digital readouts prompt the user for the application, language, and number of axes to be displayed on the initial start-up screen.”

Getting to work faster means that more time is spent machining and less time making calculations.

Other Technology

While the screen, interface, and cycles are the important features of a DRO, other options, such as quality linear encoders, can make an operator’s job easier as well.

“The accuracy and repeatability of the linear encoders prevent the user from making mistakes and requiring additional machining to achieve the desired part,” said Mathiot.

Another feature on some DROs is the ability to view the manual in the DRO.

“This allows the operator to get assistance on how to enter data or just receive general information about the screen he was looking at before he pressed the help softkey,” said Mathiot.