Manually Measuring Geometries

A digital readout retrofit can revitalize an older CMM

April 8, 2011

DROs for measuring 2-D and 3-D parts.

With proper maintenance, operation, and a little luck, a coordinate measuring machine (CMM) can have a long and productive life cycle.

While the motion mechanics and encoders of these machines may stay perfectly operational for a long time, the control and software can become outdated at a much faster rate. When this occurs, CMMs may become the bottleneck that every shop tries to avoid. The machines may also be shut down permanently.

“In these cases, the entire measuring process is being held back because of the original control,” explained Heidenhain Metrology Product Manager Aaron McDonald. “Purchasing a brand-new CMM also may be too capital-intensive for a lot of quality departments.”

This is when the addition of a digital readout (DRO) can be useful.

Heidenhain, for example, offers the ND 1400 QUADRA-CHEK, which was specifically designed to interface with a manual CMM. 

“This DRO is used almost exclusively as a retrofit product,” said McDonald. “As you know, the mechanics and encoders on an old CMM can often work just fine, but if the control is ancient, [it can be] difficult to use. This is understandable as the metrology software market has advanced as much as any software during the last 20 years.” 

Quality departments can replace an old control with a new DRO and leave everything else on the machine the same.

“This can turn a barely usable CMM to a modern machine that anyone can use,” said McDonald.

Measuring 3-D Contours

Modern DROs can support measurement in four axes. In addition to the X, Y, and Z linear axes, they have an auxiliary axis, Q, for angular display. Readouts with these axes can capture 2- and 3-D features.

In addition to flat geometric features, such as points, lines, and circles, shapes like cylinders and cones can be measured. The screen then displays the feature in three dimensions.

“Today’s DROs usually utilize a large, LED, color touchscreen that can show measurement features in 3-D,” said McDonald. 

The touchscreen is also used to enter and manage the library of touch probes. Normal styli, star styli, as well as rigid and tiltable probing heads are entered via the touchscreen. During probing cycle programming, the type, length, and diameter of the stylus are automatically loaded from the library.

When a triggering 3-D touch probe is connected directly to the DRO, the measured value is transferred automatically to the program. With a rigid probing element, the measured value must be saved by pressing a key. The measured features can be clearly displayed either in three dimensions or in one of the three projection planes. With the use of a DRO, operators can create or automatically record measuring programs for repeated parts.

“Experienced manual CMM users can walk up to these DROs for the first time and begin measuring with very little training,” said McDonald.

Measured data can be sent via RS-232 cable or saved on a USB drive. 

For more information, visit www.heidenhain.com.

Newall DP700

The DP700 from Newall Electronics comes in a slim-line aluminum case.

According to the manufacturer, this readout was designed to contain all of the essential functions for all machining applications, but, at the same time, provide the operator with an intuitive and user-friendly interface.

The design allows the user to customize the feature-set he will be running. If a specific feature is not needed, it can be turned off and it will not show up in the operating menu.

Some of the functions of this DRO are center find, metric/inch conversion, zero approach, tool offsets, taper calculation, bolt hole circle creation, and arc contouring. It also has programmable memory, feed rate display, linear and segmented error compensation, and an undo function.

It uses RS-232 output cables.

For more information, visit www.newall.com.

New DRO Products Fagor Innova 40i

The Innova 40i True Vision DRO from Fagor Automation includes the basic features of the company’s Innova 20i series, including inch/metric conversion, absolute/incremental programming, axis presetting, and tool offset capability. 

The new DRO has an added TFT color screen that can display solid graphic part representation, giving the operator a high-resolution view of the part as shown in real machining time or simulation mode.  

This DRO also can display the part in multiple solid sectional views. Displays of high-priority processor screen updates provide a cleaner and faster view of the axes position, helping to eliminate manual machine overshoot. A bar graph shows the operator the distance needed to go to the next feature.

Other new features are plane and angle machining, auto scaling, auto position recall, auto corner rounding, machining in arcs, auto calculation of part angle, and even axis coupling. 

All of these features help the operator eliminate time-consuming calculations and allow him to keep the spindle in the part rather than calculate positional data constantly, reports the manufacturer. 

Pocket, bolt hole, linear hole, matrix, and turning cycles are standard features. Productivity features include part centering and tool offset and radius compensation.

Another new feature, constant surface speed enables precise spindle control, including constant surface speed. In real time, the DRO varies the spindle analog command voltage based on the position on the diameter.

For more information, visit www.fagorautomation.com.