Product category:
Miscellaneous machine tool equipment (fixtures, rotary tables etc.)
News Release from: Renishaw | Subject: QC10 ballbar
Edited by the Manufacturingtalk Editorial
Team on 28 June 2005
Getting the most out of a machine tool
A machine tool may be designed to maintain a particular tolerance, but wear and temperature changes will affect its capability to maintain factory specifications unless checked regularly.
A machine tool may be designed and built to maintain a particular tolerance, but wear and temperature changes will affect its capability to maintain factory specs Despite wear and environmental factors, Hamilton-Sundstrand - US manufacturer of aerospace fuel handling systems, auxiliary power units (APU) and wing flap actuation systems - ensures its machines, both old and new, can 'cut it' on tight-toleranced parts by using the latest calibration and probing technologies
This article was originally published on Manufacturingtalk on 7 Mar 2001 at 8.00am (UK)
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The Grand Junction, CO plant has been in operation since 1985 and specialises in the machining of extremely tight-toleranced complex housings, forgings and hog-outs.
Most parts have complex geometries that require four- and five-axis CNC equipment to produce typical aerospace tolerances of 0.001in true position, 0.0005in diameter, and surface profile of 0.002in.
All this has to be accomplished with a battery of machines that includes many transferred into the plant in 1985, along with new equipment purchased annually.
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Utilising creative process planning, a consistent machine tool maintenance programme, and technology developed by Renishaw, Hamilton-Sundstrand has learned how to get the most out of all its machine tools by monitoring its manufacturing processes, machine tool performance and product quality.
Parts made by the air-inlet cell provide a good example.
The cell produces air-inlets for APUs and components for aircraft environmental systems.
The air-inlet part family is processed with multiple lathe, machining center and grinding operations.
One specific horizontal machining center operation generates two machined bores to 0.001in concentricity, regardless of feature size (RFS).
These features are difficult because the two bores are dimensioned from a datum bore previously machined on a lathe.
This datum bore is on the backside of the part, nearly 12in away along the Z axis.
One of the two bores, a liner bore, is over 4in long, with a total tolerance of 0.0007in.
The second is a 5in diameter bore with 0.001in total tolerance.
It has six vertical slots creating a severe interrupted cut.
To ensure these difficult features are generated to specification, Hamilton-Sundstrand employs a variety of machine calibration and probing strategies.
On its Kearney and Trecker horizontal machining center, chipmaking does not begin until Renishaw's MP3 probe aligns the fixture and part to the machine's axis system.
The probing program automatically downloads the fixture offsets, aligning the workpiece in all three axes; then all peripheral features are machined.
This 20 min machining operation causes the machine tool to heat up, resulting in linear expansion in the machine tool's geometry.
To compensate for this normally occurring error, before finish cutting the liner bore and the interrupted bore, the center line of the part is probed a second time.
This re-calibrates all machine axes to the operating temperature of the machine tool.
The probing routines are defined internal to the CNC program, which ensures probing time is minimized.
Each probe cycle takes less than two minutes.
This minimal time and money spent probing guarantees part tolerances will be met, thus saving the expense of costly rework or even scrap.
The first piece is inspected on a DNC Sheffield CMM to verify that the machine tool setup and probing routines have been adjusted to optimal settings.
The CMM is equipped with a Renishaw TP20 probe fitted to a motorized PH10 probe head, allowing the peripheral features and bore concentricities to be inspected in one simple setup on the CMM.
This data provides a baseline to monitor product quality in process, prior to final inspection on subsequent parts.
* Ballbar and laser tests catch and correct machine inaccuracies - personnel regularly monitor all the company's CNC machine tools' performance parameters with quick tests using Renishaw's QC10 ballbar.
At the first sign of any non-conformance in parts, the machinist sets up and conducts a ballbar diagnostic test.
Taking less than 20 min to complete, the test checks 14 different geometric parameters in each of the three machine planes tested - XY, XZ and YZ.
The QC10 ballbar tracks machine movement to +/-0.5 micron, and has a resolution of 0.1 micron.
Errors in servo mismatch, linear compensation, squareness and axis backlash are easily identified, then corrected by maintenance personnel.
Additionally, the ballbar enables maintenance personnel to save days when troubleshooting, and the periodic check help reduce unscheduled downtime by tracking trends in machine performance.
Problems can be identified before a machine tool goes down, allowing for scheduled repairs, rather than production crises.
The ballbar has also helped reduce the time needed to complete routine preventive maintenance.
Ballbar data allows the maintenance technician to determine the true extent of any corrective action a machine may need.
In many cases, the machine requires fewer adjustments than normally scheduled.
While ballbar monitoring is extremely helpful, it does not provide all the information necessary for in-depth evaluation and calibration of a machine tool.
For example, the ballbar can identify scale-mismatch or linear compensation error, but it does not provide the means to compensate for the error.
For this, Hamilton-Sundstrand uses a Renishaw ML10 laser calibration system.
With its 0.1ppm accuracy and 1nm resolution, the laser can precisely evaluate linear and angular movement along a machine axis and can measure, adjust and verify pitch and yaw errors.
One of the most important features of both the laser and ballbar systems is the integrated software.
Both packages are easy to learn and have step-by-step prompts that make operation and data interpretation quick and simple.
The ballbar and laser software packages are written in similar formats, which facilitates ease of use.
Hamilton-Sundstrand's maintenance technicians, manufacturing personnel and management staff have developed such a high level of confidence in the ballbar and laser, that test requirements are written into machine buy-off cycles for every purchase order for new equipment.
All new machining center purchases include spindle probing as a 'must-have' option.
The combination of machine tool probing, automated CMM inspection, ballbar diagnostics and laser calibration enables Hamilton-Sundstrand to understand, monitor and utilise the full capability of all the company's machine tools - new or not - for the highest uptime and output. Request a free brochure from Renishaw ...
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