Machine shops that grind metal or alloy surfaces flat to remove material or achieve a precise thick- ness now have endlesspossibilities to improve their precision aswell as production speed and control withmore advanced, automated units.
Today’s rotary surface grinders offer sophisticated sensors and controls that can reliably achieve tighter dimensional tolerances, flatness, parallelism, and surface finish inmuch less time. The equipment can be usedto grind flat metals, alloys, and ceramics toprecise dimensions before polishing.
Operator control over the process is unsurpassed with the new automated grinders asthe user can enter specific requirements. Forexample, 712 RPM on the spindle, 22 RPM onthe table, with a down-feed rate of .003 in/min,with a certain dwell cycle. Essentially, the machine can be programmed to meet just aboutany requirement.
Compared to traditional grinding equipment with manual controls that require experienced machinists familiar with the nuancesof each machine, these automated units consistently produce higher quality parts in lesstime. As a result, a growing number of machine shops are installing new grinders thatcan be operated by less experienced personnelwhile still achieving the desired results.
Solving the Skilled OperatorRetirement Problem
In machine shops that work with metalsand alloys, factors such as thickness, parallelism, and surface condition are often dictated in the specifications. Grinding is alsooften used to remove significant amountsof material to bring a stock sheet or plateto precise dimensions.
To do this, machine shops primarily usesurface grinders with a reciprocating table anda horizontal spindle that turns the grindingwheel, but the process is very slow.
“Reciprocating table grinders are precise,but the material removal rate is slow and multiple passes are required,” says Erik Lawson,Engineering Manager at Winona, MN-basedDCM Tech, a designer and builder of industrial rotary surface grinders.
Older rotary surface grinders are anotheroption but can be problematic in the handsof less experienced operators. With limitedcontrol of spindle speeds as well as manualcontrols, the older equipment requires sophisticated operators that can factor in complexcalculations. Considerable expertise and experience are required, which can be a challenge as skilled operators retire.
Automated Rotary Surface Grinders
In modern vertical spindle, rotary tablesurface grinders, the table rotates with theworkpiece held firmly in place underneatha vertical spindle. The grinding is not performed by the peripheral edge of the wheelbut by the entire diameter of the abrasive surface, which facilitates grinding performanceand consistency.
“With rotary table surface grinders, the entire part passes through the wheel, which ismore efficient than reciprocating table grinders that may have workpieces wider than thegrinding wheel,” says Lawson.
Today, surface grinders are designed withmuch more advanced sensors and controlsthat automatically maintain very tight tolerances, removing material down to withinone ten-thousandth of an inch of the finalthickness. Digital technology allows for aninterface with easy-to-use touchscreen controls. When combined with automation, surface grinder operators are no longer requiredto be highly trained individuals.
For example, rotary units such as DCM
Tech’s IG 280 SD, with a 24-in. variable-speed
table and 20 hp variable speed grinding
spindle motor, make it possible for virtu-
ally anyone to successfully operate a unit.
One example of innovation available in this
model involves the automation of the initial
contact between the abrasive wheel and the
part, which typically had to be finessed by
the operator. With this updated option, ad-
vanced sensor technology detects vibration
and can automatically fine-tune not only the
pressure of the spindle motor but how quickly
it moves the wheel down onto the part. When
the machine senses the abrasive wheel has
contacted the part, it automatically begins
the grind cycle.
“Automatic part detection eliminates theneed for the operator to do time-consuming, error-prone ‘manual touch-offs wherethey would manually feed the [grinding]machine until it just touches the surface ofthe part before backing off and restarting it,”says Lawson.
With regard to production efficiency, theadvanced rotary surface grinders are alsomuch faster than reciprocating grinders because the units can get much closer to therequired precise dimensions before any finishing steps—reducing or even eliminatingsome lapping and polishing steps.
With a conventional surface grinder, if astock with standard thickness needs to beground down, an operator would stop short ofthe required removal and leave an unpolishedsurface. Using another machine was often required to remove the remaining material butthis can take excessive time and labor.
“A rotary surface grinder will usually finish the work of a reciprocating grinder in a
controls that can
surface finish in
much less time.
Advanced Rotary Surface GrindersDeliver Endless Possibilities andTighter Tolerances
By Del Williams
DCM Tech automated rotary surface grinders can be used to
grind flat metals, alloys, and ceramics to precise dimensions be-
fore polishing, significantly reducing lapping and polishing steps.
All photos courtesy of DCM Tech.