Cycle time is where money getsmade. Volumetrics, gate design, tem-perature controls ... mold makers use ahost of tools to fill a mold quickly. Butafter that’s done, the mold still has to becycled. How fast the core can be movedin and out impacts production.Traditional hydraulic cylinders are fast.But ASIC reports that in some applica-tions, a GSX actuator can enhance cyclerates by letting related operations getstarted sooner. This is possible becausethis kind of actuator constantly feedsthe core’s actual position and motionstatus back to the controller.

Longer tool life is an added benefit.“Every time we can replace a hydraulic

spi

Distance Covered is 18.250”Mass is 200 lbs.

GSX Actuator

Seconds

80

60

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.25 .50 .75 1.00 1.25 1.50

Cleaner,Quieter and LessExpensive to Run

Those aren’t bad goals for anydesigner; especially if you’re workingin a field that’s traditionally plaguedby noise and contamination issues.

In 1999 Milacron issued a paper thatdiscussed the rational for their all-electric injection molding machines(IMMs). In it, they recounted theadvantages of digital electro-mechani-cal over the hydraulic motion controlsystems their industry traditionallyused. The highlights of that discus-sion included:• Accuracy & Repeatability – hydraulic

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Due to a closed loopfeedback system,GSX linear servoactuators can be programmed with adesired velocity rateand accel./decel.ramping. Thisenables the user tooptimize productthroughput andmachine life.

You need to create a “nothing” exactly where youwant it to make most injection molded plasticparts serve their intended purpose. A typical moldassembly is comprised of 1. Stationary platens,2. The core, 3. Linear guides, 4. Actuator (or cylinder) rod, and 5. Electro-mechanical actuatoror hydraulic cylinder.

Figure 1

cylinder with an Exlar electro-mechanical actuator, we can virtuallyguarantee a longer tool life.” Nicholscontinued, “That actuator lets us getthe core inserted faster without justslamming the mold together violently.Less stress means longer life.”

Retasking the same actuator ondifferent projects is easy. Especiallyin retrofit situations, ASIC alwaysaddresses reuse in their cost analysis.According to Nichols there are cases

Technology Reporting from Exlar

GREAT IDEAS THAT WORK

Whether for vacuumcleaners, hearing aids,or blood filters, engi-neers who design the

tool systems for injection moldedplastic parts face challenges familiar toeveryone: “How fast; how accurate;how long; and (like always) howmuch?”

In many cases, the right answer toeach of these questions has been madepossible by re-evaluating the role thathydraulics have traditionally played inthat arena.

For generations, hydraulic cylinderswere the motion control devices ofchoice for moldmakers. But today,when it comes to creating the precise,rapid motions that typically happen inthese molds, electro-mechanical actua-tors with integrated motors (like theExlar GSX Series) are getting moreattention. According to Jeff Nichols,President of ASIC Corporation, a sys-tems integrator headquartered in WestChester, OH, “In many respects, mold-making is about creating voids. It’seasy to put resin where you want it --the trick is making sure nothing goeswhere something else needs to be later.”

It’s a boy-girl thing. Molds aregenerally male/female assemblieswhere the male (or core) forms thefinished part’s concave surface. It cre-ates the all-important “nothing”. On alaptop shell, that void houses the elec-tronics; on a plastic plate the voidscreate separate places for baked beansand potato salad.

How To Create Nothing – Faster

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140 dBDamage To Ears

Car Horn

In A Factory & A TrainLoud Office

Quiet Office

Hospital And Library

Noise DuringRunning

Operation

120 dB

100 dB

80 dB

60 dB

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0 dB

60.6 dB

Roboshot a-50 B

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Average 59.3 dB

Noise Evaluation59.0 dB

where an actuator spec’d for one moldhas more power than needed becauseit could be reused on another assem-bly that did require that additionalpower. “These actuators are reallysimple to retask. You just plug a lap-top into the drive, feed it a newmotion profile, and it’s ready to go.”said Nichols.

So, how difficult is it to retrofithydraulic cylinders with electro-mechanical actuators? The Exlaractuators that ASIC uses are truly“plug ‘n play”. A hydraulic cylinder’stwo hoses are replaced with a pair ofelectrical connections. The mountingflanges are all industry standard. Andbecause the GSX has an internalmotor, both have the same form factor.Thus, for comparable stroke lengths,the GSX units fit in the same space.

Exlar Corporation1470 Lake Drive WestChanhassen, MN 55317www.elxarcorp.com

fluid can heat up, hoses can expand,valves can stick. These variables allaffect accuracy. Digitally controlledmechanical drives are more accurateover the long haul because they don’tuse those components.

• Set-up Precision – digital controlpermits operators to set tighterover/under tolerances.

• Utility Costs – Milacron identified a50-90% power reduction when theycompared their own comparably-sized all-electric and hydraulicIMMs. The actual connected powerrequirements for their all-electricmachines were just 25% of thatneeded by their hydraulic equiva-lents.

• Oil Costs Eliminated – not only isthe initial cost of oil purchaseremoved from the cost equation, butso are the ongoing costs for monitor-ing, disposal and cleanups.

• Cleanroom Ready – By completelyeliminating the possibility of oilleaks, Milacron pointed out that anall-electric machine became theobvious choice for a host of medical,electronic and other such cleanroomapplications.

• Noise Levels – Plant noise is alwaysunder scrutiny from workers’ com-pensation insurance agencies. Byreplacing hydraulics with electro-mechanical motion controls, noiselevels on the new Milacron machinesdropped by over 30%.

A complete copy of the originalMilacron paper can be downloadedat:

http://plastics.milacron.com/

Ω Ω Ω

When Milacron developed their all-electric line of injection molding machines, they achieved a 30%+ reduction in noise levels. An operator running the “roboshot a-50B” measured hereworks in an environment very similar to that of the engineers who designed it.

(Nothing, continued)

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For more information on these and other unique motion control solutions,contact:

Sound level chart copyright 1999, Milacron, Inc. Reprinted with permission. T-Lam is a trademark of Exlar Corporation.

(Cleaner, Quieter,Less Expensive, continued)

The remote electronics for a GSX actuatorrequire very little space. For IMM moldapplications, they’re often put in a smallrolling cabinet that sits next to the machine.1. Line filter, 2. Power supply, 3. Servo con-troller into which you download the desiredmotion parameters. (Photo courtesy ofASIC Corp. www.asiccorporation.com)

Technology Reporting from Exlar

GREAT IDEAS THAT WORK

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Inside a GSX Actuator:The actuators referenced by Jeff Nichols in the storyabove have an internal electric motor. Because an inverted planetary roller screw drives the shaft and the internal stator rotates the planetary assembly, these actuators fit in the same space as hydraulic cylinders with the same stroke lengths. Inverted Planetary

Roller Screw

Encoder or Resolver Feedback

Preloaded AngularContact Bearings

Neodymium Iron Boron

Magnets

Brushless ServoMotor with T-Lam™Stator

InternallyThreaded

Cylinder

Sealed, Chrome Plated Output Rod

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