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EQUALIZER straightening machine

A casting can come out of the die a few tenths of a millimetre out of shape. Our EQUALIZER measures it with lasers, presses each arm only as far as it needs, and measures it again until the part is in tolerance. We built it for the drum spider of a washing machine. It works with an operator, or in a line with robots.

See how it works
  1. Bins full of die-cast aluminium drum spiders in a die caster’s plant.
    01Cast by the thousand
  2. A gloved hand sets a drum spider into the fixture of the EQUALIZER.
    02Into the fixture
  3. The front of the EQUALIZER: the operator starts the cycle and the tool comes down onto the spider.
    03Measured and straightened
  4. In a robot line: a robot carries a spider into the EQUALIZER.
    04Or in a robot line

Why a casting comes out bent

Aluminium shrinks as it cools, and a casting never cools evenly. The stresses that leave behind pull the part out of shape, and every part a little differently.

  1. 01

    Uneven cooling

    A thick hub cools later than thin arms. The part shrinks unevenly and pulls itself out of shape.

  2. 02

    Out of the die, into water

    The part is pushed out of the die while it is still hot and soft. Die casters who ask us for a straightening machine usually cool it in temperature-controlled water tanks, where the heat leaves it fast.

  3. 03

    Gates and overflows cut off

    Trimming releases the stresses that were held in the gates and overflows, and the part moves again.

  4. 04

    No two alike

    Each casting bends its own way. No fixed press stroke corrects them all: each part has to be measured.

A few tenths at the drum

The spider holds a washing machine’s drum on its shaft, bolted to the drum at the end of each arm. If the arm ends are not in one plane, the drum sits crooked on its shaft. Nobody sees it on the part. At spin speed the whole machine feels it: the drum wobbles, the cabinet shakes, and the bearings take the load.

Manually, it is trial and error

Without a machine, an operator measures the part with a gauge, presses it in a hand press and measures it again. The casting springs back by a different amount every time, so the result depends on the person and the shift.

ManuallyWith the EQUALIZER
MeasuringA gauge, one point at a time, the part taken outSix lasers at once, two on each arm, the part in its fixture
How far to pressAs far as the operator judgesCalculated for each arm from its readings, past the line by the springback
SpringbackFound out afterwards, and pressed again by feelMeasured again at once; pressed again only if needed
The resultDepends on the person and the shiftThe same tolerance on every part
A recordNone, or a tick on a sheetEvery part’s readings and its OK or not OK on the machine
The operatorAt the press all shift, one part after anotherLoads the fixture, or only feeds a conveyor

Measure, press, measure again

The EQUALIZER repeats it until every point is in tolerance, then shows the result on its screen. In the drawing, the first part needs a second press on one arm; the second part is done in one.

On the machine, step by step

Hover over a step to watch it.

  1. The operator sets a drum spider into the fixture of the EQUALIZER and steps back.
    01LoadedThe operator sets the spider into the fixture and starts the cycle. The fixture holds it in place.
  2. Close up: two laser sensors over one arm of the spider in the fixture.
    02Measured at six pointsTwo lasers over each arm measure its height. The software compares every point with its target.
  3. Close up at the end of an arm: the straightening tool comes down onto it and lifts again.Real speed
    03Pressed where it is bentEach arm has its own straightening axis. It presses its arm only as far as the readings call for, a little past the line, because the casting springs back.
  4. From the side: the tool comes down onto the spider, holds and lifts.Real speed
    04Held, released, measured againThe lasers read the part again. An arm still out of tolerance is pressed again, with a smaller stroke.
  5. The machine’s screen with a green bar: PART IS OK, and the readings of the last parts below it.
    05OK or not OKWhen every point is in tolerance, the screen says PART IS OK. The readings of every part stay on the machine.
  6. In a robot line: a robot reaches into the EQUALIZER for the spider and swings out with it.Real speed
    06Or loaded by a robotIn a line, a robot sets the part in and takes it out. The machine works the same way.

Steps 01 to 05 were filmed at our plant during testing. Step 06 is from the robot line at our customer’s plant.

Inside the EQUALIZER

A compact machine on one frame, built around the part it straightens.

  1. 01

    One straightening axis per arm

    Three axes, so each arm gets its own stroke. Servo-electric with ball screws, or hydraulic.

  2. 02

    A positioning axis

    A fourth axis brings the part to the same place for every measurement.

  3. 03

    Six laser distance sensors

    Two over each arm. They read the part in the fixture, so it never has to be taken out to be measured.

  4. 04

    Our own software

    System Manager on a touch screen: the cycle, alarms, the readings of the last parts, and a recipe for each part.

  5. 05

    Safe at the opening

    A light curtain guards the front, and a signal tower on top shows the machine’s state from across the hall.

  6. 06

    A fixture for each variant

    The fixture is made for your part. A new variant gets its own fixture and its own recipe.

The EQUALIZER from the front: the signal tower green, the screen, and the straightening tools around the spider behind the open front.
The EQUALIZER at our plant.
The fixture behind the open guard: a drum spider in place, the brass guide bushings and the straightening tools around it.
The spider in its fixture.
Close up: the laser sensors over the end of one arm, labelled for that arm.
Two lasers over every arm.

Two EQUALIZERs, six robots

At a die caster’s plant, two servo-electric EQUALIZERs work in a line with six FANUC robots. Operators feed the castings to the conveyors. The robots take each spider from there, load the machines and unload them.

Straightening machines
2
Robots
6
Laser points a part
6
The robot line from above: an EQUALIZER on the left, yellow FANUC robots in the middle, and conveyors full of spiders on the right.

The line, from the bin to the machine

The conveyors hold a buffer of castings, so the machines keep working while the operator brings the next bin. Nobody holds a part at a press.

Real speed
The line from above, in real time.
An operator sets a drum spider into a nest on the conveyor and walks back for the next one.
The operator feeds the conveyor
A long conveyor full of spiders in green nests; behind it an operator feeds the next ones.
A buffer of castings
Close up: a robot gripper takes a spider from the slide at the end of the conveyor.
Picked from the slide
A robot reaches into a machine with a spider while another robot works behind it.
Into the machine
From above: two robots hand a spider on between the stations.
Six robots share the work
The drone flies over the line: robots, machines and conveyors behind the guarding.
Over the line

When no catalogue machine does the job

Some jobs fit no standard machine: a part only your plant makes, a tolerance only your customer asks for. Then we design and build the machine ourselves, the way we build our robotic cells. The EQUALIZER is one of them.

  1. 01

    One team for the whole machine

    Mechanical, electrical, software and automation engineers work on it together, under one roof.

  2. 02

    Designed around your part

    We start from your samples, your drawing and your tolerance. The fixture is made for your part.

  3. 03

    Built and tested at our plant

    We build and wire the machine, and run it with your parts before it ships.

  4. 04

    Commissioned at yours

    We set it up in your plant, train your operators and hand over the documentation.

  5. 05

    Ready for robots

    The same machine works with an operator today and in a robot line later.

The EQUALIZER in brief

Machine
EQUALIZER straightening machine
Solution
Special Machines
Part
Die-cast aluminium drum spider of a washing machine
Measurement
Six laser distance sensors, two on each arm
Straightening
Three axes, one per arm: servo-electric with ball screws, or hydraulic
Positioning
One axis for the part
Control
Touch screen PC, System Manager
Result
OK or not OK for every part, readings kept
Safety
Light curtain at the opening, signal tower
Variants
A fixture and a recipe for each
Loading
By an operator, or by robots in a line: two EQUALIZERs with six FANUC robots at a die caster
Delivery
One piece; tested at our plant with your parts, commissioned and trained at yours

Castings: degating and grinding

Robots cut the gates and risers off castings and grind the cut faces.

Measured in the image: final control

A machine that checks every part with our own vision software, then packs it.

Questions we are asked

Which parts can the EQUALIZER straighten?

We built it for die-cast aluminium drum spiders: three arms around a hub. The principle, measuring the part in its fixture and pressing it where it is bent, works for other cast or forged parts too, with their own fixture, measuring points and axes.

Send us your part and its drawing, and we will tell you what the machine for it looks like.

What tolerance can it reach?

It depends on the part. Straightening is bending, not machining: the arm is pressed a little past the line and springs back. How close a part can come depends on its thickness, the strength of the alloy and the axis that has to be straightened.

So we set the tolerance with you for each part, from your samples. The machine then presses and measures again until every point is inside it.

Why not press every part with the same stroke?

Because every casting is bent differently, and springs back differently. A fixed stroke straightens some parts and bends others the wrong way. The EQUALIZER measures first and calculates a stroke for each arm of each part.

Hydraulic or servo?

Both are possible. The two EQUALIZERs in the robot line are servo-electric: their ball screws need no oil and set the stroke very precisely. Hydraulic axes give a lot of force in a small space. We choose with you, from the part and the force it needs.

What happens to a part that stays out of tolerance?

The machine shows it as not OK, so it can be kept apart from the good parts. Its readings stay on the machine with all the others.

Can it work in a robot line?

Yes. At a die caster’s plant two EQUALIZERs work with six FANUC robots. The robots load and unload the machines; the operators only feed the conveyors.

Do you test the machine before it ships?

Yes. We build it at our plant and run it with your sample parts. Your team can come to the factory acceptance test and see your own parts straightened.

Send us your part and its tolerance

Every special machine starts with a part that no standard machine handles well. Send us samples and the drawing, and we will work out the machine with you.

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