CNC Brand Profile

Koei MFG Die Casting Trim Presses: The Japanese Builder Behind the Flash

Nobody photographs the trim press. The die casting machine gets the photo. It is enormous, it holds hundreds of tons of clamp force, molten aluminum goes into one end and a finished-looking part comes out the other, and it is the machine the customer wants to see on the plant tour. Then the part gets carried twenty feet to a smaller, quieter machine that shears the ugly off it, and that machine has no story attached to it at all. It just runs.

This is a brand profile, not a spec sheet. Koei Manufacturing Co., Ltd. has been building that second machine since 1963, out of Takarazuka in Hyogo prefecture, and it has never built anything else worth mentioning. Here is what a trim press actually does, where this company came from, why its presses have four posts instead of a throat, and what to look at if one comes up for sale.

What the Trim Press Is Actually Doing

A die casting die does not fill itself politely. Metal is injected under pressure, and pressure finds every seam. It squeezes out along the parting line as flash, thin and sharp. It fills the runner and gate that fed the cavity. It pushes into overflows, which are deliberate extra pockets that catch the first cold, oxidized slug of metal so that garbage ends up somewhere other than in the part. And it leaves a biscuit, the puck of leftover metal in the shot sleeve. When the die opens, the part comes out wearing all of it, and by weight the scrap can rival the casting.

The trim press holds a trim die, which is essentially a shearing tool shaped to the part. The press drives the ram down, the die halves close, and every piece of unwanted metal is cut away against a matched edge in a single stroke. Trimming and shaving are related but different. Trimming shears off the bulk, the flash and gates and overflows. Shaving is the finer pass, taking a thin layer to clean up a surface or bring an edge or a bore to size. Koei builds for both, and the two machines currently on our floor split exactly along that line, a 35 ton trimming unit and a 10 ton shaving unit.

Koei Manufacturing, and the Year It Started

Koei Manufacturing Co., Ltd., ?????????, started in 1963 as one man's operation in Takarazuka, in Hyogo prefecture, on the Osaka side of the Kansai industrial belt. It incorporated in 1976. Its registered capital today is 10 million yen, which tells you the shape of the business better than any brochure does. This is not a conglomerate. Sixty-plus years in, it is still a focused, independent press builder run by a president, currently Hideoshi Omata, in a building in a technology park in a mid-sized Japanese city.

That matters because it explains the product. A company this size does not diversify its way to survival. It survives by being the one people call for a specific machine, and by that machine not coming back. Koei's answer to sixty years of competition was to build the same category of press better and faster rather than to build more categories.

Flash is not an interesting problem. It is a permanent one. Every casting ever made has come out of the die wearing metal that has to be sheared off, and it always will. Koei built a sixty year company on the permanent problem instead of the interesting one.

The Numbers Koei Opened Into

1963 is not a neutral year to start a press company in Japan. From 1955 to 1970 the Japanese economy grew at an average nominal rate of about 15 percent a year, against 6 to 10 percent across the other advanced nations. The car industry went vertical inside that. Japanese vehicle production ran 1.88 million units in 1965, passed West Germany to become the second largest in the world at 3.15 million in 1967, and cleared 4 million in 1968. Passenger car sales compounded at roughly 32 percent a year, going from 590,000 units in 1965 to 2.37 million in 1970. Private car ownership went from 6.3 million to over 10 million between 1965 and 1967 alone.

Every one of those vehicles carried dozens of aluminum and zinc die castings. Housings, brackets, covers, pump bodies, carburetor and transmission components, and later the switch and trim hardware that filled an interior. Appliances did the same thing on a parallel curve. That is millions of castings a year, each one arriving at the end of the cell wearing flash, and each one needing a press and a die to take it off. Koei did not have to invent demand. It had to be close to Osaka, be reliable, and be there when the volume arrived.

From Stamping Machines to the KPH Line

The technical history is short and it moves in one direction. In 1980 Koei developed hydraulic stamping machines. In 1982 it began manufacturing the high-speed hydraulic bench press, the KPH line, which is still the backbone of the catalog. The 1,000th machine was built in 1991. The 2,000th in 2001. Electric and hydraulic servo presses arrived in 2014 and 2015, and in 2023 the company added a press inspection business, which is a telling move for a builder with several thousand machines in the field and no plans to abandon them.

The KPH range runs six models. KPH-3M through KPH-35M, spanning 1.5 to 3 tons at the small end up to 15 to 35 tons at the top. Open heights of 250 to 400 mm, shut heights of 100 to 200 mm, motors from 0.75 to 5.5 kW, ram strokes of 150 to 200 mm, tank capacities of 30 to 65 liters, weights from 370 to 1,500 kg. The word that repeats through the specification is speed: approach speeds of 195 to 400 mm per second, retraction at 245 to 290. A press that spends less time traveling and more time working is a press that makes its cycle time back on volume parts, which is the only kind of part anyone die casts.

Why Four Posts and Not a C-Frame

This is the engineering decision that defines the trimming press, and it comes straight out of the physics of the job. A C-frame press is open at the front, which is wonderful for loading and terrible for offset loads, because an open throat deflects and springs under an off-center force. A trim die is almost never centered. Flash does not distribute itself symmetrically around a casting, gates and overflows sit where the metal needed to go, not where the press would prefer them, and the shear load lands wherever that geometry puts it. Push a C-frame off center often enough and the ram cocks, the shear gets inconsistent, one side of the die wears faster than the other, and you start chasing burrs that were not there last month.

Koei's trimming press is a four-column design built specifically for die casting, and the four-pillar guide system is there to take that moment instead of letting the frame absorb it. The ram stays square regardless of where the load sits, which means the part comes out the same on Friday as it did on Monday and the trim die lasts. The other advantage is access. A four-post frame is open on all four sides, so the press can be fed and unloaded from whichever direction the cell layout wants, by robot, by conveyor, or by hand. Koei also offers load cells and cushion options on the machine, which is what you fit when the press is going into automation and somebody wants tonnage data off every stroke.

Where Koei Sits in the Market

The trim press field is small and regional, and most buyers only cross-shop two or three names.

Multipress is the default answer in an American foundry and it is a good one, but its trim press range starts at 20 tons. Italpresse sells the systems argument, casting cell and press from one supplier. Kurtz sells breadth of frame style across three casting processes. Koei's argument is narrower and, for small castings, more useful: Japanese-built high-speed hydraulics, four posts as standard rather than as an upgrade, servo-hydraulic pressure control, and machines that go down to 10 tons for parts that do not need or want 20. If you are trimming small aluminum and magnesium components, that bottom of the range is not a rounding error, it is the whole reason to look.

The Two Machines on Our Floor

Resell CNC currently has four Koei MFG presses, two of each model, all built in 2021, all never installed and still crated. They make a clean side by side, because they are the two halves of the same job.

Two details in that table are worth more than they look. The first is the stopping time. Both machines stop in 125 milliseconds with a 135 millisecond maximum and 30 mm of over-drop, and those are published, measured numbers rather than a claim. On a press that descends at 300 mm per second with an operator's hands anywhere near the die area, brake performance is the safety system, and a machine that ships with a stated stopping time is a machine whose builder expected to be held to it. The second is the Daikin Super Unit on the 10 ton machine. That is a hybrid hydraulic power pack from Daikin Industries, an IPM motor under inverter control driving an autonomous-select tandem pump, which means the unit only spends the power the stroke actually needs. Daikin's own press case study reports a 72 percent reduction in average power consumption and a 100 liter tank in place of a conventional 200 liter one. Less oil to buy, less oil to heat, less oil to cool, smaller footprint.

Why Used Koei Presses Hold Value

A trim press is a simple machine doing a repetitive job, which is exactly the profile that survives resale. There is no spindle to rebuild, no way slides carrying a cutting load, no toolchanger. There is a frame, four columns, a cylinder, a power unit and a control. Frames do not wear out. What wears is seals, hoses, the pump and the electrics, and all of those are replaceable line items rather than reasons to scrap a machine. A twenty year old trim press with a tight frame and square columns is still a twenty year old trim press that works.

The specific case for Koei on the used market is that the machines are Japanese-built, the four-post configuration is standard rather than a premium option, the control is servo-hydraulic instead of a bang-bang valve stack, and the tonnages start low enough to suit small-part work that a 20 ton minimum cannot serve efficiently. The constraint is support. This is a small builder in Hyogo with no large North American service network, so parts and documentation are a real consideration and a buyer should price that in. The counterweight is that the wear items are largely standard hydraulic components rather than proprietary assemblies, and a competent hydraulics shop can keep one running. Machines like the four on our floor, built in 2021 and never installed, sit in a different category again, because there is no wear history to discount at all.

What to Check When Buying a Used Trim Press

These are the inspections Resell CNC handles before a press moves, and they are the same ones worth running on any machine you are looking at anywhere.

Column condition and squareness. Run your hand down all four posts. Scoring, pitting or a polished band in one spot means the ram has been running out of square. On a four-post press the columns are the accuracy, so damage there is the one finding that changes the number.

Bushing and gib wear. Check ram play at full open with the press off. Any perceptible rock at the top of the stroke will show up as burr variation at the bottom.

Cylinder and rod. Look for a scored rod, weeping seals or an oil film that keeps coming back after it is wiped. Rod chrome damage means a reseal will not hold.

Stopping time, verified. If the machine states 125 milliseconds, have it demonstrated. Brake and valve response degrade with age and it is the number that protects the operator.

Two-hand control and light curtain function. Test both palm buttons independently, confirm anti-tie-down, and confirm any guarding actually interrupts the stroke rather than just the next cycle.

Hydraulic power unit and oil. Pull a sample. Milky oil means water, dark or varnished oil means heat. Check the pump for noise at pressure and confirm whether the unit is a conventional pump or a hybrid like the Daikin Super Unit, because that changes both the power bill and the parts path.

Bed and bolster. Inspect T-slots for spread or cracking around the mounting pattern, and check the bed for dish. A trim die that will not sit flat will not shear evenly.

Control and electrics. Confirm the console powers, the teach or auto mode functions, and that the PLC is a supported platform. On an import, ask whether the documentation exists in English and whether the machine is wired for your plant voltage.

Tooling and what comes with it. Ask whether any trim dies, bolster plates or die-change hardware are included. Tooling is often a significant fraction of the value and it is routinely left out of the conversation.

Crate and installation history. On a machine sold as never installed, confirm that with photos of the crating and check for corrosion from storage. Sitting still is easier on a press than running, but only if it sat dry.

Who Runs These Machines

Aluminum and magnesium die casters, first and mostly. Automotive suppliers making housings, brackets, covers, pump and transmission components, and the small structural and cosmetic hardware that fills a vehicle. Appliance and power tool manufacturers casting motor housings and gear cases. Electronics and lighting work casting heat sinks and enclosures, where magnesium shows up for weight. The common thread is not the industry, it is the volume. A trim press earns its place when the same casting comes down the line thousands of times and every one of them needs the same metal removed in the same place. Anything below that volume gets deflashed by hand, and anything above it gets a press and a die and never looks back.

Resell CNC Take

Secondary equipment is where the value hides in this trade. Everybody bids the casting machine, so everybody pays for the casting machine. The trim press that has to sit next to it gets treated as an afterthought right up until somebody realizes the cell does not run without one. Four Koei presses built in 2021 and never taken out of the crate is not a machine we see often, and the reason it is interesting has nothing to do with the badge. It is a simple, rigid, fast press with a stated stopping time and no hours on it.

Frequently Asked Questions

What is a die casting trim press?

A die casting trim press is a hydraulic press that shears excess metal off a casting after it leaves the die, including parting-line flash, the gate and runner, the overflows and the biscuit. A trim die mounted in the press closes on the part and cuts all of it away in one stroke. Trim presses for aluminum and magnesium work typically run from about 8 to 100 tons.

Who makes Koei MFG trim presses?

Koei Manufacturing Co., Ltd., ?????????, of Takarazuka, Hyogo prefecture, Japan. The company began in 1963 as an individual operation and incorporated in 1976. It builds high-speed hydraulic bench presses in the KPH line, electric and hydraulic servo presses, and a four-column high-speed hydraulic trimming press designed specifically for die casting.

What is the difference between trimming and shaving in die casting?

Trimming shears away the bulk of the excess metal, meaning flash, gates, runners and overflows. Shaving is the finer secondary pass that removes a thin layer to refine a surface or bring an edge or bore to size. A shaving press is typically lower tonnage than a trimming press for the same family of parts.

What tonnage trim press do I need?

It depends on the shear length and thickness of the material being cut, not on the size of the casting machine. Die casting trim presses generally range from about 8 to 100 tons, with small aluminum and magnesium parts served in the 10 to 35 ton band and larger or thicker castings needing more. Sizing should be done against the specific trim die and part, since an undersized press will not shear cleanly and an oversized one costs floor space and money for nothing.

What is a Daikin Super Unit?

The Super Unit is a hybrid hydraulic power pack from Daikin Industries that combines an IPM motor under inverter control with an autonomous-select tandem pump, so the unit draws only the power a given part of the stroke requires. Daikin's published press case study reports a 72 percent reduction in average power consumption and a 100 liter tank replacing a conventional 200 liter tank on the same application.

Are Koei trim presses worth buying used?

For the right application, yes. A trim press has no spindle and no cutting-load slides, so the frame and columns are the accuracy and those do not wear out in normal service. Wear items are seals, hoses, pump and electrics, which are replaceable. The main consideration on a Japanese small-builder machine is parts and documentation support in North America, which should be priced into the deal, though most wear components are standard hydraulic parts rather than proprietary assemblies.