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June 7, 1999

12 Min Read
An introduction to injection molding metals and ceramics


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WHAT IS IT?

  • PIM is an established manufacturing technique for producing small, complex, tight-tolerance, high-performance, net-shape metal parts.

  • PIM is a cost-effective alternative to machining or investment casting parts. It offers tremendous single-step parts consolidation potential and design flexibility.

  • In PIM, plastic pellets filled with fine metal or ceramic powders are injected into a mold. After molding, the plastic is removed from the part. The remaining metal or ceramic part is sintered to full density. Part density dramatically increases during sintering. After sintering, MIM parts have mechanical, wear, and corrosion resistance properties equivalent to a machined metal. All typical secondaries, such as plating and heat treating, can be applied to sintered MIM parts.

What's It Cost?

  • A PIM development facility costs at least $600,000 in capital expenses and probably another $1.4 million in operating expenses for the first two years. Capital expenses for full-scale commercial production can start at around $3 million.

  • PIM molding machine pricing is similar to plastics molding machine prices. Generally, PIM machines are 100 tons or less. Capital expenses also typically include compounding systems, debinding units, sintering furnaces, and secondaries.

  • PIM powder pricing varies widely, from less than $10/lb to more than $600/lb. Precompounded feedstocks cost from $10/lb to $25/lb or more.

Why Use PIM?

  • PIM offers lower unit costs-typically 25 percent less than a similar machined part, and 50 percent less than a similar investment cast part.

  • PIM has better surface finish, greater precision and detail, simplified product designs, fewer part numbers, simplification of the manufacturing process, and shorter production lead times. PIM parts are recyclable.

  • Conventional machining makes you pay for the shape every time you make the part. With PIM, the part price is based on the size, not the shape.

Is My Part a PIM Part?

  • PIM is best for small, complex part designs. Typically, if your part can fit inside a tennis ball, it could be a PIM part. However, larger parts are still possible.

  • Production runs can range from 10,000 to more than 1 million units/year.

  • PIM powders can be custom blended to provide performance properties to suit specific applications. n PIM parts can be designed like injection molded plastic parts. Tighter tolerances means many traditional metal-working secondaries can be eliminated.

*Information provided by MIM molders Megamet Industriesand Injectamax Corp., and consultant IMS.


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WHAT IS IT?

  • TXM is a process for the high-speed injection molding of semisolid thixotropic metal alloys. Magnesium alloys are the most widely used today. Zinc alloy parts are coming into production. Thixomat Inc. presently is running trials in TXM aluminum alloy. Aluminum alloy trials in a production operation will occur before year's end. Thixomat holds the exclusive worldwide TXM licensing rights, and has trademarked the process Thixomolding.

  • TXM produces net shape molded metal parts with properties and characteristics far beyond those of traditional diecast metal and injection molded plastic parts.

  • TXM machines are similar in appearance to accumulator-assisted, reciprocating screw plastics injection molding machines. JSW and Husky are licensed machine builders.

  • Metal alloy chips are fed into the machine barrel through a feedthroat blanketed with inert argon gas to prevent oxidation. Heater-band barrel heating and screw shear transform the chips into a semisolid slurry. The slurry is collected in an accumulation zone ahead of the nonreturn valve, then injected at high speed into the preheated, vacuumized mold.


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The rapid growth in the sale of TXM molding
machines, while starting from a low base, has
rapidly accelerated in Asia in recent years.
Many feel that North Aemrica and Europe
are about to take off on a similar trajectory.

What's It Cost?

  • Industry sources say licenses cost about $50,000 per company with a sliding royalty fee based on machine tonnage. Contact Thixomat for details.

  • TXM molding machines, presently 75 to 1600 tons, cost about twice as much as plastics molding machines, ton for ton. Presses more than 2000 tons are in development.

  • TXM chips cost $1.60 to $1.85/lb.

Why Use TXM?

  • TXM is a proven, high-volume, net-shape metal parts manufacturing process.

  • TXM material flow is laminar, resulting in low porosity. Barrel temperature control results in shot-to-shot repeatability. Dimensional variations typically are one-fifth to one-eighth those of precision diecasting.

  • TXM is environmentally friendly. It uses no suspected ozone-depleting gases, as does diecasting, and no sludge or dross is generated. It also uses less energy. It's worker friendly, too. No foundries are involved and there's no danger of exposure to molten metals. TXM materials are recyclable.

Is My Part a TXM Part?

  • TXM can produce a variety of appearance and non-appearance parts. Magnesium alloy TXM parts are lightweight and stiff with inherent EMI/RFI shielding characteristics, excellent thermal conductivity, and good vibrational damping properties. Some parts have been molded with walls .5 mm thick and less.

  • Existing diecast and plastic parts have been successfully converted to TXM, but parts designed specifically for TXM take maximum advantage of the materials and process.

*Information provided by Thixomat, Thixotech, JSW, Husky.


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PIM market snapshot

Pim is growing and it's growing fast. Everyone in the businessagrees on that. How far and how fast it is growing has alwaysbeen a subject of debate. There are no hard numbers. Randall M.German says that PIM is already very close to being a billion-dollarbusiness worldwide. He expects PIM will be a $2 to $3-billionbusiness by 2010. German is the head of the P/M lab at Penn State.

He and Robert G. Cornwall of Innovative Material Solutions(IMS) have compiled the most comprehensively researched book inexistence on every facet of PIM. The book, PIM Industry MarketReport, is generally regarded around the world as the PIM Bible.Published in 1997, a second edition with updated information isscheduled for publication this fall. Things are changing thatfast.

Some U.S. MIM custom molders say that German's numbers areexaggerated. They say the domestic U.S. market for MIM, the world'slargest, averages only around $75 million in revenues. But othersfeel that German is exaggerating on the right side of the bar.They say that $500 million is probably more realistic. Still,German is confident in the accuracy of his market assessments.He's seen more than most.


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Factors Fueling Growth

As head of the PIM Consortium and through his technology transferand consulting work, German has been closely involved in plantexpansions and startups at both custom and captive molders. Manyof these companies, particularly captive molders, keep thingsquiet for a variety of competitive reasons, including better marginsfor existing products by using PIM.

Speaking of margins, German says that for every dollar of capitalinvested, a plastic molder can expect about $1.50 in sales. Forevery capital dollar a MIM molder invests, it's more like $6.50.There is a 100-µm-diameter part micromolded in nanoscalemetal powders that is in production today. German estimates thatsuch parts could cost $8.00 apiece.

That's one reason why he totally discounts the traditionalmeans of calculating growth in terms of tons of powder shipments,as is practiced in the powder metallurgy (P/M) industry. MIM partsare small and getting smaller in some cases, so powder shipmentsare minuscule by comparison. Nevertheless, powder suppliers aremaking out well in PIM. Iron powder suitable for PIM sells fortwice as much as it costs to make, for instance.

He says that there's been significant growth in PIM in areasof which established PIM custom molders may be unaware. For example,some companies have already begun investigating the feasibilityof molding powdered wood for toys. PIM magnets are a booming business.German says that more than a million different magnetic componentshave already been identified as candidates for conversion to injectionmolding.

Then there's an $8-billion U.S. market in hard-metal cuttingtool inserts. More injection molding machinery OEMs, hot runnerand fluid power system manufacturers, and other makers of moldand machine components are turning to PIM for more cost-effectiveparts. And there's been growth in areas like high-temperaturelighting using molded ceramics, and in precious metal powder moldingof jewelry. PIM is also growing in top- secret defense and ordinanceapplications. And German adds that every automaker already usesMIM parts.

Future Growth

He believes one major factor fueling growth is the number offirms successfully entering into the business. For every one thatfails, two more come in. Failures are generally the result offalse economic and technical assumptions. Many of the newbiesare coming in from routes other than P/M, as was traditionallythe case, and the newcomers are more adept at the customer serviceside of doing business, which will increase volumes.

German estimates that there are about 40 PIM powder suppliers,serving around 400 PIM molders worldwide. The field has yet tobecome big enough to generate the kind of part volumes necessaryto significantly bring powder pricing down, though prices aredecreasing.

But the newcomers are joining the establishment in bringingin more business, which may help reduce materials prices. Germanand others feel this situation is similar to the introductionof some high-priced engineering thermoplastics that today arepriced more like commodity resins.

Despite the many challenges faced by this new industry-includinghigh tooling costs and long turnaround times, a lack of uniformstandards, and its fragmented infrastructure-German and othersagree that PIM is growing. Current growth reportedly has beenpegged by many in the field at 30 to 40 percent/year and is expectedto continue at around 22 percent/year over the next five years.

 

Contact Information
Penn State, P/M Lab
University Park, PA
Randall M. German
Phone: (814) 863-8025
Fax: (814) 863-8211
Web: www.pmlab.psu.edu

Innovative Material Solutions Inc.
State College, PA
Robert G. Cornwall
Phone: (814) 234-8735
Fax: (814) 234-1874
Web: www.imspowder.com


TXM market snapshot

As an established large-scale manufacturing business, TXM isless than five years old. Nevertheless, there are already morethan 30 TXM production licensees around the world. They will haveat least 150 TXM machines in operation by the year 2000. Capacityis expanding internationally and newcomers are entering the field.But demand still outstrips supply.

The rapid growth in the use of this safe, environmentally-friendlyIMMC process has been pulled along by markets requiringthe manufacturing cost-savings and the superior performance propertiesof the tight-tolerance parts TXM produces consistently in highvolumes.

It has become a globally accepted manufacturing method. Butthere still is room for improvement. Key TXM companies are developingnew technologies to increase yield and reduce manufacturing costs.These include CAE, faster ingot chipping technologies, improvedmachinery materials of construction, improved recycling and regrindhandling methods, and hot runners. Growth continues nonetheless.

"Most of the growth is not replacing diecastings. It'sreplacing engineering thermoplastics," says an official ofthe Inter-national Magnesium Assn. of McLean, VA. To date, TXMhas proven to be more of a competitive Y2K threat to molded plasticsthan to diecast metals.

Asian TXM Tigers

Portable-computer housings, mobile phones, digital camerasand camcorder housings, mini-disk players, TV cabinets, powertool casings-a growing list of hot sales opportunities in a growingnumber of growth markets for molded engineering thermoplastics-aregoing instead to molded magnesium alloy.

TXM zinc alloys are expected to have similar success replacingtraditionally popular materials in plumbing fixtures. Large TXMautomotive parts in magnesium alloy are just down the road, andTXM aluminum alloy automotive parts may be right around the corner.

The overwhelming majority of TXM growth has been in the Asia-Pacificregion (see chart). JSW sources say 90 percent of the machinesit has sold are used to mold consumer electronics, IT, and telecommunicationsparts, mostly in Japan and Taiwan. Growth continues, despite thegeneral economic slowdown in parts of the region.

Automotive TXM Aluminum

Nonappearance TXM automotive parts have begun to appear, allbenefiting from the cost savings, weight reduction, design freedom,and improved strength of molded magnesium alloys. Automotive hasbeen familiar with diecast magnesium for more than a decade andits use is growing.

Molding aluminum, like automotive, is a Holy Grail to some.In contrast, the diecast aluminum market is 20 to 30 times biggerthan diecast magnesium's. Automotive is expected to be the biggestmarket for TXM aluminum alloys, which are expected to sell foraround 65 cents/lb. There is activity among TXM molders and suppliersto develop fracture-free superalloys for screws, barrels, andnon-return valves capable of withstanding the high corrosion andthermal shock of a semi-solid aluminum slurry.

At the same time, Thixomat has entered into a joint developmentproject funded by the U.S. Department of Energy, Alcoa Aluminum,and the automotive sector. Creating TXM aluminum alloys with improvedmoldability is among the project's goals.

Also, Thixomat reports that overmolding TXM alloys with plasticis gaining in popularity in the automotive sector, and in thehome appliance and power tool markets. Licensed molding machineOEMs are already designing metal/plastic multimolding cells.

Market-Pull Margins

Thixomat plans to start installing TXM molding machines inits new headquarters this year. The machines will be used forprototyping and pilot runs for new production licensees. Thosealready up and running that IMM contacted agree that thebiggest challenge they presently face is meeting demand. "It'sdefinitely more a case of market pull rather than technology push,"says one. Apparently, another challenge is counting profits. Saysone plastics custom molding TXM convert:

"I know the machines cost twice as much, but what's thecost of a machine got to do with it? In the past, we found thateven with high-volume, high-quality plastics moldings, the bestwe could ever expect was 20 to 25 percent gross. Now, we won'teven look at a TXM part with margins under 35 percent.

"We're getting 50 to 60 percent margins on better jobs,like those with parts properly designed for the process. You canget a plastics molding machine for half the price, but you'rereally talking about doing different types of parts."

Comparison of physical properties

Material

Density
(g/cm3)

Melting Point
(ºC)

Thermal Conductivity
(W/mK)

Tensile Strength
(MPa)

Yield Strength
(MPa)

Elongation
(%)

Strength-to-Weight Ratio

Young's Modulus
(GPa)

Magnesium alloy
(injection-molded)

AZ91

1.82

596

72

280

160

8

187

45

AM60

1.79

615

62

270

140

15

180

45

Aluminum alloy
(die-cast)

380

2.70

595

100

315

160

3

106

71

Steel

Carbon steel

7.86

1520

42

517

400

22

80

200

Plastics

ABS

1.03

90 (Tg)

0.2

35

*

40

41

2.1

PC

1.23

160 (Tg)

0.2

104

*

3

102

6.7

Tg: Glass transition point

Contact Information
Thixomat Inc.
Ann Arbor, MI
Stephen LeBeau
Phone: (734) 995-5550
Fax: (734) 995-5558
Web: www.thixomat.com



A complete glossary of terms is also available.

Here is a list of resources for IMMC.

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