Qin Y. Micromanufacturing Engineering and Technology

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Regarding micro-sheet-forming production,

the follow ing are the particularities which need

to be paid attention, especially for the forming

of sheets of less than 100 microns in thickness

and feature sizes less than sub-millimeters, the

reasons for which will be explained in the follow-

ing sections of this chapter, wherever appropriate:

1. The need to use proper materials which are

micro-formable, either under cold, warm or

localized heating conditions;

2. Speci al care in the handling of the raw materi-

als (e.g. guiding thin strip, holding the strip

during forming, etc.) and in collecting scrap,

parts/components effectively;

3. Const raints on the tool layouts due to the lim-

ited space and closeness of miniature/micro-

tools, and, hence, constraints on tool design;

4. The process capabilities, which are prescribed

largely by the tool fabricat ion capabilities,

including tool coatings and the assembly of

miniature/micro-tools ;

5. Miniaturization of the forming machinery and

improving the precision of the machinery at the

corresponding scales;

6. Tool cost issues, including process chains for

micro-tooling, effective tool life affected by

susceptibility to wear, fragile structures, dam-

age to the tools caused by manufacturing, etc.

MANUFACTURING PROCESSES

AND FUNDAMENTALS

Traditionally, sheet metals may be defined as

metal having a thickness of between 0.4 a nd

6 mm, while micro-sheet forming usually deals

with sheet metals of which the thickness is usually

below 0.3 mm. Therefore, thin strips or coils may

be proper words for defining these materials.

As with conventional sheet metal forming,

major material conversion mech anisms in micro-

sheet forming include shearing/cutting, bending,

unbending, stretching, compr essing, stress relax-

ation, etc., and their combinations.

Being the same as for conventional sheet metal

forming, the mechanical properties of the materials

such as elasticity, plasticity, stress strain relations,

strain rate, work hardening, temperature effect,

anisotropy, grain size, residual stress, etc., are very

important for understanding material deformation/

separation mechanisms. The effects of grain sizes

and orientations, and grain-boundary properties,

are especially significant in micro-sheet forming,

considering their effects on the definition of the

overall stress/strain relationships, sheared-section

qualities, bending curvatures, springback phenom-

ena, stress relaxation, etc. For given micro-struc-

tures, the effects are more significant, in terms of

the relative ratios between the grain sizes and the

strip thickness/feature sizes/part dimensions.

The follow ing sheet-forming processes may be

used in micro-sheet forming.

Manufacture of Sheet Metal Parts

by Blanking/Punching

Cutting may be used to separate larg e sheets into

smaller pieces, to cut out a part perimeter, or to

make holes in a part, and can be accomplished by

shearing action between two shared-cutting edges

through the following stages of the material: (a)

plastic deformation, (b) fracture initiation, and (c)

separation (Fig. 8-1). The parameters that

FIGURE 8-1 Stages of a shearing/cutting process.

CHAPTER 8 Forming of Micro-Sheet-Metal Components 131

influence the shearing/cutting quality signifi-

cantly include: punch-die clearance, punch veloc-

ity, sheet metal materials, cutting tools, lubrica-

tion, alignment of the tools, strain rate, etc.

The clearance between the punch/cutting

tool and the die is a very important parameter

(Fig. 8-2). For the clearance in conventional sheet

metal forming, 4–8% of the sheet thickness is

recommended. With too small a clearance a

greater cutting force is required; and the fracture

lines tend not to intersect, while with too large a

clearance excessive burr siz es develop. The best

clearance value depends on the sheet metal type

and thickness. The recommended clearance

may be calculated from C ¼ at, where t is the

sheet thickness and a is a factor (provided from

different sources).

The value of a for micro-blanking/punching

needs to be determined by addressing actual cases

because of the large influence of the micro-

structure (size, orientation and grain-boundary

properties) relati ve to the overall scale of the part

dimensions and/or cut geometries. For example,

due to the size effect, the formation of edge draw-

in, shear/plastic deformation and fracture/burr

(Fig. 8-3) will be affected more significantly than

that in a macro-blanking/punching process, by the

micro-structure of the material. The level of

the effect depends largely on the number of grains,

the grain orientation, the possible number of slid-

ing planes, etc., at the cutting areas. It was

observed that the shearing resistance actually

increases as the process/part dimensions are

scaled down, but not in a linear manner [1]: this

may be due to the limited number of sliding planes

and the constr ained position in which the shearing

is taking place. A small number of grains may not

be able to allow shear deformation to the same

extent as would a poly-crystal which has a large

number of grai ns and grain boundaries [9]. The

strain rate in shearing/cutting plays an important

role, especially on the cutting quality, e.g. burr

formation. It has been established that high veloc-

ities in blanking can lead to a decrease in the

blanking force and improved quality of cutting

sections [10]: a dynami c fracturing mechanism

and increase of the temperature locally for a short

period of time may contribute to this. The same

principle can be seen in high speed chopping of

metal billets for forging/forming. Considering

that in micro-forming, the sheet metal is relatively

thin, how the temperature factor could contribute

to this is not clear. However, as a general

FIGURE 8-3 Illustration of the influence of grains on the

sheared section.

FIGURE 8-2 Illustration of the influence of the punch/die clearance.

132 CHAPTER 8 Forming of Micro-Sheet-Metal Components

principle, using a higher speed in cutting should

normally help to improve the cutting quality.

A practical problem associated with micro-

blanking/punching is that the punch/die clearance

required may not always be met. For example, for

the stamping of a 20 mm thick sheet metal strip,

the ideal clearance would be 1–2 mm. This would

be a challenge to tool making and to the guiding of

the tools (machine set-up and tooling). Even if it is

possible to achieve this in fabrication and assem-

bly, the dynamics characteristics of the machine

and too ling, including the resulting deflections,

are very likely to cause an offset of the punch or

the die of more than 1–2 mm. As a consequence,

damage to the tools is likely to occur constantly.

When using larger clearance values than the ideal

values, burr formation in micro-forming of thin

sheets may not be avoidable, if conventional pro-

cess configurations are employed.

For micro-sheet metal parts, especially those to

be used in im portant electronics products and

MEMS, the presence of burrs may not be accept-

able. Therefore, a post-process for burr removal

may be necessary, e.g. laser ablation or mechani-

cal methods. Burr-free blanking/punching pro-

cesses have been explored in the past for the form-

ing of thick sheet metals, and recently there were

also attempts to use these to form thin metal strips

[11]. The process of using half-distance piercing

without separating the material, then using a

counter-punch to eff ect a counter-direction pierc-

ing (pushback) to complete the blanking/punch-

ing (Fig. 8-4), is feasible for eliminating burr for-

mation for strips as thin as 50 mm. The several

stages, including two stages shown in Fig. 8.4,

can be accommodated using a progressive die

design in micro-stamping, e.g. punching for pro-

ducing pilot holes, half-blanking (which may also

be supported with a soft counter-punch), push-

back blanking to complete the blanking opera-

tion, and, finally, clearing the cutting or cutting

off the parts, etc. For micro-forming, e.g. where

the sheet metal thickness is less than 50 mm, con-

trolling the half-blanking depth precisely will be

crucial, and involves the control of not only the

machine ram and the punch motion with the tool-

ing, but also guiding and holding the metal strip

inside the tooling.

Another useful process configuration called

laser-assisted micro-stamping may be used for

improving the quality of the cut section and

extending the capabilities of the process such as

the stamping of greater aspect ratios (the ratio of

the cutting thickness to the cutting area dimen-

sions) and high strength materials, including

brittle/difficult stamping materials. The process

is described in Chapter 10. The laser heating will

provide a reduction in the strength of the local

material and improve the flowabili ty of the mate-

rial at the cutting section.

FIGURE 8-4 Illustration of a ‘burr-free’ punching process.

CHAPTER 8 Forming of Micro-Sheet-Metal Components 133

Manufacture of Sheet Metal Parts

by Bending

Bending in sheet metal forming may be defined as

the straining of the metal around a straight axis. A

neutral axis plane exists for the sheet metal around

which the top section of the material may be

stretched during bending while the bottom section

is compressed (Fig. 8-5). Bending operations may

be performed using punches, rolls, wipe dies, the

downward movement of the bending tools,

depending on the bending processes, i.e. V-bend-

ing, U-bending, edge bending, etc., that are nor-

mally used in conventional sheet metal working.

The manufacture of micro-sheet metal pro-

ducts, such as those used in electronics products

and MEMS, often needs bending to produce 3D

profiles/sections. Typical applications include

micro-electric contacts/fingers/switches, 3D pro-

files for mechanical and thermal-mechanical sen-

sors and 3D sheet metal frames/housing for optical

devices and micro-sensors. The manufacture of

these items may also require photo-chemical etch-

ing to produce fine geometry, while using bending

to complete the 3D profiles/sections.

In employing bending for making micro-pro-

ducts the bend angle, bend radius, bend allow-

ance, length of bend, etc., are still key process

parameters (Fig. 8-5). The calculation of the strain

value in bending, the minimum bend radius , the

bend allowance, etc., may still be effected with the

simplified equations that are normally used for

macro-/miniature parts. These, however, need to

include considerations concerning size effects.

Similarly to the case of blanking/punching, the

relative grain size to the sheet metal thickness,

grain distribution and grain-boundary conditions

at the bend section will have significant influences

on the bending process and bending quality: a

universal definition in terms of the level of these

influences does not exist.

One of the main challenging issues in the bend-

ing of thin sheet metals is to prevent the distortion

of the sheet and to overcome springback-related

problems (Fig. 8-6). Sheet metal may recover

FIGURE 8-5 Illustration of a sheet metal bending process and parameters.

FIGURE 8-6 Illustration of the springback phenomena in

sheet bending.

134 CHAPTER 8 Forming of Micro-Sheet-Metal Components

elastically after manufacturing, not only after

bending, but also due to possible changes of the

state of the stresses during/after secondary pro-

cesses, e.g. after trimming, i.e. the cutting of

neighboring material which affects the stress bal-

ance in this or another section. This often occurs

when micro-parts with condensed features or cut-

ting/bending sections are produced with a pro-

gressive die-forming/stamping configuration.

The springback may occur immediately after the

release of the forming force, or occur due to the

subsequent release of the residual stresses, and

results in the distortion of the shape of the part

or instability of the dimensions of the part under

service conditions. The amount of springback in

bending is dependent on the ratio of the bending

radius to the sheet metal thickness, the yield

strength and Young’s modulus of the material,

the micro- structure in the bending sections, and

the closeness of the forming/cutting features.

The component form errors resulting from the

springback may be compensated for by properly

designing the die and the bending parameters, or

introducing extra processes. Rebending, overbend-

ing, bottoming or stretch bending are the techniques

often used to eliminate the errors caused by the

springback in conventional sheet metal forming.

It may be difficult to employ some of these tech-

niques in micro-sheet forming, either due to the

complexity of the geometry in small areas, or due

to the difficulty in adding extra tools or forming

stages in the limited tooling space, etc. Other limita-

tions are those due to cost considerations. Feasible

compensation measures include optimization of the

bending stroke, bending angle, tool shape, punch/

die clearance, etc. In-process measurement of

springback plus adjusting the bending angle

or bending speed is possible, if proper sensing

(e.g. displacement and angular sensors, non-

contact sensors such as laser-based sensors, etc.),

an effective feedback loop and analysis, and

control of t he actuators can be ensured. T his is

achievable mainly for simple bend geometry, not

for a complex stamping process.

To avoid difficulties in hand ling micro-

components/parts and in the fabrication of micro-

tooling, non-contact processing approaches such

as laser-assisted bending may be introduced to

achieve accurate bend geometries [12].Forexam-

ple, short-pulse excimer laser radiation is able to

result in a required level of thermally induced stress

in very thin surface layers of a sheet metal, and the

deformation of the thin sheet in the radiated area

may be effected in the forms of bending by the

released stresses. Laser heating can also assist in

forming of 3D micro-sheet structures effectively,

e.g. combining bending and twisting [13].

Deep Drawing of Sheet Metal Parts

Deep drawing is a sheet metal-forming process

used industrially to produce cup-shaped, box-

shaped and other complex-curved hollow-shaped

sheet parts. Micro-cups/micro-boxes may be

produced with similar process configurations

(Fig. 8-7) for micro-housing applications, such as

for the packaging of micro-sensors and micro-

actuators. As for conventional deep drawing, the

major parameters which influence the process

and product quality include the dimensions of

the blank, the punch and die dimensions, especially

the punch corner radii, the clearance between the

punch and the die, as well as the blank-holder

geometry, the interfacial conditions and the hold-

ing pressures. Deep drawing is a more complex

process than shearing/cutting and bending because

it usually combines processes such as bending,

unbending, stretching, compression and shearing,

depending on the part geometry to be produced.

These processes become more complex when the

micro-structure of the sheet metal becomes a dom-

inant factor as the scale decreases [2].

The drawing ratio (DR ¼ diameter of the

blank/diameter of the punch) achievable is usually

about 2.0 (the limiting drawing ratio (LDR)),

depending on the sheet material thickn ess and

micro-structure. With fine-grain sheet metals,

controlled friction at the contact surface of the

blank-holder with the sheet, the sheet with the

die, the punch to sheet metal interfa ces, and pos-

sibly providing counter-pressures under the sheet,

the LDR value could be increased. A major chal-

lenge faced in micro-deep drawing is to achieve

these DR values within a limited space, which

CHAPTER 8 Forming of Micro-Sheet-Metal Components 135

usually limits the tooling arrangement. Control of

the inte rfacial conditions is even more difficult.

Ideally, no other media should be used, and

enhanced complexity of the tool/material inter-

face conditions should be avoided. The actual

LDR achievable in micro-deep drawing produc-

tion also depends on how the blanks and the

formed cups will be toggled with the sheet metal

strips in the forming/stamping layout design, since

the blanks and the finally formed cups are unlikely

to be detached from the strip during forming/

stamping due to the difficulties associated with

handling these small objects, while a reasonable

production rate may have to be maintained. This

is a special issue to be addressed, compared to the

laboratory-based protot ype process development.

Common defects in drawn thin-sheet parts

include the formation of wrinkles (due to buck-

ling), material fracturing (especially at the punch

and die corners), and surface scratching (Fig. 8-7).

Wrinkles often occur when very thin sheet metals

are to be drawn (the material most likely buckles),

such as 20 mm thick sheets. Blank-holding will be

crucial, but it may not be easily arranged due to

the limited space for tool components in micro-

deep drawing. Fine-grain materials and materials

with superplastic flow characteristics will be help-

ful in overcoming the fractures which often occur

at the punch corner (small radius) and the flange/

cup wall interface. Smalle r cups with thin sheet

metals may not be achievable, due either to exces-

sive springback for shallow geometries or due to

FIGURE 8-7 Illustration of the deep drawing process, influential parameters and part failure forms.

136 CHAPTER 8 Forming of Micro-Sheet-Metal Components

the initiation of fractures arising from the use of

small punches, similar to what can occur in a

piercing process. Again, the avoidance of these

features will also depend on how the blanks are

to be toggled with the strip.

Redrawing is usually neces sary, due to the lim-

itation in the achievement of a feasible reduction

value of a cup, in one stroke. Redrawing or reverse

redrawing, even introducing an annealing process

and ironing, is possible for miniature cups. These

steps are unlikely to be introduced in the forming

of a micro-cup, due to the difficulties occurr ing in

the handling and alignment of the workpiece, etc.

Ideal processes would be those without the need

to reposition the workpiece while the tools are

being changed.

Other Micro-sheet Metal-forming

Processes

Other micro-sheet metal-forming processes

include: (a) incremental (or dieless) forming –

micro-sheet metal parts or micro-features on sheet

metals can also be produced in incr emental form-

ing forms, such as by using CNC-controlled ham-

mering, piezo-electric actuated micro-probes for

dimpling (high frequency vibration actuated), by

which micro-features in small and large areas of

thin sheet metals (down to 10 to 20 microns thick-

ness) can be produced [14]. (b) Isostatic pressing –

ultra-thin metal foils may be pressed into a die

with grooved surfaces to produce micro-channels.

Foils as thin as several microns can be formed to

produce such channels within the range of several

to tens of microns [15] . (c) Embossing/coining is

also possible for use in producing surface micro-

textures on the thin sheet metals, e.g. using silicon

tools, on thin aluminum sheets, fine-grained alloy,

amorphous alloy, in the cold and hot state, etc.

[1,4].

GENERAL CONSIDERATION S

FOR MANUFACTURING

Similarly to the plann ing for conventional sheet

forming, the following aspects may have to

be checke d with a view to implementing micro-

forming processes (some details concerning these

issues being described in the next sections):

Whether the maximum stamping-force require-

ments, machine static/dynamic characteriza-

tion can be met with the available machines;

Whether the machine strokes and manufactur-

ing precision requirements can be met with

available machines and tools;

Whether the production rates achievable are

acceptable, also considering the thickn ess of

the sheet metals to be dealt with, the precision

requirements and tool life factors;

Whether the raw materials obtainable meet the

requirements, in terms of mechanical proper-

ties, grain sizes and dimensional tolerances for

production;

What the stock/tool layout for progressive die

design will be, including how the scrap and the

parts will be despatched;

Whether the tool design/manufacturing capa-

bilities meet the requirements (especially

micro-tooling capabilities, involving the whole

process chains);

Whether the punch/die clearance (recom-

mended) is achievable by toolmaker(s);

Whether a burr-removal process is required

(for high quality/performance parts);

What extra care for handling fragile thin strips

and the structural parts stamped will be

required, including that for careful strip/

blank-holding designs;

Whether a push-pull set-up with two feeders or

just a single feeder is to be used for pulling/

feeding the sheet metal;

What extra measures for dealing with

springback and distortions of the sheet parts

with dense geometrical features will be

required;

How the scraps and parts will be collected from

the tool system and the machine;

How the process monitoring will be implemen-

ted (force, velocit y, energy, etc.);

How the tool condition, e.g. wear, breaking,

damage to the co ating, will be monitored;

Whether a cleaning process is needed and a

clean environment should be maintained;

How the parts will be packed/transported;

CHAPTER 8 Forming of Micro-Sheet-Metal Components 137

How the parts/products will be inspected (off-

line or online, or both), etc.

FORMING TOOLS

General considerations for tool design and manu-

facture for micro-sheet-forming production

include: the scheme for progressive die forming/

stamping or transfer die forming/stamping (need

to give careful consideration to the part sizes, fea-

tures and sizes, use of the strip material, etc.); the

availability of the die-working space provided by

the machine as well as the connection to the feeder

(s); the stock layouts considering micro-forming

characteristics (especially the closeness of the fea-

tures) as well as transport requirements; the

blank-holding design considering limited spaces

and precision; the feasible punch penetration dis-

tance (taking into account the punch diameter/

free length ratio); the punch/die clearance achiev-

able with micro-tooling capabilities; web forma-

tion and limitation due to space arrangements and

its potential effect on the distortion of the parts;

the ejection/removal of the small/t hin parts and

scraps (if needed); burr generation and removal;

punch stiffness/strength and assembly require-

ments (with lim ited spaces); the transport of

the thin part/scrap ribbon at high speed; main-

taining the flatness of the thin strip during trans-

port; considerations for the implementation of a

dry stamping process and its effects; the micro-

tooling process chains and capabilities in dimen-

sion tolerances and surface finish; tool materials

and cost; micro-tooling cost (considering the

process chains); assembly and inspection techni-

ques for micro-tools; the interfaces with the

machine; special arrangements for the guiding

of the punches/moving parts of the tooling; the

proper selection of bearings and guides, prestres-

sing parts, if possible; tool surface polishing;

tool surface coating, etc.

Forming tool design and manufacturing is a

particularly challenging area for micro-sheet

forming, and is mainly associated with the size

effects induced as the scaling factor decreases:

1. Punch-die clearance in micro-stamping needs

to be redefined (closely relating to the material

properties qualified at micro-scales and to the

micro-structures at the deformation/shearing

sections). The recommended clearance

(4–10% of the sheet thickness, Fig. 8-2) for

conventional stamping may not be correct.

Increasing the punching velocity would affect

the shearing section quality positively, which

would, in turn, relax the clearance require-

ments.

2. For cutting thinner strips, tight clearances

down to one to several microns may be needed,

which may be achievable but at high cost. Con-

straints to this include whether the tool-fabri-

cation capabilities are able to achieve one to

several microns accuracy in manufacturing

individual tool parts, to align these within a

similar accuracy after assembly, and whether

the dynamic characteristics of the tooling are

able to maintain the tool bending, the tool off-

set due to loading eccentricity and clearance

between the bearings and guidin g pillars to be

within a similar precision range (a tool system

is illustrated in Fig. 8-8). Tool damage/break-

ing could be easily caused by these factors.

3. The reduced sizes of the cutting geometry

restrict the punches to only a very short free

length (to maintain sufficient stabi lity). As a

consequence, it may be difficult to punch the

scrap out of the die exit (Fig. 8-2(c)), if the

punches are too short. It also requires extre-

mely accurate control of the punch stroke to

ensure that the stamping operation is com-

pleted.

4. Due to the limited space available, the number

of tool parts/elements for constructing the tool-

ing may have to be reduced to avoid difficulties

in fabricating these parts/elements and assem-

bling them in tiny spaces, as well as reducing

the assembly errors accumulated. Using com-

pound tool designs may be considered.

5. The design of the pilot pins for positioning thin

strip needs to be carefully done, by which the

pins could correct the position of the strip ( Fig.

8-9), and help to reduce the positional errors

significantly, thereby relaxing the stringent

requirements on the strip feeder(s), in terms

of feeding accuracy.

138 CHAPTER 8 Forming of Micro-Sheet-Metal Components

6. To prevent damage to the workpiece surfaces

(e.g. coated strips for electronics applications)

and to prevent sticking of the scrap and micro-

parts to the tool surfaces, dry stamping will be

needed, for which special tool materials such as

ceramics tools and self-lubricated tool coat-

ings, etc. should be considered.

7. In micro-sheet forming, gravity cannot be con-

sidered as the main force being applied to the

part. Unwanted surface forces such as van der

Waals, electrostatic and surface-tension forces

are dominant at such a scale. As a result, con-

cepts for handling parts/scrap deployed in con-

ventional forming (largely considering the

gravity force of the parts) do not usually work.

Parts may not drop out automatically and con-

necting these to the strip may be feasible in

some cases. However, separation may still be

needed, depending on the end uses and

customer’s requirements. A vacuum system

directly connected to the dies or proper loca-

tions within a tool system will be helpful for

collecting the scrap and even micro-parts.

Micro-tooling capabilities and proces s chains

(e.g. mechanical cutting, EDM, laser treatment,

coating, electro-forming, chemical etching, etc.)

are especially important, which significantly pre-

scribe the feasibility of realizing the processes and

achievability of the requi red scales of the micro-

parts, while maintaining proper production rates

FIGURE 8-9 Illustration of the function of the pilot pins.

FIGURE 8-8 A tool system for micro-sheet forming.

CHAPTER 8 Forming of Micro-Sheet-Metal Components 139

and product quality, and low manufacturing cost.

These are addressed in several other chapters of

this book.

MANUFACTURING PRESSES/

MACHINES

Traditionally, sheet metal forming may be

effected either with mechanical presses or hydrau-

lic presses, the latter usually being of larg e scale.

These presses are usually not of sufficient preci-

sion for micro-forming applicat ions, and they are

not compatible, in terms of scale, for the forming

of the miniature/micro-sheet metal parts. Conven-

tional, large-scale presses may be optimized/

upgraded for the manufacture of miniature/

micro-sheet metal parts with the required

enhanced precision. Their manufacture may also

be achievable through the use of delicately

designed and fabricated forming tools. Conven-

tional forming tools may be designed primarily

for manufacturing metal parts with precisions in

the millimeter range. However, with some specific

engineering modifications implemented in these

machines they could be optimized for micro-

forming applications. BSTA from Bruderer is a

machine which can operate at up to 1400 spm

and a press force of 300 kN [16]. Incorporated

in the machine are specific modifications such as

guides that are insensitive to thermal influences,

additional features to secure high precision, and a

counterbalance system ‘acting irreversibly’ to the

movement of the ram with a view to keeping the

machine free from vibration. The guides and

levers that control the ram movement are

arranged in such a way that the tilting of the

ram due to the ap plication of an eccentric load

does not affe ct the position of the punch: this is

achieved by placing the theoretical center of grav-

ity of the ram at the tip of the punch.

Machines of smaller size such as bench-top

machines may be built with newly enhanced ele-

ments/parts and/or designs particularly for micro-

forming applications. This category of machine

is of normal size but incorporating new concepts

dedicated to micro-forming. A high-precision

stamping press was developed jointly by Schuler,

PtU Darmstad t, ILT, IPA and other partners [17].

The machine has a modular arrangement and a

high rigidity design. In this machine, linear motors

are used for driving the ram. Linear driving has

the advantage of high and reproducible accuracy.

Lubrication is not needed and maintenance can be

avoided, hence it is an attractive option for clean-

room manufacturing. Other beneficial features

include low noise emission and high reliability

and endurance.

A new, low cost, bench-top machine dedicated

for micro-sheet forming is being developed at the

University of Strathclyde [8], in collaboration

with its EU MAMSICRO conso rtium partners

(Fig. 8-10). A linear-motor driving mechanism is

used. The maximum frequency of the machine is

1000 strokes per minute (spm), the maximum

force is 5.3 kN, the vertical position resolution

is 0.1 mm, and the load measurement resolution

is 0.1 N.

FIGURE 8-10 A bench-top micro-sheet-forming ma-

chine, designed by the University of Strathclyde.

140 CHAPTER 8 Forming of Micro-Sheet-Metal Components