Assembly automation and product design

A part whose basic shape is a cylinder or regular prism whose cross section is a regular polygon of five or more sides is called a rotational part.. A rotational part is one whose basic

ssarily or iente d) using

con ventional hopp

er fee ders (see not

1 A first digit of 0-8 is for parts that can be fed easily (but not necessarily oriented) using conventional vibratory or nonvibratory hopper feeders Parts having characteristics making them difficult to feed, irrespective

of basic shape, are assigned a first digit of 9 Difficult-to-feed parts include those that are flexible, delicate, sticky, light, overlap, large, very small, nest, severly nest, tanlge, severly tangle or are abrasive.

2 A part whose basic shape is a cylinder or regular prism whose cross section is a regular polygon of five or more sides is called a rotational part.

3 A part whose basic shape is a regular prism whose cross section is a regular polygon of three or four sides is called a triangular or square part.

4 A part whose basic shape is a regular prism is called a rectangular part.

5 L is the length and D is the diameter of the smallest cylinder that can completely enclose the part.

6 A is the length of the longest side, C is the length of the shortest side, and B is the length of the intermediate side of the smallest rectangular prism that can completely enclose the part.

Part is not ALPH

A symmetric

[co

de t

he main featu

re o

r fure

s, csinLPHA asymmetrsee no

te 3)

1 A rotational part is one whose basic shape is a cylinder or regular prism having five or more sides The part is not difficult to feed.

2 The part does not require orientation end to end.

3 A main feature causing ALPHA asymmetry is one defining the to-end orientation of the part.

end-4 These are parts that will orient themselves with their principal axis vertical when placed in a parallel-sided horizontal slot.

5 A BETA-symmetric step or chamfer is a concentric reduction in eter The cross section can be circular or any regular polygon of four

diam-or mdiam-ore sides Discrete projections, recesses diam-or irrelevant features should be ignored in choosing this digit.

6 The reductions and increases in diameter forming the groove must be concentric The cross sections can be circular or any regular polygon

of four or more sides Discrete projections, recesses or irrelevant tures should be ignored in choosing this digit.

fea-7 These parts have an ALPHA-symmetric external shape but their center

of mass is not at the geometric center of the part.

8 If exposed features are prominent but the symmetry caused by these features is too small to be employed for orienting purposes, then the symmetry is said to be slight asymmetry.

9 A BETA-symmetric part does not require orientation about its principal axis.

10 A main feature causing BETA asymmetry is one that completely defines the orientation of the part about its principal axis.

11 Some parts can only be fed one way However, when a choice exists, the technique employed and hence the code can be affected by the delivery orientation.

or 5)

1 A part whose basic shape is a regular prism whose cross section is an equilateral triangle or square is called a triangular or square part The part is not difficult to feed.

2 Part does not require orientation about its principal axis.

3 A part has rotational symmetry about a specified axis if the part’s orientation is repeated by rotating it through a certain angle (less than

360 deg) about that axis.

4 When the envelope of a part is a perfect cube, the principal axis should

be selected according to the following priorities:

a Any axis about which the part is 90 deg rotationally symmetric.

b An axis about which the part has 180 deg rotational symmetry and clearly not 90 deg rotational symmetry.

c An axis about which the part has 180 deg rotational symmetry and almost 90 deg rotational symmetry.

d When a part has no rotational symmetry and there is more than one main feature, the principal axis should be the axis of symmetry of one of the main features.

When utilizing the above rules and multiple choices still exist, then the axis that will provide a code with the smallest third digit should

be selected as the principle axis.

5 Part does not require orientation end to end (it has 180 deg rotational symmetry about at least one transverse axis).

6 A main feature causing ALPHA asymmetry defines the end-to-end orientation of the part and distinguishes the end and side surfaces.

7 The various aspects of a part resting on a plane are called natural resting aspects.

8 If exposed features are prominent but the symmetry caused by these features is too small to be employed for orienting purposes, then the asymmetry is said to be slight asymmetry When the part is 180 rota- tionally symmetric about a certain axis, slight asymmetry implies that the part is almost 90 deg rotationally symmetric about the same axis.

9 Steps, chamfers or through grooves are features which result in a deviation of the silhouette of the part from the silhouette of its envelope.

10 These are parts that will orient themselves with their principal axis vertical when placed in a parallel-sided horizontal slot.

1 A part whose basic shape is a rectangular prism is called a rectangular part The part is not difficult to feed

2 180 deg rotational symmetry about an axis means that the same entation of the part will be repeated only once by rotating the part through 180 deg about that axis.

ori-3 Part can be oriented without utilizing features other than the dimensions

6 A feature is too small, if it is too small to be employed for orientation purposes.

7 A part having no rotational symmetry means that the same orientation

of the part will not be repeated by rotating the part through any angle less than 360 deg about any one of the three axis X, Y, and Z The X- axis is parallel to the longest side of the envelope, the Y-axis is parallel

to the intermediate side and the Z-axis is parallel to the shortest side.

8 A main feature is a feature that is chosen to define the orientation of the part All the features that are chosen to completely define the orientation of the part should be necessary and sufficient for the pur- pose.

Often, features arise in pairs or groups and the pair or group of features

is symmetric about one of the three axis X, Y, and Z In this case, the pair or group of features should be regarded as one feature Using this convention, two main features at most are needed to completely define thed orientation of a part.

9 Sometimes, when a part has no rotational symmetry, its orientation can either be defined by one or by two main features Under these circum- stances the part code is determined by the following in decreasing order

of preference:

a Choose one main feature, if it results in a third digit less than 5.

b Choose two main features if they result in a third digit less than 5.

c Choose one main feature, if it results in a third digit greater than 5.

d Choose two main features if they result in a third digit greater than 5.

10 The symmetric plane is the plane that divides the part into halves that are mirror images of each other.

D DIG IT

Flexible A part is considered flexible if the part cannot maintain its shape under

the action of automatic feeding so that orienting devices cannot function factorily.

satis-Delicate A part is considered delicate if damage may occur during handling,

either due to breakage caused by parts falling from orienting sections or tracks onto the hopper base, or due to wear caused by recirculation of parts in the hopper When wear is the criterion, a part would be considered delicate if it could not recirculate in the hopper for 30 min and maintain the required tolerance.

Sticky If a force, comparable to the weight of a nontangling or nonnesting part,

is required to separate it from bulk, the part is considered sticky.

Light A part is considered too light to be handled by conventional hopper feeders

Overlap Parts will tend to overlap in a feeder when an alignment of better than

0.2 mm is required to prevent shingling or overlapping during feeding in single file on a horizontal track.

Large A part is considered to be too large to be readily handled by conventional

hopper feeders when its smallest dimension is greater than 50 mm or if its maximum dimension is greater than 150 mm A part is considered to be too large

to be handled by a particular vibratory hopper feeder if L > d/8, where L is the length of the part measured parallel to the feeding direction and d is the feeder

or bowl diameter.

Very small A part is considered to be too small to be readily handled by

conventional hopper feeders when its largest dimension is less than 3 mm A part

is considered to be too small to be readily handled by a particular vibratory hopper feeder if its largest dimension is less than the radius of the curved surface joining the hopper wall and the track surface measured in a plane perpendicular to the feeding direction.

Nest Parts are considered to nest if they interconnect when in bulk causing

orientation problems No force is required to separate the parts when they are nested.

Severely nest Parts are considered to severely nest if they interconnect and lock

when in bulk and require a force to separate them.

Tangle Parts are said to tangle if a reorientation is required to separate them

when in bulk.

Severely tangle Parts are said to severely tangle if they require manipulation to

specific orientations and a force is required to separate them.

Abrasive A part is considered to be abrasive if it may cause damage to the

surface of the hopper feeding device unless these surfaces are specially treated.

THIRD DIGIT

Parts will not tangle or nest

StickySticky

Discs

or shortcylindersL/D ≤ 1.5

LongcylindersL/D > 1.5

FlatpartsA/B ≤ 3A/C > 4LongA/B > 3CubicpartsA/B ≤ 3

Discs

or shortcylindersL/D ≤ 1.5

LongcylindersL/D > 1.5

FlatpartsA/B ≤ 3A/C > 4LongA/B > 3

CubicpartsA/B ≤ 3A/C ≤ 4

Parts will not severely tangle or nest

Part’s orientation is defined bygeometric feature(s) alone

Part’s orientation is notdefined by geometric

de-fined bygeometricfeature(s)alone

Part’s tation is notdefined bygeometricfeature(s)alone

Part’s tation is de-fined bygeometricfeature(s)alone

Part’s tation is notdefined bygeometricfeature(s)

Parts tend tooverlap dur-ing feedingFlexible

Non-flexible

Parts do nottend to over-lap duringfeeding

Parts tend

to overlapduring

Data sheets showing feeding and orienting techniques catalogued under part codes.

L Hopper wall

t, F R

n = 0.2s

t t o

A device coding system is used to categorize orienting devices for vibratory-bowl feeders by their important characteristics The purpose of the code is to provide

a systematic method for listing orienting devices and arranging the data sheets

in this section The first digit of the 2-digit code represents the basic device configuration (flat or sloped track with or without a wall projection) The second digit is used to distinguish the various device modifications Samples of devices with their various codes are shown below.

0.22D

f acceptance

of orienta

tion c

Probabilit

y o

f acceptance

of orientati

D

= 0.2

0.0

0

0.81

de angle, θmax degrees

Imin/X

8 PC␥f

␥f

␥

hB

θ, degs

2YDc

=1.0

Catalog of the various types of nonvibratory feeders with general design data.

BLADED WHEEL HOPPER FEEDER

Suitability

Cylindrical parts, sphericalparts, disc shaped parts such asnuts, washers, etc

Principle

The rotating bladed wheel isused to agitate the parts so thatthey tend to fall into the trackand slide out of the hopper inthe desired orientation

General features

The track is arranged so that it is tangent to the circle erated by the tips of the rotating blades at the point where theblades enter the hopper

gen-General data

Angle of inclination of the track = 0.79 rad (45⬚) Number of blades in the wheel = 4−6 Blade width to length ratio, w/r = 0.3 Maximum linear velocity of the blade tip = 0.70 m/s

Hopper

PartsTrackBlades

m reciproion

frequenc

ty (m/s)

Θg

ss critic

al rotational

frequen

cy, n

c π 2D/g

␮

ss feed ra

te, F/

ωN0.25 0.20 0.15 0.10 0.05