State of Odd-Form Equipment Technology
Presented at ATE 2000
A highly diverse mix of various shaped and sized components, combined with
limited component packaging standards, make the automation of odd-form
assembly one of the more seemingly challenging tasks on the assembly line.
In reality, with the commercial availability of odd-form automation equipment
from several industry suppliers flexible enough to handle virtually all
odd-form assembly requirements, odd-form automation is just as attainable
and justifiable as other standard assembly automation processes.
to the success of odd-form automation are component locating and
handling options flexible and robust enough to handle the wide
variety of components typical to this type of assembly. In addition,
solutions must adequately compensate for any board variances, body-to-lead
variations, and lead-to-lead tolerance stack-ups to ensure accurate
insertion/placement. To determine which locating and handling options
are best suited to automate your odd-form assembly, you must first
carefully evaluate the component mix, volume, part variance, and
words: odd-form, automation, locating, handling.
Although in the past the words "odd-form" put fear into the hearts
of most manufacturers, today's odd-form assembly products are technically
advanced enough to handle this challenge without difficulty. The question
is no longer whether or not there is equipment capable of successfully
automating odd-form assembly, but whether or not the proper assembly technology
and equipment are matched to the required task. With careful assembly requirement
evaluation, and knowledge of available technologies and equipment, total
success in odd-form assembly can be achieved without the anxiety and risk,
which often accompany an equipment purchase.
By being clear on your needs, both now and for the future, and working
with your supplier to provide a complete assessment of those needs, you
can determine how much accuracy, speed and flexibility are required. In
doing so, you can match these requirements with the best suited locating
and handling strategies, and in turn determine the optimal odd-form assembly
equipment for the job.
are two categories of information to be evaluated to best accomplish
this; the application requirement information, and the production
is the mix of components to be assembled? Is the mix low (1 -
3 part types), medium (4 -5 part types), or high (6 or more part
you assembling similar types of components (such as a variety
of DIPS), or are there many different styles of components which
vary significantly in size and shape?
is the range of variance in the body-to-lead and lead-to-lead
geometry of the parts?
percentage is surface mount and what percentage is through-hole?
is the volume of odd-form components to be assembled? (low, medium,
many boards per panel? How many insertions/placements per board?
many of each part number do you need to place or insert? Are
the parts "balanced" or are there many more of some
types which need to be placed/inserted than others?
lead cut/form or lead snap-in retention required? Is clinching
of leads after insertion required?
pin-in-paste being used?
many shifts a day are you running?
are your throughput requirements?
type of packaging are you using?
type of packaging is available?
often do you need to change over to a new board?
are your standards for the number of systems supported per operator?
is very helpful to work with and communicate these issues with
your supplier. By providing information on the number of boards
you need and the number of parts you have, you can determine what
kind of machine or machine combination is needed to achieve your
desired throughput. By evaluating the component mix, you can then
determine the best way to handle those parts. The part mix, part
consistency, and part packaging will also determine your flexibility
extremely important flexibility issue is the frequency of required
board changeovers. For example, one automotive manufacturer runs
its line three shifts a day using the exact same or very similar
boards. They aren't extremely concerned about flexibility. Speed,
accuracy and throughput requirements are obviously the priorities.
On the other hand, a contract electronics manufacturer may change
over boards several times a week. They require the greatest flexibility.
AND HANDLING OPTIONS
Once you have carefully reviewed and evaluated your application and production
needs, there are several viable locating and handling options available
from industry suppliers, one or a combination of which will provide the
maximum payback and productivity for your current and future application
LEAD LOCATING TECHNOLOGIES:
Direct Lead Acquisition:
This method is used for through-hole odd-form parts and locates components
by their leads with dedicated grip fingers. This more dedicated approach
is highly suitable for lower mix applications and components requiring
lead form or retention during insertion, such as splayed DIP's.
Figure 1. Illustration of a splayed DIP; an example
of a component requiring lead retention during insertion.
There are two general approaches to this method:
approach typically uses upward viewing cameras to locate SMT part
leads, and X-Y viewing cameras to locate through-hole part leads.
Upward viewing cameras can be very effective for odd-form SMT applications
(where the leads can be viewed in profile and a majority of the algorithms
required have already been developed), but more limited for odd-form
through-hole due to the great variety and difficulty of imaging the
various lead tip configurations as illustrated in figure 2 below.
Vision used to image the ends of through-hole leads creates issues
with lighting and algorithms. Application specific algorithms must
be developed for each new lead variation to accurately see the ends
of leads due to the varying surface geometries of lead tips versus
the simple lead profile of surface mountable parts. Profile (X -Y
viewing) imaging can be easier to light and develop algorithms. Due
to issues with shadowing and the need to obtain the X - Y coordinates
of the lead pattern for insertion, use of profile imaging requires
viewing in both the X and Y planes. Both upward and X - Y viewing
cameras require passing parts through a vision station at the cost
of cycle time.
limitations when imaging through-hole component leads with an upward
viewing camera only; difficulty verifying lead tip configurations.
Scanning: This profile viewing technique is similar to the
vision based X-Y viewing technology mentioned above. Using a laser
rather than standard vision to image leads, this method has the
same profile viewing benefits as the X-Y camera technology. It
identifies and then compensates for variances between the expected
and the actual offset of component leads. Similar to vision, the
laser scanning technology requires passing the part through a viewing
area, which may not meet the requirements of higher throughput
Registration in the Feeder:
This method physically locates through-hole part leads while the part
is still in the feeder, and then the part is gripped by the body for
placement/insertion. This is a simple approach which allows you to keep
constant control of the part. In addition, the flexibility gained through
use of body gripping allows for effective assembly of parts ranging from
geometrically stable parts (using a simple handling strategy), to parts
with greater geometric variance (using a more flexible, adaptive compliant
handling strategy). When matched with a flexible handling strategy, picking
a part by the body versus the leads provides greater agility, allowing
it to handle component brickwalling and to meet other common odd-form
COMPONENT HANDLING TECHNOLOGIES:
The following handling technologies are available in many different types
of heads or grippers (single, multi, compliant, etc.), as well as with
automatic head, finger, and other tool changers. Tactile sensing must
be included in all these technologies for successful insertion/placement
detection. Vision can also be used with any of these handling technologies
Pneumatic vacuum picking is the handling of parts with a vacuum tip or
quill which when placed on a flat surface of a component will pick
up, move, and place the part using vacuum suction and release. This
handling technology is most commonly used for placement of surface
mount components which are more likely to have a flat surface to
Vacuum technology can be very cost effective as an add-on if you already
have a surface mount machine and are using existing tools, or if you
are only using these specific surface mount part types. However the technology
is limited to parts that can be vacuum picked only, and many odd-form
parts are not typically surface mount devices and do not necessarily
lend themselves to vacuum picking. Parts not easily vacuum picked can
be adapted by adding special flat surface pieces to each part which is
then removed after part placement on the board.
Pneumatic Actuated Fingers:
This technology makes use of air pressure to open and close gripper jaws,
typically tooled with dedicated fingers. It is the most simple and least
expensive type of handling technology, but limited due to the fact that
gripper jaws controlled by air pressure alone are either completely open
or completely closed. Although this is not a problem when picking a part
from a feeder, placement on a densely populated board can be limited.
Servo actuated technology is the handling of parts with jaws operated
by a small electric motor in the grip which allows movement of the jaws
to any pre-programmed point. It makes it possible to handle different
sized parts on densely populated boards due to the programmable motorized
movement of the jaws without having to open fully after placing/inserting
a part. However with the advantage of the programmed movement comes the
disadvantage of increased complexity of mechanical design and software
This technology handles parts with jaws operated by air pressure, but
also has controlled opening and closing of the jaws by use of a specialized
cylinder. The cylinder allows incremental movement of the jaws, as with
servo-gripping, but without the need for electric motors and drives or
the extent of software programming. In other words, adaptive technology
combines the simplicity of simple pneumatic actuation with the flexibility
of servo actuation.
jaws have a grip release that automatically opens from any size
or shape part within a few thousandths of an inch for insertion/placement
into densely populated boards. There is no need for application
specific programming for jaw positioning. Self-adapting tools
easily accommodate high density and brickwall applications.
The handling technologies outlined above are integrated into many different
physical forms for execution by different suppliers. Some are combined
with, or in addition to others, and some overlap others, but the physical
manifestation of these technologies generally falls into one of the implementation
strategies outlined below. These strategies help to take the application
and technology requirements we have defined to this point and match them
with the physical performance levels needed to best handle the job.
This strategy makes use of a single dedicated tool for handling odd-form
components. It can also be equipped with automatic head and/or finger
changers and used with vision location when required. Handling technologies
used with single-tool strategies include:
(for SMT or mixed technology applications)
single-tool grip generally has the least weight
so it can move quickly and is the least complex
implementation choice, however it is also the
least flexible and can therefore only be used
for very low-mix applications. Automatic head
or finger changers can generally be used to improve
the flexibility, but with the cost of increased
cycle time. Single-grip tool strategies are best
used for applications requiring low flexibility
with only one to three different part styles
to be assembled, and with medium to high throughput.
This strategy makes use of several tools on one head,
turret, or indexing wrist, which are then used to
assemble several different part types simultaneously.
Component "balance" is a huge issue with
multi-tool handling and must be carefully evaluated
to make this a viable option; even systems equipped
with automatic head and jaw changers are subject
to this problem. For example, if you are using a
five-up tool and have six parts to be assembled,
the gripper can only pick up five of them, and then
must go back again to get the single left-over part.
This causes loss of much of the speed advantage over
other more flexible methods. In addition, depending
on the part types, vision location may be required.
Handling technologies used with multi-tools include:
(for SMT or mixed technology applications)
component assembly is "balanced", this
strategy can provide more speed and more flexibility
than a single-tool approach, and can typically
handle up to six part types without the need
to change heads or jaws. If more than six parts
need to be assembled, head or jaw changes will
likely be required. Tool changing can be more
complex since jaws and grip modules must be matched
as well as the combination of jaws and applications,
and therefore this strategy is best used for
applications with a well balanced, medium parts
This strategy consists of two general approaches:
Compliant Tools: This 2-D approach can
accommodate a variety of through-hole and
SMT odd-form component styles and lead variations.
It normally does not require vision location
if the part is geometrically consistent.
The typical handling technologies used with
this strategy are:
the single-plane compliant tool can accommodate
a variety of odd-form parts without the need
for vision, it cannot compensate for tilted parts
such as Capacitors, SIP's, hybrid SIP's, Inductors,
MOV's, TO-220's, and many others. Therefore this
strategy is best used for applications with a
lower parts mix which only require compensation
for skewed or twisted parts, such as Connectors
or other "precision" molded parts that
are not tilted.
Compliant Tool: This tool facilitates body
gripping regardless of part geometry or condition
and does not require lead find tools since
control of lead location is never lost. Using
this 3-D adaptive technology approach, the
assembly head can fully comply with all six
degrees of freedom, thus creating a totally
flexible handling strategy able to accommodate
virtually all odd-form through-hole and SMT
component types. It can also handle all part
tolerance variations, including tilted, skewed,
and twisted parts, as illustrated in figure
3 (shown at end of paper). The handling technology
typically used with this strategy is:
adaptive technology combines the most flexible
handling method with a simple mechanical design.
It is capable of handling odd-form through-hole
and surface mount components without head or
finger changes, and is therefore best suited
to applications requiring a medium to high mix
of component types with varying tolerances and/or
many board changeovers. Although the adaptive
technology is much more flexible, a multi-tool
used in a well-balanced application without the
need for tool changes or retooling may be faster.
The mix-tech handling strategy uses two or more of the
appropriate handling technologies and strategies listed
above to handle both through-hole and a wider variety
of SMT components on the same system. Handling technologies
used with these tools include:
technology tools provide the necessary flexibility
to handle both through-hole and SMT mixed technology
applications, however the degree of flexibility
and throughput achieved is dependant on the handling
technology used. This range of capabilities provides
many benefits, but the addition of more tools
also adds more complexity to the system.
Equipment solutions are easily identified when properly
matched with the required odd-form tasks. Component
mix, volume, and throughput requirements are the
most important issues to consider when evaluating
which locating and handling technologies are best
utilized for the automation of your odd-form assembly
is necessary to give weight to the importance
of each issue as it relates to the ultimate productivity
of your current and future assembly line requirements.
Once you have established which requirements
are the most critical to the success of your
business, they can be matched to the most effective
locating and handling technologies, and your
odd-form automation solutions will become clear.
3. Drawing illustrates an adaptive compliant
assembly head compensating for body-to-lead
and lead-to-lead variations in three dimensions
(allowing for all six degrees of freedom).
Copyright © 2004
CHAD INDUSTRIES, INC