P.E.
S COLLEGE OF ENGINEERING, MANDYA
(AN AUTONOMUS INSTITUTION AFFILIATED TO VTU, BELGAUM)
A report on” REPORT ON RECENT TECHNOLOGIES IN
WORKHOLDING DEVICE”
In partial fulfillment of the requirement for the academics
MECHANICAL ENGINEERING
2018-2019
Submitted By
SANJAY C R 4PS15ME090
VARUN P G 4PS15ME119
KIRAN KUMAR N R 4PS16ME041
SYED MUHEEN 4PS15ME114
ADARSH K N 4PS17ME400
5th SEM
DEPARTMENT OF MECHANICAL ENGINEERING
P.E.S.C.E MANDYA
Submitted to: Mr RAKSHITH D. S. Assistant professor Department of mechanical
engineering PES Collage of Engineering Mandya.
CONTENT
1. ABSTRACT
2. INTRODUCTION
3. TYPES
4. ADVANTAGES
5. REFERENCES
RECENT TECHNOLOGIES IN WORK HOLDING
DEVICES:
ABSTRACT
How a part is held is often as important as how it is cut. From another viewpoint,
how a part will be cut often determines how it needs to be held. Here, we take a
look at an assortment of applications and the approaches that can be taken to
narrow the workholding options to what will fit best. From barstock to blanks,
from tiny parts to thin-walled or irregular shapes, and from Swiss turning to part
movement throughout a cell, holding the part securely without damaging it
requires a thorough understanding of the advantages and disadvantages of each
option
INTRODUCTION
Workholding refers to any device that is used to a secure a workpiece against the
forces of machining. The most basic workholding device is a simple clamp, but
workholding can also involve complex fixtures that are custom-built for particular
parts. Other common workholding devices include vises and chucks, as well as
indexers or rotary tables that are able to change the part’s position while it is held,
so the machine can reach various features. In most machining applications,
workholding also locates the part. On a machining center, for example, a vise or
fixture may also provide the precise position and orientation where the machining
program expects to find the workpiece.
1.Modular Tooling Interface Doubles As A Universal Work holding
Device
This company uses a modular toolholding interface in both conventional
and alternate ways.
This Peabody, Massachusetts, manufacturer produces harmonic drives used for
precision motion control and mechanical power transmission applications in
nuclear power and aerospace industries, among others. According to Steve Foley,
shop supervisor, 50 percent of his machine operators’ time is dedicated to job
change-over. That fact, combined with lot sizes that typically range from two to 25
work pieces, means that reducing setup times in this short-run, JIT production
environment is paramount.
Years back, the company adopted block-style tooling to allow faster tool changes
on its lathes. It has since modified all its lathes to accept the Cap to modular
tooling interface from Sandvik (Fair Lawn, New Jersey). According to Mr. Foley,
one of the reasons for the switch was that the Cap to interface offered improved
rigidity versus the block-style tooling, especially for ID turning operations.
However, there was still work to be done to speed part fixturing time. Some work
pieces traveled across different types of machines, and the work piece would have
to be indicated to each machine. It dawned on Mr. Foley that the modular tooling
interface he used for quick tool changes could also be applied to work holding.
Now, equipment such as lathes, gear hobbers and inspection devices uses the Cap
to interface as a work holding device so that lengthy indicating time is eliminated.
Modular Tooling And Work holding Interface
The Capto modular tooling system has been available for a number of years, and it
can be used for milling, drilling and turning (static and rotational) operations. The
system consists of a cutting unit (part of the toolholder) that couples with a
clamping unit installed in a lathe’s turret or machine’s spindle. Its tapered, three-
sided polygon coupling centers and aligns the toolholder in the clamping unit,
providing 0.0001- to 0.0002-inch runout, according to Mr. Foley.
To use the Capto coupling as a workholding interface for his lathes, Mr. Foley
installs a receiving clamping unit on a faceplate mounted in the lathe’s spindle.
Custom toolholders are made from boring bar blanks that have the Capto C6-sized
coupling (this is the largest available coupling size). The boring bar blank is
machined to accept the different types of parts the company machines. According
to Mr. Foley, the Capto system reduced part change-over time from 5 minutes
(using a straight shank tool that requires indicating) to 30 seconds.
The Capto interface is especially effective working in conjunction with a nifty
“lollipop” workholding method used to secure small, bell-shaped workpieces for
lathe work, spline machining and OD inspection. The part, called a flexspline,
begins as a 15-5PH stainless steel forging. Its ID is machined to leave a wall
thickness of approximately 0.06 inch. A final wall thickness of 0.01 inch is
attained through OD turning.
The OD turning is easier said than done, though, because the flexspline’s shape
and thin wall present unusual work holding challenges. The part by itself can not
be clamped in a lathe’s chuck because the very thin walls would not provide
adequate support during the turning operation. Mr. Foley mounts the part on an
arbor machined from a Capto boring bar blank. However, because of the bell-like
internal profile, voids exist between the arbor and work piece inner surface. To fill
these voids, a low-melt-temperature alloy is poured through a bore that is
machined down the center of the toolholder. Once the alloy solidifies, then the part
and arbor bond together to become one. The alloy provides the wall support
required to machine the part to the desired 0.01-inch wall thickness.
Once the part’s OD has been turned, the part becomes concentric to the arbor and
Capto coupling, and succeeding operations no longer require indicating. For the
flexspline, the next operation is machining a spline around the perimeter of the
part’s “bell mouth.” Similar to the lathes, the gear hobber uses a Capto clamping
unit attached to a faceplate installed in the machine. Once the hobbing operation is
completed, the part is delivered to an inspection device to perform rotating
concentricity runout checks. Mr. Foley topped a precision grinding head with a
Capto clamping unit, having confidence that the Capto interface would not
adversely affect runout inspection. Once machining and inspection are completed,
the flexspline is removed from the arbor by simply heating and melting away the
low-melt-temperature alloy. It is then ready for assembly.
2.Jaw Nuts Minimize Jaw Change Time
Dillon’s Fast-Trac jaw nuts.
Fast-Trac jaw nuts are designed to convert standard chucks into quick-
change chucks, reducing jaw change time by as much as half. This
system is said to enable users to pre-assemble the next operation jaws
while the machine is running a separate job, thus minimizing jaw change
time and maximizing productivity and profitability.
Dillon jaw nuts, T nuts and keys are available to fit all popular power
chucks from 6" to 24" in diameter, including Forkhardt, Gamet, Howa,
Kitigawa, Matsumoto (MMK), Nikko, Pratt Burnerd, Röhm, Samchully,
Schunck, SMW and more. They are ideal for workholding applications
requiring durability and high strength such as high-speed machining,
according to the company. Dillon also offers a special T-nut design and
manufacturing service for custom workholding requirements.
3.Modular Vise Clamps Two Workpieces
Hoffmann Group’s Garant Xpent five-axis vise.
Work holding deviceThe Hoffmann Group has released a module for its
Garant Xpent five-axis vise. The center jaw, which can be optionally
fitted to the base rail, enables users to clamp two workpieces with just
one vise and process these parts in a single operation. This enables
efficient clamping strategies that lead to an increase in productivity.
The vise is based on a modular design concept. Clamping modules, base
rails and spindles can be individually combined, and the convex
clamping modules can be turned 180 degrees. The newly developed
center jaw offers another bonus in terms of flexibility. It is immediately
available as an accessory for sizes 0 to 1S. It will soon be available in
sizes 1 and 2. The existing range of attachment rails, each with two
clamping stages, is fully compatible with the new center jaw.
The vise provides clamping force as great as 40 kN and 90 Nm of
torque. It is available in three different heights and two widths. Base
rails are available in lengths of 360 to 1,050 mm. The 1S size was
specificaly developed for three- and five-axis machines with small
spindle gearboxes.
4.Collet Chucks Overcome Distortion for Automated Gear
Machining
To accommodate its customers’ need for just-in-time orders of small
batches of gears, this company’s automated manufacturing cells rely on
collet chucks that overcome a common distortion issue arising from
tapping and heat treatment.
The production of gears has changed dramatically over the past 25 years
for Global Gear & Machining of Downers Grove, Illinois. While the
shop once focused on dedicated pieces of standalone equipment, each
pumping out one type of gear in batches of hundreds of thousands, this
production method is no longer viable. Its customers now want gears in
small batches delivered on a just-in-time (JIT) basis to avoid the cost of
stocking large amounts of gears for their manufacturing operations. To
meet these demands and maintain its competitiveness, Global Gear has
turned to completely automated, flexible manufacturing cells that enable
the shop to cost-effectively produce higher volumes of gears in smaller
batches with JIT delivery. Most importantly, the cells can quickly and
easily change over from one gear type to the next.
With the automated cells, the company has been able to increase its
output while maintaining its existing workforce and taking on more
work. Job lot sizes may be lower, but part tolerances are tighter than
ever, and cell change-overs now happen daily.
5.Fixturing Components Improve Range of Applications
The bearing wheels feature a roller bearing and a cover made from
nylon, polyacetal, UHMW, PEEK, urethane, steel or stainless steel.
They are flat, crowned or radial to suit a range of applications. Bearing-
and stud-mount versions are available. Outside diameters range from
¾" to 1".
Spring-loaded, hand-retractable plungers lock items in place for several
applications. They are used to prevent any change in position due to
lateral force. Available in a range of inch threads, the styles include
standard, low profile, compact, slim compact, D-ring, cam lever and
weldable.TG GripSert carbide gripper inserts are designed for low-
profile clamping with no dovetail work piece preparation. With
serrations designed for steel, hardened steel, titanium and aluminum,
they feature two rows of teeth at different angles to maximize the pull-
down effect and prevent lifting of the work piece. They are ideal for
upgrading existing vise jaws. The fasteners include pin-holding and
expanding-pin versions for applications with limited space for traditional
receptacles. These fasteners are an alternative to nut-and-bolt assemblies
for quick change-overs and installations. They are used to attach
fixtures, plates, machine covers and more, joining components with
moderate clamping force.
5.Schunk
The Schunk Vero-S Aviation product line is designed to rigidly clamp
large parts accurately and enable the user release the part enough to
allow the part to move (compensate) due to the stresses of machining
without fully releasing the part. The clamp/unclamp and reclamping of
the stress-relieved part can be done in under a minute without losing the
established primary reference datums, according to the company. This is
accomplished through the use of four modules: the first module is fixed
in all axes to establish the primary reference point; the second module
allows the work piece to compensate in one axis (X axis); the third
module allows the work piece to compensate in two axes (X and Y); and
the fourth module allows compensation in all axes including height and
angularity.
ADVANTAGES
Workholding Advantages of Barstock
Barstock is versatile raw material. It’s easily held, easily fed and has significant
capacity for many parts per bar. Usually we think of barstock and bar feeders in
relation to turning machines. But those same advantages realized in turning
operations can also be applied to the vertical machining center.
The push to manufacture workpieces in a single part handling to reduce
workhandling and cost of production has brought the multi-processing technology
of the mill-turn machine. The application of a bar feeder to a VMC provides the
ability to continuously supply the machines with blank material. Therefore, as
long as the workpiece’s major dimension fits within the circumference of the bar,
an unlimited variety of workpieces can be machined, including families of parts.
See how this workholding/handling marriage gives machining center production
capacity limited only by the amount of barstock that the feeder can hold.
Understanding CNC Collet Chucks
When considering the purchase of a CNC lathe or turning center, it is important to
ensure that the workholding system is matched to both the machine’s capabilities
and the type of work that it will be doing. But workholding for turning is usually
fairly basic: The selection comes down to chucks or collets.
As a universal workholding device, a three-jaw chuck functions well for many
common turning applications. It can hold a range of part sizes, is capable of
operating at reasonable rotational speeds and achieves good accuracies.
However, there are many applications where a jaw chuck is not the best
workholding option, which has led to the development of a range of alternative
solutions. The most common among these is the CNC collet chuck.
Take a look at when to consider the collet chuck and what kind might be best for
a given application.
Change this Chuck: Save Setup Time
Precision parts machining shops are increasingly faced with the need to accept
higher-mix/lower-volume work. Putting a job on a machine tool and running it for
long periods of time is not as common as it used to be, and the definition of
medium- and high-volume lot sizes has changed.
To maximize production efficiency, shops look to shorten the time required to
change-over a machine tool from one job to another. In a turning application, one
area in which a shop can save time is workholding, generally found in the form of
universal clamping devices such as the three-jaw chuck. And one practical
solution is a quick-change interface.
Changing jaw chucks on lathes has always been time consuming, but some
products are geared towards reducing this bottleneck. Learn about one system,
designed for any process requiring frequent change-over, that can reduce the
time needed for replacing a three-jaw chuck from 45 minutes to 30 seconds for
single-part and small-series production runs.
Workholding for Swiss Turning
Because of its versatility, Swiss turning has found its way deep into the precision
turned parts market. To make the most of this technology, a look at workholding
considerations is in order.
For the most part, workholding on a Swiss is about collets. On a conventional
fixed headstock lathe, the collet and spindle are fixed. They function as a rotary
axis only. The Swiss-type moving headstock uses the spindle as both a rotary and
linear axis. This design allows for very close coupling of the cross-fed cutter and
the point of maximum workpiece support, which is nearest the spindle nose—on
a Swiss, the guide bushing.
As a result of this design, long, slender parts can be efficiently turned without
deflection or the need for tailstock or steady rest support. The guide bushing is
actually another collet that, in Swiss turning, must be extremely precise.
Read about the basics of collet design for Swiss machining, alignment tricks for
non-round bar shapes, and how to get the most effective workholding in very
small applications.
Applications Determine Workholding Solutions
In turning operations, workholding options often present some difficult choices.
While the three-jaw chuck is the obvious choice for certain larger parts, and
collet-nose chucks are the clear choice for most low-volume, high-tolerance work,
the spectrum of turning jobs is far too broad to be able to chart the best
workholding choice for each application.
Most shops find that the majority of their work calls for one or the other, but
rarely can a company count on either the three-jaw chuck or the collet nose to
cover its whole lineup. Each situation should be examined to determine the most
appropriate workholding option.
Read about a contract job shop in Cleveland, Ohio, that faces constant decisions
between chucks and collets for handling its parts. For this shop, part size is often
used as an initial guideline, but accuracy requirements, cutting speeds and
change-over times also come into play.
Handling Parts in a Robotic Cell
For many shops, workhandling—how a part moves from point A to point B—
creates more questions than what the best workholding options are. The more
automation is involved in a manufacturing process, the more attention must be
given to handling the part.
When a shop implements a robotic cell in its CNC machining operations, for
instance, the goal is clear: Save money through better spindle use, more efficient
use of labor and more consistent production. But special attention must be given
to other factors as well, such as grippers, part orientation, guarding, door
openers, part in-feed and out-feed devices, vision systems, and the total
integration of the mechanical and electrical components.
REFERENCE:
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