A modular fixturing system is a versatile alternative to a single–purpose, dedicated fixture used along with CMM.

1. MODULAR FIXTURES FOR
INSPECTION SURESH LAL S R
Assistant Professor
Department of Mechanical Engineering
Government Engineering College,
Wayanad

2. Contents
 Introduction to jigs and fixtures
 Principles of location
 Modular fixtures
 Components
 Applications
 Merits and demerits

3. Jigs and Fixtures
Jig Fixture
Fixtures - are strong and rigid mechanical devices which enable
easy, quick and consistently accurate locating, supporting and
clamping, blanks against cutting tool(s) and result faster and
accurate machining with consistent quality, functional ability and
interchangeability.
Jig- is a fixture with an additional feature of tool guidance.

4. Elements of Jigs and Fixtures
 Base and body or frame with clamping features.
 Locating elements for proper positioning and
orientation of the blank.
 Supporting surfaces and base.
 Clamping elements.
 Tool guiding frame and bushes (for jig).
 Indexing plates or systems, if necessary.
 Auxiliary elements.
 Fastening parts.

5. Principles of Location
 Any rectangular body may
have 12 degrees of
freedom. 4 along each
axis;2 translational and 2
rotational.
 By properly locating,
supporting and clamping
the blank, its all degrees of
freedom are to be arrested.

6. Principles of Location
 The basic principle used to locate the
points is the six point location of a
rectangular block (3-2-1 principle).
 Provide a rest to work-piece on three
points on the bottom XY plane. This will
stop the movement in the - Z axis, rotation
with respect to the X axis and Y axis (five
motions).
 Rest the work-piece on two points of side
surface (X-Z), this will fix the movement of
work-piece along +Y axis and rotation with
respect to Z axis (three motions).
 Provide a support at one point on the
adjacent surface (Y-Z) that will fix the
movement in –X direction (one motion).
 The remaining movements are restricted
by a clamping device (3 motions).

7. Principles of Location
 One or more surfaces (preferably
machined) and / or drilled / bored
hole(s) are to be taken for reference
 Locating should be easy, quick and
accurate
 A minimum of three point must be used
to locate a horizontal flat surface
 The locating pins should be as far apart
as feasible
 V-block and cones should be used for
self-locating solid and hollow cylindrical
jobs.
 Holes provide an excellent method for
locating. Eleven motions can be
restricted using a pin locator along with
a diamond pin locator to accommodate
tolerance on the distance between the
holes and their diameters

8. Limitations of Fixtures
 Can have complicated designs.
 High initial set up costs (and time).
 Can use a lot of material and be bulky.
 Loading, unloading and reloading of the same
parts, is time consuming.
 Can wear away over time.

9. MODULAR FIXTURES

10. Modular Fixtures
 A modular fixturing system is a
versatile alternative to a single–
purpose, dedicated fixture.
 Constructed from a kit of
interchangeable components, the
modular fixture is easily
reconfigured for any work holding
application.
 The modular fixture will hold the
component of different
configuration, size and shape
without much efforts to locate,
align and clamp the component on
the fixture.

11. Modular Fixtures
 Modular systems are ideal for intermittent or one–time
use. They are commonly used to:
 Stage parts for CMM inspections
 Hold work pieces during machining
 Position parts when bonding or assembling
 The modular system saves time and reduces cost.
 When not in use, the fixture can be dismantled for
convenient storage.

12. Fixturing Principles
 A set of fixturing principles should be followed to
ensure the part is stable enough to allow for
repeatable and reproducible measurements
The principles are:-
 3 point of support
 3 point nest
 Part clocking
 Part holding
 Adjustability

13.  The photo shows a
sculpted part in a simple
3-2-1 nest, with 3 base
datum locators and the
overhead clamp force
applied inside the
triangle formed by the
three base locators.
 The two pins clock the
rotation, and the end-
stop provides the final
locator.
 The opposing pin
standoff is used to force
the part against the front
two pin standoffs.

14. Positioning of Part in the Fixture -
Manually
 Determine the part position according to the
measurement needs.
 The features to be presented for
measurement.
 Accessibility of CMM probe to these features.
 Immobilization of parts.
 3-2-1 location principle (3 support points, 2
orientation points, 1 stop point) and clamping.
 Out of three support points one is fixed and
other two are adjustable.
 Rough determination of difference of height
between supports.
 Mounting the fixed support.
 Mounting the adjustable supports.
 Vertical and horizontal adjustment of part
using spirit level or dial gauge.
 Lockup the part with clamps.

15. Positioning of Part in the Fixture
–Software Based
 FixtureBuilder is a 3D-modelling
software package designed to allow
the creation and documentation of
fixturing set-ups.
 The software can be used with a CAD
model of the inspected part, which
is imported into FixtureBuilder, so that
the fixture can be built around it.
 The entire set-up, along with the
inspected part, can then be exported
into inspection programming software.
 FixtureBuilder supports most CAD
formats including IGES, SAT and
STEP. A translator add-on module is
available for Pro/E and CATIA.

16. Fixture Plate/Base Plate
 Base plates are precision ground
within tight tolerance that are key to
the quality of the modular fixturing
system.
 Base plates are available in standard
and custom sizes with a choice of
threaded holes: M4, M6, M8.
 Cast aluminium base plates are
coated with hard coat anodise to
resist wear and scratching and are
available in sizes upto 1500 mm X
3000 mm.
 The base plates are made
 Thermally stable
 High wear/ abrasion resistant
 Low friction surfaces.

17. T–Slot Base Plates
 Provides infinite adjustability in multiple axes.
 Laser engraved reference scales and alpha identified
T-slots facilitate repeat setups.
 A cross-slide assembly is included in the kit. The cross-
slide allows infinite positioning of components between
the T-slots. It can also be set at any XY angle. The
lockdown clamps are used with a thumb-screw and
locknut, which attach to a T-nut in the t-slot.

18. Modular fixture components
 Standoffs
 Adjustables
 Magnets
 Clamps
 Towers
 Miscellaneous
 Suction cup
 Trays

19. Standoffs
 Standoff - to elevate and
locate part.
 Pin standoff – to elevate
and locate the part
against the pin.
 Spring loaded pin
standoff – to locate
within a hole or slot of a
part.
 Standoff adaptor – for
step clamps
 Rotator standoff – to
secure parts against
stops/supports.

20. Standoffs - Application

21. Adjustables
 Adjustable jack stand - to
allow height variable up to
22 mm.
 Adjustable slide – to place
components in between
holes on the plate
 Adjustable angle plate –
ideal for holding the
components at an angle
 Adjustable V – post – for
holding the cylindrical parts.
 Adjustable pivot joint – for
positioning the component
at any angle

22. Adjustables - Application

23. Magnets
 Plane magnet – for
holding the steel or iron
parts
 Pin magnet – for holding
and locating parts.
 V magnet – for holding
cylindrical parts and bent
tubing.

24. Magnets - Application

25. Clamps
 Tension clamp - for quick
and easy clamping.
 Screw pusher clamp – for
pushing and holding a part
against stops.
 Tension clamp bracket –
to hold a tension clamp at
an angle.
 Three jaw clamp – for
holding round parts at one
end or at middle, allowing
the probe around the part
without interference.
 Hold down clamp – for
more clamping force

26. Clamps - Application

27. Towers
 To hold a part vertically

28. Miscellaneous
 Cone – to rest a part on a
rounded point for a
single-point contact.
 Resting pin– to rest a
part on rounded point.
 Vertical base plate– for
holding components
vertically.

29. Miscellaneous - Application

30. Suction cups
 For holding plastic, glass, polystyrene and other
non-ferrous parts

31. Fixturing kit

32. Vision fixtures
 Modular fixturing for vision
systems or multi sensor
machines.
 It create a faster and
repeatable way to fixture the
part for consistent and
accurate inspection.
 Each vision fixture is made
with a precision acrylic base
plate that allows for
backlighting and a clear, clean
view of the part.
 Fixturing component can
quickly be threaded into the
base plate and arranged in
any configuration.

33. Vision fixtures
 Renishaw offers two
vision fixturing options.
 Quick load corner (QLC)
 Interchangeable vision
fixture – for vision systems
450 mm x 450 mm or larger.

34. Advantages of Modular Fixtures
 Quick and easy to use.
 Repeatable and reproducible.
 To save time, multiple parts can be fixtured on a plate at
one time or sub-plates can be used to automate the
inspection process even further.
 Document the part setup.
 Can reduce fixturing costs.
 Improves productivity.
 Better access to the entire part – unobstructed probe
path.
 Eliminate the need of traditional fixtures.

35. Applications
Inspecting parts for -
 Aerospace
 Automotive
 Electronics
 Industrial
 Medical
Along with-
 CMMs
 Vision systems
 Non-contact scanning
 Optical comparators

36. Manufacturers

37. References
1. Farhan U and Tolouei-Rad M., Design of modular fixtures using a 3D-modelling
approach, 19th International Congress on Modelling and Simulation, Perth,
Australia (2011), pp 405–411
2. Liu Cheng-liang, A systematic Conceptual Design of Modular Fixtures ,
International Journal for Advanced Manufacturing Technology (1994) pp 9:217-
224
3. Kumar KN, Naveen and AswathNarayan M S, Design and fabrication of Modular
Fixture for CMM Inspection, International Journal of Research in Engineering and
Technology, sep 2015, pp 406-411
4. Renishaw CMM modular fixtures, Technical specification, H-1000-0078-02-A
5. Renishaw Vision modular fixtures, Technical specification, H-1000-0079-02-A
6. Renishaw Equator modular fixtures, Technical specification, H-1000-0057-02-A
7. R&R Fixtures brochure_20131
8. Alukeep Modular Fixturing System Product Brochure