jig and fixtures

1. CHAPTER 3: CLAMPING
PRINCIPLES
DMA 3122 JIG AND FIXTURES

2. 3.1 Basic Principles of Clamping
Clamp should firmly hold the workpiece without distorting it
Should overcome the maximum possible force exerted on workpiece by using
minimum clamping force
Easy to operate
Vibrations should tighten the cams and wedges in the clamp design(if any) and
notloosen them

3. Prinsip reka bentuk pengapit
(clamping)
• 1. Kedudukan
• 2. Kekuatan
• 3. Produktiviti
• 4 .Tenaga pengeluar

4. Kaedah Pengikat
• Screw and hand lever
• Hand screw
• Screw and hand nut
• Cam
• Toogle
• Wedge
• Pneumatic or hydraulic cylinder

5. CLAMPING
GUIDELINES
Locating the workpiece is the first basic function of a jig or fixture. Once
located, the workpiece must also be held to prevent movement during
the operational cycle. The process of holding the position of the
workpiece in the jig or fixture is called clamping. The primary devices
used for holding a workpiece are clamps. To perform properly, both the
clamping devices and their location on the workholder must be carefully
selected.

6. Positioning
the Clamps
The position of clamps on the workholder is just as important to the overall
operation of the tool as the position of the locators. The selected clamps
must hold the part against the locators without deforming the workpiece.
Once again, since the purpose of locators is to resist all primary cutting forces
generated in the operation, the clamps need only be large enough to hold
the workpiece against the locators and to resist any secondary forces
generated in the operation. To meet both these conditions, position the
clamps at the most-rigid points of the workpiece. With most workholders,
this means positioning the clamps directly over the supporting elements in
the baseplate of the workholder, Figure-3-23a.
In some cases the workpiece must be clamped against horizontal locators
rather than the supports, Figure 3-23b. In either case, the clamping force
must be absorbed by the locating elements

7. For workholders with two supports under the clamping area of the workpiece, two clamps should be used —
one over each support, Figure 3-24a. Placing only one clamp between the supports can easily bend or distort
the workpiece during the clamping operation. When the workpiece has flanges or other extensions used for
clamping, an auxiliary support should be positioned under the extended area before a clamp is applied, Figure
3-24b.

8. 3.2 Type of Clamping Device
Clamping Device purpose is to hold work in the correct relative position in the
fixture and to ensure that the job is not displaced under cutting forces. It is also
necessary for clamping the jig to the work.
The most efficient scheme of clamping means that the clamping should be
adequate and at the same time, the clamping device design should be such that the
operating time of jig or fixture is least possible. Thus for high rates of production,
quick-acting clamps are essential whereas simple clamps may be adequate for small
batches of work.

9. 3.2.1 Lever Clamp
Clamp levers are mechanical components which allow efficient tightening and
loosening of screws by turning the lever without the use of tools. Their best feature
is the ability to work in tight spaces: just pull up the lever to release the threaded
serration engagement (This will stop the screw from turning even if the lever is
rotated).
Video : https://youtu.be/hMe1-pIIEH4

10. 3.2.2 Chuck and Vise
What is the function of the chuck?
A chuck is a specialized type of clamp used to hold an object with radial
symmetry, especially a cylinder. In a drill, a mill and a transmission, a chuck holds
the rotating tool; in a lathe, it holds the rotating workpiece.
What is a vise clamp used for?
Clamps and vises are essential when a project requires securing materials for
cutting, sanding, gluing, drilling, soldering and more.

11. 3.2.3 Screw Clamp
There are variations of the screw-type clamp. Numerous styles of commercial
clamps have been developed to include advantages of the screw clamp and reduce
its disadvantages. The efficiency of the screw clamp can be improved by using
swing clamps, hook clamps and quick acting knobs. Swing clamps combine the
screw clamp with a swinging arm which pivots on its mounting stud.
Video https://youtu.be/lljH2EKBoqo

12. 3.2.4 Hinged Clamp
These utilise hinged lids for loading and unloading the components. Generally the
clamp is made integral with the hinged lid. Fig. 28.40 shows an arrangement using
combination of hinged clamp and hinged bolt.
This type of clamp is often required when it is necessary to move both the clamp
and the bolt completely out of the way for the loading of component. The jig casing
is designed such that the lugs are provided for locating the hinge pins. In order to
save the operator’s time, a coil spring is used to hold the washer under the nut.
Video https://youtu.be/ORz8nzUM3Mc

13. 3.2.5 Toggle Clamp
These are fast acting clamps. These have the natural ability to move completely
free of the work, allowing for faster insertion/taking out of parts. The holding force
to toggle clamps compared to the application force is very high. Fig. 28.51 shows
the four basic clamping actions, viz. hold down, pull, squeeze, and straight line
action.
Video https://youtu.be/ud0TsgXRneI

14. 1. Direka untuk memegang bahan kerja dengan cepat dan
mudah dikendalikan dengan tangan tanpa memerlukan
alat lain.
2. Ini sangat berguna apabila sebilangan bahagian bahan
harus dimesin dengan efisyen dan mungkin
menggunakan jig untuk menahannya.
3. Dalam kes ini, adalah wajar untuk mendapatkan bahan
kerja masuk dan keluar dari jig secepat mungkin dan
masih boleh dipegang dengan selamat.
4. Kaedahnya ialah jig memegang bahan kerja sehingga
hanya dapat bergerak dalam satu arah, misalnya, masuk
atau keluar dari atas, dan hanya dapat dilakukan jika
pengepit toggle clamp tidak digunakan.
5. Bahan kerja tidak akan selamat Sekiranya dipegang
pada bahagian meja mesin kisar.
6. Jika dipegang dengan jig maka satu-satunya cara ia
bergerak adalah dengan pegangan bergerak ke atas

15. Benefits of Using Clamps
 An efficient system
The installation of hand tools such as clamps, for example, is very simple and quick, and
they are highly reliable in terms of performance. In order to ensure accuracy and speed
in the work that you do, you have to use clamps that are efficiently set up. The high
clamping ability of this tool makes it possible to reduce the number of fixtures required
for a particular application, which reduces the amount of time spent on such a project.
 Easy to be adapted
Clamps can be adjusted in height according to the height of the workpiece. In particular,
this is the case with the Cam-action model, which is often used on rough forges and
castings because it has a snap action. Adaptable screws are available for T-slot clamps
as well as strap clamps, allowing you to adjust the braking force to your preference.
When working with materials of variable thicknesses, such as wood, metal, and plastic,
many of these clamp models have a very high exertion force and are very adjustable,
which is very useful when working with flexible materials.

16. Benefits of Using Clamps
A tool with a versatile approach
The market today offers a variety of adjustable clamp types for use in various
applications. The toggle clamp is the most versatile clamp available on the market
among all the commercial clamps found on the market today. In order to
differentiate a clamp from another, a number of factors must be taken into
account, such as handle placement, handle design, and pressure ratings.
Provide enough safety
These clamps have been designed in such a manner that they guarantee a high level
of safety during use. In addition to locking the tool into place, the locking
mechanism also keeps the workpiece securely in place as well.In this way, slips or
loose grips can be prevented from causing accidents due to the slightest slip.
Toggle clamps have the advantage of being able to exert a high level of force on
the workpiece. This is a major benefit of using clamps because they have a superior
hold power, which makes them safer.