A presentation on tool presetting used in CNC .

1. Tool Presetting
Subject :Computer Integrated Manufacturing
GUJARAT TECHNOLOGICAL UNIVERSITY
BIRLA VISHWAKARMA MAHAVIDYALAYA, V.V. NAGAR
BATCH A-7 (MECHANICAL)
130070119094 Vani Chirag
130070119095 Vishwani Nilesh
130070119096 Vyas Jalay
130070119097 Kamli Nehal
GUIDED BY : Prof. P.M.Agrawal

2. Introduction to tool presetting
 Manual method of touching the tool to the workpiece
after the first cut to measure the tool offset in order to
obtain the correct dimensions on the workpiece is a slow
process and consumes precious machine time.
 The setting of tools in advance at a place away from the
machine tool or offline, in special holders is known as
presetting of tools.
 A presetting device is used to preset axial and radial
positions of the tool tip on the tool holder.

3. Why is tool presetting required??
 To reduce unproductive time.
 To increase rate of utilization of CNC machines.
 For significant decrease in setup times.
 To reduce cost.
 For greater accuracy.
 To obtain faster and reliable tool measurements.

4. Methods of tool presetting:-
 Manual method of tool presetting.
 Automatic tool presetting.
 Tool presetting can be performed with the machine in
operation, measuring tools in metrology instruments
(such as calipers or micrometers) and inserting in the
CNC, the measurements are obtained.

5. How is tool presetting done??
• The relationship of the tool with reference to the tool holding
mechanism requires a special attention during CNC machining
process.
• The actual point to be programmed in a CNC part program is the tip
of the tool whereas the axes will be moving with respect to a known
point in the spindle, e.g. the centre of the spindle in case of
machining centres.
• It becomes therefore necessary to know precisely the deviation of
the tool tip from the gauge point on the spindle.
• Tool presetters use various technologies like manual touch-
off,optical projector and laser.
• In some sophisticated presetting systems, the offset values are
recorded by an RFID (Radio Frequency Identification) chip
integrated into the tool holder to carry the offset value.

6. • In this system the base is provided with
the exact taper as used in the actual
machine tool.
• The assembled tool is therefore placed
in the spindle taper.
• The measurement is done with the help
of micrometer head, which is attached
to a U-clamp as shown in figure.
• The U-clamp can be moved manually
on a post ,which has precise location
slots that are separated by exact
distance(e.g. 25mm).
• The length of the tool can therefore be
measured by the measurement of
micrometer plus the slots along the
post.
Simple mechanical type tool
setting device

7. •A device that can measure length as
well as diameter of a spindle tooling is
shown in figure.
•The tool measuring probe moves on
two precise axis to measure both the
length and diameter of a spindle tooling
unit.
•The display is shown digitally so that
there is no error in measurement .
•Furthur, they are provided with a serial
port for outputting the measured values
directly into any tool management
system or a personal computer for the
purpose of generating the tool offset
values.
Automatic Presetter

8. •In CNC turning centre
many machine tool
manufacturers are provided
an integral tool setting
device as shown in figure.
•The measurement arm
consists of a probe tip which
when extended will meet
tool tip in two perpendicular
directions for directly
measuring the Z and X
offsets.
Presetter:By probe tips

9. Tool setter Laser
• Toolsetter system is typically mounted on
the table of the CNC machining center,
and can also be used to detect tool
breakage. Usually the equipment consists
in a simple system that emits a laser beam
to a receiver. This beam is interrupted
when the tool is in its normal state, and
when there is tool breakage the beam
reaches the receiver, which immediately
indicates the failure of this tool to the CNC
machine.
• To detect tools dimensions, the toolsetter
identifies when the laser beam is
interrupted by the tools and record
automatically the respective coordinates
X, Y and Z on the CNC command.

10. Automatic External Presetter
 The automated external presetter contains a
transducer mounted in fixed point outside the
machine tool that allows measurement of the
tools off the machine, accurately and quickly.
 The correction data generated by the
presetter can be transferred in real time and
with complete confidence to the CNC control.
 The dimensions of the cutting edge of the tool
relative to the reference point, are properly
determined, i.e, the tool is mounted in its
holder and is placed in a presetting
equipment that has the same characteristics
of the housing of tools support in the CNC
Machine.
 One example of this type is optical presetter.

11. Various manufacturers of tool
presetters and toolsetter:-

12. Why has importance of tool
presetting reduced??
 Tool length and tool diameter compensation
facilities available in modern CNC machines
have brought down the importance of tool
presetting.

13. Conclusion:-
• Presetting is invaluable to production facility of any
capacity,and has benefits to both low and high volume
industries.When the product is low volume then it is
generally a high cost,high precision part and therefore
any error can be very costly,especially if the part is
scrapped or has to be re-machined.
• Likewise,if the products is high volume(as in the
automotive industry) then it is just as important to
produce good parts at each stage of the manufacture in
order to prevent continued operations on a component
that may already be scrap from previous operation.
• Thus,tool presetting reduces unproductive time
considerably.

14. References:-
• CAD/CAM by P.N. Rao.
• CAD/CAM by Ibrahim Zeid.
• CNC Fundamentals and Programming by
P.M.Agrawal and V.J.Patel.
• http://www.cnccookbook.com
• http://www.helmancnc.com