Tool PresettingSubject :Computer Integrated Manufacturing

GUJARAT TECHNOLOGICAL UNIVERSITYBIRLA 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

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.

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.

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.

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.

• 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

• 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

• 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

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.

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.

Various manufacturers of tool presetters and toolsetter:-

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.

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.

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