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Tool handle is the key interface between cutting tool and CNC machining center machine tool spindle. Tool handle failure will lead to tool handle can not play a role, resulting in short tool life and abnormal cutting process.

The more typical tool handle failure has the following forms:

- Chips wrap around the shank, causing the shank to wear due to friction between the shank, the workpiece and the chip.

- Intermittent cutting forces cause surface fatigue of the shank.

- Shank deformation due to cutting force.

- Cutting heat and cutting temperature lead to a phase change in the material structure of the shank.

- Oxidation and corrosion of the shank.

- Wear and tear of spare parts, fittings and connecting surfaces.

So how do you decide when to change the handle

First check the CNC machine spindle wear and automatic tool changer alignment

CNC machining center wear spindle will lead to runout problems, affect the accuracy of the tool handle, reduce the quality of achievable workpiece and processing efficiency. The quality of CNC spindle can be evaluated, such as checking its T.I.R. (radial runout).

It is essential to keep the ATC (automatic tool change device) aligned. If the ATC does not grip the tool handle well, damage will be caused to the spindle and the tool handle, and tool performance and tool life will be significantly reduced.

01 Assessment of tool handle wear

A worn shank will not provide good accuracy and will wear the tool quickly. It will also lead to poor machining surface roughness and may even damage the CNC machining center spindle.

Cone wear/fretting wear

Check whether the positioning cone is worn or damaged. Any problems with the cone will directly affect the machining accuracy. If the cone has any defects, the tool handle should be replaced.

If there is a clear mark on the cone, fretting wear may have occurred. Fretting wear occurs when two rigid parts (the shank and the spindle) rub against each other. Fretting wear is caused by a poor fit between the shank cone and the spindle. Vibration and heat are caused by the wear. If you see small copper indentations or marks on the cone, the handle is wearing away. Fretting wear is often easily mistaken for oxidation, and the shank should be replaced as soon as it becomes apparent. If the new shank rapidly frets, or if the shank sticks to the spindle, the spindle needs to be ground again.

Handle taper fretting wear mark

When the shank is inserted into the spindle, the worn cone will cause eccentric positioning, which is called "jumping". In processing, beating will cause premature wear and failure of the tool, but also cause excessive vibration resulting in poor machining surface roughness, at this time, additional processing is needed to correct it. Vibration can also lead to spindle fatigue heat generation and spindle bearing damage. T.I.R. (Radial runout) is used to measure the axial deformation of the tool in the shank assembly. For every 0.02mm runout, the tool life is reduced by 10%.

Bushing and spring chuck

Bushings have special grooves and patterns that hold the tool firmly and will therefore wear out faster than the chuck. Worn bushings can cause tool failure earlier, and when bushings wear becomes apparent, they should be replaced to maintain the accuracy and performance of the tool-handle assembly.

Texture on the bushing due to inadequate clamping force

If there is any damage to the outer or inner diameter of the bushing it should be replaced. Tool rotation in the inside diameter of the bushing will cause damage to it, so look for traces in the inside diameter, once damage occurs, the bushing will not be able to effectively clamp the tool handle, resulting in a reduction in clamping force and accuracy.

02 Preventive Maintenance

When not in use, the handle should be wiped clean and sprayed with a light coating with rust prevention function. When the handle is put back into use, the "oil" should be wiped off before use. The coolant should be used in the correct concentration, so that not only can play a cooling effect during the cutting process, but also can prevent the tool handle rust.

Since knife handles are made of metal, they can rust or create pits if not handled properly. If a worn or damaged shank is still running on a good quality spindle, it will cause premature spindle failure.

The main shaft puller is a key part that maintains the connection between the main shaft and the tool handle. If there is a problem, the tool handle will fly out of the main shaft. Some spindle pullers are hollow to allow coolant to flow through the shank. When in use, a clamping mechanism within the spindle pulls it in, thus keeping the shank on the spindle. The main shaft puller needs to be checked regularly for wear, cracks or other signs of damage. The defective main shaft puller needs to be replaced, otherwise it will be dangerous.

In order to ensure the performance of the handle, the overall environment must be kept clean. The shank is required to operate within the micron tolerance. Any dirt, dust, oil, chips or other contaminants that remain on the spindle, the taper of the shank and the front end clamping system will cause poor T.I.R.(radial runout), resulting in premature wear of the tool, shank and machine tool spindle. Regular preventive maintenance, including regular cleaning and inspection of machine spindles and tool handles, is recommended to improve machining performance.

It is also recommended that the T.I.R. of the handle assembly be checked regularly to verify that the handle is worn. Proper assembly of the handle assembly is required using specific tool assembly equipment to keep the production floor safe and prevent premature damage to the cutting tools. Proper maintenance and use of tool handles is the most cost-effective way to improve machine productivity, reduce downtime, and reduce the number of unqualified workpieces. Shank cost, although a small part of the processing cost, has a large impact on productivity and cost-effectiveness.

03 Practical criteria for tool handle maintenance

1. Clean all accessories and spare parts, handle (shank and head) and spindle regularly. Apply a coat of oil to prevent oxidation when not in use.

2. Store the handle in a clean, dry place.

3. Visually view the wear of the shank, such as the trace of fretting corrosion. At the same time visually view all accessories and spare parts: bushings, spindle nails, nuts, etc. Replace them if necessary.

4, do not excessively twist the screw, can not exceed its given torque limit. The wrench cannot be clamped without torque screws.

5, can not exceed the hydraulic clamping system recommended screw revolutions. Periodically control the pressure of the hydraulic chuck with a calibration meter.

6. Follow the tool instructions.

7, the use of Yaken shank, can not exceed the highest speed and the maximum clamping force of the shank.

The use of the handle must comply with the use of the handle and maintenance rules

- Otherwise it will accelerate the accuracy loss of the shank

- Otherwise, the gripping force of the handle will be reduced

- Otherwise, it will affect the accuracy of the spindle of the processing equipment holding the tool handle

- When customers use the handle in actual processing, the abnormal use of the handle is caused by non-compliance with the operating rules. Because the manufacturer does not understand the actual situation, it can not effectively provide after-sales service, and improve the working efficiency of the injection molding workshop. Thus reducing a lot of labor costs. At the same time, it also reduces the raw material belt and the corresponding auxiliary equipment beside the injection molding machine, and improves the utilization rate of space. In addition, due to the use of central feeding, corresponding to reduce a lot of single equipment, save energy and reduce maintenance costs.