CNC metal spinning machine tool will have several problems after using a long time, you can know some basic and common problem in this article, the main problem includes spindle, clamp, hydraulic station, cylinder, bearing, lead screw and so on.

1. Clamp runout

Clamp need to control the runout in spin forming, the clam runout over 0.5mm,the bottom of metal spun products is easy to scratch when is bear the unbalance pressing force. The bearing of tailstock is easy to wear. There are four keys factors effect the clam runout.

Clamp mold: if the flatness of clamp mold is not good, the clamping will run out. You can grind the clamp surface to improve the flatness tolerance.

Bearing of the clamp: if the bearing of clamp is weared after a long time work, you can spin the mold and clamp mold together 10 minutes, then stoping the spindle spinning, you put you hand on the bearing position a while, if the bearing is broken, the temperature is higher than normal.

The hydraulic or air cylinder is deformation: when CNC metal spinner operate error or CNC program mirror, a crash occurred can make the cylinder deformation. You need to change a new hydraulic cylinder.

The flatness of mandrel is not good: you can use the turning tool to process the bottom again and make it flat within 0.02mm.

2. Spindle problem

Spindle stop: If you find that spindle will stop working suddenly in the thick or hard metal spin forming, it proves that the spindle torque is not enough, you need to increase the output torque. There are three ways to improve the spindle torque. At first, you can buy a more powerful motor. Second, you can increase the pulley diameter of spindle or reduce the pulley diameter of motor, the principle is deceleration and torque increase. Third, you can use heating to make metal soft to reduce the spinning force.

Spindle bearing: when the spindle working is louder, you can touch the spindle when the spindle is stopping, you can find the temperature is higher if the bearing is damaged.

3. The hydraulic cylinder of Tailstock stop

If the hydraulic cylinder of tailstock can not move, you can check the solenoid valve, pump or the motor of the hydraulic station which doesn’t work. If there is a problem with one of these three parts, the hydraulic cylinder of tailstock will stop work.

The exterior surface of hydraulic cylinder need to use a cotton cloth to clean the surface, it will wear more quickly if the surface is dirty with metal filings and dust, you can brush the lubrication oil to reduce the abrasion of hydraulic cylinder and tailstock after cleaning. If the gap between these two parts is bigger after wearing, the clamping runout valve is bigger.

The hydraulic oil in the will be dirty when it have been used for a long time, you have better to change the hydraulic oil, otherwise it will block the pump or solenoid valve.  

4. Repositioning accuracy

Repositioning accuracy refers to the consistency of results obtained when the same task or the same batch of parts are executed repeatedly on the same equipment or mechanical system under the same conditions. It is very important for the tolerance of the machining products.

When the CNC metal spinning machine have worked after 5 years, if you can find that the spinning gap valve change in the production, such as one work piece spinning gap is loosens, but another is tightens, it proves the repositioning accuracy is not good. There are three main factorseffect the repositioning accuracy. At first, the bearing of X-axial and Z-axial lead screw is damaged after long term operation, you need to change the bearing. Second, the ball of the lead screw is worn out and the ball size reduce, you can change the ball. Third, the backlash will effect the repositioning accuracy, you can use the CNC system to set the compensation valve.

How to check the repositioning accuracy: you can put a dialgauge in the tool mounting, then use the CNC handwheel to operate the dialgage to move and touch the mold, you stop to move the diameter when the dialgauge valve meet 0.5mm, you can read the absolute coordinate in the display screen of the CNC system (such as it is 145mm). Then you operate the dialgage leave the mold about 100mm distance, you can operate the dialgage to touch the mold and the dialgage valve is the 0.5mm again. You can read the absolute coordinate in the display screen again (such as the valve 145.03mm).

You follow the steps above several times, you compare the different absolute coordinate, it the value difference is less than 0.02mm, it proves that the positioning accuracy is good, if the valve difference is more than 0.02mm, it proves that the positioning accuracy is not good. The repositioning accuracy has better to control within 0.07mm in metal spinning.

5. Belt

Belt will be broken when it have worked over 5 years, you can replace it every three years.

6. Coupling

Coupling is a component connect the planetary reducer and lead screw. If you usually use the CNC metal spinning to form the hard and thick metal sheet or tube, the coupling is easily to break, you need to check when it is used about two years.

7. Tool mounting

Many CNC metal spinning machines are assembled the tool mounting that is used in CNC turning industry, actually CNC spinning force is bigger than CNC turning force, the tool mounting is easy to damage as the rigidity and strength is not enough, so you have better to choose a stronger tool mounting when you use it to make heavy duty spinning (the stainless steel thickness is over 2mm).

There are two common tool mounting used in CNC metal spinning in the following, the first type can be endured stronger spinning force, but the second type is easily to control the synchronism of two roller spinning. If you spin the hard and thick metal (stainless steel thickness is over 4mm), you had better choose the hydraulic and fixed tool mounting.

8. Planetary reducer

There are tow planetary reducers in X-axial and Y-axial to connect the motor and coupling, it used to reduce the X-axial and Y-axial motor speed while increasing the output torque. The gear of the Planetary reducer is break after a period of time, if you need to spin thick and hard metal, you can choose the planetary reducer that reduction ratio is large. Such as the 2mm stainless steel spinning use the 1:2 reduction ratio, 4mm stainless steel spinning use the 1:8 reduction ratio.