When talk about CNC spinning machine tool, many people will think of CNC lathes, after all, from the structure and principle, CNC spinning machines and CNC turning lathes have a lot of similarities. In theory, when you assemble a spinning wheel (it is also called spinning roller) instead of turning tool in the CNC turning lathes, CNC lathe also can make spinning forming. The CNC spinning machine also can turning metal when you put the turning tool on the tool mounting. You can think that the CNC spinning machine has stronger force and quicker spindle speed and feed speed than CNC turning lathe.

Working principle

1. Put the blank on the mold

Someone will ask, how put the blank on the mold centre. There is two ways, at first, you can process a centre hole in the blank and put it in the mold centre. Second, you can use a pneumatic rack to keep the blank in the mold centre.

2. Tailstock cylinder press the blank

The tailstock cylinder press the blank on the mold, it make the blank follow the spindle turning with pressure, otherwise the blank will move out when it is pull or press by roller. The cylinder pressure can be adjusted by hydraulic pressure station. Too much hydraulic pressure will cause the clamp bearings to wear easily, Too small hydraulic force will cause the relative movement between blank and mandrel.

3. Spindle turning and roller move
The motor starts to drive the spindle to rotate, the rack will move back, then the roller will move to form the blank according to the path of CNC program. When the spin forming ending, the hydraulic cylinder will move back, the metal spun products can remove from the mandrel (it is also call mold).

Cross slide 

1.How roller move

CNC system control the motor to drive the X-axis and Z-axis lead screw is transformed a rotating motion into a linear motion.

2. The structure

The cross sliding table is composed of X axis and Y axis‌ : two vertically arranged linear motion modules. the X axis moves horizontally as the foundation and the Y axis superimposed on it moves vertically to form a cross structure.

3. Transmission mechanism

The rotary motion of the motor is converted to linear motion by lead screw (high precision, high load) or synchronous belt (high speed, low cost). The lead screw movement produces directional clearance, which needs to be compensated in the system and the motor

4. Guide rail

Guide rail ensure that moving parts slide along fixed trajectories, reducing friction and deviation.

5. Drive and control

‌● Motor type ‌: servo motor (closed-loop, high-precision) drive, with encoder real-time feedback position, forming closed-loop control.

● Coordination exercise : The control system (such as numerical control system or PLC) coordinates the two-axis motion to realize the interpolation operation of complex paths (such as arcs and slants).

Machine tool accessories

1. Spindle

Now it is easy to buy a spindle from the spindle factory , except spindle need achieve speed and force requirement, it also needs to control the dynamic balance. Spindle is commonly used the pulley for deceleration, The belt will skid when the spindle is overloaded with roller force.

2. Bearings

It is different from CNC lathe, CNC lathe needs high accuracy and high speed bearings, but CNC spinning machine needs the bearings with less accuracy and stronger force, roller and cone bearings are more practical to withstand axial and radial force for CNC spinning machine.

3. Lead screw and guide rail

There are many companies sell the lead screw and guide rail, you can ask them to choose the right specification, usually we choose the guide rail of the roller slider to reduce the wear rate. The brand HIWIN is a good guide rail and lead screw company in China.

Tailstock cylinder

1. Little-size 

When we design a little size metal spinning machine to form the thin and soft metal, such as the aluminum thickness is less than 2mm, the steel thickness is less than 1.5mm, the diameter is less than 500mm, we can use the air cylinder to press the blank, air cylinder work faster and the the pressure is less and instability.

2. Middle -size

When we design a middle size metal spinning machine tools to form thick and hard metal, you can use the hydraulic pressure cylinder, it can output stronger pressing force to clamp the blank tightly.

3. Large - size 

When the length of hydraulic cylinder is over 1.8 meter, you can design two hydraulic cylinder, cylinder 1 is used to clamp the blank, cylinder 2 is used to reduce the distance, it can improve the rigidity of cylinder 1 and reduce the clamp runout.

CNC system

International CNC system manufacturers have FANUC (Japan), Siemens (German), Heidenhan (German), MAZAK (Japan), MITSUBISHI (Japan), FAGOR (span), GSK (China), KND (China), FANUC is a Global CNC system industry leading enterprises, market share accounted for more than 50%, Siemens is a famous Germany company that focusing on the development and integration of CNC systems, SINUMERIK series covers intelligent solutions from popular to high-end. Chinese CNC systems are mainly known for their cost performance.

Assembly accuracy control

1. The concentricity of spindle and hydraulic cylinder

The spindle and hydraulic cylinder need to control concentricity accuracy is less than 0.01mm, otherwise the clap runout is obvious, the bearings of spindle and clamp wear quickly, the metal spun products accuracy is not good.

2. The perpendicularity of X-axis and Z-axis

The perpendicularity of X-axis and Z-axis needs to control 0.02mm, otherwise the lead screw will deform and the positioning accuracy is not good, it will wear lead screw and guide rail quickly.

3. The same level of spindle centre and roller centre

It needs to control the spindle centre and roller centre keep a level, roller and spindle are not at the same level will have a significant impact on machining accuracy and workpiece quality ‌. Specifically, if the roller tip is higher than the center of the spindle, it may lead to roller can't reach center of the spindle, it affects the final quality of the workpiece. On the contrary, if the roller tip is lower than the spindle center, it may cause vibration during the spin forming, affecting the machining stability and surface finish.

CNC lathe modification

Can we refit a CNC lathe into a spinning machine

Many people want to refit a CNC lathe, because it is more cheaper than a CNC spinning machine, it can save machine cost for a factory. Commonly the refitted CNC lathe can spin the thin metal, such as the thickness of aluminium is less than 3mm, stainless Steel thickness is less than 1.5mm. If you use it to spin the thick metal, the lead screw will wear quickly because the specification is not big to bear stronger spinning force. On the other hand, the spindle speed of CNC lathe is slower, the exterior surface of spun products is not smooth. At last, the process time is long as the feed speed of CNC lathe is slower. When you know all about this details, you can decides whether you need to refit a CNC lathe.

Machine design

If you know the basic know of CNC lathe, you can understand CNC spinning machine more easier, the basic lathe structure of CNC spinning machine is similar with CNC lathe, in order to improve the spindle speed, process force, feed speed, you can need to adjust some parameter and specification of machine tool accessories.

Casting lathe bed : casting lathe bed need thicker thickness to bear spinning force and improve the rigidity of the machine bed.

Spindle : CNC lathe uses the gear reducing, but CNC spinning needs servo motor to achieve endless speed change, Pulley deceleration is conducive to overload protection when the spindle torque is less than the roller torque in the spinning. 

Lead srew and guide rail : CNC spinning requires larger guide rail and lead screw to work fast and bear strong force.

Key machine date  

Feed speed : 8000mm/min -  It decides processing time of each piece

Spindle drive AC vector : 32 KW  - It decides spinning force and spinning thickness  

Main spindle speed : max 1000 rpm  

Tailstock stroke : 1200mm - It decides Max remove distance  and spinning length.

Tailstock force : 30KN - it decides clamp force 

X-axis stroke : 450mm - it decides Max spinning diameter 

Z-axis stroke : 450mm - it decides Max spinning length 

CNC control system : Siemens

Amount of roller : Sync 2+

Machine types＞＞

The difference between double roller and single roller 

Machine cost : double roller is more expensive than single roller.

Spinning accuracy : double roller have better accuracy of metal spun products.

Thinning rate : double roller have bigger thinning rate.

Process ability and stability : double roller is better .

If want to spin the soft and thin metal, such as aluminium thickness ＜2mm and steel thickness＞1.5mm , we suggest you buy the single roller CNC spinning machine, If you want to spin the thick and hard metal, such as the aluminium thickness ＞ 5mm, steel thickness ＞3mm, the stainless steel and special metal ＞, you can choose the double roller.

How to choose a right CNC metal spinning machine ＞＞

The hot metal spinning machine

When we spin forming some hard metal that the ductility is not good, such as superalloy (high temperature alloy), Inconel 718 and 625 (nickel- based alloy), TC4, Aerospace aluminium 7075,  A286，Hardox,  SUS630, these metal are hard to spin by cold spinning and it is easy to break as the poor ductility. Heating to different high temperatures can effectively improve the elongation of the material and reduce the breakage and springback of spinning, the toughness of metal and spinning force will reduce in hot spinning, so hot spinning is very popular in the aerospace metal spinning products.

There are different heating ways in hot spinning, Propane combustion temperature can reach ‌2000℃, it ican quickly heat and reduce material deformation. Propane flame stability is strong, support accurate adjustment of fire intensity, It is mainly used in sheet metal spinning. High-frequency heating based on the principle of electromagnetic induction, the high-frequency current directly generates eddy currents inside the metal, which can realize rapid heating without heat conduction and greatly shorten the processing time, the heating efficiency is more than ‌90%‌, and the energy consumption is much lower than that of traditional resistance or flame heating, it is mainly used in the tube spining.‌

Three roller - Flowing forming machine

The three-wheel spinning machine is usually composed of three rotating wheels, symmetrical layout of 120 degrees, Three-wheel spinning has great advantages for the strong and thin spinning of cylinder parts. In addition to the material thinning and strength improvement of cylinder parts, three-wheel spinning greatly reduces the waste of materials. For example, the fuel tank of an aircraft, the shell of a missile, the cylinder of a hydrogen cylinder, the shell of a rocket.The surface roughness of high-precision models can be controlled below ‌Ra0.4μm, the diameter accuracy can achieve +-0.1mm.‌‌

Machine structure

The structure of metal spinning lathe

CNC metal spinning lathe have three structures, vertical bed lathe is suitable for little-sized  metal spinning machine, slant bed lathe is suitable for the middle - sized metal spinning machine , flat bed lathe is suitable for the large - sized metal spinning machine.

Little-sized vertical machine

When the max diameter is less than 300mm, the height is less than 200mm, the height of the spindle of the small vertical spinning machine can be adjusted to 1.2 meters, it is convenient for workers to load and unload materials. In addition, the vertical spinning machine occupies a small area, it greatly reduces the utilization of factory space. If the height is over 200mm, vertical machine is hard to remove the metal spun product from machine.

Middle-sized slant machine

When the max blank diameter is less than 800mm, the inclined bed design (usually 30°-45° tilt) allows the iron chips produced by cutting to naturally slide to the chip removal machine, avoiding the wear of the accumulation on the tool and the machining surface, while reducing the impact of thermal deformation on the accuracy. The inclined bed has a larger cross-sectional area and better bending and torsional resistance than the flat bed. The cutting force is consistent with the workpiece gravity direction, reducing vibration and improving processing stability. The X direction ball screw is affected by axial gravity, effectively eliminate reverse clearance, improve repeated positioning accuracy, especially suitable for high-precision parts processing.

Large -size flat machine

When the diameter of blank is over 800mm, it is suitable to design the flat machine , because the blank weigh is heavy and it is hard to put the materials in the CNC metal spinning machine by hand, it needs a crane to load and unload the materials and metal spun products, flat machine is convenient to put the materials or assemble the mandrel from the top of spindle. On the others hand, flant structure is easy to assemble the machine components.

Why the wheel shear spinning use the vertical

Wheel Wheel metal spinning is designed by vertical bed, because wheel is heavy and it is high temperature after spinning, vertical design is helpful to upload and load by mechanical arm, on the other hand, vertical spindle reduce the spindle weight effect the bearing, it has high precision when it work, The Z direction ball screw is affected by axial gravity, effectively eliminate reverse clearance, improve repeated positioning accuracy, especially suitable for high-precision parts processing.