1. Strict Selection of Corrugated Roller Material
The uneven of raw material of corrugating roll leads to the uneven of inner heat transfer, of expansion while working, and distortion.This will cause poor formation of fluting paper which resulting in collapsed flute. With high strength and toughness, good hardenability, no obvious temper brittleness, special Steel D50CrMo is used as the material to producing corrugating roll.It is the premium alloy precision forging steel featuring stable property and even heat transfer. Our raw material shell thickness is more than 70mm, the thicker shell can reduce deformation and keep stability during production.
2. Precision Welding Can Be Inseparable
Both ends of the roller body should be heated to release the size of the inner bored hole. After the spindle heads are put in, the roller body and the spindle heads should be held tightly after natural cooling. When everything is ready, a driving fit interface has been formed between the roller body and the spindle heads by means of preheating, welding or bolting. Special care should be taken when welding, because finished corrugated roller body’s temperature will rise constantly when the roller is running, and the roller body also bears pressure of the steam from the inside of the roller body, which will form the so-called “pressure vessel”. In view of this, the roller body and the spindle heads joint must pass the pressure test. When the welding process finished, the work piece shall be put into the furnace for high temperature tempering to reduce stress.
3.High Hardness from Vertical Quenching Process
Intermediate frequency quenching can guarantee both the hardness and harden depth we need. Our harden layer depth can reach to 8-12mm. With harder base material as foundation, the lifetime of our corrugating rolls are greatly extended. After different heat treatment process, the corrugated roller surface becomes more wear-resistant and durable. Some manufacturers groove their lower rollers before the rollers’ were harden, because it is relatively easy to work with soft materials. By this could cause problems in the later heating process for the rollers, which will make the hardness of the rollers change. After heating treatment we cut slots of lower roll though this process needs more time but makes uniform hardness.
4. Rigorous for Precise Grinding
After heat treatment and the cutting slots, the roller shall be put on high precision automatic CNC grinding machine to do finish grinding. Almost every set of corrugating rolls are needed to be designed and customized separately according to the width, diameter, flute height, corrugated paper GSM, speed and cardboard physical index requirement. The designed flute profile is copied on a costly diamond tool. When grinding wheel and diamond tool touch together, the flute profile is dressed on grinding wheel. By grinding wheel grind each flute several times until the accuracy is within our technical permitted requirement. The Siemens control system play a key role in guarantee the accuracy.
5.Durable from Supersonic Tungsten Carbide Spraying
Tungsten carbide corrugated roller producing technology is different traditional corrugated roll. Because of the particularity of tungsten carbide material, the requirement of the base material hardness is higher, flute profile before tungsten carbide spraying is more precise, which is needed to match the performance of tungsten carbide. Spraying technology is the key, which can ensure the hardness and binding force of tungsten carbide.Most advanced Praxair JP 8000 HVOF tungsten carbide spraying equipment and technology is adopted and Praxair 1342 super hard tungsten carbide powder is used for our corrugating roll. Before tungsten carbide spraying, we do sand blasting treatment on the surface which make rough surface to increase adhesion of tungsten carbide powder.
6.Repeatedly Polished, Smooth As a Mirror
Meijia adopts special polishing crafts, such as the corrugated rollers use America Praxair 1342VM series super hard tungsten carbide roller, special customized polishing wheel. With our company’s fully automatic CNC corrugated roller producing process’s special polishing machine and our independent grinding polishing technology R&D, the tungsten carbide roller’ s surface finish degree can reach Ra<0.6μm, which will improve the accuracy of the flute profile, and make sure the quality of the corrugated roller.
7.Strict Test to Keep Improving
Before and after the surface treatment including tungsten carbide plating or hard chrome coating of corrugating rolls, it is needed to check the size, hardness, precision, flute profile, and simulation feeding paper. Special projector is used to check the flute profile and feeding different GSM paper to ensure the performance of corrugating rolls.
After making concerted efforts in R&D and manufacturing through many years, Qingdao Meijia has perfectly solved the technical problem that the production loss being caused due to the insufficient quality of corrugating roll.
Problems during paperboard production
1.The designed parameter of flute is not in line with the manufacturing parameters, and the smooth finish of the roll surface is inadequate,causing a high tension of corrugating roll during the running process,that made a poor meshing and resulting in fluting paper broken.
2. The uneven of raw material of corrugating roll leads to the uneven of inner heat transfer, of expansion while working, and distortion.This will cause poor formation of fluting paper which resulting in collapsed flute.
3.The insufficient precision of corrugating roll and unstable materials lead to the flute teeth deforming during the running process, which can cause bad meshing and unstable operation,and resonance will be occurred while critical value being reached.This is how high-low flute being caused in corrugated board.
4.If the camber of corrugating roll is designed irrational, it will cause uneven local pressure, which leads to a series of problems such as poor lamination, inner liner frothing, heavy scoring on inner liner, corrugating paper rippling etc.
Solutions from Meijia's Technology
a. Meijia,in accordance with the different customer needs and on-site situation, has developed special flute type,which circle parabola is adopted for the medium-high outline,solving the problems like collapsed flute,poor lamination,inner liner frothing,heavy scoring on inner liner from the very beginning.
b. With scrupulous attitude, Meijia adopted multi-directional detection to enable the parameter of the produced corrugating roll perfectly match that of the designed one. In this way, to keep a smooth and stable operation. The unique tungsten carbide techniques largely improves the abrasive resistance and extend the service of life of corrugating roll. The special polishing method enables the surface finish reach Ra＜0.3μm, successfully solving the problem of broken fluting paper owing by its technical defects.
c. Special Steel D50CrMo is used as the material to producing corrugating roll.It is the premium alloy precision forging steel featuring stable property and even heat transfer.
d. A complex tempering process is conducted for the material to further enhance the stability. Adopting vertical intermediate frequency quenching technology to change the organization structure, strengthen the hardness, and maximize the capability of anti-thermal deformation.
e. The unique way of ultra-high pre-expansion is adopted to deal with the high temperature and pressure inside the corrugating roll,and improve the capacity of anti-fatigue strength and elastic strength,enabling corrugating roll to avoid deformation and uneven expansion during the following use.It has perfectly solved the problem like resonance(the main reason why collapsed flute and high-low flutes happened),which caused by deformation,unstable texture,uneven expansion during running process.
f. The special flute design from Meijia:
(1) The same meter of single corrugated board can be saved up to 5‰.
(2) The volume of glue can be saved up to 5‰ thanks to a better lamination between fluting paper and linerboard.
