A: AC motor for small power machine, and DC motor for large power machine (above 37KW).
The AC motor has simple structure, low cost, and low failure. But its speed changing section is small, so the torque after speed changing is small.
The DC motor is stable at low speed running, and has large torque and complex structure. The price of the governor is expensive. 
Along with the development of the technique, the AC motor is also used for large power machine. The machine will be equipped with a frequency converter for changing speed.
 

Q: Metal pipe forming types?
A: Rool bending forming, UEO forming, slot forming, plate sleeve forming, roll sleeve forming, milling forming and restraining forming.
 

Q: The requirements of steel strips of PE-X/Steel/PE-X multi-layer pipe?
A: (1) the steel strip surface shll be clean without oil, rusty stain and dust, and have no worn and mark.
(2) The elongation percentage of the strips shall be smaller than 30%, and the tensile strength shall be larger than 275Mpa.
(3) The thickness of and allowable tolerance shall conform to requirements stipulated in GB 708—1988ofGB 709—1988.
(4) The hardness of tin-plating strips: the strips whose thickness below 0.5mm is T-2; the strips whose thickness above 0.5mm is T-2.5 or T-3.
 

Q: If it needs to clean the bore after stopping the extruder?
A: If extrude PE or PPR, it is no need to clean the bore. If extruer PEX, it must clean the bore. This is because the PEX is thermosetting material. Heating will leading to make the array among the cross-link molecular form mesh structure, which is irreversible.

Q: The working principle of eddy current detector?
A: The eddy current detector is used to detect whether there is any perforation at welding seams or not. If the welding seam is not strong, the detector can not detect this defect. Its working principle is signal multiplication. If there is perforation at welding seam, the output signal will has abnormal flutuation.

Q: Aluminum foil coating process for stable PP-R?
A: Coating of aluminum foil for stable PP-R is a core technique. The aluminum strip with film coating is very thin (say, 0.15mm in general), so it is difficult to coat the aluminum foil outside the PP-R inner pipe without air. We coat the inner pipe with aluminum foil through 11 sets of die step by step. Fix the buttom of aluminum foil and inner pipe at first, and then coat the aluminum foil step by step.
 

Q: How to ensure close adhesive for different pipe materials and expansion coefficients?
The pipes of different materials have different expansion coefficients. The expansion coefficient difference between the steel and plastic is large. If slip over the plastic pipe with the steel pipe simply, the linear function of the plastic will make the plastic pipe elongate when the enviroment temperature change greatly. If adhere the steel and plastic pipe together by thermosol, the change of environment will not separate them.

Q: How treat the steel strip surface to reach optimal adhesive strength of thermosol?
A: The strip surface shall be clean without oil, dust, and shall be dry, has a certain of roughness. In general, use the coating strip to meet the production requirements.

Q: How to add pigments?
A: In general, add 3%-4% pigments mixing with PE fully, and then extrude by extruder. The ingredient of the pigment is mainly PE or PP-R (depends on differenet plastics). While the white pigment is relatively difficult, and its main ingrediant is titanium dioxide powder.

Q: The temperature during welding steel pipe is over thousand degree. Will this temperature melt the inner thermosol leading to ahesive problem at welding seams?
A: This is just on of our technical core. The precise welding technique and composite process will efficiently ensure inner pipe will not be affected during welding.

Q: How to solve aging problem?
A: We usually add 3% antiaging agent, so as to keep the plastic performance without generating crackle under sunshine for 20 years. The antiaging agent has blank and blue, and the cable usually use black one.

Q: How to closely adhere the nanometer antibiosis layer to the inner wall of the inner pipe?
The nanometer antibiosis layer is very thin, and its ingredient is mainly PE or PP-R (depends on different plastics). The antibiosis layer and inner pipe are co-extruder by two extruder, so they are merged together completely.