Can Core Mold Vibration Pipe Making Technology Produce Qualified Pipes Reasonably?

To reasonably produce qualified pipes using core mold vibration pipe making
technology, the requirements for the main equipment should be given priority.
However, the quality and reasonable configuration of other auxiliary equipment
such as molds are also crucial during the production process.

(1) Molds

The core mold vibration pipe making process requires the vibration force
generated by the vibrator to be transmitted to the concrete through the mold to
the maximum extent. From the formula for the vibration force required for
concrete pipes, it can be concluded that on the premise of ensuring the wear
resistance, smoothness, concentricity, and roundness of the inner and outer
molds, the lighter the mold, the more favorable the process. To meet the above
performance requirements of the mold, wear-resistant steel is used for the
friction parts of the mold during production, and the precision control points
are finished by precision machining. After manufacturing, deformation treatment
should be carried out to remove welding and bending stresses of the
cylinder.

According to feedback from enterprises using imported and domestic molds and
on-site tests, compared with domestic molds, imported mold steel has better
quality, lighter weight, and better vibration effect. After nearly ten years of
use, the mold deformation is minimal, and most areas show no rust. However,
since the price ratio between the two is about (2.5 ~ 3): 1, it is difficult for
most enterprises to accept. In fact, the main problems of domestic molds are not
technical but related to cost, sales price, and manufacturing integrity. It is
suggested that product enterprises and equipment manufacturers in the industry
work together to ensure the quality of cement molds.

(2) Roll Welding Machines

During the production of core mold vibration pipe making machines, the main
causes of transverse cracks in concrete pipes are the rebound of the steel
skeleton and the contact between the roller disc and the skeleton due to the
excessive diameter of the outer steel skeleton. Therefore, the requirements for
the steel skeleton roll welding machine are firm welding, accurate dimensions,
and the end ring ribs should have a tight winding function.

(3) Mixing Equipment

The impact of mixing machines on concrete quality mainly includes: the type
of mixing machine, the distribution and rotating speed of mixing arms; the ratio
of the apparent density of the added loose concrete to the geometric volume of
the mixing drum; and the feeding sequence of various materials.

For cement products, forced mixing machines are generally used, commonly
including vertical forced mixing machines and double horizontal shaft mixing
machines (horizontal mixing machines are also called semi-forced and
semi-gravity mixing machines because the concrete in the upper part of the
mixing drum falls by gravity). To improve and ensure that the linear speed of
all concrete in the vertical shaft mixing machine drum is as consistent as
possible, resulting in more uniform mixing, on the basis of the early vertical
shaft forced mixing main machine, a planetary rotating mixing main machine with
rotating mixing arms has been developed.

Due to the differences in the contact area, structure, and speed between the
mixing arms and concrete, double horizontal shaft mixing machines are more
suitable for plastic concrete, while vertical shaft forced mixing machines and
planetary rotating mixing machines have better mixing quality for stiff
concrete.

During the core mold vibration pipe making process, the dry hardness of
concrete is 20 ~ 60s. It is recommended to use vertical shaft forced mixing
machines and planetary rotating mixing machines for concrete mixing.

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