Steel Detailing | Precast Detailing | Estimation

Tag: table

  • Difference between Normal Table and Tilt up Table

    General Details about table:

    • Tables are used for fabrication of precast panels in factories or yards with good quality, finish, curing and low time consumption.
    • Different types of materials used for tables like timber, aluminum and steel. But steel is mainly used for tables because it’s good for repetitions, gives good vibration to concrete, it’s not easily damaged and tables do not expand when it’s wet, etc.
    • The cleaning process is also easily done for steel tables with the help of air blowing or cotton waste.
    • In the yard there are different types of tables used for fabrication.
      For example normal fabrication tables and tilt up tables.

    Normal table:

    • Normal tables are mainly used to fabricate most of the precast panels.
      (Refer Fig 1)

    Fig 1

    • Advantages:
    • Normal tables will not take more manpower for cleaning and fabrication of precast panels.
    • The maintenance is easy
    • The cost is low when compared to other types of table.
    • It can easily fix where we need to fabricate the panels.
    • It will be fixed on the floor, so the visibility of the table is good for all.
    • Disadvantages:
    • It’s not suitable for doors or big opening panels. Because in case of lifting panels it may break.
    • Normal table needs additional lifting support.

    Tilt up table:

    • The tilt up tables are mainly used for Doors and big opening panels and also other types of panels. (Refer Fig 2 & 3)
    • The tilting process allows the precast concrete element to be removed safely and without damaging it.
    • The titling tables are designed in particular for mobile use and can be quickly transported from the yard.
      Fig 2


      Fig 3

    • Advantages:
    • This table is good for fabricating and lifting the door, opening type of panels.
    • Hydraulic Tilt up Tables reduce manufacturing time because it’s not require more pouring time to lift the panel from table.
    • Vibration technology based operation ensures qualitative compaction of concrete and a consistency in quality.
    • It’s very high level of concrete compacting with low noise.
    • Minimal costs when transporting the tilt up table.
    • Disadvantages:
    • Manpower is necessary and also needs knowledgeable people for handling.
    • The maintenance is difficult
    • The cost is high
    • It’s not movable, so we need to collect materials at a nearby table.

  • The Signficance of the “Mould” Face in Precast Panel Detailing

    The Mould Face

    This post attempts to explain the following two questions, for those starting to learn the precast trade:

    • A lot of fancy words are thrown around. Near face. Far face. And mould face. What does it all mean?
    • How should shop drawings be marked vis-a-vis the mould face, and why should they be marked as such?

    What is a precast panel?

    These my friends are precast panels:

     

    What panels look like.

     

    • You can build things quickly and cheaply, if you build with precast panels. Your other option is to fabricate on site. The problem with this is that it: (i) is more expensive, and (ii) the construction is a lot slower.

    What is the mould face?

    • First you have to understand how the panels are “fabricated” (i.e. how they are made). Concrete is poured into a mould, on a table. It looks something like this:

     

    Showing a panel on a table, in its mould.

    So then what is the near face / far face / mould face?

    • The near face is the side of the panel which is exposed to the air. This is the face of the panel which you can see.
    • The far face (or mould face), is the face of the panel which is lying on the table.

    What is the significance of the mould face?

    • The mould face has a smooth finish (or should have one).
    • You do not want a building which has the ugly face of a panel exposed for everyone to see. The architect will be baying for your blood, and moreover it is a very costly remedy. Some precasters, in order to avoid this problem, “trowel” the near face (i.e. the face which is exposed to the air). “Trowelling” is when you smooth the surface of the panel with a tool so that it looks nice.

    When you draw a panel, you want to indicate on your drawings that the mould face is on the building exterior.

    • Why? So that the smooth side is seen by people and the ugly side is hidden from view.
    • “But won’t people on the inside of the building also see the ugly side of the panel?” you ask. Not necessarily. Most of the time, the panel is not visible on the inside of the building because the architect will put up plaster or there will be something hiding the panel from view.

    Standard Shop Drawing Practices

    • People draw elevations assuming they are looking at the near face first, rather than the far face.

     

    This diagram should certainly clear things up for you:

     

     

    Shows the near face and far faces on the marking plan – also notes where the exterior of the building is.

     

    I hope you learned something. Any questions, please ask.