21.1.11

Engineered marble plant : a guided tour

Visiting an engineered marble ( cultured marble ) plant will surely help you understand the product a little better. I've described in prior posts the engineered marble (cultured marble) production process (Breton block plant).
I've also referred to cultured marble in this post as many, especially in North America, use this term - cultured marble - to define engineered marble, my intention is not to confuse my readers so I will include both terms. In truth when I refer to engineered marble, I'm referring to a product which is made with polyester resin bonding and using Breton technology, it's high quality cultured marble.
So this post will be a guided tour through an engineered marble (cultured marble) plant, as in every industry our production inputs will be mainly raw materials. The whole production process of engineered marble can be divided as follows:
  1. Engineered marble block fabricating unit
  2. Staging
  3. Sawing the engineered marble block
  4. Engineered Marble Surfacing
  5. Slab or tile fabrication
    1. Engineered marble block fabrication unit

     This is the heart of the whole engineered marble business. This unique production unit is responsible for combining all the ingredients accordingly and thoroughly mixing them. The main raw materials used in producing engineered marble is marble chips (several sizes), marble dust, resin, and coloring pigments.
    A block can weigh more than 7 tons, so accordingly each block will need that much quantity of raw materials. If we add a 30 minute production cycle for each block and a 2 shift day we are looking at more than 30 blocks, which is equivalent to 210 tons of raw materials per day. That's more than 8 truck loads of raw materials arriving daily.
    So factories need a nice and well balanced warehousing for all these different types of materials. Many textures are made with the mix of more than one raw material, it's just like baking a 7 ton cake. And to guarantee the same exact textures in the whole lot, well everything has to be done precisely the same way, and maintaining the same momentum. What does this mean? Mixing the ingredients has to be made at the same moment, if you exchange order between blocks you might end up with a slightly different shade.
     So on the right you'll see a photo of exterior silos these usually are used with micronized dust and small marble chips.
    In the inside of the plant you'll find another feeding unit for raw materials, being a mixture of several types of grit sizes and types, each one of these storage units will be synchronized by the main computer which will load the exact quantities necessary as per the formula for each type of product.
    Every time Research and Development creates a new product, the production manager will have to industrialize it, which may mean new warehousing and feeding facilities.
    I do know that some factories do feed manually some of the raw materials needed, however the human error factor is great and shade differences may occur due to the human factor.
    I guess we are ready to pass on to the next phase in production. Which is the forming of the block.

     I've done some labelling on the photo to help you visualize the process. In A you'll find the control tower, here is where the machine is controlled, it may also control all the conveyor feeding and weighing system. The machine needs a lot of inputs regarding the production of each color, mixture speed, timing, discharge timing, vacuum pump activity, vibrocompressing, etc. are in most cases specific to each type of product.
    B is the entrance for all raw materials, you'll see a conveyor belt for the bigger chips, a screw conveyor is also visible, it falls into a automatic scale (looks like an inverted cone), the resin comes in a small tube which may not be visible and is in a waiting area before discharge.
    D shows the mixer, it has horizontal shaft with arms that are in constant movement, in a few minutes the whole 7 tons will be effectively mixed together. The block plant in the photo is not the current Breton version, as the new Breton plant uses vertical mixers, so above the block machine you'll have a 3/4 floor high area for the mixing.
    The (C) clean molds go in the back end of the block machine (G), although I think their might be a front end machine installed. This front end, will have a higher production cycle, but maybe due to space or some other reason, has made them invest on such machine. The most effective machines are like the one in the photo, empty mold in on one end, and block out the other end.
     The mold goes in through the G area, stops underneath the mixer, where it does a back and forward movement to help distribute the mix correctly. Then follows to point F, all these movements and even the mixing is done in a vacuum chamber, this is essential to guarantee a high quality product. The vibro compression unit has 6 engines, they basically vibrate and compact the block during several minutes. If you work at the factory you'll feel the floor vibrate, feels like a little earth quake.
    The chemical process initiates when the resin is staging waiting for discharge into the mixer, the hardening process takes about 2 hours. After this period the molds can be disarmed, the point I in the picture is exactly this. You will see some blocks in the molds and other with the molds dismantled.


     2. Staging

    A few hours later, the block hardens and can be moved into storage. The storage time for a block is equivalent to the time it needs to solidify completely. This may vary, due to the type of product and temperature. In the summer staging is quicker, in the winter it tends to be slower, the best situation would be warehousing and making the block in a controlled environment, which not every plant has. Due to the quantity of space these blocks may occupy, sometimes they will be warehoused and stacked outside.


    3. Sawing the Engineered Marble Block

    After the block is sufficiently cured, and as soon as the blocks are needed to comply with production needs, they will be sawn. They are normally sawn using either horizontal gangsaws or vertical gangsaws. The horizontal gangsaws are the ones most of you normally have or have seen, the block sits still and the diamond blades move and cut the block into slabs.
    The vertical gangsaws are specific to the engineered stone production namely the block plants. Since all blocks are rectangular and have the same size, the diamond blades maintain a vertical movement, while the block moves through them. Before the block is sawn it's calibrated on the sides to guarantee a perfect cut, being the block which does the movement, it has to move perfectly straight, any deviation will cause warped slabs. The vertical cutting is very precise, 10 mm slabs is really easy to do with vertical saws and very little breakage.
    The vertical saws are relatively quick in 5 hours you'll have a 3 m long block cut into slabs.



    4. Engineered Marble Surfacing

    From this point on, it's very similar to natural marble. Although engineered marble has tough tolerances to comply with due to CE Markings, which implies a precision calibrator and a lot of quality control mechanisms.
    You'll have a slab loader at the begining of the line, and as the slabs are all rectangular and similar, Breton has a very quick horizontal slab loader which guarantees top performances to a surface finishing line.
    The next phase will be the calibrating of the slab, while in a engineered quartz production plant calibration is made on both surfaces of the slab, the engineered marble plant normally just calibrates one surface.
    Resining lines are part of the surface finishing line, although it only applies to the traditional range of material, the one that uses big chips. These materials have big pieces of natural marble on the surface, and many natural marbles have to be resined, so the same applies to engineered marble. When we deal with micro chip textures, the process is direct from the calibrator to the polisher, no resining needed as their are no pours.
    The polisher is normally a Frankfurt type, the more polishing heads the better, the speed of these types of lines can go over 4/5 linear meters per minute, which gives you a good daily output compared to the traditional marble industry.


    5. Slab or Tile Fabrication

    Right after the polishing unit, you'll have polished slabs extracted from the production line. Many production lines will have a slab extraction point before the tile cutting and packing plant, which makes everything a lot more efficient.
    The extraction of slabs are normally made by vacuum activated robots (JOT) . However due to the velocity of the production line which can be superior to the JOT cycle, some factories have an intermediate warehousing unit or a branched out slab packing line. The slabs are classified with visual inspection an separated accordingly at this point.
    The slabs that continue to the tile plant will be cut with automatic multi disc cutting machines, first vertically, and after horizontally.


    After cutting is made the engineered marble tile, will be bevelled on all 4 sides, just before visual inspection and packing.

      4 comments:

      Technical said...

      Hi Tomson, another great post.
      Few words about curing: In my knowledge the only block plant with a controlled temperature curing is Rover. After the moulding phase the blocks are moved inside a temperature controlled room where will stay several hours and this could be considered as a post curing. This process bring two main benefit: 1) the complete and uniform curing of the resin 2) limited release of VOC from the materials once processed . Need to point out that the complete curing of engineered stone, without a proper curing, may take months or even years.
      I.e: In the past manufacturers got complains from buyers due to the fact that when opening containers of delivered slabs the smell of "resin" (actually styrene) was very strong.
      With the new EU regulations coming in place this situation will not be allowed any more.Rgds

      Tomson said...

      Once again thank you for contributing. I've actually mentioned the VOC issue on this post: http://granitequartz.blogspot.com/2011/01/reconstituted-stone-or-engineered-stone.html
      Most Manufacturers will have to add a special staging area for blocks with special extraction units for the styrene. 2011 this is surely going to be an issue regarding the engineered stone business.

      tony wu said...

      You will never see this granite stone ever,very cool than you can imagine

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