Paver Moulds – All Questions Answered

Paver moulds for "dedicated" paver machines are a very important consi­deration for the operator. As with coarse and fine aggregate, cement, and pigment, mould wear must be considered each time the machine cycles. However, expenditures for moulds is a constant sore point in the paver busi­ness. Mould quality and mould wear are subjects that have not been fully addressed. So, here in this article, we throw light on all things related to paver moulds and you can find the answers to all your questions regarding the same.

 

What Does a Mould Consist Of?

 

A paver mould consists of several things. First of all, it has a tamper head which has been bored, drilled and tapped to fit to a "main tamper head plate" designed by the machine manufacturer, precisely located plungers (or steel spacers) welded to the tamper head which vary in length according to the stone thick­ness, with angles welded to its open ends on which are bolted the tamper head shoes. The tamper head shoes are the next component of the paver moulds. These are numbered and fitted to "mated" cores. The "main tamper head plate" has become a standard feature on most modern paver production equipment and allows for bolting on vibrator units without having to change these units from mould to mould and is a perma­nent part of the production machine.

Next the paver moulds have a "mould box" structure containing an adequate number of cores to pro­duce approximately 10.5 square feet (1 square meter) in the general shape of the desired paver and in a total thick­ness which includes designed thick­ness of the paver plus estimated com­paction of 10 to 20 percent. The mould box is equipped with wear plates on the rear and front which will vary in size to compensate for the varied sizes of production area between the interme­diate wear table and the rear wear table. The mould box may have welded-on retaining parts such as wings or braces, and feed drawer rails. The mould box may be cast, welded together, or flame-cut from solid steel.

In recent times, most moulds are flame-cut. Steel quality and any special treat­ment to improve the lite of the box has a reduced affect on the cost of produc­ing the mould.

Now that you completely are aware about the components of the mould, next question that would come into your mind would be the life of the mould. Find below the answers to it.

How Long Should a Mould Last?

 

Mould life is entirely dependent on three factors;

  1. Material and method of manufac­ture of the mould box.
  2. Local aggregate and required com­paction vibration.
  3. Care by the owner.

There are several schools of thought on what materials and methods should be used to manufacture the mould box in order to maximize value (from the mould producers viewpoint) Extra hard steel boxes tend to wear longer but can be unfriendly to machine vibra­tion while milder steels tend to be more tenacious against cracking, but wear faster. The idea of medium hard steel with "hard facing" welded on the bot­tom edges of the mould box has proven best for mould wear and trouble-free life. The insurance factor vis a vis the "hard faced" mould box raises the price of the mould above the cost of extra hard steel but offers the least problems.

The extra hard steel generally wears evenly from top to bottom during its active life, whereas the "hard faced" box can wear with a slight concavity above the hard-facing material. As a general rule, the mould has outlived its usefulness by this time. The difference in life of a ''hard faced" box and an extra hard steel box is generally signifi­cant enough to justify the extra cost.

Moulds and tamper head shoes wear from abrasive action of the concrete mix being compacted. Aggregates vary in abrasion, hence these parts wear quicker where high abrasion is present. Harder aggregates also promote quicker wear.

An owner can extend the life of moulds by keeping mould changes to a minimum, cleaning and oiling after each use, properly fitting mould box and tamper head when changing, and keeping tight all fastening devices. Charting mould usage is also very important.

In consideration to all these things, you could easily determine the life expectancy of the moulds. Here is what it can be.

What is the Life Expectancy of a Mould?

 

Optimum mould life may be 10,000 machine cycles or 40,000 machine cycles depending on the quality of fabrication and secondarily on operator upkeep. Very few moulds can be consi­dered usable after 40,000 machine cycles and by this time the amortized cost is between 20 and 30 cents per cycle. An inexpensive mould that lasts 10,000 cycles will amortize at 60 to 80 cents per cycle, even with reduced upfront costs.

After the completion of these cycles, the moulds are completely worn and it is best that you get rid of such moulds and change them as using such moulds can have consequences. Here is an insight on what these consequences could be.

What are the Consequences of Using a Worn Mould?

 

A worn mould speaks loudly about a company. A worn mould box or cham­fers on the tamper head shoes will cause problems for the installer and the paver purchaser. A mould wears and increases the size of the pavers in the mould box at indifferent rates; ultimately pavers will not fit together during installation. Production prob­lems can occur with worn tamper head shoes. Tops may pull off as well as increase the opportunity of chipping while pavers are being vibrated into the sand box. Worn out shoes help acceler­ate the wear of the mould box by allowing material to squeeze around the top of the stone.

So, with such life expectancies and the needs to change the moulds at regular intervals, there is one more thing that you will want to linger and question upon, which is the initial cost of the mould as to what it should be. Read on to know the answer.

What Should be the Initial Cost of the Mould?

 

The initial cost of a mould is almost meaningless when considering all fac­tors involved in the life of a mould. Knowing the makeup of a mould and keeping an eye on mould wear are investments that return great divi­dends. Quality pavers and paver instal­lations are everyone's concerns. Life cycle costs on capital and expendable equipment are, as well.

Today, moulds can be purchased at various prices (in U.S. dollars) from a low at $7,000 up to $11,500 for the same configuration.

Conclusion

So, this was all about the paver moulds and the various questions related to their components, life expectancy, costs, and the care required. Moulds are important hardscape tools to consider for the purpose of paver installation, however, due to less knowledge about them, since the subjects have not been raised much, as well as the high expenditure associated with them, they are quite an ignored equipment. However, with this article, we have all your questions answered and we hope that it has helped clear the air regard­ing mould quality and wear. Also, there are not very high costs associated with it and you can always increase the life expectancies with proper care and measures. So, use these necessary hardscape tools for your projects and have better and stronger paver structures installed.