The two primary manufacturing processes used to produce Marco FRP Grating products are Pultrusion and Open Molding. Both processes produce high quality, uniform construction.
High quality, well designed, pultruded grating, which resembles metal bar grating, is stronger, lighter, equally corrosion resistant, and in most cases, is less expensive than molded grating. Additionally, pultruded grating comes in larger panels and can be built to custom panel sizes. In most applications, pultruded fiberglass grating will represent the best product and the lowest price.
Molded fiberglass grating has equal strength in both directions and is made with square or rectangular grid patterns. Since it was developed much earlier than pultruded grating, it is widely used and performs well in many applications.
Comparison of Molded and Pultruded Grating:
|Molded Grating||Pultruded Grating|
|Imagine a giant 4 ft x 12 ft
waffle iron (mold). Liquid resin and continuous fiberglass roving are
systematically laid in the mold, layer after layer manually, to produce
the desired thickness and panel dimensions. The finished molds are set
aside for a predetermined time to allow the panel to cure. The panel is
then ejected from the mold. The molds are cleaned and prepared for the
process to begin again.
The one piece interwoven square mesh construction of molded grating produces two primary benefits: maximum corrosion resistance and high strength.
Because the grating is "cast" in one piece, there is no mechanical joint between bearing bars, unlike the pultruded grating where the glued joints can give way in heavy continuous traffic or after prolonged service.
The high percentage of resin (65%) in molded grating offers superior corrosion resistance. The molded grating with a square mesh pattern offers increased load capacity and panel utilization due to this bi-directional trait.
Cutting access holes in the molded grating does not weaken the panel and does not require additional or costly supports (unlike pultruded grating that must be re-supported and edge-banded).
|The pultruded grating product
is a mostly mechanized process. Fiberglass of different shapes such as:
strand, mat and veil are pulled through a liquid resin bath and a heated
die where the bar is shaped and the resin is cured. These pultruded
bars can be cut into 12 ft, 15 ft or 20 ft lengths. The bars are then
taken to a workstation and drilled (6" or 12" on center) on the sides to
accept the crossbars. The drilled bars are spaced proportionally for
the width of the panel; 3 ft, 4 ft or 5 ft. The final step is to seal
the entire cross bars and holes with corrosion resistant epoxy resin.
The pultruded grating provides increased load capacity with moderate levels of corrosion resistance. The components (bearing bars and cross bars) are pulled by machine to have a higher glass content. Its superior load capacity to molded grating is a result of the higher glass to resin ratio (65% glass to 35% resin). However, the lower resin content reduces the corrosion resistance as compared to the molded grating.
The pultrusion process is automated and produces a consistent, high quality finished product.
Assembled from bars, the pultruded grating can offer a wide variety of panel sizes and substantially reduce "scrap loss" not always possible from molded grating panels.