April 15, 2013
Feliz Rubber Eraser Day!
Here’s some interesting facts about erasers! Read more here at The Great Eraser Caper.
An eraser by any other name? Originally, what we now call an eraser was referred to as a “rubber” because the tree resin it was made of “rubbed out” pencil marks. An eraser isn’t called eraser by eraser manufacturers, either. Their name for the little erasers on pencil ends: “plugs!”
More and more of today’s erasers are made from something other than rubber! While some of the “pink” erasers you find on pencils are made from synthetic rubber blended with pumice (a grit that enhances its ability to erase), an increasing number of erasers are made from vinyl.
How erasers are made:
Today’s pencil erasers are made from either a synthetic rubber compound or from vinyl. In either case, the raw material is blended to the proper consistency and is put into a machine called an “extruder.” The eraser material is forced through a small hole producing a long ribbon of eraser.
Each ribbon is cut into strands about three-feet in length. If the eraser is made of synthetic rubber, the strands are placed in a “vulcanizer,” which cooks them under pressure to cure the rubber. When cool, the strands are put into a rotary cutter and chopped into bits—called plugs. (Vinyl eraser strands go straight to the rotary cutter—vinyl does not need to be vulcanized!)
Rubber eraser plugs must be tumbled to round-off the edges. The tumbler is a big drum that rotates slowly—and holds 600 pounds of rubber eraser plugs at a time! Vinyl eraser plugs do not need to be tumbled—they’re ready to insert right from the cutter.
The eraser plugs are placed into a rotating hopper, which as it turns, lines up the plugs one after another, and sends them down a conveyor line to the machine that will place them on the ends of pencils.
Small bands of metal, called “ferrules” are placed into another rotating hopper that lines up the ferrules and sends them, one by one, down another conveyor line to the machine that eventually places them on the ends of pencils.
The ferrules and eraser plugs move along their conveyors to an insertion machine. The inserter is made up of a series of plungers that move in and out. Painted pencils are carried along another conveyor line past the inserter.
First, the machine cuts a small recess around the end of the pencil.
Next, a plunger presses a glue-filled ferrule onto the end of each pencil. Then another plunger presses an eraser plug into each ferrule. The pencils move down the line to still another set of plungers that push the erasers firmly into place. When the glue dries, the pencil is complete!