The principle of metal spray marking as supplied by IEL is based upon melting and then blowing aluminium or aluminium bronze particles through a stencil onto the hot product. The stencil is in the form of a disk or a rimmed wheel with the characters concentrically cut out of the disk or the rim using laser. The disk is then rotated much like on a daisy-wheel printer for character selection. Each character marked is unique in form permitting recognition of the character should part of it be damaged by handling or other causes. The stencil disk is kept clean by an integral cleaning system minimising servicing requirements.
The principle is shown in Fig.1.
Wire is drawn from the two spools into the arc-gun where an electrical potential of 40VDC is applied across them. As the wires pass through the gun, they make contact at a point in front of the stencil disk at which point an arc is formed melting the wire. Compressed air is then blown through the resulting pool of metal forming a spray of hot particles. The spray then pass through the stencil character in the disk, through a window cut-out in the combined heat-shield / sensor door and onto the product to be marked. Sensors detect the level of consumables to warn when these are approaching exhaustion.
DOT MATRIX PAINT AND STAMPING.
The principle of dot matrix is totally different to Metal Spray. Here the characters are formed from a matrix of dots produced either by paint or by stamping using pointed pins fired into the metal surface using compressed air.
As shown on the sketch, the dots are formed by a string of inline nozzles or pins inclined at an angle where the top nozzle or pin forms say the top bar of a 7 and the bottom one, the bottom bar of a 2. By passing the marking block, containing the nozzles or pins, over the product to be marked and then firing the solenoids that operate these at measured distances thus generating the characters. Rather than passing the block over the product, one can of course reverse this i.e. keep the block stationary and move the product.