Tangential Plotters - Edward Mathias & Co

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Tangential Plotters

Info. & Technical
TANGENTIAL KNIFE CUTTERS
Do not confuse these with drag knife or “tangential emulating” drag cutters.

HISTORY
It is now almost 40 (yes, forty!) years since the first plotters arrived in UK.
Very few people can pronounce the word tangential let alone understand it but they might be surprised to know that many of the machines surviving from that era can still cut more accurately than many modern machines.

WHY?
Because although those early machines were driven from internal font modules and could not be connected to computers (computers were in their infancy at that time) the cutting action of those machines was tangential.

HOW DO TANGENTIAL CUTTERS WORK?
Much as you would do when cutting with a scalpel.
When cutting a line you would point the blade in the direction of the cut.
When cutting a tight corner you would lift the blade out - turn it to point in the direction of the next cut - then lower it back into the media.
When cutting a curve you would progressively rotate the blade to keep it at a tangent to the curve.
The derivation of the description “tangential” cutter.

ADVANTAGES OF TANGENTIAL CUTTERS
(When they are used and set correctly)
Their natural action cuts cleaner sharper corners.
They are better at cutting thick and tough materials.
There is less chance of distortion when cutting fine detail and small characters.
Weeding is easier because there is less chance of start/finish point errors than with drag cutters.

WHY?
Unlike drag knife cutters which depend on the cutting resistance of media to align the blade tangential cutters have mechanisms to “steer” the blade to point in the correct direction whether it is in the media (cutting) or out of the media (positioning) so they have no need to twist the blade in the media in tight corners (particularly undesirable in thick and tough materials) and because the blade is “steered” there is no need for the blade to be offset and therefore no need to devise clever mechanisms or software to compensate for the disadvantages of blade offset.

DISADVANTAGES OF TANGENTIAL CUTTERS
The superior precision of tangential cutters makes them more expensive to manufacture and that makes them more costly to buy.
Their higher cost is their one and only disadvantage.

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