Cutter Offset
Info. & Technical
This machine setting is usually decribed as cutter offset or blade offset but a more accurate description would be cutter offset compensation or blade offset compensation and although it is very important that it is set correctly many plotter users fail to do so because they don't understand it or know how it affects cutting accuracy.
Before you read further you should read how drag knife plotters and tangential plotters work in different ways and why cutter offset is important on one but does not apply to the other.
A SIMPLE WAY TO UNDERSTAND CUTTER OFFSET
When you turn a corner in your car your rear wheels take a slightly different route to your front wheels so to avoid your rear wheels bouncing over kerbs you ensure that your rear wheels have reached the corner before you turn.
Although you may not think of it as such you execute an offset manoeuvre at every corner when you drive a car.
To do that manoeuvre you need to be aware of the distance between your front and rear wheels.
If you were driving a long vehicle you would do a greater offset manoeuvre because the distance between front and rear wheels would be greater.
HOW DOES THAT RELATE TO YOUR DRAG KNIFE PLOTTER?
For a drag blade to be dragged into pointing in the right direction it is designed to cut behind centre and just as your rear wheels want to bounce over kerbs a drag knife wants to cut across corners.
The natural action of a drag knife is to create rounded corners.
To avoid creating rounded corners drag knife plotters use cutter offset compensation.
BUT IT ONLY WORKS IF YOU SET IT CORRECTLY.
CUTTER OFFSET COMPENSATION
Is it Important?
If you want your machine to cut distorted text and rounded corners - NO.
If you want your plotter to cut correctly it is VERY important.
If you have a tangential cutter it does not apply.
What is cutter offset ?
The distance from the point at which a blade cuts to the point around which it rotates (its axial centre).
What does offset compensation do?
Why does it exist?
The natural action of a drag knife would create radiused corners.
Without compensation for blade offset a drag knife cutter cannot cut sharp corners.
See:- Drag knife plotters
How is offset compensation achieved ?
All modern drag knife plotters have a routine, usually built into their firmware, to manoeuvre the blade on a path which compensates for the blade offset.
Is it automatic ?
Almost, but you must give the plotter the correct information about the offset of the blade in use.
It is usually a distance between 0.25mm and 1.0mm
Graphtec Plotters use a different system.
What is the setting usually called ?
Offset - Blade Offset - Cutter Offset - Knife Tip Offset - Cutter Compensation
How is it set ?
On the plotter control panel (usually), it may also be controllable in (some) software.
Recommended setting is usually supplied with the blade or Smart Knife.
Instructions for how to set it on your plotter can always be found in the manual.
If you can remember where you put the manual!
CHECKING AND SETTING CUTTER OFFSET
Most modern plotters have a built in test to check cutter offset which you should use if possible but here is an alternative test you could try.
Use a media colour on which it will be easy to see the cut.
Use an undamaged blade and set the correct pressure for the media.
Do not release the pinch rollers or remove the media until all tests have been completed.
Use the recommended offset setting for the blade type in use.
If you don’t know the recommended setting for the blade type use the default setting.
Choose a font where the letters have straight lines and sharp square corners.
Helvetica or a similar style.
Cut an upper case E at about 20 - 25mm
An upper case E is ideal for this test because it has lots of straight lines and square corners.
Cut it again.
At offset settings one and two steps above the recommended offset setting - Do not change any other settings.
And Again.
At offset settings one and two steps below the recommended setting - Do not change any other settings.
Examine what you have cut.
Look at the corners - ignore start/finish corners.
Where corners are radiused - offset is too low.
Where corners have triangular peaks - offset is too high
Where corners are square and sharp - offset is correct.
PLEASE NOTE
These instructions are for setting the compensation for the offset of the blade in use.
Depending on your machine the setting you may need to adjust is usually called
Blade Offset - Cutter Offset - Knife Tip Offset - Cutter Compensation
Cutter offset affects the sharpness of corners only, it does not compensate for other inaccuracies, distortions, software errors or machine faults.
When trawling through menus you may see settings for offset angle and offset force.
They are not related to cutter offset - they are for engineers only - DO NOT ADJUST THEM.