Step by step
Line the camera up with the bed
A picture of the bed you can place a design on, where the design lands on the machine exactly where you put it on the screen.
Before you start
Anybody who has a camera fitted and has not yet trusted it.
- The camera fitted and bolted down so it cannot move.
- A piece of scrap big enough to cover most of the bed.
- Twenty minutes, mostly waiting for the machine.
Stop the camera moving, before anything else
Everything after this measures where the camera is looking from. If the camera can shift, even a little, the measurement is of a position it will not be in tomorrow.
A camera taped to a lid that opens and closes will be out again by the afternoon. Bolt it. If it is on the head, check the bracket screws.
Say where the camera rides
There are two kinds. One rides on the head and sees a small patch under it. One is fixed above the bed and sees all of it at once.
They are calibrated differently, so tell the software which one you have before it starts. Getting this wrong is the reason a calibration runs and produces nothing usable.
Let it engrave one dot and watch it
On a head camera this is one job. The machine engraves a single dot on the scrap, then moves the head to places it already knows and watches how that dot travels through the picture.
From one dot it works out how much the lens bends the picture and how the camera is lined up against the head. You do not need a printed chessboard and you do not need to click on anything.
For a fixed camera, the card then the target
A camera above the whole bed is two jobs. First wave a printed card in front of it at several angles, which teaches it the lens. Then let the machine engrave a target on the scrap, which teaches it where the bed is.
Do them in that order. The lens has to be known before the target means anything.
Prove it before you trust it
Do not go straight to cutting. Draw a box around something on the camera picture and mark it lightly, at low power, on the scrap.
If the mark lands on the thing, the camera is right. If it lands next to it, the calibration is wrong and the accuracy check will tell you by how much, as one number rather than a feeling.
How to know it worked
- A light mark drawn round something on the picture lands on that thing.
- The accuracy check reports a miss you are happy with, in millimetres.
- Moving the head and looking again does not change where things appear.
When it goes wrong
4Everything lands a few millimetres out, always the same way.
The line-up is off rather than the lens. Run the alignment again; do not start nudging it by hand until you have.
It is right in the middle and wrong at the edges.
That is lens distortion, not alignment. Teach it the lens.
It was right last week.
Something moved. The camera, its bracket, or the bed height. Check the bracket screws before you calibrate again.
The calibration finishes but nothing lines up.
You may have told it the wrong kind of camera. Check whether it rides on the head or is fixed above the bed.
The tools this used
A camera lets you put a design exactly on a piece of scrap, an odd offcut, or…
Calibrate from one dotOne engraved dot is enough: the machine moves the head, watches how the dot…
Teach the app your lensEvery lens bends the picture a little, and a wide one bends it a lot.
Check camera accuracyEvery step can look right and the whole can still be off.