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Understanding alignment

When printing on a board with existing features, alignment is key to ensuring your materials are dispensed right where they should.

In this article, we will explain the goals of alignment: what it does, what it doesn't do, and how we try to optimize it as a tool for printing.

Core Principles

There are things the alignment process does and things that it does not do.

The alignment process does:

  1. Detect the position of the substrate. It will move the circuit to the correct XY position.
  2. Detect the rotation of the substrate. It will rotate the circuit to match the physical orientation of the substrate.

The alignment process does not:

  1. Detect or adjust the scale / size of the circuit

How it works

The first thing to know about alignment is that it's all based on the measurement of two alignment points. The software will automatically pick two points for you, but you can choose new points by clicking on other circuit features. For this example though we will use the default points selected by our software.

The first of these points is the anchor. You will see it at the brighter of two points selected when the gerber is loaded.

alignment1

The anchor (or pivot) is the point at which the circuit will rotate around. This initial point has a fixed XY position and does not ever move.

The second point is what we use to determine the rotation of the circuit. So in the example below you can see a green circle illustrating all possible locations where the circuit could end up based on where you drop the probe for the second point.

rotation-gif

As the XY position is coupled with rotation, you do not need to worry about physically positioning your board on the V-One to match what is shown in the software.

If the software loads the file in an orientation that does not match your board (i.e - 90 degrees rotated), the software will rotate and position the circuit correctly as long as you measure the appropriate points during the alignment process.

The software can rotate the circuit to any postion and rotation as long as it stays within the printable area

Gaming the system

Since we don't scale the circuit or change the anchor position, you may ask, "What happens if I drop the probe somewhere other than that circle around the anchor?" This leads us to a slightly more in-depth look at how we actually do the math.

When the circuit is loaded in the software, the relative position between the two points are found. Once the anchor point is probed, it now also has a fixed XY value. From here we'll take whichever point you probe and draw a line back to the anchor. Wherever that line intersects the green circle is where your second point is assumed to be.

alignment-2

In the above example you can see what would happen if you drop the probe on points where the second feature couldn't possibly fall (colored Xs) and the corresponding point where the feature is placed (matching dot).