A locking cam design and a spiral cam design are only similar in that they are both cams. There’s a very important difference in the geometry which makes them rather dissimilar. In order for a clamping cam not to self-loosen due to vibration, it needs to have the property that small changes in angle do not decrease the clamping pressure. For a simple point-contact cam, that means that it’s locally circular. “Locally” here is a mathematical usage; it means that the derivative of contact distance with respect to angular cam position is zero.
Therefore a spiral is non-locking everywhere, because its distance changes constantly, and a circle is locking everywhere, because its distance is constant. To make a locking cam, splice together a spiral and a circular arc. You can do this multiple times to get a cam with multiple locking positions. But you can’t make this kind of cam locking in all positions unless it’s a circle. In other words, you can’t get continuous locking positions out of a single cam.
To get continuous clamping positions, use an adjustable parallel. It’s a standard machinist’s setup tool. It’s just a pair of sliding wedges that can be fixed with respect to each other. These can be FDM printed by using an overlap joint with a fixed bolt or two on the bottom and a slot on the top. Use a threaded knob on the top to tighten. This will be taller than the work, but what’s tall is away from the edge where milling clearance really matters.