What is an Autoleveler

In this context, an autoleveler is a bit of softeare that reads your G-Code file – the one output by PCB-GCode – and adds a bit of clever math to it.  To prepare “autoleveled” G-code is quite easy, just open the autoleveler, point it to the G-Code of interest, and hit “go”.  Out the other end comes your G-Code with the autoleveler magic included.

Why use an Autoleveler

Unless you have an amazing milling machine (I don’t – mine is made out of plywood.  Nice plywood, but plywood nonetheless) – you will have challenges getting the work surface perfectly flat.  How flat is ‘good enough’?  I don’t know for sure, but I do know that the best I can manually level my PCB + the natural ‘waves’ in the surface of the PCB conspire to make the milling experience very frustrating.  Some parts milled too deeply, others just a scratch in the copper, other parts nothing at all.  Remember, the copper layer on a one ounce PCB is only 1.34 mils thick (2oz = 2.68 mils).  And if you are trying to do 50 mill on center SMD pads, you will really need an autoleveler

How it works

This is really a two part process.  The “magic” code inserted into your G-Code will ‘probe’ the surface of the PC board, making a “topographical map” in memory of the variations around your Z axis 0.0 point, keeping track of the high and low points.  Here is a video of my system probing a PCB.  Probing Process.  Notice a few things:

1. I already manually leveled the PCB to within 1 or 2 thousandths of flat (still not good enough)
2. You can see a probe in the background that is connected to the “probe in” port of my milling system.  This is a mandatory part of the probing process.  This probe is a sewing pin rigged through some plastic pipe in which is a bolt for some weight to ensure good contact to the PCB.
3. I homed all axis before starting
4. I use the same tool for probing as for milling – and I don’t touch the tool between probing and milling

When probing is done, the modified G-Code uses the information from this ‘topographical map’ to make fine adjustments in your Z axis ‘on the fly’.  Here is a video of my Z-axis during milling of a trace.  You can see there is quite a bit of ‘fine tuning’ that is happening.  Probing Z axis adjust. [stextbox id=”warning” caption=”Check your probe-in wiring”]Before probing, double check that the wiring to your tool and to the probe-in of you milling machine is complete and functional.  Otherwise you could damage the tool and/or PCB.[/stextbox]

 Autoleveling Software

I have tried at least 4 or 5 different versions, and some work, some don’t.  The one I settled on is easy to use, flexible and it works.  Based on my experience I can recommend it.  I have even used it on G-Code generated from CAM-BAM for engraving brass plaques, and it worked great. The software is from www.autoleveller.co.uk/.  Older versions of the software are no charge.  Pay the man the 20 pounds for all his hard work and you get access to the latest versions (which I recommend).  The interface is very simple, easy to use and the results are spot-on.  Consult the website for more information.     NOTES FOR INCORPORATION

Lesson 2:  Set up the ‘probe in’ signal on your CNC machine 

To avoid punching holes in your PCB, you need to wire-up and configure the “Probe In” line using the StepConfig Wizard (EMC).  I already had all my inputs brought to an opto isolation board so wiring up and configuring this line took only a few minutes.  For my installation, I needed to check the “invert signal” checkbox for the Probe In line.  For the actual probe, I use the same bit I will be using to mill.  I do not move the bit at all between probing and milling, I just disconnect the wire and turn on the spindle.

Lesson 3:  Calibrate your setup.

The copper on a 1oz PCB is 35 µm or about 1.4 mils (.0014″) thick.  That isn’t much if the surface of the PCB is ‘waving around’ by 3-4 thousandths or more!  I recommend playing around with this calibration board and ‘futzing’ with your settings until you have the best results possible.