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.

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.

 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  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.

Auto Leveler Screen Shot




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.

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