Tormach MicroArc and Fusion 360 and 4th Axis

Tormach MicroArc 4th Axis Arrives

At last a 4th axis drive for the Tormach PCNC440 ! 

tormach microarc 4th axis

I have waited 4 years for this to be available and did not hesitate to put in my order to Tormach for one of the new MicroArc drives.  Probably the best way to get a good idea of this product is to watch John Saunders’ video.

The MicroArc wasn’t a low cost buy and because 4th axis was not around when my 440 was originally shipped, I needed a fitting upgrade kit as part of the order.   Having placed my order with Tormach it took exactly 7 days for DHL to arrive on my doorstep with the shipment.  Quite amazing considering the difficult times we are experiencing at the moment.

It took me about one hour to fit the new stepper driver and additional wiring.  As ever there were good clear instructions from Tormach.   I switched on the 440, enabled the 4th axis in PathPilot and I could control the A axis from the PathPilot screen.   Very impressed.

I watched John Saunders video on the MicroArc and how to do 4th axis programming in Fusion 360.  I drew up a simple model in Fusion but could not get it to produce working GCode.  I had some comms with John and he gave me some pointers.   The model had a rotational repeat pattern but while I could run a single op code, if I tried to run the rotational pattern the post processor came up with an error message and would not output any code.

I thought at first it was because I was only using a Fusion hobbyist licence and that 4th axis maybe was not possible.   A really helpful dialogue with Shannon McGarry at Fusion cleared up that issue so it must be something else.

After some experimenting I discovered that you have to set the axis of rotation in the post processor dialogue options list.   All then worked fine. 

We are up and running on 4th axis !

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Making a Brocot Escape Wheel using Fusion 360 and Tormach PCNC440 CNC milling machine

A Steep Learning Curve

My wife has presented me with a sign that has just got JSN written on it.  It is to remind me when I answer the phone to a ‘can you just do’ enquiry…… to Just Say No.

I try my best to live up to her expectations but sometimes something comes along that should really be a JSN job but which scratches an itch.   You know what I mean.   You think about it and you do all the right mental arithmetic in your head and the answer keeps coming back to the same – don’t even think about it.  But the the other side of my brain is screaming at me … what a challenge, what a learning experience, what fun to have a go at it.   Providing the asking party is aware of your thought process or lack of it and accepts that it might just go belly up and never come to fruition then why not ?

Back to the story – 10 days or so ago I had a call from David Pawley who is a turret clock expert extraordinaire to say someone he knew was after an escape wheel for a turret clock and was desperate.   David passed on the details and a couple of days later the potential customer arrived on our driveway.  After a suitably socially distant conversation and a rubber gloves inspection of the old damaged wheel …. I got sucked in and turned the JSN sign over to face the wall.

Brocot 30 tooth escape wheel
The original Brocot 30 tooth escape wheel that needed a new one making

As you can see it is not an ordinary escape wheel and I had to delve into one of my favourite books ‘Wheel and Pinion Cutting in Horology’ by J Malcolm Wild FBHI in order to learn about Brocot Escape wheels.   Malcolm is a great guy and his book should be on any clock experimenters bookcase.

The Brocot is no ordinary escape wheel.   In fact it is a real challenge.   Not a simple fly cutter job.  Traditionally it would be cut in an indexing device such as a lathe with two different cutters, one for the curve and one for the notch.  I didn’t have these so I thought I would probably upset the traditionalists and try to use CNC.

Read all about the adventure and see the result in this pdf download …….

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Experiences and understanding FlatCAM PCB milling program

FlatCAM Write Up – Experiences and Procedures

After a lot of editing I think the attached document will give an in depth understanding of how to use FlatCAM based on Version 8.5.   The document is based on our experiences and a steep learning curve.  We now have a repeatable process for milling PCBs from Gerber and Excellon files exported from a PCB design package.

The document may well have mistakes and we would appreciate feedback good or bad.

How to use FlatCAM document download

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Supply, IC2 and USB connections over CAT5 connection

CAT5 Breakout Board

One of our group of ‘silver experimenters’ is building an Arduino based celestial camera tracker.   This will be deployed in the garden and he needed all control to be routed back inside the house.   The garden installation consists of a USB webcam mounted on a servo controlled platform all powered by 12V DC.

We pondered long on how we might remotely connect to the garden.  The crucial thought was that the Arduino servo board was a two wire interface using the I2C format data exchange.   Given that the USB needed four wires and the DC supply two wires we had a need for an eight core cable connection.  It seemed like a length of CAT5 cable would do the job and we could elegantly use standard CAT5 sockets.

The PCB was designed in Design Spark and milled on the Tormach PCNC440 using FlatCAM.

There is a problem with running USB over more than 5m but I did some tests at 10m and all seemed fine which should be adequate for the application.   

The breakout boards had a male and female USB connector fitted and the connections had to ‘cross over’ on one of the breakout boards to maintain continuity.   We also paired the Data + and Data – connections with the +5 and Ground twisted pairs in the CAT5 so the Data + and Data – were not twinned together.

Nothing technically magic but a simple solution to a project need.

CAT5 breakout board for USB, I2C and DC supply
CAT5 breakout boards for USB, I2C and DC supply

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Arc and Circle I and J code calculator for GCode cutting paths

I & J Arc Code Calculator (with updated spreadsheet)

I had a need to hard code a circular PCB cut out CNC code that would cut four arcs around a milled PCB and leave four breakout tabs to retain the board in place in the blank until the job was finished.

To create I & J codes you need to know the start point, end point and radius of the arc.   The end point becomes the X and Y.  The  delta X and Y location relative to the radius centre point X and Y becomes the I and J values.   You can also add a depth of cut value for Z as part of the block.  Note that the Arc is assumed to run anticlockwise when using a G3 code running from start point to finish point.   Use G2 if you want a clockwise motion.   The principle is the same with both rotations.

You end up with a block code of the format G3 (G2) Xa Yb Zc Id Je where a,b,c,d,e are the coordinate values.  I found that working with positive and negative values when trying to find the I and J values relative to the centre was hurting my brain.   A spreadsheet was needed …..

Screen shot of I and J calculator spreadsheet
Screen shot of I and J calculator spreadsheet for G2 and G3 coding with examples based on CW and ACW arcs around quarters of a circle with small gaps between each arc.


You can download the sheet as a ZIP file from the link below.

Arc and Circle Calculation Sheet for GCode

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