Mill Turning on the Tormach PCNC440

I just dared to hit run on my first attempt at Mill Turning.  I need to qualify this in that the first run I was cutting air above the set up.   It looked OK so I put the real material in the spindle and I got a turned part as designed in Fusion 360.   I didn’t part it off and you can see the result below.

Mill Turning set up for first trial run

Mill Turning is where you place the material you want to shape (usually a rod of some kind) in the mill spindle instead of a milling tool.   The tools are mounted on the milling table (see above in the vice) and are completely stationary but move via the actions of the table in the X axis and the spindle in Z.   The software is conned into thinking the material is really a milling tool and that the tools are the material.

It has taken me the best part of a week to work out how to model this in Fusion 360 and I have been helped enormously by watching Jason Hughes on YouTube.  It involves allocating a different Work Coordinate for the location of each tool.

If I can get this more streamlined and get some better lathe tooling in place to support it, then I will be able to turn clock pillars.   This was the last stumbling block in moving to CNC assisted clockmaking.

Tonight I am a very happy bunny.  A glass or two of Merlot with dinner perhaps ?

Update – For a full write up on the process and how I got there go to my mill turning page and download the pdf.

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Clickspring Therapy

Some days you walk into the workshop and while you know you have long term projects lurking, you just feel like having a distraction therapy day.  For me this usually means adding some tooling in some way or other.  Yesterday was one of those days.

While looking around I spotted one of my storage boxes with all the parts I had accumulated to make some table tooling grip nuts as shown by Chris at Clickspring.   These are similar to a commercial item.  As I now have a tooling plate on the Tormach with a matrix of M8 holes it seemed like a good ‘all in one day’ project and would satisfy my therapy distraction.

Chris did not give any dimensions in his write up but there is more detail in his Patreon video which is subscription only.   One gem he passed on was using a piece of 1mm thick material to offset the three jaw chuck to create an eccentricity to the locking nuts.

I have created a page detailing my approach here.

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Tormach Tooling System and a Spanner in the Works

Tormach provide a rather nice tooling system for their milling machines.   This is known as the TTS.   There is a master collet permanently fitted in the spindle.  If you have the automatic tool changer option fitted this collet is depressed by a compressed air driven ram.   This opens its jaws to allow grabbing of individual sub collets holding the tool of choice.

The great bonus of this system is that you can have all your regular (and not so regular) tools permanently mounted in collets ready to go.  Press the button driving the ram and push the next tool home.   This also means you can populate the tool table in the PathPilot CNC driver program with all the tool length offsets without having to measure each time you do a setup.

It does mean quite an investment in the sub collets.   These are available for all manner of capacities both metric and imperial either with fixed diameter grips or standard ER ranges.  There are also custom tools such as the Super Fly and Shear Hog plus fittings to take a Haimer shank.

What was always a fiddly job was mounting a new tool in a collet and trying to contra-rotate the collet tightening nut while holding the body.   This is now no more ….. I have just taken delivery of Tormach’s simple but elegant solution to this.

It is a ball race mounted in a block but a ball race that only rotates in one direction.   You simply push the collet shank into the ball race and it is gripped tight.  To loosen the collet you simply put it in from the other side.  Magic !

Now you have probably realised I am a bit OCD and like things in their place and ordered.   Having got the tool gripping sorted I would now need two spanners to fit the collets of my most popular ER16 and ER20 nuts.  That was one too many spanners for my liking and was tying up standard shop spanners (which also have their allocated place in the shop …. oh dear how sad is that).

Now I happened to have a strip of 50mm wide Ground Flat Stock sat idle and Fusion 360 was calling.  A quick drawing on Fusion delivered a customised spanner sized to suit the two most popular sizes of collet I use.    I ran the CAM and off to the 440.

I put a piece 6mm hardboard on top of my tooling plate and put a couple of M8 holes at 75mm spacing on the centre line of the stock and fastened it down through the hardboard into the tooling plate on the 440 bed.   I made sure the Z clearance was OK for the screw heads (important !) and hit go.

It was the first time I had machined GFS and the 440 handled it well.  I now have a nice customised spanner hanging on the wall above that fancy bearing block.

Disclaimer : –  This post and many others on my website feature references to Tormach and its products.  I have no connection to Tormach Inc financially, commercially or otherwise.  I acknowledge that Tormach®, Tormach Tooling System®, TTS® and PathPilot® are all registered trade marks of Tormach Inc.

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Milling Circuit Boards Update

I have made some good progress on taking a PCB design Gerber copper and Excellon drilling files into CNC.  I think it is worthy of a full write up but while that gets put together here are some comments.

First of all the conversion process using FlatCAM is very straightforward and I like the fact that you can default save your GCode startup and end routines along with other default settings.  Note that I had to scale the drilling data by a factor of 10.  Apparently this is not unusual.

The fun starts once you have code ready to run on the CNC.  The board design I was working on was a single sided copper design.  Single sided board tends to always have a curvature with the copper on the inside of the curve and the fibre glass outside (if you see what I mean).  This is probably the manufacturing process with the copper and its adhesive ‘pulling’ the board.

Double sided PCB tends not to be so bad in this respect and the effect is balanced out by the two coatings.   My board was therefore much more bowed than a double sided one.  (Incidentally FlatCAM allows for double sided board designs).

If you think about the geometry of what is going on it is critical to make sure the PCB material is flat on the milling table.   The greater the included angle of the milling cutter tip the worse things get if there are variations in surface height.  A height variation equates to a widening of the tool cut.  See the image below. (Not to scale).

I initially used 6mm MDF as my sacrificial backing board to protect my tooling table.   When I checked the MDF for flatness with my Haimer I was disappointed with the result.  Increasing the MDF to 12mm made a huge difference and good enough for the purpose.   This could have been a different manufactured MDF so the change of size is not definitive.

Initially I clamped the PCB to the MDF with a number of woodscrews around the periphery.   On checking with the Haimer this was not good with visible variations that I could impact by pressing on the PCB surface.

Next step was to replace the woodscrews with strips of 10mm square aluminium with a 1.5mm step on one edge.  These were screwed to the MDF on all 4 sides of the PCB blank and this dramatically improved the flatness to a point were it was adequate.  Pressing the board surface did not change the Haimer readings.

Flatness having been solved I addressed the cutter problem.   I had ordered some 10 degree included angle cutters from China but while they were in transit I got to talking with Think & Tinker in the US.   They were incredibly helpful and suggested that I should consider a 60 degree included angle cutter with a 5 thou tip.   They also suggested I try their lubrication to improve the cut quality and to also help protect the tool from wear.   Their tools also come with a fixed collar which means you can change out the cutter without having to reset your Z zero.

This 60 degree cutter worked a treat and the results were startlingly good.   I did not use the lubrication from T&T but instead used my normal FogBuster fluid (QualiChem ExtremeCut 250C) on a gentle repetitive puff.  This seemed to work and kept the dust damped as well as improving the cut.

While I could run the spindle at up to 10,000 RPM, I kept it down at 6,000RPM with a cutting speed of 3″ per minute (75mm).  I had a Z clearance of 0.1″ and depth of cut of 0.005″.  (Sorry for the mixed dimension standards but PCBs tend to be designed in Imperial but I prefer to work in Metric).

After the milling of the copper was complete I drilled all holes at 0.6mm (24 thou) using a carbide drill sourced from Drill Services of Horley (UK).  This was simply a change of tool, registering the tool length and loading the drilling GCode produced by FlatCAM.   The drilled holes were spot on dead centre in the copper lands.

In closing I would like to say how impressed I have been with the Tormach.   I had milled the copper one day and switched off for the night.  Next day I switched on the mill and absolute referenced XYZ and put the drilling tool in the spindle and hit go.  The holes were smack on dead centre in the lands without having to tweak anything.

It has been an interesting challenge that my friend had set me and he has gone away with a good looking PCB and my knowledge base has improved which is what it is all about.


A more detailed write up to follow.

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Another Haimer tip bites the dust or at least the mill bed

When I was at NYC CNC I saw that John was selling posters as shown below.

I didn’t realise the significance until I started doing CNC …..

I had been doing OK on breakages of late then like buses, two came along at once.  One was excusable (to my conscience) but the second was a disaster always likely to happen.

I had the Haimer held in a collet in the Myford VMB manual mill.  This means you need both hands occupied to contra rotate the collet and spindle when locking and unlocking.   I just overdid the realise pressure and the Haimer dropped out onto the mill bed.  Crunch, expletives, gloom, expense.  The tips are not cheap at GBP20+ each but Amazon do sell them.

There is the same issue to a lesser extent on the Tormach when releasing the power drawbar even though you are holding the Haimer the sudden momentum of the drop from the collet can sometimes catch you out if the mill table is close.

While discussing my gloom with a friend he suggested putting some sort of protection around the tip when loading and unloading from the spindle.   The Haimer is not an ideal shape for gripping something along these lines given its curved surfaces.  However after some thought a solution was found.   I drew a simple cylinder in Fusion that was 40mm long, 38mm OD and 32mm ID and 3D printed it.  Note these dimensions are for the Haimer FH 3D Taster version.

The cylinder sits over the probe and rests on the outer rim of the tip mounting.  The 32mm ID is just tight enough to squeeze the Haimer rubber gasket and so hold the tube in place.

Not only is this useful for mounting and dismounting the Haimer but it also works as a general protect guard when not in use.

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