cnc milling – Page 12 – Woody's Workshop

February 15, 2018February 5, 2020

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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February 5, 2018February 19, 2018

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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January 27, 2018February 5, 2020

FlatCAM Update and experimental copper cutting

I’m quite pleased with progress converting GSpark PCB gerber files to CNC with FlatCAM. The conversion process is straightforward and the resulting GCode looks OK.

I have tried cutting copper using the cutters I have to hand but quickly realised I need to get some much finer ones in carbide. My tests with modified dental burrs does not work or at least not for very long before the burr goes blunt and the cut width degrades.

I have ordered some 10 degree included angle 0.1mm wide cutters but they won’t be here until February.

The picture shows two runs. The left hand run used 30 degree cone shaped burr and the right hand run used a modified teardrop burr. The initial cut on both was where the stars are.

The left hand cut left severe copper burrs which were easily removed using a scalpel blade flat to the surface of the board.

The right hand side was clean of all burrs but gradually degraded in quality as the cutter became blunt.

The teardrop burr was ground to half diameter in an attempt simulate a more normal engraving cutter profile. I must have drawn the temper in the grinding process.

More experimentation needed once the better cutters arrive.

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January 23, 2018February 19, 2018

Welding and being well and FlatCAM

Welding Course

Despite being laid low with flu since New Year I’ve attended two of the evening welding classes much to the contrary advice from my wife. With hindsight she was right – I should not have gone the first night such was my state of health.

The focus so far has been on MIG welding and I am slowly getting the feel of things. Too many variables to start with what with power, angle of attack, closeness to the job and of course wire feed rate.

How anyone did welding without the modern auto dimming helmets astonishes me. They are amazing.

Not much else to report given the state of health but clearly I have now started to creep back into the workshop so health and state of mind must be improving. Made a note in the diary to get a Flu Jab next year.

FlatCAM

Anyway more interesting stuff – my friend has asked if I can mill a prototype printed circuit board on the Tormach for him. My initial thoughts were to bring the design into Fusion and do the CAM there. However a conversation with a friend in Namibia lead me to FlatCAM which is a wonderful little program. It takes the Gerber files from the PCB design package and converts them to GCode. It is simple to use and produces nice code listings. It gives you options to add your own GCode initialisation strings. There are a few YouTube videos out there if you are interested.

More results to report when we have milled some copper.

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December 28, 2017February 24, 2018

Tormach PathPilot Version 2 Release – Issues with Shared Folder

I ordered my upgrade to newly released Version 2.x.x of PathPilot for my PCNC440 machine and to be honest the instructions for doing the upgrade were clear and straightforward. Care is needed as this is a complete clear out of the old version so backups needed to be taken of your GCode files and your Tool Table etc. Don’t fret however as all this is talked through quite clearly in the downloaded support document (TD10530).

The software loaded well but I then had a couple of problems.

Prior to the upgrade I had a shared folder on my desktop PC that allowed me to blob across the GCode files to the 440 machine without leaving my desk. After the upgrade this shared folder had disappeared and try as I might, refused to return. I could ping the Tormach so it was on my network but it was not being seen from a data point of view.

I eventually gave up and posted the problem with Tormach. They came back quickly with a fix as follows. This is a simple to do and assumes the ‘green light’ on the internet button (on the status PathPilot page) is lit.

When in the PathPilot working screen, press CTRL+ALT+X to bring up a terminal window. (A word of warning here …. my keyboard silicon protector overlay supplied by Tormach had legend that did not match the keys underneath …. check what you are really pressing …)
Type gedit smb.conf.share and click enter on the keyboard. This should launch the file for editing. (Note: 1 space between gedit and smb.conf.share)
Change “security = share” to “security = user”
Reboot the PathPilot controller
Open a folder mapping dialogue on your desktop PC File Explorer and map to an unused drive letter. Note the format is something like “\\tormachpcnc\gcode” but read the instructions from Tormach.

The other issue I had initially is that I could not load DropBox which is a new facility on PathPilot. As by now I had solved the shared folder issue, this was less of an issue but belt and braces called and finally it loaded OK.

Note that you must reduce the number of folders seen by DropBox on the Tormach or it will flood your memory storage space. Tormach give instructions on how to do this by listing the folders that need to be ignored. You cannot cherry pick them from a dropdown list but instead you need to paper list them and then manually enter them. Also note that any folders you are blocking that have more than a single word name format need to be encapsulated with ” ” when entered in the blocked folder list (unless you have underscored any spaces). I reduced my DropBox folders ‘seen’ on the Tormach to just one which will contain my GCode files.

DANGER – do not simply delete the DropBox folders that are not of interest in the PathPilot File screen or you will delete them permanently from the DropBox cloud storage. All your pictures of Auntie Agnes with her Sherry at Christmas will go down the tube ….

Upgrade Documents on the Tormach Site can be found here and you will need the following two documents

TD10345 Networking PathPilot

TD10530 Upgrading to PathPilot V2.x.x

I have posted this information on the NYC CNC Forum and John has also created a document in his site Library.

Good luck with the upgrade. The resulting code isn’t dramatically different but general presentation of graphics and fonts is better and the conversational programming is slightly changed.

Finally I cannot emphasise enough how responsive Tormach Tech Support are if you have an issue. Without their help I would probably still scratching my head regarding the above.

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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