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Member postings for Steve Withnell

Here is a list of all the postings Steve Withnell has made in our forums. Click on a thread name to jump to the thread.

Thread: Feeds and Speeds! 0.4mm milling cutters...
05/06/2019 17:58:44
Posted by Joseph Noci 1 on 31/05/2019 20:19:00:
Posted by Steve Withnell on 31/05/2019 18:08:53:

Looks fantastic Joseph!

One other poster had a strong recommend for 60 deg cutters - sounds like you are at the other end of the range with 10 deg cutters?

The PCB I'm looking to cut is pretty exotic stuff - RT6035HTC. As you say, the cladding is 35um.

What I've just discovered is the substrate is ceramic loaded with PTFE! Ceramic doesn't sound good at all, but worth a try. Otherwise its going to have to be back to chemi-etch which I really want to avoid.

The board is for a 300Watt 2.4GHz amplifier (think solid state microwave) so needs excellent heat tolerance hence the ceramic.

Steve

Hi Steve. I am not really advocating specific included cutter angles at all - My approach is to use the largest angle possible, in keeping with the complexity of the board to be engraved. If your flavour is 0.1" pin spacing with one track between pins, then a 45deg cutter will do fine. The advantage of wider angle cutters is the robustness of the tip improves, and wear is less. Control over width of engraving does suffer though. A 45deg cutter will cut a much wider groove for smaller depth increase than will a 10 degree cutter. So a lot depends on how well you can control cutting depth, how rigid the machine is, etc. A floating head controls depth just fine, assuming a good vacuum system for chip removal so that the float rides on clean BURR FREE (!) PCB.

RT6035HTC is a Rogers laminate. It is still quite flexible, ie, it is not like a ceramic kitchen tile....The ceramic is added not really to increase heat resistance but to increase the dielectric constant, so that strip-line lengths are reduced, ie, wavelength of RF propagation reduces, so stripline dimension reduce ( Wavelength = Wavelength in free space / Sq Root of the dielectric constant). PTFE already has a constant around 4 ( effectively halving the propagation wavelength)or so, and the ceramic can take this up to 7 or 8 quite easily.

Engraving this material is in fact a lot easier than normal FR4...The laminate is not glass hard as the ceramic powder is embedded in PTFE, so the cutter penetrates and cuts quite easily - easier than in fibreglass. The problem with RF circuits on this type of laminate is that you normally remove large areas of copper, ie, it is not just track isolation as in normal digital or analogue circuitry. Striplines that form the inductors and capacitors in uWave RF PCB circuitry have very critical dimension tolerances and proximity to other conducting surfaces, worsening with increase in frequency..

And removing large copper areas on a laminate with even a 90deg cutter is tedious as best...You would need to use carbide flat end mills for that, and depth control is critical if you wish to maintain your stripline size computations...

One of my Career Lives was in uWave RF design - up to 76GHz, so experience has burnt many of my fingers...

regards

Joe.

PS - I presume this is for a radio Amateur application? 300 watts in the 2.4GHz ISM band may otherwise land you in none-to-tepid water...

Interesting! Yes it is for an Amateur Radio application - Oscar 100 satellite. Not me by the way, just enjoy building the stuff. I managed to finish a 2.4Ghz filter to sit in front of the PA which looks like it is proving close on 50dB suppression of the mixer signal whilst the insertion loss is c0.5dB at the centre frequency.

I've been playing with FR4 and with a brand new 5mm carbide cutter, the large areas skim off really nicely. I've experimented with 2mm, 1mm and 0.5mm milling cutters and getting good results. The is no requirement for 0.1inch matrix for this board. My 'customer' has simplified the PCB design, so I might get away with 1mm cutter for the edge of the tracks and a 5mm cutter to remove the waste areas.

Given 5G is targeting 76GHz then there will be plenty of work to keep you busy! Lancaster Uni have developed some backhaul radio systems at 94GHz. for 5G, so lots of interesting stuff going on.

Regards

Steve

31/05/2019 18:08:53

Looks fantastic Joseph!

One other poster had a strong recommend for 60 deg cutters - sounds like you are at the other end of the range with 10 deg cutters?

The PCB I'm looking to cut is pretty exotic stuff - RT6035HTC. As you say, the cladding is 35um.

What I've just discovered is the substrate is ceramic loaded with PTFE! Ceramic doesn't sound good at all, but worth a try. Otherwise its going to have to be back to chemi-etch which I really want to avoid.

The board is for a 300Watt 2.4GHz amplifier (think solid state microwave) so needs excellent heat tolerance hence the ceramic.

Steve

Thread: ST Governor
31/05/2019 17:58:29
Posted by Philip Burley on 31/05/2019 16:08:06:

I have been making up a ST governor for a ST beam engine . The spring like belt supplied is far too long , Has anyone else found this ? or what else can be used as a belt ?

regards Phil

I have one of those belts, but never used it. I've assumed it joins just like a Meccano belt where one end is a tight spiral that you 'screw' into the open end. It must be joined in some way?

Steve

Thread: Feeds and Speeds! 0.4mm milling cutters...
30/05/2019 21:18:21

Well I got that one wrong - turns out they are not cutters but drills! So I do need to look at getting some engraving cutters...

I'll also take a look at ramping, I've seen the function in the CUT2D screens but not tried it out yet.

Next stop Woody's Workshop!

Regards

Steve

29/05/2019 19:12:59

I've just bought some 0.4mm milling cutters, to try to cut some isolation tracks in a PCB. Now I know 0.4mm is pretty small, but cutter in hand, it's scary small.

Max spindle speed is 7000rpm - so given I use a 0.04mm depth of cut - any views on what the maximum cutting speed should be? My calculator says 50mm per minute, but these things look like they will shatter with a hard stare!

I know 7000rpm is way short for a cutter of that diameter, but I need to work with what I have.

The other question would be plunge rates - not only for the 0.4mm cutter, but any cutter. It's something I've never worried about with a manual machine, but no 'feel' with a little CNC means I do need to think about it now.

Regards

Steve

Thread: MACH 3 Display Question
18/05/2019 21:00:57
Posted by JasonB on 24/04/2019 09:08:39:

Did you get your touch screen up and running Steve?

I did use Cut2D for the first few test items but have not used it for any actual parts. agree it is quite easy to get the hang of but I have not found F360 CAM any harder to pick up and that is what I'm using now. As it imports a STEP file you get heights which you don't when using a DXF in Cut2D and no need to join all those vectors together.

HI Jason,

Got too absorbed with the KX1 You are right, the 16:9 ratio screen works well, but using a 23 inch monitor I already had. The Mach3 screens are properly proportioned and there is plenty of room for the Jog flyout. I've a bit of sorting out to do then I will move onto a touch screen.

I've cut quite a few things using CUT2D, I've just cut some holes in a case and have screws in different planes interfering , which wasn't obvious until I machined them! So I could do with a package which will show all features before generating the toolpaths.

The KX1 is really sweet, wish I'd got one years ago! A few trivial bugs the max spindle speed was set at 5,000 rpm, which I've now reset to 7,000 rpm as per spec.

One thing I'm not comfortable with yet is working out plunge rates and suspect I'm being a bit too gentle!

Regards

Steve

24/04/2019 08:27:25
Posted by William Orr on 31/03/2019 17:58:51:

I am a complete Novice at CNC machining

my set up is Mac 3 and a 3axis mill

dedicated PC with screen Off line

anyone near me willing to show me how to work it??

between Salisbury and Southampton

i am conversant with machining teqniques as I am a time served toolmaker just not up with CNC

William

 

 

Hi William,

 

I've just started out on this journey. I'm using Vectric Cut2D as an easy way to generate G code for Mach 3 and it's by far the easiest piece of CAD/CAM software I've tried so far.

 

Steve

Edited By Steve Withnell on 24/04/2019 08:27:59

Thread: Making Holes in Copper Sheet
19/04/2019 13:18:03

Thanks folks. I've so much going on I'd forgotten I had a set of step drills, if they won't go all the way, I can use a boring bar to get to a push fit with the pipe. The pipe is very short (it's not a plumbing job) around 20mm and needs to be a precise fit, which is why I thought about teasing out to size with a boring bar.

Will report back...

Steve

19/04/2019 09:43:28

I need to make two holes in copper sheet, nominally 22mm. Nominally, because I want the hole to be a push fit for a selected piece of 22mm copper waterpipe.

One sheet is 1.5mm thick and 55mm diameter overall and the other 3mm thick and 105mm diameter. (If you read the same magazine that I do, you will know what this is for )

My plan was to sandwich each sheet between two pieces of 18mm ply and clamp it down onto the mill table, then drill out to 19mm. Then use a boring tool to creep up to the push fit diameter.

The questions - is this the best way of achieving the goal? What do I need to manage to ensure a nice clean hole and what spindle speed should I run the boring tool at?

Many thanks in advance

Steve

Thread: Using a propane cylinder for partable compressed air.
05/04/2019 14:03:35

As a practical question, just how much useful air can you store? Gas bottles are filled with say propane in its liquid state which vaporises as the pressure is released from the bottle. This allows for a huge volume of gas to be available from quite a small cylinder. Compressed air - the receiver on my 1.5HP compressor doesn't store enough enough for any useful purpose (even running my Victoria or spraying it, the pump is forever kicking in). Amateur mistake, I should have bought a bigger one...

Steve

Thread: MACH 3 Display Question
30/03/2019 08:33:40

Cheers Jason.

Steve

Thread: WT2527 15cc Glow Engine
29/03/2019 14:59:18

Lovely job Craig. Thanks for sharing the photo's, there is a lot of effort required to keep on top of the photo's whilst trying to produce a quality set of parts, which can be tough enough!

Regards

Steve

Thread: MACH 3 Display Question
29/03/2019 14:46:39

Thanks John. I'm just setting up a WinXP SP3 workstation and I've found a couple of touchscreens I've found have XP support, one is 4:3 and a couple are 16:9, So just interested to know what aspect ratio Mach3 is designed for.

The 4:3 one I found is meant to be used as a PoS terminal, so might be more rugged than the standard desktop screen.

I have run Mach3 demo version on my laptop, but the aspect ratio looked a bit off, which is why I thought the native design was for 4:3.

Best regards

Steve

29/03/2019 10:36:55

I'm looking to buy a new touch screen as my Mach 3 control panel (I don't have Mach 3 to play with yet). Do 16:9 or 4:3 aspect ratio screens work best?

Like many of us, I don't have acres of space so thinking a 12 or 15" panel is enough...

I'll be using the locked down version of Mach3 as provided by ArcEurotrade.

Best regards

Steve

Thread: Where have all the Mondeo's gone
08/04/2018 21:06:28
Posted by SillyOldDuffer on 08/04/2018 20:25:12:
Posted by KWIL on 08/04/2018 14:51:28:

False status.

My dad's job once involved sharing an office with a succession of interesting characters en-route to new challenges. One of these chaps answered an ad in the local paper for a second-hand car and was invited round to take a look.

When he got to the address, it turned out to be a minor stately home in large grounds near Bath, where he met the owner - one Arnold Weinstock. Remember him? His obituary describes him as Britain's premier post second world war industrialist. At the time he was making huge profits with GEC.

What car was the super-rich industrial magnate selling in the local rag? He drove a very ordinary Ford Cortina.

Dave

And he only had one house - how times change!

Thread: Help choosing a smartphone
01/03/2018 11:30:22
Posted by Otley on 27/02/2018 11:51:45:

I’m looking for advice on how to proceed from anyone of a similar outlook to myself. What physical size phone have others gone with? 16Gb or 32Gb or more – or less? SIM only or pay as you go? How much to spend? Etc. Any advice welcomed!

Thank you.

Just been through this myself. I've seperated the problem into two parts - the phone and the service contract. Three are charging me £12 a month for 12GB of data + unlimited text and calls. So stopped using the house phone for outbound calls. See how much you spend on outbound calls to get the overall cost difference. I 've had the phone for a couple months or so and no matter how hard I use the phone, I haven't managed to use 5GB in a month, so 12GB is equivalent to "unlimited" in my case!

Next problem is then the phone itself. Samsung are fantastic phones, my wife has had them for along time. However, the latest Samsung is £750!!! Not happening. We now have three different Motorola phones in the family and all are good. They are built by Lenovo who have a good reputation. Two of the three were bought as special offers from Carphone Warehouse, service is great and they are easy to deal with. The third was bought from an online outfit offering the phone Moto X4 as the sharpest price, but rapidly turned into a nightmare which took weeks to sort out.

Reading your post, sounds like the X4 (with its 3 cameras and all metal case) is too big and heavy - albeit fantastic value for money. Take a look at a Motorola G5Plus, still big but lighter and it will give you a starting point. It's the right sort of processor and memory capacity to provide at least say 3 years usage before obsolence kills it.

https://www.carphonewarehouse.com/motorola/moto-g5-plus.html#!colour=grey&capacity=32GB&dealType=sf

Whatever phone you go for, do check/challenge the processor as this will determine longevity and the satisfaction you get from using it. Just like driving an underpowered car is a constant source of frustration.


Not having had my own smartphone before, I've been amazed at the huge volume of free and useful applications in the playstore.

Steve

Thread: When is 9mm not 9mm?
04/01/2018 17:46:39

Another combination to watch for is 1/4" and 6mm in brass and copper round bars. The last two suppliers I've used off eBay don't differentiate between the two sizes...When I asked why they had shipped 1/4inch instead of 6mm, it was because they had 1/4inch in stock...

Thread: Private Messages
02/01/2018 18:36:29

Mystery solved! I thought my account had been hacked when all these PM's started turning up...

Happy New Year!

Steve

Thread: Myford ML10 headstock bearing play
01/01/2018 10:15:04

The runout on my first lathe was nearly 0.1" and would still make perfectly good parts! Really bad runout will still deliver round parts From a novice point of view (which I will always be at this game), knowing how your machines perform is more important than seeking perfection (which you will never achieve) in them.

Don't buy a collet chuck to make the runout go away - most turned parts are produced in either a 3 or 4 jaw chuck with only a few specialist jobs needing a collet chuck. I have all three - but 75% of jobs are done in the three jaw. 20% are maybe done in the 4-Jaw. A few are done on the face plate. Doesn't leave a lot of jobs that NEED a collet chuck.

I'm definitely with Jim and Hopper on this one.

A more important check might be to see if it is actually turning parallel, rather than taper and work on reducing any taper. This is easy to do - just stick 100mm of 25mm steel bar in the chuck and take a light skim over it's length and see it the start and end diameters are the same. If not - someone in the group who knows the ML10 better than me will advise next steps!

Happy New Year

Steve

Thread: Using a fly cutter
30/12/2017 13:20:33

My first lesson using a flycutter was that the typical ones sold on eBay don't have anywhere near enough rigidity or mass for anything only the lightest of work. I 'made' one one by bolting 25mm square bar (with a piece of 10mm silver steel as a cutter) to the 250mm face plate on my lathe and used that to face off some large chunks off ally. I don't think the finish would have been as good on the mill.

Regards

Steve

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