Milling a PCB on a cheap CNC machine

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Talkiet

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#233581 22-Apr-2018 19:40

It's not _totally_ straightforward but I think I am getting close to nailing the settings. It seems that the cheap 0.1mm cutters I am using are hugely inconsistent. I get massive differences in trace widths with the same settings from cut to cut... Grrr. Might have to look for some that cost more than 25c each!

1st - MDF to see if I had the size right
2nd - No autolevelling. With a 0.1mm depth of cut, this is a critical feature to use
3rd - Perfect quality of cut, but traces a bit thin and design not yet reversed (as it's a bottom layer)
4th - Reversed ok, traces still too thin
5th - Nice thick traces but several areas where they ran together! shorts all over the place
6th - Traces still too thin and on doublesided board so not usabe
7th - Traces too thin... Grrr, I thought I was learning
8th - with some soldered headers. Traces ok but spacing between traces and ground plane far too narrow - impossible to solder
9th - over-rode width of cutter and added a few extra passes to dramatically increase isolation of traces. Nice clean and sized traces. Good amount of room to ground plane so should work. Is doublesided so have to sand of the copper on the other side. Might try again with even more passes on a single sided board.
PHEW!!!!

Working on the 10th now but I think the traces are going to be way too thin... Just about run out of single sided blanks too!

Cheers - N

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hio77

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#2000786 22-Apr-2018 20:10

progressing atleast...

keen to see how you get on with this, hopefully you get good enough to be a good source ;)

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Talkiet

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#2000798 22-Apr-2018 21:06

I only have this size blank at the moment and the trace sizes are (in theory) about .25mm... It would be great if I could actually get them to reliably be that fat, but the bit to bit variation, and runout each time I mount a new bit are adding quite a bit to the nominal 0.1mm bit size. I'm kicking myself for not realising sooner and leaving the bit in place after I got a nice fat trace... I have been changing bits regularly to make sure I was experimenting with sharp bits.

The point is, if I had the luxury of being able to use 0.5mm traces with 0.3 spacings, this would be easy at this stage. I have 2 boards which would theoretically work and all the traces show good continuity and nothing broken, but based on macro photos with a ruler, the traces are regularly under 100 microns and that's cutting it a bit fine I would think... I have the last attempt running for tonight at the moment (actually youtube live! - https://www.youtube.com/watch?v=gNaCQZA4ZUE ) so I hope that works well. Early signs are the trace width should be Ok, I just hope the depth of cut is ok as well.

I think for big fat traces I could do it now...

Cheers - N

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Talkiet

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#2000799 22-Apr-2018 21:07

Bonus points if anyone can work out what the board is for, and what hardware is on there. :-)

Cheers - N

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dfnt

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#2000801 22-Apr-2018 21:15

An ONT for 10gbit fibre

Quic referral link https://account.quic.nz/refer/276294 free setup code R276294EBWOBK

Talkiet

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#2000802 22-Apr-2018 21:18

Heh... I can't even be bothered upgrading my 100m fibre to 'gig'... Everything is already more than fast enough.

N

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hio77

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#2000805 22-Apr-2018 21:23

Talkiet: Heh... I can't even be bothered upgrading my 100m fibre to 'gig'... Everything is already more than fast enough.

N

salt in the wound.....

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Talkiet

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#2000824 22-Apr-2018 22:33

12th time's a charm!

Everything seems to fit and traces/clearances are good. I'll probably have an early night instead of trying to solder tired :-)

Cheers - N

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hio77

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#2000830 22-Apr-2018 22:53

i'd say it looks like a nano but far too long for that...

Time to dig up my more unique shaped micros...

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Talkiet

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#2000832 22-Apr-2018 22:58

It's tiny alright, but not a Nano... it's pretty teensy for how powerful it is...

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hio77

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#2000833 22-Apr-2018 23:11

Talkiet:

It's tiny alright, but not a Nano... it's pretty teensy for how powerful it is...

N

duh. i was lining the wrong traces!

your wording takes all the fun out of guessing!

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neb

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#2002443 25-Apr-2018 17:31

Speaking of milling stuff, what are people's favourite CNC devices? I'd been drooling over the rev.2 Pocket NC, mostly because they've finally added a tool probe, but a friend of mine swears by his ShapeOko, which admittedly is a different beast from the Pocket NC. Not that I plan to get either, the Pocket is about $3-4K US and I can't even remotely justify it, but it'd be interesting to see what people are using and what their experiences are.

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Talkiet

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#2002454 25-Apr-2018 18:21

The pocket NC looks cool, but the work envelope is insanely small. I get that 5 axis is another level entirely, but it's not clear to me if it could mill aluminium at all, and in that size the use would be severely limited.

I am actually about to embark on building a much stronger CNC machine, using the one I just got as a functional template (ie. the new machine is going to be similar so I can copy all the electronics etc, while making the frame a lot stronger, and moving to a larger spindle with ER20 collet, and perhaps moving to fixed gantry and moving work surface. It will also be a bit bigger, in the order of build volume 900*900*about 400 vertical travel (I know Z travel doesn't really always mean build envelope for CNC)

I'm going to be using linear rails all round, not the round ones, so it should be very very rigid. I'm not going to be compromising on rigidity, so the entire frame will be built out of at least 16mm aluminium, perhaps 20mm, and perhaps doubled in some areas. I'll likely also fill the gantry with concrete as well.

When I get slightly further along, I'll consider if I want to build 2 instead of one - on the theory that it's probably saleable - but only for pickup in Chch!!!!!!!!!

As for your question - there was nothing around that satisfied my requirements so I got this Chinese 6040 (already built and all the bugs worked out) to learn about the process and see if it was even close enough to rigid enough for what I wanted. Ultimately it CAN work 6061, but the speeds I have to drop down to in order to get a reasonable surface finish and not have too much deflection are so low to make it not really useful. It will work well enough to make some donor parts for it's successor though.

If there was someone in Chch with good welding skills (really good, professional quality) then I would potentially be interested in collaborating. (If not, I will get everything watercut and bolt / glue together)

Cheers - N

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neb

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#2002458 25-Apr-2018 18:30

Yeah, admittedly drooling over the Pocket NC is possible for me because I don't have a fixed use for it, so anything is interesting.

Will you be posting in-progress photos as you build it? Sounds like perfect maker porn.

Talkiet

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#2002461 25-Apr-2018 18:33

I always have the best intentions of posting progress, but it's usually sporadic at best :-) I'll certainly give updates... However there's a youtube series on a New Zealander building a granite based CNC machine I can highly recommend.

https://www.youtube.com/watch?v=gUFeoDf1YvM&list=PLw9YzKPg2guwQWLkz8_BoMfvQ8Ttsq-57

Push through his kinda slow style to start with - he's very very good and there's some EXCELLENT bits of info/techniques in there.

Cheers - N

Please note all comments are from my own brain and don't necessarily represent the position or opinions of my employer, previous employers, colleagues, friends or pets.