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  1. #37
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    Default Re: Which bits to use for PCB milling?

    Hi Jesper,
    I agree with Roger, 6mm is too big for your machine, its just not rigid enough to contain the cutting forces.

    I would expect surface speeds of 200-500 m/min for good , sharp carbide.

    You will have to halve that (100-250 m/min) for HSS.

    Download a demo of HSMAdvisor.

    I would be using flood cooling, it improves the cut quality. Note that Roger is very keen on MQL and his description of it suggests comparable results.

    do one of you have a link to a small CNC mill that will at least do aluminum perfectly - and also be ok/fine with steel and stainless?
    Many a small, even Chinese, can do aluminum pretty well. Steel and stainless are A WHOLE DIFFERENT GAME AGAIN. The rigidity required for steel is
    an order of magnitude better than a machine that can do aluminum.

    You may note that I have two spindles, the 24000 750W one I linked to. I had hoped that I could do steel with it as well.....WRONG!!! I had to learn the hard
    way, cutting steel requires a high torque and slower speed spindle with a very rigid machine with high levels of thrust to cause the tool to bite into the material
    and resist the counter forces.

    Ergo I made my second spindle, 6.2Nm, 3500 rpm with a ER25 toolholder and a 1.8 kW Allen Bradley AC servo. It works well. Despite my machine being all cast
    iron and steel I could wish for still more rigidity.

    Craig



  2. #38
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    Default Re: Which bits to use for PCB milling?

    Hi Roger ...

    & many thanks for your feedback. It is indeed helpful to get some experienced "eyes" to take a look and make suggestions

    >> I suspect that the 6mm cutter may be too big for your router. Especially on the RH cut. << ... RH means "right horisontal"... ? ... About the cutter: Would you say that a 4mm cutter would be more suitable?

    >> I suspect that you need some lubricant on the cutter. If all else fails, try some WD-40, or even SAE-30 oil. << I have some motor oil for my car which I can see is SAE-30. Will try this.

    >> I also suspect you need sharper (and new) cutters optimised for aluminium. Chinese carbide is not always 'sharp'. << ... As it is I will be cutting both aluminum & copper but from speaking with a cutting tool manufacturer here in Denmark I understand that the same cutters can be used for both materials. Apparently they pose similar challenges to the cutter ... Would something like this cutter be appropriate:

    End-mills 2-flute Short 1.5D - OSG WXL 1.5D - End mills, Drills - FrezyCNC.eu .... There's a 4mm, 6mm shank cutter a bit down the page.

    BTW I like your saying "I suspect" ... I would say it is a subtle & diplomatic way of trying to diagnose something from the other side of the world

    Cheers,

    Jesper

    P.S.: There's a CNC workshop not too long from where I live (25 kms - far in Denmark but I reckon just around the corner in Australia ... ) and he has offered to buy tools for me. I will ask him tomorrow if he has a suggestion/a cutter that I can buy from him (4mm?) ...



  3. #39
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    Default Re: Which bits to use for PCB milling?

    Hi,
    those OSG tools are expensive, OSG is good but those prices are over the top.

    Try drillman1....much better value and nothing shabby about Kyocera Tycom:
    https://www.ebay.com/str/CARBIDE-PLU...p2047675.l2563

    Craig



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    Default Re: Which bits to use for PCB milling?

    Hi Jesper,
    just saw this, NSK is very good:

    High speed spindle with controller unit

    Craig



  5. #41
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    Default Re: Which bits to use for PCB milling?

    Hi again,

    & thanks again for your feedbacks.

    @Craig: As it is I have been looking at drillman1 previously when you first mentioned this vendor as a good source of tools. And I would really like to buy from him.

    The issue, however, is that living in Denmark we pay a 25% tax on the goods cost AND shipping costs when we buy something outside of the EU market having a value of more than USD 12. AND we pay an additional USD 25 handling fee for having the state handling these taxes. I don't mind paying the taxes but I do have a quibble paying USD 25 for tax handling every time I buy something that price-wise is in the "vicinity" of USD12.

    Thus I prefer finding EU market vendors for items that have costs in the USD 12 - USD 150 region so as to not pay the handling fee for lower value things. Not to mention that shipping time from the US or Asia to Denmark is long - and adding to this the tax department's handling time which is also a couple of days. All in all the most feasible place to buy tool parts would be either Denmark or Germany.

    When you originally suggested Kyocera-Tycom I did a search on the internet for a vendor within the EU but I didn't find any. It appears that most of the KT sales are in the US - if the search results can be taken as a guide for this.

    >> High speed spindle with controller unit << ... This could be interesting but I have to narrow my focus also money-wise as my main area is audio electronics - which in itself can be quite a costly affair. So in a first round I hope to make the machine I have bought work just quite fair for prototypes and small production ... or use it to make another CNC mill/router. Will have to ponder this over the next weeks.

    I have also been thinking about your TO-247 PCB milling: Unless you use very high voltages in your system I don't see why you need to consider arcing from a practical point of view ... There may of course be something that I do not know about (and there undoubtedly is!) but arcing typically is an issue at high voltages and high humidity. Just wondering

    @Roger & Craig: I have been thinking about the lubricant or fluid cooling and I would much prefer to not use any oils or the like. As it is I am sort of a "start-up" and I work from my home ... Thus using oils may spray out on the walls - or elsewhere - something I'd like to avoid. I found this video yesterday on youtube showing how to mill in steel with a router resembling mine: The person here has enclosed the water on the steel surface with something white (silicone?) - a process that would be feasible for me.



    @Craig: Do you think this would be beneficial for normal copper/aluminum work with bigger sized end mills (3 - 4mms) like e.g. face milling?

    And now, completing this post, I'd like to say again that I really do appreciate the feedback you have given ;-)

    Cheers,

    Jesper



  6. #42
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    Default Re: Which bits to use for PCB milling?

    Your taxation system is simply obscene.

    Cheers
    Roger



  7. #43
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    Default Re: Which bits to use for PCB milling?

    >> Your taxation system is simply obscene. Cheers Roger <<

    Well, no doubt there are many views on this ... Overall I find it to have many positive aspects as well (Denmark is considered the country in the world where people are happiest) but in this case charging USD 25 to potentially handle taxes on goods worth USD 12 is less "feasible" to me.

    And then just a P.S. to Craig: I have already downloaded G-wizard which I am trying to acquaint myself with.

    Have a good day,

    Jesper



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    Default Re: Which bits to use for PCB milling?

    Quote Originally Posted by evalon View Post

    Also - just out of curiosity - and if it's interesting to you! - do one of you have a link to a small CNC mill that will at least do aluminum perfectly

    Jesper
    Hej Jesper,

    "Perfectly" is difficult to define...

    I have a small CNC and it does mill aluminium with very satisfying results, better than what I expected when I built it. Mine is a moving table type, so the gantry is fixed, which increases the rigidity and that is good for a CNC. I have a hobby room inside my house, in the living area, so I don't use any chemicals or cooling. My spindle is a 1.5kW air cooled one with ER11 collet. Normally I am using 4 flute 4 and 6mm cutters which I am buying from Jula. I am very happy with those, and those are actually pretty cheap as well. There are different schools for milling aluminium, some claim that 2 flute is the way to go, but for me 4-flute works best. I think the secret is to find your optimal speeds, which depends not only on feed and speed calculations, but also on your machine. No point pushing the cutters too hard because that will only cause problems, on the other hand, if you feed too slow it will result in rubbing and far too much heat and melting/welding.

    Here is a short video where I am milling aluminium:



    I have never tried steel and probably never will.

    [url]https://adapting-camera.blogspot.com[/url]
    [url]https://www.youtube.com/c/AdaptingCamera/videos[/url]


  9. #45
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    Default Re: Which bits to use for PCB milling?

    Hi Jesper,
    if you want to mill heavy copper PCBs then you will need small diameter endmills. I have found no European supplier that can even get close to
    to drillman1 and I assure you I have looked and looked repeatedly, you can get small endmills in the EU but very expensive, even more expensive
    than your tax burden.
    If you buy $100-$200 at a time and the $25 fee doesn't look so bad.

    If you want to try steel get a 3mm endmill, spin in at 6000rpm and have a go. You will need coolant or it will smoke up in 30 seconds. Routers such
    as your Kress have very low torque, especially at low revs and then they are inclined to stall and thereafter unless you are quick on the Estop you will
    snap the tool. This is exactly what happened to me. I did get some results but it cost quite a few tools to do it. That's why I spent $2000 making a new
    spindle, you don't think I would do that unless I had to?

    By all means try machining steel, it may work OK, then again it may not, you may encounter the same problems I had.

    If you read Rogers description of MQL then you will see that he used kerosene and olive oil and in such small amounts that it doesn't pollute your work space.
    You can cut dry, try it, it may work OK for you. I've found that flood cooling improves the cut quality and tool life that much that I can't do without it irrespective
    of the extra complication.

    Try HSMAdvisor.

    Craig



  10. #46
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    Default Re: Which bits to use for PCB milling?

    Hi,

    Unless you use very high voltages in your system I don't see why you need to consider arcing from a practical point of view
    Wrong! I work with inverter welders day and day out. Typically DC Link voltages from 320VDC to 400VDC for PFC boost single phase machines
    ant 585VDC and up to 800VDC for PFC boost three phase machines. If you are not concerned about flashover think again, it happens.

    My servo drive will have, to start with, a 320VDC DC link but when I start trying to get its maximum output, 2.65kW, I'll need to go to a PFC boost
    arrangement of 400VDC otherwise I will blow supply fuses all the while.

    Craig.



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    Default Re: Which bits to use for PCB milling?

    Hi both .. Just a brief reply as the evening is closing in ...

    @A_Camera: Thanks for posting & linking to your video. IMHO it looks quite good the aluminum you have milled. I also took a look at your youtube video list and noticed the difference between your Z-axis spindle assembly #1 and #2. And I guess that a major part of my issues are related to a Z-axis spindle that is neither sufficiently rigid nor has the weight in the right places (and maybe the router motor). Regarding your link to Jula I couldn't sign up as it appears that one has to be from Sweden - right? When signing up there is no option for other countries ...

    @Craig: ...

    if you want to mill heavy copper PCBs then you will need small diameter endmills.
    The thing is that as far as I can see drillman1 doesn't have endmills going down to 0.2 or 0.25 mms. And for now I think I also have to consider what I apparently need to be able to reliably - i.e. not an excess of wasted tools - mill PCBs at the sizes that are relevant to me. Reading your posts it looks as if it could be a quite expensive and time-consuming affair. So time to ponder ...

    Wrong! I work with inverter welders day and day out. Typically DC Link voltages from 320VDC to 400VDC for PFC boost single phase machines
    ant 585VDC and up to 800VDC for PFC boost three phase machines. If you are not concerned about flashover think again, it happens.
    Ok, fine. As I wrote in my post there may of course be something that I do not know about in this field - my main reason for posting the above was that I was thinking that if you didn't know then maybe I could contribute a bit here. But apparently not.

    I will see if I can find a link to Roger's MQL method ... And also take another look at HSMAdvisor.

    But I must admit that I look forward to a bit of weekend. It has been a week with many new inputs so my mind looks forward to some rest

    Best wishes from over here,

    Jesper



  12. #48
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    Default Re: Which bits to use for PCB milling?

    If you want really narrow gaps between traces it is customary to use a V-bit cutter rather than a 0.25 mm cutter.
    How well they would work with the really thick copper layer you are talking about is another Q, but you can get small-angle V-bit cutters.

    A web site to really take a long look at is Precise Bits at https://precisebits.com/ These people really do have the goods for this sort of thing - but not cheap.

    Those import taxes are incredible. Do they charge similar amounts on gifts sent to you?

    Cheers
    Roger



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Which bits to use for PCB milling?

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Which bits to use for PCB milling?