1. #1
    Hi Guys.

    So i am new to the whole CNC thing.

    Over the past few weeks i have purchased a whole load of bits from eBay to get me going.
    I have a range of bits with 2 flutes and 4 flutes in various lengths. So far all have been end mill with a few that are Vcarve 60degrees.

    Depending on the materials, these are the parameters:
    Feed: I have slowed the machine right down to between 5mm/sec to 20mm/sec.
    RPM: Using a Kress settings 1-6 (6k - 25k)
    I know for the different materials you need to cut at different RPM's and different feed rates.
    Clamping: Using Clamps to hold down in addition to double sided sign tape.
    Passes: I know to make less work on Lucy machine i am doing multiple passes on most materials, only cutting a max of up-to 3mm a time.

    I aim to mainly cut:
    Foam board (upto 19mm)
    Dibond (probably upto 5mm)
    Acrylic (Upto 12mm)
    MDF (upto 12mm)
    Other woods (uknown as yet).

    I have been having quite a few issues with my machine over the past week (call it teething problems). I know initially i was feeding too high, which i have knocked right back.

    1. Acrylic / Dibond Rough edges
    2. Head jumping and losing steps
    3. The Z axis 'appears' to slip down.
    5. The cut going off track
    6. Missing steps.
    7. Acrylic melting the cuts together.

    So i have some questions which may help the situation:
    1. Do the number of flutes matter?
    2. Does the quality of bit make a big difference (most currently from chin probably).
    3. Are there recommended rules of thumb rates for feed / rpm. I know there are really complex calculators for them.
    4. Anything else that may help?

    Thanks in advance.

    ---------------------------------------------
    Machine stats:
    Just as a reminder,
    I have a 1m x 1m,
    Dimension: 3 + 1 (mirrored)
    Drive type: Belt
    X / y Axis frame: 20x80mm V Slot
    Last edited by CrazeUK; 10-03-2017 at 04:42 AM.

  2. #2
    Best cutters for acrylic are single flute cutters or 2 flute at most. 4 flute cutters would need high feed rates but suffer from clearing the chips hence melting the cuts back together.

    Can't remember what your machine looks like, so can't comment on the jumping/slipping/going off track probkems. Post a pic of it? Feed rates are subjective and dependant on your machine. I could tell you what I use for MDF but it wouldn't be much help as my machine is probably different from yours....

    Sent from my HUAWEI VNS-L31 using Tapatalk
    Neil...

    Build log...here

  3. #3
    Quote Originally Posted by njhussey View Post
    Best cutters for acrylic are single flute cutters or 2 flute at most. 4 flute cutters would need high feed rates but suffer from clearing the chips hence melting the cuts back together.

    Can't remember what your machine looks like, so can't comment on the jumping/slipping/going off track probkems. Post a pic of it? Feed rates are subjective and dependant on your machine. I could tell you what I use for MDF but it wouldn't be much help as my machine is probably different from yours....

    Sent from my HUAWEI VNS-L31 using Tapatalk
    Hey, Thanks for your response.
    Fate had it that you posted that message and my 2 flute bits arrived through the post
    You where totally right, it made a massive difference, the cut quality and no crazy'ness from Lucy.

    I have now ordered some single flute bits as i am still not quite happy, i know the machine slipped a few times, also i am still getting melted bits stuck to sometimes the bits, most of the time the acrylic. I am getting there, especially on the thicker acrylic (5mm+).

    I think i still have an issue with slipage in the belt, so need to sort that out.

    Outside of the single flute for acrylic, what other bits should i be looking at.
    For:
    MDF (upto 10mm)
    Aluminium (is upto 5mm possible on my machine)
    Dibond (3mm/5mm)
    Foam board (upto 19mm, the 4 flutes seem fine, but are they the best for it?)

  4. #4
    Its a repeated question when somebody starts.

    The answer:

    Sizes:


    you need 3 major sizes:

    3mm or/and 1/8"

    6mm or/and 1/4"

    12mm or/and 1/2"


    Flutes:

    You will need 2 flutes cutters mostly. 1 flute cutters are specific material and you dont need them at the beginning until you know what you are doing and why exactly are needed. They are not a necessity if you have HF spindle.

    In rare occasions 3 flute cutters are perfect, like straight cutters for wood, special ones for aluminum. You dont need them at the beginning.


    Material:
    Carbide. Given the current prices of cutters, dont buy HSS except for special jobs, making custom cutters of them and bigg cutters that you need for 1 off jobs.


    Type:

    for the 3mm you need 3 lengths. Short/stub , 10mm and extra long 16mm. All 3 degree spiral. Buy this x10 and even more. learn and test with these as they are cheaper to break.


    for the 6mm you need same, 3 lengths- stub,~ 22mm,~ 35mm , same as above, spiral.

    12mm- only straight and here even carbide tipped will do the job. Dont buy spiral, they are expensive and you can not resharpen them yourself. $$$. best would be insert bits. You need here 30mm long and 50mm long, plus 20mm wide and 50mm wide for surfacing.


    Thats all you need for a couple of years untill you know what you are doing exactly


    Eventually for composite materials you willneed 2, 3 and 6mm diamond shaped like chipbreaker bits

    for engraving you need only 60degree bits for normal jobs. Eventual 90 degree for rare jobs and 3 degree for fine engraving. best 6mm shank / 1/4.




    Of course you will need more stuff but that will cover all normal needs. HSMAdviser and starting to understand whats happening is better investment than buying blindly bits. I have a box worth >1k$ in small bits, have bought all possible and then narrowed things with time, so i know what i am talking about.


    Ball nosed bits are another territory, you will need all possible nose tips 0.5 to 6mm if you are to dive in 3d machining, and possibly make your own shank adapters or you will need some serous cash invested.


    For example I could meet all normal orders in plastic,aluminum and composite with the following bits, all quality brand micrograin carbide. : 1mm ball nose, 2mm spiral 5mm LOC , 3mm 16mm LOC spiral, 3mm ball nose, 6mm straight flute 22mm LOC, 6mm ball nose, 6mm 60 degree V cutter , 12mm 30mmLOC instert bit CMT.
    project 1 , 2, Dust Shoe ...

  5. The Following 3 Users Say Thank You to Boyan Silyavski For This Useful Post:


  6. #5
    Quote Originally Posted by Boyan Silyavski View Post
    1 flute cutters are specific material and you dont need them at the beginning until you know what you are doing and why exactly are needed. They are not a necessity if you have HF spindle.
    But don't forget that single flute cutters can (with a little practice) be easily re-sharpened off-hand with a suitable grinding wheel.
    You think that's too expensive? You're not a Model Engineer are you? :D

  7. The Following User Says Thank You to magicniner For This Useful Post:


  8. #6
    Quote Originally Posted by magicniner View Post
    But don't forget that single flute cutters can (with a little practice) be easily re-sharpened off-hand with a suitable grinding wheel.
    I am a big fan of resharpening as it saves money. Thats the reason i have bought myself fine diamond plates to resharpen the flat bottom surfacing bits. And thats why i use straight 6mm bits for wood. If you mean straight 1 flute bits, yes, positively are easy to resharpen.

    But to tell you the truth from the moment i bough insert tooling, i could say only WOW, quality and life time are not achievable by any other bit. So i always try to do the job with the insert, unfortunately the smallest cutter is 12mm 1 flute, but its incredible.
    project 1 , 2, Dust Shoe ...

  9. #7
    Quote Originally Posted by Boyan Silyavski View Post
    Its a repeated question when somebody starts.

    The answer:

    Sizes:


    you need 3 major sizes:

    3mm or/and 1/8"

    6mm or/and 1/4"

    12mm or/and 1/2"

    ......
    Wow, thanks for that. This needs to be a sticky!

    Its a great place to start.

    I did forget to mention this is just a "hobby" machine, alo a learning machine in advance of my friend ordering a industrial capacity one.

    The only Collect i currently have is 6mm (they are expensive on the Kress), I am looking into getting a 3mm one too.
    I bought a whole load of Carbide and HSS bits of ebay (cheap and cheerful with a range of sizes) to get me going.

    Even with the 2 flute, I have already broken 3 x 3 mm bits (once out of stupidity, moving the head whilst i was aligning the bit to a whole).

    I did find swapping the 4 flute to 2 flute made a massive cutting difference.
    Someone mentioned getting a single flute for acrylic?

    I am still getting a bit of a problem with melted acrylic piling up around the bit, this then suddenly grows as more is backed up.

    Is there a correlation between temperature of the bit vs the build up of melted material around the bit?

    As for sharpening, i think i will avoid that for now, this machine is a steep enough learning curve for now! lol

    Thanks again, this is awesome.

  10. #8
    Acrylic needs brand new sharp cutters and sturdy machine so the cut is excellent. On small machines is best to scratch it rather than digging in it, or it will melt easily. One flute are nice but not all a center cutting, meaning not very good for drilling holes as the tend to go off center.


    here bellow is a general suggestion for cutting acrylic using 3mm / 1/8" / cutter

    Click image for larger version. 

Name:	Acrylic.PNG 
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ID:	21107
    project 1 , 2, Dust Shoe ...

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