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  1. #1
    Hi all,

    'New' to the forum, although I have been browsing for over 4 years.

    Eventually starting to CNC build process... MKI

    I've done a LOT of reading, and calculations from several members (too many to mention)

    Machine Aim:
    • To mostly cut 6mm MDF, plywood etc.
    • Also to cut 20-25mm woods (mixing from soft to hardish(oak))
    • Aluminium cutting (3mm) - maybe somewhere down the line...


    I want to have the ability to cut A2 size (i.e. 420mm x 594mm ) - So with cut size, clamps etc:
    Cutting size: 480 mm x 640 mm

    Hardware etc:
    For hardware I was thinking:
    Nema 23 (3.1Nm) - Drivers [ Was thinking some 50v Drivers from CNC4You - powered by 36v ? ]
    SBS20 rails + Support blocks
    RM1605 Ball Screws and nut (Above 2 items from Chai - I've made contact and he said he is still shipping to UK and ready to take my order)
    Aluminium Profiles (40x80 heavy duty, Ix: 26.87cm4, Iy: 101.19cm4) - The Support Rails will be bolted on top of them, so extra stability...
    Router/Spindle: Looking at the Makita RT0700CX for now.
    The Z Axis has the ability to move 140mm, but will initially only us ~40-60 of that - unless I drop the table/raise the machine.

    The entire machine will be bolted down on a bakelite(?) top (super flat strong surface) with steel support under the top.
    (Will see if I need to weld a movable table one day...)

    Software, I've played around with bCNC and got a Arduino with grbl running on two Nem17's with a CNC Shield (Drivers DRV8825 - Will not use these on final machine)

    Below is my design so far: [Version 4 mind you, but at a stage where I feel confident to post to ask for further assistance and advice from experienced people ;) ]
    (Some final adaptions from JoeHarris, but really, the credit goes to the entire MyCNCUK Forum member builds!)

    Click image for larger version. 

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    Your input and thoughts on the design would be most helpful!

  2. #2
    Clive S's Avatar
    Lives in Marple   Stockport, United Kingdom. Last Activity: 12 Hours Ago Forum Superstar, has done so much to help others, they deserve a medal. Has been a member for 5-6 years. Has a total post count of 2,309. Received thanks 402 times, giving thanks to others 35 times. Made a monetary donation to the upkeep of the community. Is a beta tester for Machinists Network features.
    HI Jacques Welcome to the forum. CNC4you do some very good 3.1Nm motors and are a good buy but you are limiting yourself with the drives AM882 or EM806 are much better and can be run them at a higher voltage 68V would be about OK. If you are mainly cutting MDF etc then 10mm screws for X and Y and 5mm on the Z.

    Think about the router as the Chinese 1.5kw or 2.2kw water cooled with VFD are a much better bet.

    Don't be temped to buy a kit of electronics as they are never matched as you will know if you have been reading the forum for the past 4 years.

    Start a build log so all the questions etc will be in one place.. Good luck with the build
    ..Clive
    The more you know, The better you know, How little you know

  3. #3
    Thanks Clive.

    Spindle: http://www.ebay.co.uk/itm/170745857956 ??

    It has a ER11 Collet - are you limited to the cutters? (What Collet size do people recommend ?)
    [ Any recommendations on spindles + water cooling systems anyone? ]

    My thinking for the Makita RT0700CX was I could use it on the CNC & Other project. But in reality, a dedicated spindle is more realistic.

    Thanks about the reminder about buying the Kit's... Originally I was thinking 4Nm Nema's. It is only a slight increase to got from 3.1Nm to 4Nm, but I'm not sure if the 3.1's are an overkill already...

    About 10mm for XY & 5 for Z - I want to keep my options open to eventually cut small Aluminium parts (for toy cars etc - so 4mm) later down the line - but as stated, not essential.

    Jacques

  4. #4
    Clive S's Avatar
    Lives in Marple   Stockport, United Kingdom. Last Activity: 12 Hours Ago Forum Superstar, has done so much to help others, they deserve a medal. Has been a member for 5-6 years. Has a total post count of 2,309. Received thanks 402 times, giving thanks to others 35 times. Made a monetary donation to the upkeep of the community. Is a beta tester for Machinists Network features.
    Quote Originally Posted by Jacques View Post
    Thanks Clive.

    Spindle: http://www.ebay.co.uk/itm/170745857956 ??

    It has a ER11 Collet - are you limited to the cutters? (What Collet size do people recommend ?)
    [ Any recommendations on spindles + water cooling systems anyone? ]

    My thinking for the Makita RT0700CX was I could use it on the CNC & Other project. But in reality, a dedicated spindle is more realistic.

    Thanks about the reminder about buying the Kit's... Originally I was thinking 4Nm Nema's. It is only a slight increase to got from 3.1Nm to 4Nm, but I'm not sure if the 3.1's are an overkill already...

    About 10mm for XY & 5 for Z - I want to keep my options open to eventually cut small Aluminium parts (for toy cars etc - so 4mm) later down the line - but as stated, not essential.

    Jacques
    The 2.2Kw has a bigger collet but the 1.5Kw can be got with a bigger collet as well you will never really use a bigger end mill that 6mm on a machine like that. The water cooling is just a small fish tank pump about 3 and about 1 ltr Tupperware container.

    The 3Nm motors are more than big enough if you can go with belt drive all the better as then you can use a 1:2 reduction if you need to.

    I think you might have to beef the frame up as well.
    ..Clive
    The more you know, The better you know, How little you know

  5. #5
    Hi Jaques,

    Clives suggestion to use 10mm screws is correct and it mostly do everything you want, even small stuff. But if you really want flexabilty then connect motors to screws using Timing belt and pulleys with 1:1 ratio then you have option to change up or down if required. Also and much better reason to use Timing belts considering the drives your thinking to use is to lessen resonance which affects motor performance/smoothness.

    I'd also urge you to use Profiled linear rails rather than cheap Round rail Chai sells. While Round rail does work ok the slight extra cost of profiled rails makes huge difference to machine stiffness and reliabilty. It will also increase sellabilty and value much more than the extra cost difference.

    Also with Motors you'll notice No Difference between 3.1Nm and 4Nm motors. The important thing to look for is inductance you want Lowest inductance possible. This will allow higher RPM and more torque for same voltage compared to High inductance motor.
    Again Clives advice of AM/EM drives and 60-70Vdc is sound advice you'd do well to take up. Esp when using Slaved motors.!

    For Components contact Fred Lee here and get a quote. He's good to deal with and his stuff tends to be slightly better quality than Chai's. Esp the End bearings for the screws.
    http://www.aliexpress.com/store/314742

  6. #6
    Thanks JazzCNC

    It's not very clear on the design, but the intent is to use a belt with pulleys, 1:1 timing. (Very similar to JoeHaris' design) - as I've read, it helps with resonance and gives me the ability to do 1:2, or 2:1, or other rations if I allow a variable positioning of the Nema (which is the intent)

    I looked at Profiled Linear rails - just seems to cost a tad more... although, would be easier to fit to the Aluminium profile... Will see what pennies I can get out the couch :)

    Thanks for the 3.1Nm vs 4Nm motor advise - I think that's one tick I can put next to - "Buy Nema 23, 3.1Nm motors" :D

    Once I have all the input and design tweaks, I'll know what length ball screws to get - So recommendation so far is RM1610 (with the end an extra 15mm for the pully) [This should give a resolution of 0.05mm (at full step) and 0.00625mm at 1/8 step - that actually pretty decent! ]

    As for Slaved motors, should I go with 3 Nema's (One belt connecting both Y Axis to one Nema ?) - this will save on buying one driver and Nema, but worth it ?

  7. #7
    Quote Originally Posted by Jacques View Post
    I looked at Profiled Linear rails - just seems to cost a tad more... although, would be easier to fit to the Aluminium profile... Will see what pennies I can get out the couch :)
    Dig deep because worth every extra penny.

    Quote Originally Posted by Jacques View Post
    Thanks for the 3.1Nm vs 4Nm motor advise - I think that's one tick I can put next to - "Buy Nema 23, 3.1Nm motors" :D
    Remember Inductance not all motors are the same even if same Nm rating.

    Quote Originally Posted by Jacques View Post
    [This should give a resolution of 0.05mm (at full step) and 0.00625mm at 1/8 step - that actually pretty decent! ]
    Don't Full step action will be rough and Don't really think of Micro stepping to increase resolution and more to do with having smooth running motors. Buy Digital drives and you'll get lovely smooth motors with less Micro stepping.

    Quote Originally Posted by Jacques View Post
    As for Slaved motors, should I go with 3 Nema's (One belt connecting both Y Axis to one Nema ?) - this will save on buying one driver and Nema, but worth it ?
    Yes that's what I would do using 10mm pitch screw with 1.5:1 ratio which increases torque and still gives decent performance. I've used this setup on machines with heavier gantry than yours so know it works ok.
    Last edited by JAZZCNC; 26-01-2016 at 08:40 PM.

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  9. #8
    I am looking into the HIWIN Rails - and many people on the forum suggests 20mm because of grease, access to bearings etc. So I take it 20 is good,15mm bad ?

    The motors I am looking at can be 3mH if you couple them in series, 12mH in Parallel configuration.

    Those drivers are nice, 100 nice - will have to save up for them....

    Busy re-designing for the Linear Rails... will post new design within the next week.

  10. #9
    Quote Originally Posted by Jacques View Post
    I am looking into the HIWIN Rails - and many people on the forum suggests 20mm because of grease, access to bearings etc. So I take it 20 is good,15mm bad ?
    No good or Bad about it really just 20mm are easier regards fitment etc but 15mm will still easily handle any forces.

    Quote Originally Posted by Jacques View Post
    The motors I am looking at can be 3mH if you couple them in series, 12mH in Parallel configuration.
    Think you may have got that wrong way round but if not then don't buy them.!! You want them wired in parallel and 12Mh is way too high.

    Quote Originally Posted by Jacques View Post
    Those drivers are nice, 100 nice - will have to save up for them....
    AM882 drives can be bought from Ali express for around 50-60. Also you can buy Hi-win rails from BST automation on Ali express much cheaper tyhan you'll find them in Uk.

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  12. #10
    Clive S's Avatar
    Lives in Marple   Stockport, United Kingdom. Last Activity: 12 Hours Ago Forum Superstar, has done so much to help others, they deserve a medal. Has been a member for 5-6 years. Has a total post count of 2,309. Received thanks 402 times, giving thanks to others 35 times. Made a monetary donation to the upkeep of the community. Is a beta tester for Machinists Network features.
    Quote Originally Posted by Jacques View Post
    I am looking into the HIWIN Rails - and many people on the forum suggests 20mm because of grease, access to bearings etc. So I take it 20 is good,15mm bad ?

    The motors I am looking at can be 3mH if you couple them in series, 12mH in Parallel configuration.

    Those drivers are nice, 100 nice - will have to save up for them....

    Busy re-designing for the Linear Rails... will post new design within the next week.
    20mm is good because they are much easer to mount than the 15mm especially on the Z.

    Zapp motor are a good buy http://www.zappautomation.co.uk/elec...tor-48577.html
    or CNC4you as I suggested before https://www.cnc4you.co.uk/Stepper-Mo...s/Nema23-3.1Nm

    Drive about 53 http://www.aliexpress.com/store/prod...570168083.html or similar
    ..Clive
    The more you know, The better you know, How little you know

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