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    Red face your thoughts r welcome / Ultimate engraving precision

    Hello Gents ,

    after some search i found the forum and decided to join because i will build my own router/engraver machine (hobby use) and will be needing advice from experts like you all to avoid mistakes

    A little about me
    im an expert user of SolidWorks and in my free time i enjoy 3d printing my projects in both my PLA and resin/SLA printers.

    What would be special with this machine? To archive the highest performance in precision as possible.
    Goal is to build an engraving machine so i can use the smallest 0.1mm bits to engrave my tiny designs for family and friends !
    A working area of 40cmX40cm is plenty for me so i can have space to secure down my parts. .

    I like to stay away from belt systems just in case i will want to do any light milling on aluminium parts or other soft metals.

    So questions before i decide the skeleton design :

    1-What i need ?Simple ballscrews or preload precision ballscrews ?

    2-For what step motors i should be looking for ? I read the term microsteping. Is this something i need to consider for my working area 40x40cm?

    3-What else i need to order to control this xyz step motors?

    4-What software?

    5-Where can i order the above parts in Europe (/ebay maybe?) ?

    Sixth and last question for now : Them machinist milling machines also use preload precision ballscrews to archive there precision?


    THANK YOU in advance for your time and your replies and sorry for my poor English!

    Similar Threads:
    Last edited by oniromastoras; 01-22-2020 at 04:53 AM.


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    Default Re: your thoughts r welcome / Ultimate engraving precision

    Hi,

    1-What i need ?Simple ballscrews or preload precision ballscrews ?
    Rolled ballscrews C7 grade are good to 50um per 300mm and economically priced. A 20mm diameter screw about 600 long with support
    bearings would cost about $100, the same thing in C5 ground ballscrew will cost over $1000. To achieve 0.1mm accuracy C7's are fine.
    To get to 0.01mm then you need C5's (or better).


    2-For what step motors i should be looking for ? I read the term microsteping. Is this something i need to consider for my working area 40x40cm?
    You will use microstepping no matter what the size of your machine. It is tempting to believe that microstepping vastly increases the resolution of a plain old
    stepper, and to a small degree its true, but the real value of microstepping is smoother motion without midband resonance which plague steppers.
    You will see a lot of hype about closed loop steppers....and most of it is just that....hype. Don't be taken in. There are some advantages in closed loop
    stepper design but insufficient to justify the premium paid.

    What you should look for instead is LOW INDUCTANCE steppers. You will see that I have posted extensively on the absolute requirement of low inductance in
    steppers. I imagine you will want 23 size steppers, they should be 1mH-2mH, 1mH preferred and reject anything over 2mH. Low inductance means that the stepper will
    turn fast without losing steps whereas a high inductance motor will not only lose steps but stall over a few hundred rpm. LOW INDUCTANCE is a MUST, it is as important
    as torque.


    The next thing you can do is get the best high voltage drivers you can. 80V Gecko's would be nice, but pricey. Leadshine AM822's are reasonably priced ($75)
    and 80V capable. Next you want, ideally a transformer type power supply of 72 or 80V. Switchmode supplies are cheaper but transformer types are so much more forgiving
    and have vastly superior overload characteristics.

    The alternative to steppers is AC servos. Chinese manufacturers are producing some very credible servos and drives. They still attract a preminum over steppers
    but the difference is much less than it used to be. If you really want speed servos are the go.

    I have always used Mach, first Mach3, but for the last five years Mach4.

    To use Mach4, my own recommendation, you will need an external motion controller, like an Ethernet SmoothStepper by Warp9. It is not the only choice but it is a popular
    choice among Mach users. Avoid cheap Chinese controllers, they don't work as advertised and once they've got your money they won't help. In fact you'd swear that China
    is in another galaxy!

    The other choices, approximately similarly priced and intended to run on PC hardware are UCCNC, Centroid and LinuxCNC. Each have their own fan base.


    5-Where can i order the above parts in Europe (/ebay maybe?) ?
    I would guess that most of the motion parts like ballscrews, linear bearings/rails, steppers and stepper drivers will come from China. The prices are just too compelling to
    ignore. Software and motion control electronics are likely to be US or European made. It is my observation that many UK and European buyers shy away from US made because
    of import tax only to end up with over-priced under-performing European made stuff. Don't be a dickhead....if US is the best...get it, who cares about a little tax, if you buy the
    right product you will have it for years and years and a extra $50 in tax is nothing over that time frame.

    I have bought servos and drives from this Ebay supplier:

    fasttobuy2012 | eBay Stores

    I have also bought high quality new old stock and second hand motion components from:

    https://www.ebay.com/str/industrialpartsshop


    Craig



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    Default Re: your thoughts r welcome / Ultimate engraving precision

    Hello there Craig,

    thank you very much for all the info !
    The most important of all is the part you point out not to settle for under-performing parts trying to save some money.
    I always say “pay cheap=pay double” and agree that when a project can reach the $3000 range , trying to save $300 by avoiding quality parts is totally stupid.

    So for now ill do a market search on options for C7 / C5 rate ballscrews .
    Any recommended online shops ? brands? Do you have selling adds from members in this forum maybe?

    Thanx in advance for your replies !



    p.s.Moderators , please check why i get this message ALL the time?I have complete my registration : ”You've to complete registration process with correct data for becoming a full member.



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    Default Re: your thoughts r welcome / Ultimate engraving precision

    Hi,
    aside from the two I have listed I don't have any really special preferred suppliers.

    There are a number of purchase types that newcomers to CNC tend to make poor choices only to regret later.

    The first and most obvious is LOW INDUCTANCE steppers, most newcomers buy the highest torque unit without realising that it has commensurately
    high inductance and is very sub-par for CNC purposes. The manufacturers know there are inexperienced buyers out there and they exploit that fact.

    The second one is closed loop steppers as I've already alluded to. I have high quality five phase Vexta steppers and low lash (<2 arc.min) planetary gearboxes,
    open loop. They have not missed a step in six years that I've had them...UNLESS I do something stupid. Good steppers of adequate spec with good drivers
    and power supply WILL NOT lose steps UNLESS you demand performance beyond its capabilities.

    If you are of the opinion that you NEED high overload capability the get AC servos and be done with it. Servos have a remarkable ability to weather overloads
    where steppers fail completely.

    The next most problematic choice is round rails or square?

    Round rails, whether they are supported at the ends only or continuously on an aluminum pedestal and the round linear bearings that partner them are very
    economically priced but they suffer from lack of stiffness. Square rails and ball loaded linear cars are very much stiffer and accurate but also so much
    more expensive. Even within the general type of square rails there is a bewildering choice of designs, some very much stiffer (and expensive) than
    others.

    Your choice is round or square? I have had good success at buying second hand linear rails and cars and ground C5 ballscrews. For the same, or little
    more, than lesser components but new, you can have much higher quality and design by buying used. The second link I posted is to a Korean supplier
    of predominantly used motion parts.

    I bought from him three sets of THK (top brand) 20mm HSR (heavy duty design) rails and cars. They were new old stock. Like wise I have bought from
    him three second hand C5 ground ballscrews which I'd swear are brand new. It is worth shopping around and being patient. These are for a new build mill
    capable of cutting tough steels at what I hope is micron level accuracy.

    Another area where newcomers come unstuck is buying cheap Chinese controllers. They seldom work as they are supposed to and you'll get absolutely
    no help from them. Avoid like the plague.

    Craig



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your thoughts r welcome / Ultimate engraving precision

your thoughts r welcome / Ultimate engraving precision

your thoughts r welcome / Ultimate engraving precision