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    Question Some questions before make it REAL

    Hello, I have spent the last 2 months reading and absorbing info in this forum, and now im totally decided that a CNC is what I NEED in my life. In my country only some big factories have CNCs, the DIY market didnt exist so im trying to create this new market, not for the monetary aspect, but for the amount of possibilities it open. For example: im a student arquitect and with a CNC my arquitectural models will only be limited by my mind, not the tools.

    The idea is to create a machine capable of working with the biggest wood sheet 1,83m x 2,6m (6' x 8,5'), with a reasonable but not exaggerated Z height. 2 motors in X axis, and all 4 motors the same. After reading a lot I have a lot of questions, and I hope you can help me with them .


    Specs:
    Workable area: x= 2900m y= 1900m z=200-300mm
    Main use: Furniture
    Secondary use: Arquitectural Models, Construction modules (ex:Tree houses), etc.
    Materials: SoftWood and Hardwood, Plastics.
    Desired speed: Not sure, but for a 3m bed would be required a decent speed.
    Gantry Weight: aprox. 50-60Kg

    Sorry if there are to much questions, but I wouldnt stop until this machine is REAL.


    Questions:

    Motion system:

    1: Whats its the best motion system (Belt, RyP, etc) based in the LONG travel area I have and the precision required to make furniture?
    1b: Would the belt on belt be enought or the material resistance will move the belt in undesired ways?
    1c: Its the Rack and Pinion precise enought to the main use? what components I would need to mount with it to be usable (slave pinion, etc)?

    Motor:
    2: I have in mind to use 4x Nema34 1600oz, what did you think about that (im a man of acceleration rather than speed)?
    2b: I have come across this pack, its well matched or there are going to be any bottleneck?
    Stepper Motor Nema34 1600oz.in 34HS5435C-37B2 Single Shaft 3.5A DM860A CNC kit | eBay
    2c: Acording to the desired use, what kind of reduction would be ideal? 1:3? 1:10?

    ToolChanger:
    3: Im planing in do a easy toolchanger like this one:
    .
    As I see a simple 2.2K chinese spindle wouldnt work, what kind of spindle have a mechanism to open-close the toolholder like that?
    3a: Aircoled spindle is enought for woodworking 10-12 hours a day (18-26º Celcius range)?

    Linear Rails:
    4: Due to long work area(3m) bond togheter some linear rails is going to be necesary (same for RyP if chosen), its an easy practice or it carry to much error to the CNC?
    4b: Any special mark that offer easy to put togheter and cheaps rails?
    4c: What others alternatives are there?

    Gantry:
    5: what you think about my gantry design without legs?(ignore components and Z axis)
    Imgur: The most awesome images on the Internet

    Any other tip or idea its totally welcomed, thanks for your time I hope that in the next weeks I can give you a build-log of this monster.

    Similar Threads:


  2. #2
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    Default Re: Some questions before make it REAL

    Look on eBay for an ISO spindle that is the typical tool changer spindle but they are very expensive so most people do not have them on hobby machines

    Russ



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    Member ger21's Avatar
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    Default Re: Some questions before make it REAL

    1) Most people use rack and pinion.

    1b) If you do something like the servobelt. http://www.cnczone.com/forums/linear...570-forum.html
    You need to use a 32mm wide belt, and build it very precisely. A simple small belt on belt like the cheap hobby machines use will not work well on a big machine.

    1c) Most people use these, or build something similar: PRO Rack and Pinion Drive, NEMA 34 | CNCRouterParts

    2) 1600oz motors are a very bad choice in most cases. They are very slow, and won't run as smoothly as smaller motors. Almost everyone that buys them regrets it. For most DIY machines, smaller motors will easily outperform the 1600 oz motors.
    Do not select motors until your entire design is finalized. Motors must be well matched to the drive system you're using.

    3) As Russ said, ATC spindles are expensive, and start at about $3000.
    3a) For continuous all day use, I'd recommend a spindle with an electric fan, rather than a shaft driven fan.

    4) You can buy 3 meter rails. I have some here that I purchased.
    If you want to joint them together, the ends at the joint must be ground very precisely.

    5) It needs to be much larger.

    Gerry

    UCCNC 2017 Screenset
    [URL]http://www.thecncwoodworker.com/2017.html[/URL]

    Mach3 2010 Screenset
    [URL]http://www.thecncwoodworker.com/2010.html[/URL]

    JointCAM - CNC Dovetails & Box Joints
    [URL]http://www.g-forcecnc.com/jointcam.html[/URL]

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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    Default Re: Some questions before make it REAL

    As always thanks ger, and Russ.

    1-4: The main problem im facing is importing the parts, lets say a 3m rack or linear rail would cost 170$, that mean when it reach Uruguay with taxes, large item import, etc. The total price will be like 450-600$ for a single rack! That was the main reason the belt on belt where tempting me but probably will stick to well proved method like RyP but wouldn't have other alternative than put togheter 3 rack of 1m to reduce taxes( and probably do the same with linear rails).

    2: You get me a bit confused with the motors. I had the idea that bigger was better, in the worst case you end over-designing and that was good if you plan to upgrade your cnc in the future. The nema 34 werent planed to be using directly. The reason you say the will be outperformed is due to high inductance?

    3: Didn't expect it to be so expensive, will stick to my cheap hands to change tools . Offtopic: Ger, I see you made a 2xspindle CNC, that was because the ATC where expensive right?

    5: Maybe the draw wasnt clear, its a concept so ignore component or lenghts. The idea was to eliminate the gantry "side" parts to get better stifness, I upload a quick draw hope its more understandable. By the way I dont know to much about structures but its seems a lot stiffer this way, are there any problem I'm overlooking (apart from spending more $ in structure)?
    Imgur: The most awesome images on the Internet



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    Default Re: Some questions before make it REAL

    Use R&P.
    Increase expectations re: work hours and costs.

    Unless You have lots of time and money, do not try to make a big machine first.
    Make a small one.
    Then make a bigger one.

    Costs, work, time, scale up as the cube of worksize.
    This is why no-one has made big machines here.

    This is why my big machine has cost 5 revisions, 15.000 work-hours, 100.000€+, so far.
    I had the time, money and perseverance.
    Mine is a VMC ... which is vastly harder.
    Routers are easy, and thousands have been done.

    Look at mechmate.



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    Default Re: Some questions before make it REAL

    1) You don't need a 3m long rack. Shorter racks are easily joined together. You can also joint linear rails, but a single long rail is better. The manufacturer or seller may be able to grind the ends to join them, if needed. Yes, shipping long items is expensive. I paid $170 shipping for mine here in the US.

    2: You get me a bit confused with the motors. I had the idea that bigger was better,
    Not with steppers. High inductance is part of it, and detent torque can be an issue as well.

    Ger, I see you made a 2xspindle CNC, that was because the ATC where expensive right?
    Yes. An ATC spindle would add 50% to the machine's cost. I still haven't assembled it yet, as I'm still collecting parts. I'll have over $5000 in parts before I even start assembling anything.


    5: Maybe the draw wasnt clear, its a concept so ignore component or lenghts.
    The design is fine. But you need a bigger gantry beam, with 2 bearing blocks on each side.

    Last edited by ger21; 03-09-2017 at 08:03 AM.
    Gerry

    UCCNC 2017 Screenset
    [URL]http://www.thecncwoodworker.com/2017.html[/URL]

    Mach3 2010 Screenset
    [URL]http://www.thecncwoodworker.com/2010.html[/URL]

    JointCAM - CNC Dovetails & Box Joints
    [URL]http://www.g-forcecnc.com/jointcam.html[/URL]

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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    Default Re: Some questions before make it REAL

    HeavenKnight,
    While you can run rails end on end if they are carefully done and if you have a large CNC machine to to the machining and hole drilling, it is pretty difficult to get this perfect. You will often find that when moving a loaded bearing across two rails that are end on end will catch slightly if not done perfectly. For a worry free situation where you don't have access to a large CNC machine to help build your machine, go with the longer rails, you will be much happier in the end even if they cost you a little more up front. Like others said something going much bigger on motors is not always the right answer, many machines use NEMA-23 and NEMA-34. This really depends on the mass and speed of your given machine. Rack and Pinon is very common on larger platforms, I have a 5x5 machine and use one ballscrew and one servo to move the gantry down the middle. This approach is also used on many industrial machines, but you need to have a machine which is very sound and the gantry needs to be made so it will not rack. This is why rack and pinon is often used since there is a motor on each end of the gantry, this helps prevent racking.

    Russ



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    Default Re: Some questions before make it REAL

    im decided to use the RyP as motion system By the way CNCRouterParts have some nice parts but the price is really out of scale, a Nema34 960oz cost 120$ while for that price you can get 2 of 1600oz, Same for Racks. Was the price unupdated for some years? or a high quality motor with low inductance really scale that quick in price?


    Lets say im going to use:

    RyP(The ones listed in CNCRouterParts)
    linear bearing with 2 cars.
    60kg gantry
    expecting a speed of 600-800ipm cutting only wood. (mainly softwoods, dont matter if need to go slower in hardwoods)
    2x motors in X axis.
    What would be a correct motor size to do the job at that speed? and correct reduction, 1:3 or more?


    thanks for the tip hanermo, a have some small nema 17 that will end in a small router to gain experience before building the big one. But as shiping can last more than 1-2 months to arrive here, It would be better if I know the parts I need to buy so they come here in some months when im finishing the small router.



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    Default Re: Some questions before make it REAL

    By the way CNCRouterParts have some nice parts but the price is really out of scale, a Nema34 960oz cost 120$ while for that price you can get 2 of 1600oz
    They are in business to make money. They are going to cost more than buying directly from China. You can probably find similar motor for $80-$90, but you won't get any support. CNCRP provides excellent support to their customers.

    A 600-900oz Nema 34 motor is more than enough. They are typically geared 3:1, mainly due to pulley size availability issues.

    Gerry

    UCCNC 2017 Screenset
    [URL]http://www.thecncwoodworker.com/2017.html[/URL]

    Mach3 2010 Screenset
    [URL]http://www.thecncwoodworker.com/2010.html[/URL]

    JointCAM - CNC Dovetails & Box Joints
    [URL]http://www.g-forcecnc.com/jointcam.html[/URL]

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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    Default Re: Some questions before make it REAL

    Ger Really thanks for open my eyes. Looking more closely I se that CNCRP 960oz have 2 mH of inductance while the chinese have 22 mH. That mean a PSU of 150V would be necesary! and a matching driver. I know inductance was important but didnt know how much, now I feel the x3 cost is a lot more justified, buying an expensive motors I am saving in other components, getting more quality, and more efficiency per $ spent.

    As an example, I see it like what happen in computers. Where bad bussinesman put a lot of RAM because its the cheapest component, and people who dont know to much see these big 32G RAM ads and think they are buying a computer of other world while the rest of components are thrash.


    Continue on topic, what did you think about Geared stepers? would them simplify a lot the design and dont require this large part of metal? like plug & play direct to the pinion.
    PRO Rack and Pinion Drive, NEMA 34 | CNCRouterParts



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    Default Re: Some questions before make it REAL

    Geared steppers have backlash, and tend to be expensive.

    Gerry

    UCCNC 2017 Screenset
    [URL]http://www.thecncwoodworker.com/2017.html[/URL]

    Mach3 2010 Screenset
    [URL]http://www.thecncwoodworker.com/2010.html[/URL]

    JointCAM - CNC Dovetails & Box Joints
    [URL]http://www.g-forcecnc.com/jointcam.html[/URL]

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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    Default Re: Some questions before make it REAL

    Forget the steppers, is my opinion / advice.
    Big steppers cost same as servos, and servos are vastly better.

    A 60 kg, or even 200 kg, gantry is nothing.
    Re: mass I used to have my 200 kg gantry with nema 23 steppers, on a mill, at 1:3.
    I switched to servos, but only for marketing reasons.

    The servos get you 5x more acceleration and 3x-4x more speed.

    On a 3m bed, the speed is likely to matter.
    Not in cutting, but in 3d work and g0 rapid moves.

    Medium steppers perhaps 600 (-900) rpm top speed, servos 3000 rpm.
    Accelerations on servos 5x better, or more.
    3d work, 3-5x faster, real world.

    Otoh, the cost of the servos/steppers is immaterial.
    You will note spending on n amount of "stuff" much higher in terms of $$, ...


    I recommend a cslabs csmio-ip-s, or the cheap version (ok for router), ethernet.
    I recommend a pokeys cnc, ethernet, optionally.
    I recommend against usb anything.
    I highly recommend an mpg.

    On servos, and mpg/pokeys or csmio, you get industrial performance.
    Amazingly good stuff.
    Really.

    I have forgotten machines running, powered, for days, with machx pokeys/csmio, and never worry about it.
    Prudence dictates turning servo-enable signals off, and I have forgotten sometimes.



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    Default Re: Some questions before make it REAL

    HeavenKnight,
    If you go with Servos which do have higher speeds, you need to make some calculations. Servo operate the best and have the most torque in their higher rpm range. The servo can typically operate up to 3000 RPM as was pointed out by hanermo. If you connect that directly to a ballscrew depending on the pitch you might find that it can move your entire gantry the entire distance in two seconds or something, which is way too fast. Most people who have servos carefully select the correct pitch on the ballscrews or depending on the pitch they might have to add harmonic drive gear heads. This will allow the servo to operate at a higher RPM so more torque and allow more reasonable response on the system. The reason they use Harmonic drivers is they have no or very little backlash. Backlash in a CNC system is a dirty word, and will cause all kind of issues in your work. Steppers have high torque at the low rpm however are very common on CNC systems as the provide good performance at more reasonable prices. Servo have feedback due to encoders so they are often used on commercial hardware. I have servos on my systems and on my smaller system the servos go directly to the ballscrews and work just fine. On my larger system the ballscrews I got on ebay were designed for rapid movement so the servos could not be used directly, so I had to get some harmonic drivers, but they are expensive.

    Russ



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    Member ger21's Avatar
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    Default Re: Some questions before make it REAL

    Big steppers cost same as servos, and servos are vastly better.
    No, they don't cost the same. You can get a 1000oz stepper and a good drive for ~$150-$175.
    A Cheap 400w AC servo and drive starts around $400.

    But yes, they are much better.

    Gerry

    UCCNC 2017 Screenset
    [URL]http://www.thecncwoodworker.com/2017.html[/URL]

    Mach3 2010 Screenset
    [URL]http://www.thecncwoodworker.com/2010.html[/URL]

    JointCAM - CNC Dovetails & Box Joints
    [URL]http://www.g-forcecnc.com/jointcam.html[/URL]

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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    Default Re: Some questions before make it REAL

    Thanks for all the recomendations, as it is my first router I will stick to Steppers and RyPinion. Anyways doing furniture and structural pieces I dont need exaggerated precision except for the junctions, So I will be fine without servos complexity.

    My plan was to use to CNCRouterParts as they are of high quality and reasonable prices, but they didnt reply my mail about shiping so will start searching similar pieces. Altough I was in love with the easy of use of their parts, in special this one PRO Rack and Pinion Drive, NEMA 34 | CNCRouterParts Would be hard to find something similar in other place.

    Anyone know what's the problem with UPS and others couriers?? the estimate shiping for a 960oz nema34 is 410$, that would cost me with customs about 900 ****ing buck for a simple motor!!(and 650$ for every 1m of rack) I live in Uruguay not Antarctica. There need to be a workaround? I mean, for that price I could take some vacations in USA ans just take the pieces with my in the plane, or even better, I could cross the continent in my bike and take them with me and still be a more reasonable trade off.



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    Default Re: Some questions before make it REAL

    Mind the (Darien) gap if you do that... https://expertvagabond.com/darien-gap-photos/

    [FONT=Verdana]Andrew Werby[/FONT]
    [URL="http://www.computersculpture.com/"]Website[/URL]


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    Default Re: Some questions before make it REAL

    Seems like I have no other alternative than chinese products, I have come across this one https://es.aliexpress.com/store/prod...612.0.0.SfWGwB. Seems really great the motor with a decent 6.5 inductance and 6a/phase.

    Acording to the "32*sqrt(inductance)" formula, I would need ideally 80v, and the driver says in specs:

    DC Input Voltage = 24v-80v
    AC Input Voltage = 20v-60v
    Output Current = 2a - 6a

    What did you think about the matching driver? there is going to be any bottleneck? In my country we use 220V if that matter.
    This page show the driver info if the one I post is incomplete: JKD2060AC Two Phase Stepper Motor Driver Digital Stepper Driver 2.0A-6.0A DC 24-80V Sale - Banggood.com


    Someone has bought in Aliexpress cnc parts before? they offer really cheap shiping prices (50-70$ in UPS or Fedex), I dont want to buy something and discover hidden prices and end paying 200$ only for shiping.

    Last edited by HeavenKnight; 03-13-2017 at 02:32 PM.


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    Default Re: Some questions before make it REAL

    Quote Originally Posted by awerby View Post
    Mind the (Darien) gap if you do that... https://expertvagabond.com/darien-gap-photos/
    Remind me of Rambo movies, will visit for sure with a beer in one hand and the steppers in the other



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    Default Re: Some questions before make it REAL

    Today I advanced a lot, I have almost all the pieces I'm going to buy listed and ready to come home.


    My only concern now is that I cannot find a piece like this one: PRO Roller Drive Spindle, NEMA 34 | CNCRouterParts I have tried like 20 differents names but didnt found it anywhere, my solution is to pput togheter this 2 pieces: Pulley and Spur gear from beltingonline, but I dont know whats going to be the best way to couple them, any idea or tip in coupling?



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