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IndustryArena Forum > WoodWorking Machines > DIY CNC Router Table Machines > Build Inexpensive CNC with decent tolerances-Share your input
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  1. #1
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    Build Inexpensive CNC with decent tolerances-Share your input

    Hello! A few thoughts on starting out cheaply. This is oriented towards a small machine maybe 12x12 inches to 24x24 inchess x-y and maybe 6-8 inches z coordinate with the ability to mill Aluminum .
    First you need a CAD program..I highly reccomend TurboCad Deluxe. Turbocad has been around since 1985 and has had tons of development time put into it. TurboCad 12,14,15, and 16 all run on Vista and Windows 7 in both 32 and 64 bit OS version. Turbocad uses the same ASCIS engine that autocad does, and accepts every cad format. Does 95-97% of what Autocad does..actually it just does not have command line entry ..which you really dont need anyways.. Cost is $25 or less on amazon.com for deluxe14 with a tutorial (and it does 3d!)..Pro TurboCad is better but costs money..TurboCad is very similar to autocad...CAD has an immense learning curve..Cadcourse.com has a free 2d drawing tutorial and a really great training bundle for $65..you need the tutorials. No I dont work for turbocad...its just a great program for the money..Google had turbocad write sketchup for them buy the way..(dont use sketchup..get turbocad instead)
    As far a linear motion..stay away from ballscrews..they are great but simply cost way way too much..Go with 1/2 inch 10 thread per inch right hand turn ,single start ACME threaded rod. Mcmaster.com sells it for $7 for a 3 foot long piece and $12 for a six foot long piece..shipping is about 5-6 bucks..cant go wong..I would not use regular threaded rod from a hardware store or better grad ACME right now as you just want to get going and its going to be accurate to .0010 to .001 inch . Two start ACME and precision ACME cost a lot more..General acme will get the job done.
    As far a stepper motors go..you dont want to go too big or too small..the smallest I would go is 166 oz/in...127 oz/in wold be sort of ok..the largest..260 oz in..If you get too big of a stepper (..500 oz ect..) then you have a 15 amp fusebreaker in your shop then you will have wiring hazards and possible fuse tripping You can ge 166 oz/in 24 volt 3 amp bipolar Minebea/Astrosyn Hybrid bipolar motor for $12 ea at mpja.com..these are really great motors..remember..the ACME screw holds the gantry in position..the motor just moves it there..(there is also what is called detent torque from the motor..but you dont need a whole lot.)Go bipolar..they are stronger..the old motors are round..new motors are square....you also should have a dedicated computer there to run the CAM software that takes the CAD model and converts it to machine code or "G Code". Any old garage sale computer would work..Load Ubuntu on it .(free Linux) So you also need a second pice of software CAM.CAM takes the CAD model and translates it into "G code " for the cnc machine to read....LinuxCNC.org has ECM for free..its pretty good..in fact Shaerline uses it on their small mills. And its fully documented..Again there is better suff out there but this program would work just fine! As far as controllers for the steppers go..look around..you absolutly must have documentation and operating software for the controller..dont buy a controller without directions! Stay away from expensive controllers for now..ie.. Lizard brand..they are truly great but simply cost too much ! Buy them later when you have more money.
    You will need a general electronics book..the best on the market is wirttern by Floyd..Electronics-Electron Flow..$3 for a used copy from amazon..any edition from 1997 onward is just fine..Well illustrated expensive book new though..You also will need a book on Stepper motors and one on Industrial Electonics..again ..used..amazon.com..1997 or later..new costs too much.
    Power supply..24 volt 12 amp from Marlin Jones $25..mpja.com..they also sell the Minebea 166 oz/in 3 amp 24 volt motors for $12 ea...not the biggest..but they will get the job done..especially for you since you dont have a giant x-y table to worry about and by the way..the reason people here talk about rapid movement is that moving too slow burns wood and many people here are in a production enviroment..the 166 and single start acme will work just fine in your situation...also some people here are using $250,000 machines! or more$ ! .... Or are on a fast production line..so what applies to them does not apply to you!
    As far as a spindle goes either use a porter-cable router or much much better get a real spingle intended for aluminum/ and or precison work..about $95 if you look..read the tolerances..
    The ACME general from Mcmaster is Keystone brand and its very high quality for general acme threaded rod...Yes two start might be better..but it costs a lot more..plus its only available in precision grade..ie.. .00001 tolerance..if you can afford the precison two start ACME go for....but get 1/2 inch!.. (smaller diameter flexes or "whips" at high rpm..)
    You can build a machine cheaply that will get you .0010 to .001 ....any more precison costs a lot more.. As does the size of the machine..bigger machines cost more..just build it yourself..have a local machine shop cut and drill for you then assembl;e it yourself..Slotslva has a $25 set of plans or design it yourself..Browse the web for cnc builds.I would reccomend a combination of Aluminum and Steel..probably steel for the spindle mount as it absorbs vibration better than Aluminum..Moving parts..Aluminum..Use rubber vibration dampers here and there..As for Linear slides..certain drawer slides have good tolerances..about .001 with a 200 lb weight limit..24 inch travel..cost $25 at home depot.read the specs atthe mfg site first or look at them....PMinMO.com is a great great resource!!..To get .001 you would need the real for cnc router $95 spindle..and have it mounted correctly..Porter cable is good..but your have to buy the entire roiuter to get the spindle..Avoid general hardware stuff in critical places..use it elesewhere for bolting things together..Make sure you get the wiring right ..otherwise it creates a fire hazard!! Also I would enclose it .(use plexiglas on one side so you can see whats going on.three or more different materials snadwiched toigether yeild the best sound insulation.(good safety too..from flying broken bits..shards ect..).put a usb webcam camera with a range extender in with the machine so you can watch it and listen remotely in your living room! Put a fire alarm in with the machine..again you might not be with the machine when its running!..Put the electronics in an old computer case with a fan..Make sure the stepper controllers have the amp capacity for your steppers and the voltage you want..buy a stepper motor with a higher voltage to start with same with amps..they dont really cost much more anyways and its safer to run a 24 voilt motor with a 24 volt power supply anyways..in other words dont put 52 volts on a 3 volt motor for an extended period of time unattended..24 volts is plenty for a small system..and rig up a spray cooling set up for coolant/lubricant..along with a fan to help cool...Most of the items you need will have to come from the internet..You can use drawer slides as linear slides.. from Homedepot or Lowes ect..go look..or read the specs..some have tolerances to .001 in..24 inch long slides with 200 lb capacity cost about $20..I can not remeber which ones had the .001 spec but its on the drawer mfg website..
    If you are going to build a machine with x-y coordinates longer than 36 inches go with 5/8 inch ACME..over 4 foot x-y ..go with one inch ACME..bigger tables require a little bit bigger motors..any thing over 4 foot go with 300 oz/inch to 500 oz/in motors..On the longer length tables you would want two pillow block bearing supports on each end about 1 1/2 to 2 inches apart to help prevent whipping..also you can counterbalace the machine from above with a "slinky" type spring mounter above the moving gantry..Some types of wood dust are toxic..if you work with wood you need to know which woods!! And also could explode under certain circumstances..use a brass rod to drive a sparkless fan (mount the fan motor outside of the cnc enclosure.keep the dust out..You can make a vacuum pump out of an old refrigerator compressor if you read about it online! ..And again..soundproof it with walls made of 3 different materials..plywood..rubber..drywall..with a plexiglass window..use a cheap $75 air conditioner for the enclosure if heat becomes a problem..but again think about your fusebox in your house..dont overload the fusebox.if the steppers become hot..attach computer cpu heat sinks to them.or finned copper....again..you should watch overvoltaging the motors in an unmonitored situation due to hazards...but make sure its got heat sinks on all 4 sides so you dont get a cool spot. Buy 24 -48volt motors to begin with (if you can get a good price)..dont put 48 volts on a one volt motor..yes you can get away with it..but..?(thats just my opinion) ! Read the specs before you buy anything to make sure it is compatible with what you have..
    Thats my take on building a cheap cnc
    Good luck and stay in budget! andy

  2. #2
    Community Moderator ger21's Avatar
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    There's a lot of misinformation here. It's a bit hard to rewad, so I just scanned through it quick and will give my opinion on a few things.

    TurboCAD. Imo, not the easiest CAD package to learn. As for being a lot like AutoCAD, I think that a lot of other CAD programs are closer to AutoCAD than TurboCAD. My preference would be DesignCAD. Now owned by the same company as TurboCAD, it's cheaper, and easier to learn. But there are also a lot of free options out there as well these days.

    TurboCAD didn't write Sketchup for Google. Sketchup was around for many years before Google bought them out. http://en.wikipedia.org/wiki/SketchUp

    Don't by 24V and higher motors. Typically, the lower the voltage, the better the performance. 2V-3V motors typically work the best.

    Multiple start acme from McMaster typically has a tolerance of ±.009/ft, not .0001

    Drawer slides have tolerances far greater than .001.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

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

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

  3. #3
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    I feel differently about sketchup. It's very easy, it's free, it's fast, support is great, and there are a ton of good tutorials. I've been useing it with a free plugin to get DXF files to use with cut 2d and cambam with nothing but success. My parts come out as accurate as my machine is able to machine. I've also used it with meshcam with success. The only bad things about sketchup is doing organic shapes. I guess rendering too if you want a life like product to preview.


    On the topic of screws, I agree 1 start 1/2 10 acme should be the minimum someone should consider when buying a lead screw. It's well worth the price. However, the first thing you are going to want to upgrade once your machine is built will be the screws if you made good choices with your electronics. That's what I'm finding and will be upgrading next.

    That's all I got

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    CNC Under $300

    I would like to clarify a couple of points. I realize this forum is oriented towards the Pro machinist. In order to become a pro you have to start somewhere. As you know CNC almost everything in CNC is wildly expensive. Everyone does not have a $1000 to start out with. Its almost as bad as govenment contracting..mention the word government or CNC and empty your wallet and borrow on top of that!

    25 million people are unemployed or underemployed.
    If a functional (but maybe somewhat slow) machine can be built for $300 or under, then a new CNC buyer is born!!

    I did not want to get an electronics novice to wire up something that he does not understand and burn his house down. It takes technical knowldege to do the electricity/electronics..thats why I suggested higher voltage steppers..if the motor is rated at 24 volts and so is the power supply..its less of a risk for a raw beginner. You are of course right about running higher voltages on steppers.

    Most people have no idea how complicated CAD is. My point here is that instead of going freeware here..go with $25 and get a real CAD program. Yes Autocad, Rhino and Solidworks might be better, but all of those programs cost $2000. I like Design CAD also. And I also like some freeware. You usually dont get much training material with freeware. The same applys to ballscrews.. and high quality stepper controllers..Linear slides..ect of course they are better..but..the cost becomes a barrier to entry to the industry..

    If you only have $300..and its going to cost $1000 for a so called cheap machine..then there is no new CNC machinist.

    I am talking about rock bottom pricing here..how can it be done? Yes its an unsavory topic..drawer slides and $13 stepper motors and $7 ACME rod..but it can be done with some careful planning. Manufacturing technology has changed a lot..CNC is being used to make cheap stuff..there actually are drawer slides with .001 tolerances...computers can calculate the rate of decay of a router bit and adjust accordingly..same with metallurgical engineering and casting/pressing.

    I dont think there is any bad information in my post...some typo errors...I am just coming from a different direction than the pros who have to have the best gear...Maybe if someone has the time they could give the cheap low lend guys a hand and figure out what they should do.. I understand that advocating using general acme single start and drawer slides detracts from anyones credibility among the PRO user community...Maybe you could carefully word some thoughts on what is cheap and would work..just add a disclaimer of some sort so everyone knows its applicable to ulta low budget.. Any insight would be greatly appreciated.

    Maybe some of the pro users could weigh in? Or anyone one else! You might be able to create a new cnc machinist!
    Andy

  5. #5
    Community Moderator ger21's Avatar
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    I suggested an easier to learn and cheaper alternative to TurboCAD. That's all I said.

    As for 24V steppers, I still say don't buy them. You'll have a machine that will barely move. And wiring a 3V stepper or a 24V stepper is exactly the same. They cost about the same too. Difference is, the 24V steppers won't really work very well.

    And I never said don't use acme screws or drawer slides. I just said they weren't as accurate as you said they were.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

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

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

  6. #6
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    If a person has been bitten by the cnc bug and just has to have one .. I don't doubt that it can be done for $300. But it's not at all realistic to think you can build a machine that will mill aluminum at .001 tolerances for that kind of money. Even if you do manage to build one on that budget & cut some thin alum. stock very slowly, the machine isn't going to last long doing it. In your post you mention the use of aluminum and steel as being preferred. I agree, but have you priced aluminum & steel lately? Even at scrap yards it's not exactly cheap. I'm aware that Mach3 is available for free, but the trial version will only allow 500 lines of code. That's not much when you're actually trying to make something. A licensed version is $175.00. Adding the $95.00 router you recommend brings your budget to $270.00 and you've only scratched the surface and have a long, long way to go in expenditures. A machine made out of MDF, with whatever components you can find to meet budget, running freeware on a salvaged computer with anything you can find for a spindle will be a cnc indeed. You'll have fun building it and using it, and get much experience out of the process. You will also then know that you would probably have to quadruple your budget to even get close to milling aluminum at .001 consistently without beating your machine to death doing it. I don't want to quench anyone's zeal for trying something new, so I say go for it at whatever level you can! .. Everybody starts somewhere and it's a fascinating project to undertake.

  7. #7
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    Quote Originally Posted by Andy990 View Post
    I would like to clarify a couple of points. I realize this forum is oriented towards the Pro machinist. In order to become a pro you have to start somewhere.
    Andy
    Hi Andy,
    This site is most certainly not aimed at the Pro machinist.
    I am not a "Pro" machinist. Wish I could prove that I was so I could get a different job
    I am however a very handy person who can read and follow directions.
    I may have over 1K posts but don't assume that I am a professional machinist. While I have made money with my machine I am at best in the early stages of my journey that will never be finished.
    Most of my posts go to helping the other newbies here or I give out what I have learned in doing work or upgrades on my machines.

    As far as you have to start somewhere, I basically started here on the zone with my CNC education.
    While it would be nice for someone to build a CNC machine for $300 and be able to cut whatever they want, reality says otherwise.
    If you scrounge and look real hard you may be able to do it. It may also take three years to find all the free and inexpensive parts you need.

    $2k gets you into a ready to run Taig and it is a great running small machine that used within its limits, will teach you a lot. I also see people running several of them in small volume production environment.

    I would also say go with steppers rated for the voltage you will be running on. High voltage steppers and low voltage power supplies will just result in frustration and disappointment.

    Mike
    Warning: DIY CNC may cause extreme hair loss due to you pulling your hair out.

  8. #8
    Community Moderator ger21's Avatar
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    Quote Originally Posted by gd.marsh View Post
    I'm aware that Mach3 is available for free, but the trial version will only allow 500 lines of code. That's not much when you're actually trying to make something. A licensed version is $175.00.
    The first two months I had my machine running, I made over $900 making parts with the Mach3 demo. I had some bills to pay with that, but set enough aside to purchase my license. now that I have a license, I can make much more complicated things and I can make even more money.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

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

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

  9. #9
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    500 lines is a lot of code.
    It came as a shock to me the first time I exceeded the limit because I had been using it for months prior to that.
    If you work within the 500 line limit for a while it also makes you write better g-code.

    I think a lot of us use cam as a crutch for many things. Myself included.

    I figure that if your cable bill is over $100 a month!, and from what I hear a lot of people pay that, $175 for Mach3 is the best bargain in the world because you will spend less time in front of the TV.

    Mike
    Warning: DIY CNC may cause extreme hair loss due to you pulling your hair out.

  10. #10
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    Mass produced parts made with .00010 Precision

    Hello! As many of you know CNC has widespread use. I bought a Bottom of the line Fender Squire Affinity. It was the sample the regional manager used .. I spoke to the guy and they used a $500,000 machine to mill it. Accuracy.. .00010..
    Of course its in a mass production enviroment with a big corporation..

    But here is the point...you can buy things cheap that were mass produced with expensive equipment.
    The same principal applies to steel rod for example..There is some factory somewhere with a really nice new expensive machine cranking out standard grade steel ...( or aluminum) rod or plate thats inexpensive with .001 precision..the question is which brand (the guy who sells the $500,000 machines knows who bought em! ), who has it cheap...the same applies to other items that are mass produced..
    On items that are not mass produced..then you most likely are stuck and have to pay the going rate for a custom part...ie.. ACME nuts ect..
    Lets say you wanted a realativly cheap straight edge..buy a steel yardstick for $5..its probably .001 or better..most likely .0001
    I am doing engineering-physics and scientific apparatus protoyping so I do not really need to make parts fast, mostly complex foam molds intended to be cast metal or ceramic, and some metal parts, some wood molds.

    Anyone reading this is urged to post their thoughts and ideas on how to do cheap and accurate! Dont just read it..post a response ..what do you think?

    Quote: Mathematical and theoretical proofs are via a working machine. Its irrefutable. Patents are ok ,,but you need to prove it in a definitive manner.

  11. #11
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    Quote Originally Posted by Andy990 View Post
    I spoke to the guy and they used a $500,000 machine to mill it. Accuracy.. .00010..

    The same principal applies to steel rod for example..There is some factory somewhere with a really nice new expensive machine cranking out standard grade steel ...( or aluminum) rod or plate thats inexpensive with .001 precision..the question is which brand (the guy who sells the $500,000 machines knows who bought em! ),


    I can assure you that these guys with the $500,000 mill are not building a squire to .0001 , generally precision rod and plate would be ground and not machined ,
    suggesting watching a cnc machine remotely with the use of a webcam is an extremely dangerous thing to suggest to someone who knows nothing about the true dangers of cnc , mdf dust can flare up pretty fast and unfortunately by the time you get to your machine you may get there in enough time to watch it burn .

    as far as building economical machines I believe that most of us who had build routers have looked at most options to realistically build an economical machine and there are a lot of success stories and great ideas because of it . i think it would be to your benefit to do some searching thru the forum so that you can get some better information from people with experience ,
    i think that if your really interested in getting into cnc then you will find a wealth of knowledge here
    A poet knows no boundary yet he is bound to the boundaries of ones own mind !! ........

  12. #12
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    Hello! Thank you for the heads up on MDF dust! Here is a 10 cent solution to the webcam hazard.
    Place the webcam in a used glass jar with a hole in the cap sealed with rubber gasket sealant or household caulking to spark proof it..may a gound wire on the lid too. Problem solved.
    Andy

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