CNC for "Dummies"?

[DayneInfo]

I just found this site about a week ago. Have been reading some and have decided that before I die I have to build a CNC router. Problem is that I am ignorant. Is there a good source for basic starter knowledge? I understand (I think) that most all routers have 3 axis (X,Y,Z) but which one does what? That is how new I am. At this point I will probably buy all parts precut, buy motor /drive in kit form and all other hardware as needed. Basically just put it all together. I would just like to know when someone talks about anti backlash nut...what the heck it is.

Dwayne

[project5k]

hehehe i was exactly where you are just a few weeks ago.. but after much reading on here, i consider myself just knowledgable to be dangerous now... hehehe well, lets see.....

to answer your question, x is typically the longest axis, y is 90deg or at a right angle to that, but still flat or horozontal, and z is the up and down... most of the machines that i have seen have a fair sized x and y, and then a pretty small z... really and truely you can call each one anything you want, one could be hamburger, the other hotdog, and the last puppyspots... it dosent matter, except when your talking to someone, or trying to use the software...

heres a basic, and i do mean very basic overview of what i know thus far..
starting at the top, you have to have software to draw what you want to cut... I'm using Rhino, but there are lots of options,

then you need something to take this drawing/picture, and convert it to g code... i'm considering using meshcam, but havent decided for sure yet.

after that you use the interface software, this is the mach3, it takes the gcode and converts it into signals that come out of the LPT port on your computer...

these signals go to a breakout board, that takes the 25 pins of the lpt port and split them up to go to the next stages....

there are limit and home switches, and the drivers that all connect to the breakout board...

the drivers are the parts that convert the small signals that the computer port puts out into big signals, (high current/voltage) that actually goes to the motors...

there is also a power supply to be considered... i'm going to use old computer power supplies that i have modified to work.. the modification is really easy, and if you have an ohm and volt meter, you can do this too with nothing more than a couple screwdrivers, and an exacto knife most times.... I'm going this route cause its cheap, and the powersupplies are plentifull... you could just as easliy buy a powersupply and just plug it in, but being an electrical engineer myself, this just feels "right"

the motors can be steppers or servos, depending on your $$$ and how fast/accurate you wanna be...

the motors are connected to either screws, belts, or racks and pinions that turn the rotational motion of the motor into linear motion

there is generally 1 motor per axis, but in some cases you can slave 2 motors to 1 axis if your machine is big heavy or just due to the design you decide that you will need 2....

there is also the a axis, or 4th axis, this is generally a rotational axis, mounted on the bed and would allow things like engraving/carving on pool cues, baseball bats, candels, stuff like that that is a cylindar.. but thats much more complex....

the rest is just the machine, how stiff or sturdy, and how big is again up to your $$ and your needs....

one thing to do now, is to sit down, and really figure out what you want to do.. to you want to engrave name plates, or do you want to do 3d carvings, or what... also the materials that you want to work with is something to think about now... do you want to use a full sheet of MDF, or just engrave keychains.... this is going to decide how much $ and how big/fast/ accurate your machine will be...

my first machine is 3'x3'x12" of usable travel... this is what i would consider a mid sized unit, but is somewhat large for a "first machine" i originally wanted to start off with a 4'x8' machine, but $ and time, and skill demanded that i start smaller....

as for the frame, there are lots of options.. you could build it out of extruded aluminium, like 8020 stuff, or you could do what i'm doing and build it out of steel, or there are even plans for machines made out of mdf... all depends again on what you wanna do with it....

as im building my machine, what i'm seeing is that for most people, if the table/machine itself costs 1x, then the electronics cost about 2x and the software is another 1-2x...

I'm using 500oz-in motors, 1/2" 10tpi (turns per inch) screws, plastic simple nuts, and an all steel frame... i bought my 3 motors off ebay for about 200 give or take, my screws for about 100 or so, and the steel is mostly stuff i had left over from building my new shop... the electronics, like the drivers and breakout board i'm building all myself from scratch.. i ordered the chips from digikey, and i'm having a buddy of mine photo etch the circuit boards...

the software im using, will be mach3, at soemthing like 150-160, meshcam i think is about the same, and rhino i already had....

once you get a feel for what you want to do, start looking at the kits, and reading peoples reviews on them, there are several kits that i've seen mentioned on here that were the breakoutboards, drivers, and motors all in one bundle, im not sure if they included the powersupply or not...

hope all of this is helpfull, and not boring...

oh, and to answer the other question..... first you need to know what backlash is to know what an anti backlash nut is for....

imagine this, the machine is moving along in one direction, and stops and goes the other direction, but there is a tiny bit of slack between the nut and the screw, this slack is the backlash... an anti backlash nut is a setup that eleminates (or at least reduces) this amount of slack... this allows for a more accurate machine...
this is not the only place one can have backlash.. you can have slack at the ends of the screws, that actually allow the screw to move toward or away from one end or the other of the screw, this would contribute to backlash... there is backlash in rack and pinion as well...

now, once you absorb all of this, there is much more... theres the diff between a lead screw, and a ball screw, ball screws are more accurate, i think, last longer, move faster, are more efficient, and cost way more... but generally have very little backlash....

then theres the different types of motors, stepper vs servos.. dont ask me about servos, i dont know... but just with steppers, there are lots of variations....

drivers is another subject where there is lots to absorb, unipolar, bipolar, chopper, bla bla bla... my personal preference is bipolar chopper drives.. remember that your drivers need to match up with your motors, and then the power supply needs to work for the amount of current you will be using, and at the voltage you need...

all in all and the bottom line is this... your headed in the right direction, your on here, and your asking questions, this is a good thing.. and dont let pride or anything else get in your way... dont be afraid to ask quesitons, no matter how trivial you might think it is, its better to be informed, than to make a mistake...i really think that everyone on here will agree with me in saying that this is a good site, there are people here that have forgotten more about cnc and machining in general that i will ever know, but i keep asking thoes quesitons, and learning....

make a plan, figure out what you need to make that happen, and then get after it...

good luck!!

[project5k]

oh, and i wanted to give you a big thumbs up on your use of the word ignorant.. its so rarely that i see it used correctly... there are 2 phrases i like to use...

1) ignorance is a condition, but is treatable, are you wiling to take the medicine?

2) ignorance is just an education away from expert....

your obviously a person of relative intelligence, so once you find the information, you should be able to tackle this.....

[aggie_67]

For your consideration: I too am a newbie! Depends on your background but suggest you tackel the part you are less comfortable with first. I am very good mechanically and in the past would have done the hardware (made the machine) first; but who says an old dog can't learn new tricks, this time I made sure I could handle the software first!! Lots of free programs out there, I used A9CAD, ACE, and Mach3. Made some simple designs similar to what my ultimate objective was now feel very comfortable with software and starting on hardware.

In hindsite really glad didn't jump into hardware as after months of reading all the posts have really learned a lot about the different designs.

[project5k]

its all interconnected, change any one part, and could change 3 others... i know from a hardware standpoint, changing your desired feed rate, can really affect what screws, motors, drivers, powersupply and so on.... i pretty much had the whole thing designed to work together before i ever put arc to metal.... just to make sure that all the parts would work together...

[DayneInfo]

Thanks for the replies. I am acctually pretty good at fabrication. I can use the mill, lathe and surface grinder enough to be dangerous. I have enough woodworking equipment to start a small business. I currently run a shop where we rebuild extrusion equipment, so I have the mechanical skills. I am also not worried about learning anything new. I just have almost zero knowledge of what to do/expect. I am going to do it though...even if I get it wrong. Only thing that does worry me is that it seems to take on a life of its own. Not uncommon to see someone post the 2nd or even 3rd version of a router design and build. Might cut too deep into my fishin' time.

[krt9751]

your best bet is to have fun start out small with a small budget get the hang of it. then move on to bigger and better. at least you found this place first lots of info here. sometimes it will drive you nuts.but just have fun and welcome aboard.

[dertsap]

Originally Posted by DayneInfo . Not uncommon to see someone post the 2nd or even 3rd version of a router design and build. Might cut too deep into my fishin' time.

most part of the time the first one is the test (prototype) setup , for trial and error ,
this is where the mdf builds are great ,a sheet of mdf is cheap , and a guy can build a sturdy design which can be easily modified or turfed ,
as your building lots of times ideas may start flying , and it makes it easer to try wandering off the beaten path to try something different , without scraping a few hun worth of aluminum ,
the second is the beast , most of the errors and improvements learned on the first one , generates (hopefully) a much better system this is where we can justify the expenses because we know we can do it ,
the third one is because we are nuts and are not willing to let go of a good thing ,
its a fun hobby , once you start you ll enjoy it , if not becoming engulfed and obsessed in it

[project5k]

Originally Posted by DayneInfo Not uncommon to see someone post the 2nd or even 3rd version of a router design and build.

this is definately the route i ended up going... i first designed a 4x8, and then have just been scaling it down till i finally said, if i go any smaller, it just wont be worth my time.. and thats how i ended up at 3x3....

[dpresley58]

I'm new to this as well... Was wondering what good salvage sources would be for motors. For instance, I have access to several older HP large-format plotters as used for plotting engineering and architecture plans. Would these have useable motors? How about the smaller printers?

[rondame]

I too am new to this site and the world of machining. I took a course at local CC I thought I knew something, but found out I didn't. I worked in industry all my life and have been around this equipment. I have a lathe, milling machine Jet 16 bench top. I am looking for plans for a cnc router to cut foam for making patterns for casting. If you run across some I would be most interested in getting some or at least a place where I can find one.


Ron Dame
Shallotte, NC
rdame@atmc.net

[ahren]

Dwayne,
First off, welcome to the zone! If you're just looking for a kit, you might take a gander at Joe's CNC design -- there's a whole section of the zone dedicated to it, and it's a solid machine design. If you're interested in "rolling your own" a little more, you might check out my parts, which are designed to mount directly to 8020 aluminum extrusion. There are quite a few people who have made nice machines using them.

Best regards,

Ahren
www.cncrouterparts.com