[cowanrg]

hello everyone. i came across this site while doing some research on my own. ive gotten into several hobbies through the years, and i must say, this one has a TON of scattered information. every day i find something new and confusing. ive collected a lot, and know a lot more than i did, but little of it fits all together.

here is what i already "know". i generally know what a CNC machine is (the original goal was to make a CNC-type machine), that led me to the research. i know that its an computer-based interpretation/control system that reads input (from a file or from a user) and manipulates a machine. im good with that.

next, i am familiar with stepper motors, servo motors, and movement. i know i will be using stepper motors (for cost and for simplicity). i know generally what size to get (the biggest i can get surplus ) i know the more steps, the better, etc...

then i get confused. i am somewhat unsure of how a "milling machine" is different than lets say a drill press. i understand the differences in chucks and lateral forces. but, im still trying to grasp what makes a milling machine a milling machine, and not just a beefy drill press. BUT, for my purposes, this is irrelevant.

next, i get that steppers need controllers. that's a given. and i understand you can control a stepper with PC software. what i DONT understand is how you link stepper software, controllers, motors, etc... i dont get how it all works together. this also leads into my confusion about software. ill get to that next.

i found a few stepper motor controllers on www.kitsrus.com (kits 179, and 113 i think). 179 says it can control a motor through a PC, or direct, and you can hook up to 6 motors to a single PC. how?

i see MANY controllers online and most look almost identical, but prices vary a lot. i see many in the $50-$100 price range, and then some in the multiple $100's range. why is this? what is the main difference?

phew, so good so far. next, how does the software communicate exactly? i dont care about the technical details, but if i want to make two holes, 3 inches apart, how do i say, "move three inches right". it is all in the form of steps (which i understand), but do you have to just know how many steps is equal to an inch, or is there some interpretation?

lastly, ive seen a whole lot of software that appears like it can do CAM functions. however, what feedback is there to tell the machine where the bit is at a given time, and where it NEEDS to be? is there a way to zero the machine without feedback from the computer? it seems like you can move the bit, map the bit's movements, but the computer seemingly has no idea where the bit actually is. do you always start from a zero point, or do you just have to "zero" the workpiece?

ok, so there are my questions. as soon as im done, im posting all the stuff in a NICE Q&A on my website (which is a pretty good amount of visitors in the DIY audio realm.). this will help a few people. im pretty good with this stuff, but the information thats out there is really hard to grasp.

so, here is what i'm after for now: well, answers of course, but here is what i am trying to build/accomplish:

i currently have a 12" drill press thats 2/3HP i think (its a craftsman). i understand that they dont make great milling machines becuase they dont like a whole lot of lateral force. this is fine. ill explain later. i just recently bought a milling table off ebay. its got 11" x 7.5" travel. its decently built (~70 pounds). it has some play in it, but i can fix that.

what i "need" to do is make a machine that drills precisely. not terribly so, but i just want stuff to be lined up right. also, it would be NICE if possible to be able to cut rectangular sockets (for AC inlets, computer ports, etc...) out of thin aluminum (maybe 1/16" or 1/8" thick). the limited lateral force on a drill press should handle that.

so, i have the table, the drill, and access to surplus stores. i recently saw some steppers at a local surplus shop that appeared bigger than most of what was used for the smaller mills for around $15 each. they were 5 wire motors i think. they were pretty good sized.

i also have an extra computer thats not in use. its a 2.2ghz with all the fixings. this will get devoted to the CNC mill. one last question, ive seen parallel PCI computer cards... can i use maybe 2 paralell ports for further control? not necessarily more axes, but for maybe reading measurements (DRO fed into computer?).

well, i REALLY appreciate everyone's help. on a last note... i dont expect insanely high tolerances, precision multi-angle milling, etc... i know i cant accomplish that with what i have listed. the ULTIMATE goal is to learn what im doing, and to make a full gantry setup that would allow me 2' travel in both drirections, and full milling cababilities, so i can do more complex metal work. but for NOW, i just need a drill press thats computer controlled, so i can layout hole patterns that looks CNC'ed.

[cowanrg]

i should add that i would like most of this to be semi DIY, which means i dont want to re-invent the wheel with each piece, but maybe using someone elses project and just emulating it, or ordering the kit, etc...

i know my way around a shop for small scale work, ive never used a mill or CNC before, but im good with drill, sander, band saw, etc... and have decent metalworking experience.

im also familiar with electronics and soldering. not so much design, but i can put stuff together well, and i know power supplies, etc... i have a nice digitally temperature controlled soldering workstation and many meters, etc...

[cncadmin]

then i get confused. i am somewhat unsure of how a "milling machine" is different than lets say a drill press. i understand the differences in chucks and lateral forces. but, im still trying to grasp what makes a milling machine a milling machine, and not just a beefy drill press. BUT, for my purposes, this is irrelevant.

I milling machine is made for milling metal a drill press if for drilling metal. The quill is designed for collects a drill press is not. A milling machine has a x and y base that can width stand the cutting forces. The weight of the two is much different making the milling machine a better chose for maintaining tolerance.

[cncadmin]

next, i am familiar with stepper motors, servo motors, and movement. i know i will be using stepper motors (for cost and for simplicity). i know generally what size to get (the biggest i can get surplus ) i know the more steps, the better, etc...

What is the question? What size frame, or how much torque are you looking for?

[cncadmin]

what i "need" to do is make a machine that drills precisely. not terribly so, but i just want stuff to be lined up right. also, it would be NICE if possible to be able to cut rectangular sockets (for AC inlets, computer ports, etc...) out of thin aluminum (maybe 1/16" or 1/8" thick). the limited lateral force on a drill press should handle that.

Maybe you're looking for a harbor freight mini mill?

[buscht]

cowanrg, Good questions.

There is alot more to purchasing a stepper motor than just buying the "the biggest I can get from surplus" I've learned that you have to match the motor (electronically) with your controller, plus match the power, shaft size, mounting style, etc with your mechanical.

I don't want to make it sound overly complicated because its not. But you should design your system as a whole, not just individual parts and hope they come together.

I'll get back to that in a minute.

I'd recommend that you purchase a premade controller card, such as a Xylotex, or FET-3 from Stepperworld. My next choice would be the kit from h*o*b*b*y*c*n*c.

If you have only 3 axis of motion, these cards will hook up to the parallel port on your PC.

A computer software program (TurboCNC or Mach2) supplies the step and direction signals to the driver card which translates this into power to move the stepper motors.

The software, let's say MACH2, requires a G code program to control your machine.
This is a program that is created by the CAM portion of CAD/CAM.

CAD is the drawing (Autocad, etc)
CAM takes the drawing and created the GCODE program
MACH2 is the machine controller,It reads the GCODE, sends the proper signals to your machine, and the machine produces your parts.

How does the machine know where it is? You either have home switches and when you turn on the machine, it moves to these switches and zeros out the 3 axis. Or you move the axis around (jogging) until the endmill is where you want it, and you manually zero the axis in MACH2.

From there, the steppers and the controller keep track of where they are. Let's say you are using 200 step count motors and a screw with 10 turns per inch. That equates to 2000 steps per inch.

When you first setup MACH2 (or TurboCNC) you have to enter all this type of data into a setup file. So if the GCODE file says move 2" at 30" per minute G01X2.00F30 the software sends out signals to turn the stepper motor 4000 steps.

Back to the motors, you need to look at the controller board you are using, if its a 1.25amp board, you can't use 10 amp stepper motors. They should be rated close to the amps for the circuit board.

Also, you have to know if the control board is bipolar or unipolar and get the appropriate stepper motors. A bipolar control board will run either type of motor, but a unipolar control board only works with unipolar stepper motors.

Steps per revolution is only important for resolution. If you want to cut parts to .001", then you should get a 200 step motor. If 1/16" is good enough, then a coarser step is OK.

Good luck
Trent

[ESjaavik]

i see MANY controllers online and most look almost identical, but prices vary a lot. i see many in the $50-$100 price range, and then some in the multiple $100's range. why is this? what is the main difference?

A complete answer to your question will be The Hitchhiker's Guide to CNC Machine Building.

So I'll just pick one, the above quoted.

I use the last category. They have:
- Built in galvanic isolation on all signal inputs/outputs. No BOB needed.
- Built in power supply.
- Microstepping up to 4000 steps/rev, adjustable.
- Motor current separately adjustable for Running, Resting and Accelerating conditions.
- Current lowered when motor not running (Resting condition) for cooler motors.
- Boost input for "turbocharging" when accelerating.
- Fault detection of Overcurrent, Overvoltage, Undervoltage, Shortcircuit and other internal fault conditions.
- Inrush current limiting.
- Everything integrated in one box.
- Virtually indestructible. If you do something wrong, they will just light up a red LED and assert the Fault output.
- If used according to the manual, you can rest assured they will get the most out of your motor as long as it is within the intended range of the unit.

For each of the features you remove, a cheaper unit can usually be found. But in many cases all or part of this cost pops up another place, and requires some knowledge to get right. When removing too many, the result is not recommendable for practical use.

By using these "black box" solutions you don't (need to) learn anything about what goes on inside, just RTFM. Whether to tick this off as pro or con is up to you. Gecko and Rutex (and some others at same level) are very good compromizes. They take care of most of the tricky parts and can make up a system that can hardly be bettered performance wise.

And if you use 3 or 5 phase steppers, I don't know of any cheap/medium price drives. Then you have to open your wallet as wide as you can. But microstepping 2-phase motors does everything a 5-phase motor can.

[ger21]

the limited lateral force on a drill press should handle that.

If you put lateral force on a drill press, the chuck will fall off.

[cowanrg]

well, ive done an insane amount of research since my original posts, and thanks to all those that replied to my thread.

since the first post, here is what i have found out...

I have found some unipolar motors from an old printer that will do for now. they are most likely under-powered, but it will be fine for experimentation. they are 1.8 degree/step.

they will work with the controllers i was going to use. the controller works with 5-35vdc for the motors. i will be using fully discrete power supplies (as well as discrete controllers), so i can scale as needed.

the power supplies consist of 12-0-12 (24vdc) transformers that are rated at 5 amps each. i have some 35A 600V bridge rectifiers left over from something else, so i will use one each, and then i have some 12,000uf caps (two per supply). so, that will be in each supply for each motor.

this will be a temporary setup, just to see how everything works. i will be using it with the milling table i got off ebay, which is actually decent (except for some backlash). i will be using this setup as a CNC drill press basically. from here i will figure out what is needed for a full home-brew CNC machine.

so, maybe some questions?

is there a diagram that shows what pins go to where on the parallel port? i will be using TurboCNC, so i need to know where home switches, relays, etc... get hooked up to (as well as the actual motors).

do i NEED a breakout board thing, or can i just throw one together with a PCB and some headers?

[abasir]

they will work with the controllers i was going to use. the controller works with 5-35vdc for the motors. i will be using fully discrete power supplies (as well as discrete controllers), so i can scale as needed.

is there a diagram that shows what pins go to where on the parallel port? i will be using TurboCNC, so i need to know where home switches, relays, etc... get hooked up to (as well as the actual motors).

The connection really depends on the controller you use. Do you have the schematic for us to look at?

[Alan T.]

Unless the milling table you bought is the size of the smaller Proxxon mills then I seriously doubt that unipolar printer steppers are going to move it without some "Major" gearing down which will negatively affect any speed you would hope for.

Get some decent motors, you can get 280oz bipolar motors for about $40 each. Otherwise you are in for some frustration IMO. I tried the route you are taking and although I understand your excitement, I also understand the let down when you get a machine that "Might" move at 3-6 inches a minute.

Just trying to help.

[cowanrg]

Alan,

i understand what you are saying... im not expecting great results. but the fact is, i will have less than $200 invested in this project. its just a test run to understand how it all works. its not meant to be a usable CNC machine really.

i like to do a "dry run" first. its the only way i can learn things. i can read all i want, but in the end, i just need to tinker with it to learn. that is all this will be really.

also, speed isnt a big concern. if the table moves, ill be happy. 3-5 inches per minute is fine. i know thats slower than molasses, but i as stated above, as long as it "works", thats fine. i just need to learn from it.

the next iteration will probably have 700-1000oz motors, just because i hate doing things underkill

as for the controllers im using, here is the schematic:

http://www.kitsrus.com/pdf/k179.pdf

its at the bottom of the page. it can be used with a computer or standalone. so i guess i could have it so you could drive it with a joystick or something.

[abasir]

Here's how to connect it.
X-Axis Step - Parallel Port Pin 2
X-Axis Dir - Parallel Port Pin 3
Y-Axis Step - Parallel Port Pin 4
Y-Axis Dir - Parallel Port Pin 5
Z-Axis Step - Parallel Port Pin 6
Z-Axis Dir - Parallel Port Pin 7

Get TurboCNC (www.dakeng.com) and configure the software based on the above connections. You'll have to do some tweaking with the software (in the movement parameters) to get things to work because every mechanical setup is different. Forget about relays, limits and so on for now. Those can be added later. Learn manual control first (directly keyin the G-Codes to move the tables) before worrying about CAD/CAM.

Hope this helps.

[cowanrg]

ok, so i think i got some more figured out...

i had a test motor laying around that i wired up for testing. the controller worked. i could get into turboCNC and with the correct setup, jog the motor with the computer in both directions.

but here comes the problem! i just got my real motors today. all seems to work ok, i measured the wires and have found the wiring configuration. the motor seems to work. however, it only goes in one direction (cannot reverse directions in turboCNC, it just moves the same direction no matter what), AND it gets VERY VERY hot really quickly. the other little motor got warm after time, but these new ones seems to get VERY hot in just a few minutes. and when i mean hot, i mean too hot to handle.

right now i am feeding it just 12v. i was hoping for 24v. they are rated at 3v on the back. am i wiring it wrong? any ideas as to what's wrong? the big question is why i cant reverse it.

the controller has a external and internal mode on it. external means it takes computer input, and internal means it just runs from the board itself (has a variable resistor for speed and a switch for direction). when switched to internal, the motor works as it should. it can reverse directions, and vary its speed. but as mentioned above, on external, it only goes in one direction (but if i switch the switch on the board, it goes the opposite way.) but in either case, from ANY input from the computer, it turns the same way.

[007clint]

Funny how the Internet is - there is always more than one person thinking the same thing and the Internet links you up.

I am tackling the same project that you were thinking about last year. Did you get anywhere with it?

Can you share what you learned?