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HighOctane
10-03-2004, 12:19 PM
I hope I am posting a thread at correct place, Newbie here....I was going to build homemade cnc machine. But I need to do a few research before I can perform my objectives. The objective for me is to build a cnc machine that can do milling on woods, plastics (lexan) and maybe pcbs (circuit board). So question with your recommendation: Where would be the best place to start learning how building homemade cnc machine?

In order to build cnc, what would be the first step to do?

electronics: Such as cnc circuity?
Skills: I am somewhat proficent in electronics.

programming: AutoCad? I have AutoCad 2000.
Skills: No skills, especially in mm type measurement, would like to learn it.

Tools/materials: Building a desk cnc? I am pretty good with cutting woods with band saw, table saw, and brench press drills. I am able to assembly them will hammer and nails, glue, and screws.

I have went through many other's builder website and read their work in progress. I seem to understand the picture they are doing but not the depth of making sure the cnc milling can do precise cutting and engraving according to program or g-code converter. So with your help would be much appreicated.

Arthur

BigDaddyG
10-04-2004, 11:15 AM
High Octane,
Welcome to the world of cnc, and all the headaches that are part of the journey! It sounds like you have your ducks in a row for a Newbie. One thing you need to add to your list is your Budget! You can spend a lot on very different approches just to get the same result. For my garage shop, I have an Enco Mill/Drill machine that is converted with 3-axis of Stepper. I have a manual lathe, and am going to purchase another one to convert (just for the heck of it). The Enco (can be seen at useenco.com) is the same one that Harbor Frieght and several others offer. There are others here that can address some of the other sites / machines that are offered as a "turn key" type system. I wanted the Mill/Drill because it is a bit "Beef-ier" and closer to the actual mills on the market. That was a personal choice I made, now I am also in the market for a Bridgeport type mill that I will convert because I am needing the longer travels, and stronger design and higher tollerences that come with this type of machine. But that opens a whole ball of wax, because I am doing this in my garage I need a converter and so on (plus moving the thing around is a pain - I have my lathe and mill on casters so I can move them when cleaning).

You can purchase a Mill/Drill in the $1500-2200 range new. A cheap low end mill in the 3000-8000 range so you can see there is a big difference there. The conversion (with a little creative thinking) can range from <$500 to a reasonable >$800 or so. I am sure you will see some other posts soon that will speak of the other types of cnc machines out there. Take a look at what they all offer, how the individules think of them and what they are using them for. I my case, I can easily cut steels, where some would not fair so well with steels. But then again, you may not want too cut steals, which mean that another approch my be the one you take.

I hope I have helped you out even if only a little. Good luck and please feel free to contact me if I can help in any way I would be happy to. I have been a mechanical engineer for 20+ years, and involved in the cnc (home and at work) for close to that. I have a business that I run out of my garage where I make custom machines and rototics/ automation/pick and place machines. I work 8-5 for the insurance and the money is not bad either.

Regards,
Glen

sol
10-04-2004, 09:20 PM
My thinking is:
Begin with an inexpensive proof of concept machine. Something REALLY cheap; salvaged printer steppers and drawer slides cheap. You will make mistakes and it won't matter because you did not wreck $500 worth of components as you learned the necessary skills.

The basic entry level machine is remarkably easy to construct, it is fitting all the processes together that takes the time and concentration, and that will not happen unless there is a machine on which to work. The drawing, g-code and cutting skills can be learned a little at a time; you will see where problems develop and address them as understanding advances.

After becoming comfortable with the process it may be that the next machine should be a retrofitted mill or a quality home-made table; though you probably will not know that until working with the basic one first.

In short, build something simple and cheap and learn as you go. If you wait to understand everything before you start you'll never begin. Do not fall into the trap of planning the perfect machine while building nothing.

Oh yes.. and the beauty of this forum is when you get stuck, you can ask very specific questions and receive real answers, not vague textbook theory.

Good luck!

chuckknigh
10-05-2004, 01:03 AM
Where would be the best place to start learning how building homemade cnc machine?

How do you learn? Do you learn from reading instructions (plans) or from figuring it out yourself? I learn in the latter way.

Of course, start out by reading the myriad posts on this web site. There is more information here, than would be in a graduate level course on CNC theory. LOTS of people have posted a lot of information, and most of it is quite helpful.

Quite bluntly, this is among the most helpful group I've ever encountered.


Tools/materials: Building a desk cnc? I am pretty good with cutting woods with band saw, table saw, and brench press drills. I am able to assembly them will hammer and nails, glue, and screws.

It's easy to make something that moves -- making it move under computer control is a little bit harder.

Do you want to build the basic machine? Or do you want to convert something pre-built, over to CNC control?


I have went through many other's builder website and read their work in progress. I seem to understand the picture they are doing but not the depth of making sure the cnc milling can do precise cutting and engraving according to program or g-code converter. So with your help would be much appreicated.

Bottom line, anything that is moved by turning a knob or handwheel, can be convrted to being turned by a motor. The biggest problem in making it move is twofold:

First, you need to make sure your motors are big enough that they can provide the necessary force. The necessary force is actually surprisingly small, if you're cutting wood and plastic.

Second, the screw drives have a property called backlash. Basically, the threads on the screw, and the threads on the nut, fit together loosely. By "pushing" against only one side of the thread, it allows it to push smoothly. The problem comes when you change direction. There is a portion of a turn when you accomplish nothing, with a traditional screw/nut combination. So, your motor would turn, but the table wouldn't move. Practically, this makes circles less than perfectly round, and squares "not quite" line up.

There are many ways to handle this, and they're all well documented on this site, including some very ingenious and cheap methods. The bottom line is, take two nuts and "push" against both sides of the threads at once. That way there's no "wiggle" left in the system.

My best advise is just to build *something* and get it running under computer control. At that point, you'll realize that you want to redesign it, anyway...it's just basic human nature!

-- Chuck Knight

Rance
01-25-2005, 10:24 AM
SOL, VERY APPROPRIATE post!

Another new guy here. I'm in about the same boat as HighOctane. New to CNC but not totally ignorant. I've done a little research and continuing to do more. Areas I'm studying more in are 'Controlling a stepper from my PC', 'Dealing with Backlash', and 'Choosing CNC Software', just to name a few. I'm looking at building a 3-axis CNC Router with a dremel tool head.

Regarding Stepper motors, I'm probably going to work backwards on the first machine. [Your comment "planning the perfect machine while building nothing", fits me to a 'T'. I could (and sometimes do) easilly fall into that trap.] I'd also rather keep the cost of the first machine down to the dirt level. In working backwards though, I have several dead HP Series II & III printers. I'm thinking that there are probably several Stepper motors in those that would be a perfect fit for a first CNC machine. Any idea as to whether these might be sufficient for a first machine? Have you heard of any one else using these? If these are usable, then I could figure out how big of a machine to build from here.

Also, I just downloaded Turbo CNC and am reviewing the manual. This looks to be a good choice for my first controller. Any thoughts on this?

Thanks for any advice or comments you could provide. :)

Rance

ger21
01-25-2005, 10:39 AM
Also, I just downloaded Turbo CNC and am reviewing the manual. This looks to be a good choice for my first controller. Any thoughts on this?

Rance

Probably 90% (or more) of the guys building there own machines use either TurboCNC, or Mach2. Either is a good choice.

mvaughn
01-25-2005, 02:58 PM
I have several dead HP Series II & III printers. I'm thinking that there are probably several Stepper motors in those that would be a perfect fit for a first CNC machine. Any idea as to whether these might be sufficient for a first machine? Have you heard of any one else using these? If these are usable, then I could figure out how big of a machine to build from here.



Rance, I'm using hplaserjet stepper motors in my machine. I haven't hooked them up to the machine yet, but I have spun them and felt the torque they put out. I think they are reasonable for a small machine or moderate depending on if you gear them down.

If you watch my thread in the next week I should be to the point where I'm testing my steppers and you will get an idea of their ability at that time.