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View Full Version : Mentor needed - I fabricate, you teach cnc? L.A. California



runinbymdnt
10-03-2006, 07:25 PM
Hello - I have a small fabrication shop in Northridge Ca. nothing too special, lathe, mill, Tig, Mig and misc. I am going to build a cnc router, then if that goes well and I expect it will, I am going to convert my mill to cnc.

I could use help understanding what happens between my Cad model and the servo motors, if you know what I mean. Yes I have a basic understanding the whole process, but thought it would be cool if someone could coach me in this area.

I would be happy to do some fabrication in trade.

Thanks
JimK

Tinmuk
11-28-2006, 09:31 PM
Hi Jim,

Although I am not an expert in the entire process, I could probably help you with some of the stuff that goes on between the box and the motors. I am in San Fernando.

Robi

runinbymdnt
11-28-2006, 11:02 PM
Hello Robi,

That would be great. I didnt think I would get a response, I posted this quite a while ago. What kind of work do you do? Anything I could help you with?
My name is Jim, Glad to meet you.

Tinmuk
11-28-2006, 11:11 PM
The shop I am at now does components for medical devices. We have 3 Citizen L20's, 2 Haas mini mills, 2 Nakamuras and a Haas VF1. I do have some fab needs, but we could discuss those later.

How would you like to proceed? I could come by your shop and we could talk about CNC stuff there. Or you could come by my shop and see what we've got going. It's up to you.

Robi

runinbymdnt
11-29-2006, 01:03 AM
There is no cnc stuff at my shop, yet, so it might make more sense if I come see your place and see how its realy done. Then if you like, your more than welcome to come to my shop. I have seen cnc machines many times, I just dont fully understand what makes them tic.

Have you heard of or used Mach 3?

I will send my phone # in a private message. Call me anytime and we can plan a visit.

runinbymdnt
12-01-2006, 11:28 PM
Hey Robi

You get busy? Big job? Employee problems? Are you still interested in meeting to talk CNC?

I sent you a private message with my phone #, Call anytime.

JK

jdt
12-02-2006, 12:28 AM
Hey Jim -

If you ever have reason to be in Santa Barabara - I would be glad to help out.

I made a CNC system based on aTaig Micromill:

My goal during the development of this project was to design, build, and program all the electronics and software that turned "drawings into parts".

I designed and built the drivers that control the motion of the axis motors (bi-polar stepper motors). I wrote a windows program that interprets G-code and instructs the motor drives of what they need to do (similar function to Mach3 - but my system impliments a custom mircocontroller "interface board" to precisely control motion timing). Finally, I closed the drawing-into-parts loop by writing a "simple" CAM program to turn dxf files into G-code.

None of this development was actually an attempt to save money... I just wanted to have fun and learn something. Mission Accomplished!! Now I am having an incredible amount of fun machining metal & making parts to improve this tool and make others... a never ending cycle!!

I don't claim that this system is the most sophisitcated around. That was not my intention. I, however, am very happy with the end results - and I am now intimately familiar with every aspect of turning drawings into parts - CNC STYLE.

runinbymdnt
12-02-2006, 12:53 AM
Jdt, wow! Some hobby you have. I understood only about 10% of what you said but I liked it.
What do you do profesionally? I am asuming not this, cause you didnt do it to save money.
I do end up in Santa Barabara on occasion, but not often. That doesnt mean all your new found knowlage cant make its way down here electronicly. This forum might be a way share some of that if your interested. I know I am not the only one that doesnt quite get it.

Tell me your thoughts, well not all of them, but what do you think about me asking dumb questions and you giving answers? I think just you and I could keep that going for a while, but I bet that others would join in.

Jim

Tinmuk
12-02-2006, 12:55 AM
Yeah, we have major medical customer we do Kanban releases for and todays shipment of Delrin didn't come in. Hectic dosn't even describe it.

I have my National Guard drill this weekend. I wont be able to talk until next week. sorry.

Robi

runinbymdnt
12-02-2006, 01:07 AM
Yeah, we have major medical customer we do Kanban releases for and todays shipment of Delrin didn't come in. Hectic dosn't even describe it.

I have my National Guard drill this weekend. I wont be able to talk until next week. sorry.

Robi

National Gaurd? Thanks for that.
Lets stay in touch, I would love to see your shop and talk cnc. I may be speaking to a guy in Santa Barabara (check the post above) and I think he has something to teach me. Maybe then our conversations on the subject might be a bit more intelligent.

Talk soon
Jim

jdt
12-02-2006, 02:48 AM
Hey Jim,

By profession, I am a mechanical engineer... so I guess by nature I like knowing the way things "work", I like to experiment with new ideas and, in general, I like to make things...

Computer programming has also been an interest of mine. So, building a CNC machining system gave me the opportunity to combine all my interests.

Starting out, I didn't have to tools or resources to build the entire machine (though this will be my next project), so I bought a Mill to "convert" to computer controlled motion. My focus was to build the electronics and the software to make it happen.

The first step of this conversion is to replace the manual turning of the feed screw with a motor to do the job for you....

In basic terms, motors are pretty simple. You run current through their windings to produce a torque that makes the motor want to turn. The trick is - you have to control the current running through the motor properly to make it turn the way you want (speed, direction, force, etc...). This is the job of the motor driver - control the current (rotation) of the motor. Different types of motors (steppers, brushed DC, brushless) have different nuances that make them work; the bottom line, the motor driver controls the the current running through the motor to make it turn they way you want it to.

Attached, you will find a picture of the "X" and "Y" axis motor drives that I made. I won't go into the detail of these here, but can I expand as you like later ...

So, the drivers control how the motors turn... but they have to be told what you want the motors to do. In order for you to tell the driver what to do, you have to speak a common "language". There is an endless possiblily of lanugauges here, but an often used language is "step and direction". Each time the driver recieves a "step" command it moves the motor by a defined increment in the commanded direction. If you do this extremely fast with a small increment you get a smooth and continous motion the way you intended... THATS JUST FUN!!

So, to communicate with the driver you need to break the intended motion into thousands (maybe millions) of "step and direction" pulses (or whateever other language you have decided to speak with your driver in). The idea here is that you want to convert something you understand (like move 2 inches left and 4 inches up) into something the driver understands (like step 435,324 times clockwise and 12,034 times counterclockwise). Well, the full possibilites of what "you understand" and what the driver "understands" are endless... So a standard "lanugauge" is used in between. This is called G-code. Again, we'll get into the details later.

I wrote a program that can interpret this G-code language (remeber, this is an industry standard) and talk to my drivers in something they understand. This is what I call the G-code interpreter. It takes a known language by everybody in the industry (G-code) - and talks to my motor drivers
in whatever they understand (be they steppers, brushless, linear actuaters, whatever...).

So, the final piece of the puzzle is taking a drawing (part model) and converting it to G code. This is where the CAM (computer aided machining) software comes into play. It has to be able to take the physical geometery of the part, understand how you can machine materials, and output the proverbial G-code! Simple. Right?

Maybe not simple - but a whole lot of fun!!

runinbymdnt
12-03-2006, 10:54 PM
Thanks JDT. Sorry I have been real busy, and wil be for another week. I would love to continur this discussion, but cant put the time in right now. I too do a little mechanical engeneering, by the seat of my pant, as I have come up throuth the ranks as a carpenter then a product development engineer doing mostly steel and aluminum fabrication with some high current low voltage stuff. (Lightweight electric vehicles), long story, I'll tell you all about it if your interested.

You built that controller? wow. Electronics have allways interested me, but so does everything else, so I have not done much of it.

Thanks for the breakdown above, the G-code is my area of foggyness. I'm sure it wont be foggy for long.

I looked up that little mill on the internet. Thats a nice little machine. I can only imagine how much fun you are having. I look forward to making chips automaticly myself.

By the way, I have a Lathe, mill, welders and stuff like that. If you need some stuff made or modified, and dont have acess to those machines, I'm sure we could get it done. Let me know.

All for now

Jim K