New guy questions

[tr4252]

Hi,

My name is Tom, and I'm just getting started. I have a few questions, and would deeply appreciate some advice. I run a Tool & Die shop, but have little CNC experience except a programming class and several years as a draftsman, using autocad.

I'd like to get myself started with a sort of entry level set up, 3 axis, something not too expensive. I have a small vertical milling machine, and a somewhat specialized grinding machine; more on that in a moment.

As far as I can tell, I'll need an extra computer, software, step motor driver(s), and servos. For the sake of simplicity, let's consider the rest my problem. If I may, I'd like to categorize my questions;

1. I need to educate myself; what books, websites, and other resources would you recomend?

2. What software would serve a newcomer like me? I've been "lurking" and get the impression Mach3 is pretty good. Any suggestions for a first timer on the software? Is there anything inexpensive I could use to get started? I'd like to use autocad files, of course, where applicable.

3. I've seen a lot of driver components advertised and discussed, as well as step motors. Where does a guy start the selection process? I know what the mechanical requirements would be, but as to compatability, etc., I'm a bit lost. Would a motor/driver package from one source be the way to go?

4. As a first project, I'd like to turn two lead screws simultaneously, on the above mentioned grinder, in increments of about 6 degrees per pass. The unit is already equipped with limit switches. Can this be done with step motors, without the need to have a computer controlling the operation?

I know how irritating ignorance can be, and am openly displaying my own, but hope some of you guys will find a few moments to respond.

Tom

[NC Cams]

Answers as folliows;

1. Do a "CNC retrofit" search on Google. You'll see tons of adventures and even more ideas as it pertains to DIY CNC. You're sort of asking "what's the best one to use???" and that answer is going to vary according to what you want to do, who you talk to and how much $$$ you want to spend.

2. See #1 above. You first have to decide stepper or servo and then choose software accordingly. For your situation, steppers would me quite adequate.

3. I"d be inclined to consider 1 source. Dealing with incompatibility issues can get ugly when the software guy blames the control card guy who blames the servo/stepper guy who blames the software.

Don't forget the O/S isssue (win vs dos vs linux et al). Turns into a real cluster when you try to get all the stuff to talk to each other. I"m looking at Ajax/CNC but there are others (I need a plug and play and don't have time to deal with a science project). YOu could use Mach (whatever) as it drives steppers easily and is quite economical.

IIF IT IS A JOB (IE: occupation), go 1 source as you have to make a living and can't mess around, If it is a hobby, pick your poison.

4. In a crude word, yes with steppers. Can use a 555 IC to create step pulses at whatever rate you want. You can use a simple toggle switch to switch from CW to CCW in direction. Crude but effective.

IF you add some Red Lion counters (they have application notes that may show how to do bidirection counting via the step pulse) you can simultaneously drive the counters for crude distance quantification (IE; crude DRO).

In a word, what you WANT to do IS QUITE possible IF you know how to do some elementary circuit design and electromechnanical system integration....

[tr4252]

Thank you NC,

I hadn't even considered the operating system issue, and your suggestion to search Google under the topic you mentioned would have taken me a lot of hit-or-miss effort. I appreciate your tolerance for the "what's best" nature of my inquiry.

Steppers were the way I wanted to go; I guess I used the term "servo" a little too broadly.

It's a hobby that generates a lot of income, and I fully intend to integrate the knowledge gained to advance me on the job also, so on a serious scale, I suppose I'm in the range of 6 - 8.

Your suggestion to use IC's was the jackpot answer, for the time being. I've done plenty of circuit boards and wiring, though I confess that sometimes I didn't understand what I was building, just following a schematic. Could you indicate where I could look for the type of circuit you described?

I really appreciate your taking the time to respond. This was my first post here, and I was beginning to wonder if I'd already typecast myself as too dumb to be bothered with.

Tom

[erase42]

http://www.electronickits.com/kit/complete/complete.htm

this site offers a few non computer stepper driver boards and a couple that can work with or without a computer. With a little tinkering you could wire its forward/reverse switches to your table to get your back and forth motion. I assume its a surface type grinder, and you want to get a back and forth motion with a small stepover after each pass? Im sure that could be worked out, and a plus is that these boards allow you to control the speed to a very fine increment.
I do think that if you are going to bother to do it, you should go with the computer control. You can use a very cheap program like quickstep (50 dollars i think) to control exaclty what you want the machine to do. Instead of dealing with switches and such , the program can use actual dimensions so if one part is smaller or larger than the next you can adapt easily. The software also takes care of acceleration and decceleration for you as well. Im not a salesman for the software, but it does have a very handy teach mode that allows you to move the machine around with the jog buttons and record what you want it to do without knowing g code. I use it to automate some of my very simple machines. Ive had a lot of success with it for the money, and it runs fine on a 35 dollar yard sale computer.

[NC Cams]

The IC deal is pretty easy.

Look up LM555 on google (try National Semiconductor). Once you find it, download an application sheet. Once you do that, look for "astable multivibrator". This circuit will give you the pulse. You can easily set the output freq an duration via the instructions.

Simply feed the pulse into a dual input AND gate. Any digital ciruit handbook will show you how to control the AND gate output (IE: toggle switch with a pull up or down resistor).

When AND gate output is on, the thing will move, and won't move when gate output is off.

Direction is toggle plus pull up or pull down on the direction pin.

If the above makes no sense to you, I'd strongly suggest buying something that simply bolts together - you are going to end up doing it with a "yard sale" computer eventually so buy one and do it that way from the get go....

Yes, this is the wrong forum for explaining how to do digital circuitry but I didn't have a site handy to point the member to.....

[tr4252]

Thanks a lot you guys, this does make sense, and I appreciate the input. I don't suppose you've any idea how much this is helping me. (Much)

Hope my gluttony for information doesn't get tiresome, I guess I'm a typical "convert" in that sense.

Tom

[erase42]

Tr4 what function does your "specialized" grinding machine perform? And NC cams, dont dis yard sales, i got a really sweet velvet Elvis there once

[NC Cams]

If I give the impressio of dis'ing yard sales, I appologize.

Yard sales and local re-use center is where we find the latest and greatest state of the art replacements for our DOS driven PC's that need ISA slots.

God, I wish there was a place where you could still buy "legacy" systems at a reasonable price. Getting to be too old for dumpster diving.

(Edit follows) BTW, stay away from Packard Bell and Gateway retreads. We've found that you can't mix-n-match the stuff they used with other industry "standard" stuff. Monitors can get flakey. We haven't seen issues with Dell.

NEC monitors and Diamond video cards are real finds as are Tyan M/B's .

[Goran P.]

to answer the first 2 of your questions, the book i found the most useful was cnc programming handbook by peter smid, makes it all very easy to understand. as far as software goes ive been using mastercam for a few years now and am quite happy with it. hope this helps.

Goran

[tr4252]

erase42,

The grinder I mentioned is a unit I built for the purpose of hollow grinding knife blade bevels (I make custom knives). The X axis is powered by a DC gearmotor and its travel is controlled by movable limit switches. This part of the machine simply travels between the left/right limits continuously, is mounted to a couple of shafts using linear ball bearings. The Y feed mechanism consists of a couple of screws; advancement is done by means of built-in hand adjusted micrometers. It's the function I want to automate, so that I can run the machine more or less unattended. A second set of micrometers, also on the Y plane, angles the fixture to allow the grinding wheel edge to follow the curve of the lower edge of the blade blank. I'm content for the moment to leave them the way they are, but would like to integrate them into whatever control system I eventually use.

Tom

[erase42]

If i understand you correctly, the grinding stone moves left and right down the length of the blade a second screw causes the stone to follow the curve of the blade, and yet another screw actually rotates the stones angle so that the stone remains perpendicular to the curve along the leading edge? If so you may want to look into sheetcam/mach3 combination. they are both inexpensive programs with great support on line by the programs creaters and a set of experienced users. The reason I mention them is that between them it is possible to use what they call tangential control. If both your x and y axis are computer controlled, the program can automatically determine the angle the wheel needs to be rotated in order to keep it perpendicular to the surface. It was designed for machines like fabric or hot knife foam cutters where the cutting tool needs to face into the direction of cut. Les at sheetcam wrote a post processor for me and some others that does the job a little more smoothly than mach3s system ( unless some changes were made since i was playing with it, Art, mach3s creator is alwasy improving and making changes based on user need) Id download the demos and play with them a little. Both are fully functional but mach3 limits program lines to 1000 and im not sure what the limits on sheetcam are but its workable. Good luck with the project, Id love to hear how it turns out.

[MIKE JEFFERS]

tom
have a look at the shereline site,theres a realy useful guide to programming on there someware
as for homebuilt cnc - don't underestimate the way you will be sucked in,if you need
something to keep the money coming in just buy a turn-key solution and mess around
with the other stuff at your leisure.
mike.