Basic CNC

[Bill Gruby]

I tried. this thread never even reached first base. I'm throwin in the towel. :whiteflag:

"Billy G"

 

[7HC]

I tried. this thread never even reached first base. I'm throwin in the towel. :whiteflag:

"Billy G"

Maybe you're just having a bad day Bill, there's been useful information and discussion from the start.


M

 

[Bill Gruby]

From the beginning this thread has not been mine, it wasn't meant to be. I started it for all of the people here that knew little or nothing about CNC and how it works. I went as far as I could with my little knowledge of CNC and opened it up for everyone else. Nothing happened.

I am not complaining about it, and yes there is a lot of info here but I'm just a little surprised it has not gone any further than it has. You are the first post other than mine in a couple of days. I cannot go any further with it until someone asks more basic questions. Yes I have a few more but this is not the right time to ask them. We would start jumping all over the place with this thread and that would not be a good thing.

I have seen questions asked in other threads that were answered here before they were posted elsewhere. This is a heads up for me. I am going to leave it at that and say no more. I will watch for this thread to start again.

"Billy G"

 

[JohnAspinall]

I, for one, greatly appreciate the effort you put into this, Bill. I don't think the effort is wasted; I do have a suggestion for Version 2.

Consider a spectrum from "student-driven" to "teacher-driven".
Student driven:

• I (student) know what I want to learn, and (just as important) I know what I don't want to spend time on.
• Let's just ask questions. Sooner or later, every question will get asked, and we'll all know everything we want to learn.
• As we make progress, we (students) will ask better questions, and we'll help each other over the hard parts.

Teacher driven:

• There are many ways to learn a subject, some paths are far more efficient than others.
• Someone who already knows the subject, is better suited to picking the path.

This is a spectrum, between those two extremes. You don't have to pick one or the other; you have to pick somewhere in the middle that is comfortable for the greatest number of participants.
At first, especially in an online forum like this, I think students rush to ask questions and you think the process is going great. But the questions get more and more specific, and when that particular discussion is exhausted, so are the students! Everyone looks around, wondering what to do next because there's no obvious next question.

This is what happened here (i.m.h.o.). There's no one with the 50,000 foot view. A lot of time was spent covering every single side street in one neighborhood, but now we've got to head for another town, and all its neighborhoods. Here's where this discussion needs a high level road map.

Something else too: People have limited time, they have only a certain amount of attention to give. You give them lots of detail, how can that be bad? It can be bad by exhausting their attention that would be better spent on other things they want to learn.

In short, this effort needs to be a little more teacher driven. That doesn't mean we have to find a single expert and convince them to write posts for hours and hours. But here's where an expert can help. An expert can:

• lay out the landscape (the curriculum),
• throttle the discussion when it dives too deep
• move it on to the next big topic

(When I say "throttle the discussion" I don't mean saying "Shut up now.". I mean saying "that's a detailed topic that might be interesting for some, but is not necessary for understanding what comes next. So go ahead and discuss it on a secondary thread, but it's ok for some people to ignore that secondary thread.")

Concrete example: steppers vs. servos.
50,000 foot view: They're electric motor systems that go to a commanded position. You don't care about the differences between them when it comes to topics like writing G-code, using limit switches,.... You will need to know something about the differences when we cover topics like cost and performance, estimating your torque requirements, symptoms of things going wrong.
5,000 foot view: We're talking about choosing your motors. Both steppers and servos are systems, with driver electronics, and sometimes other components in addition to an electric motor. Because steppers are the most economical choice for many hobbyists, we will descend into more detail on steppers to begin with. If you care about servos, see...
500 foot view: We're talking about how much position resolution you can get with steppers. Blah blah, microstepping, blah blah, gearing down.....
500 foot view (different neighborhood): We're talking about holding torque in steppers. Blah blah cogging, ....
5000 foot view (different town): We're talking about what goes wrong when the machine is overloaded. This is an area where servos and stepper have different behavior. ....

I hope that gives you some idea of what might be a different way to try this again.

Disclaimer: I'm not a CNC expert. I've never built a CNC machine; I've never even operated a CNC machine. I'm simply throwing my 2 cents out there on the basis of what I read. Hope it helps in some way.

 

[DMS]

This thread could be done. We covered:

* Motors (mostly steppers, but some stuff on servos)
* Screws
* Couplers
* Motor Controllers/Drivers
* Software Controllers

Yep, that's the basics. I think we even crossed over into some intermediate and advanced stuff.

YEAH US!

Extending what JohnAspinall said, The order listed above is probably a good order for a curriculum, and is more or less the order we covered things in.

The things we haven't really covered are the CAM/GCode portion, maybe that is better off on a different thread.

 

[jumps4]

we didnt cover breakout boards very much and the different types, how they work with your operating system and better options that of course cost more.
i have been busy converting my lathe to cnc or would have posted more. I have a breakout board problem right now that is because it is too slow. even though my new controler is a usb connection it has to connect to the system i built through a breakout board. the one that came with my controlers is opticaly isolated and they are really slow ones so i ordered a hard wired db25 breakout board. this isolation thing to protect the pc can add up to be a problem. if everything you have between your pc and the drivers is optoisolated each add a little lag to the speed and the cheap ones are slow. my pc can put out 35000hz at the printer port my usb uc100 puts out 100000hz thats pretty fast but this breakout board will only process at about 20000hz so a fast pc and fast controler hits a choke point at the breakout board and slow the entire machine. the uc100 is optoisolated the drivers are optoisolated i dont need it at the breakout board also. i'm over protecting a pc that cost less than all of the other parts lol
steve

 

[DMS]

I realized I made a mistake on the "half step/full-step/microstep" post, and for some reason I can't edit that post, so I am posting a correction in a new post. Please refer to new visual aid:

Everything in the original post was correct except the diagram, and the description of full step mode. Instead of one phase being on, and the other off, both phases are always on, and each phase reverses direction alternately. That's what I get for relying on my memory :shrugs:.

 

[HSS]

I think this thread has good information and has been well recieved and I appreciate it. I have a full-time day job, as I'm sure many of you do, and I don't get on the computer everyday. It might even be a week before I turn the computer on, so just because people aren't responding to the thread, doesn't mean it isn't working. Y'all keep up the good work and it'll happen.
Patrick

 

[rogerrabbit]

Billy G,

Ok, I'll give it a shot where I would like to see this go (on a 5k ft level)

1. Types of implementations:
A. Lathe type CNC
B. Mill type CNC (i would include the home built CNC router type solutions).


For each above:
A. how do they work? (basics right? ))
B. what are the differences?
C. If I am new to the CNC world, which type should a start with assuming I have either both a mill and lathe or neither.
D. for each, buy a machine, convert existing, or build from scratch?
Something like
new: high $$$, but software & machine integrate well.
convert: med $$, but kit may not be available, anyone have experience with a kit they would like to share/
build: low $, but you need to plan ahead to make sure software works with machine.

d might be a stretch for a basic thread though.. your call?

Roger

 

[Bill Gruby]

Been waitin for this one Roger. Thank you. There it is gents, your turn.

"Billy G":thinking: