A Newbie's View

[m_c]

Hi,

I subscribed to this site a couple days ago and have been looking at various posts.
My aim is to build a cnc table for my plasma cutter, however I'm totally new to cnc. I understand the very basics of cnc (ie design a part using CAD, export to suitable software for controlling the machine, and using a magic box, it works the machine).
As a newbie, what I'm interested in, is each step in designing a suitable machine. From the various posts and sites I've looked at, the design process goes something like -

1 - design +build the table/machine mechanics
2 - size + add suitable motors/servos
3 - add suitable motor controllers
4 - install suitable software to control motors

Having read the discussions in the opensource forum about making plans for a beginner, here's my thoughts.

What I'd really like as a newbie, is something that explains each step in turn, and shows different ways of doing it (ie, for the movement - using linear slides, bearings running on bar......), and the pros + cons of each item.

Personally I'm not interested in a complete set of plans, as from past experience, this normally leads to difficulties in locating parts, and things can get complicated when you have to start modifying plans to suit what materials you have at hand. What I'd really like is a source that I could refer to when designing my own machine.

Currently I'm at the stage of skectching plans for the mechanics of the machine, and was planning on posting them to the plasma discussion forum, to see what thoughts they have about my proposed plans. But if everybody designing a machine was to do this, then the forum would become even worse for any newbies like me who come along later, and are starting from scratch.

I have found this site to be a good resource, but for someone like me who has very little knowledge, to be met by a forum discussing 20+ (a rough guess) different software programs, and discussions about various controllers, is mind boggling and could put many people off cnc. What I really want is a site that explains all these things, but not one that over simplifies things (the description of a rack + pinion, and screw + nut in one of the opensource discussions was far too simplified, as most people who are thinking about cnc, probably already have some machine experience, and would already know these things, and personally I find it patronising reading such things as I feel as though the poster is treating newbies as complete idiots).

Moray

PS. No offence intended to any other posters in the above mentioned discussions, these are just my own personal views as a newbie to cnc.

[kong]

Some valid points there moray, welcome aboard
Particularly important is the point about sourcing parts, since the price differences across the world will be large.
I think you should post your plans in the plasma forum, since this may be a big help to newcomers, especially since there are not a lot of plans/ideas around for this type of machine.

[ynneb]

Moray, I guess its a case of sifting untill you get the information you want, in the presentation style you want it. Once you have processed the information you then give it back to others in a way that you think is acceptable. It may not be the best method here, but you must remember this is a forum that caters for people from all around the world and at different levels of understanding. Read enough posts and you will get the jist of how to do what you want. Before I found this site I had never heard of CNC before. Within 4 months after that I had built my own working machine that is active duty every day. It just takes lots of reading, and posting lots of dumb questions.

[m_c]

I understand the points you have raised ynneb, however having to sift through this forum trying to understand and find what you want can be very time consuming. Also for the newbie who knows very little about cnc, even a basic intro would be very beneficial.

Personally as a newbie, I found although there are lots of helpful posts, the task of reading throught them is very daunting, and would very much appreciate a basic intro.

I also find that if I know and understand the basics, then finding out more details is far easier, as I then know what posts to search for, and can ask more specific questions if they have not been asked before.

Anyway, enough of my ramblings, I'm away to think about the design of my plasma cutter, and get some advice from the many helpful members of this forum.

Moray

PS. I'll try and get my initial doodles scanned tomorrow, and posted to the site.

[ynneb]

Moray, here is the start of a document I am working on. I was hoping people could add lots to it, so as to make it a good guide to newbies. I have lost momentum because I haven't had any submissions. Any how I think this is sort of what you are talking about.

http://www.cnczone.com/forums/attach...=&postid=35087

[High Seas]

moray
Sounds like you're looking for a "design - or style guide" and not a set of plans. Seems to me like you have a good plan in mind to approach the "daunting task" ahead
QUOTE:
1 - design +build the table/machine mechanics
2 - size + add suitable motors/servos
3 - add suitable motor controllers
4 - install suitable software to control motors
UNQUOTE

1- By making it a Plasma Cutter - you'll have some size ideas to work with, what and how big. You'll want some rigidity to keep things moving and square that should - and those tings that shouldn't. That will drive your choice of materials and their resultant weights and costs. There will be more than several approaches to the construction methods, and you'll also be looking at choosing the type of drive, threaded rod (direct drive or geared), cog drive system, belts/wires, etc. All have their advantages and associated resolution. You'll need to decide how "close" you want to cut parts and then pick a means of motion. This also ties into the choice of linear ways - so it looks simple - but, "the devil's in the details."
2 - With the above worked out it will be as you suggest - picking the size motors - and power supply.
3 & 4 - The integration of the motors (from above) with the controllers and software has seemed to be the "ART" of getting this right. You might check out what other folks are using in the "plasma world" . - software wise and then "back into" the selection of servos or steppers - or get their recommendations.
Budget and time seem to be important factors as well - so certainly you've planned accordingly - assuming you're a Scot!!

Have you looked at the downloads section? The roadmap might spark some ideas too - again moving table/gantry etc...
here's a link if you haven't tripped into it yet:
http://www.cnczone.com/downloads/new...p_document.pdf

Welcome aboard - we'll all stand by I'm sure to offer help and encouragement - as you've got questions ask away! You might consider starting a thread to "journal" your progress - or the Journal feature The site owner put together. BUT be sure and take Heaps of pickies!

Cheers - Jim

[m_c]

Just read your signature line, guess your proper name is benny?

That document you just posted the link to is the ideal start. I think you should put the first 2 pages seperate, then create seperate documents for each sub heading going into a bit more detail (or even in the same document, with links to the more detailed pages).

If I had of read that a couple days ago, it would of helped me a great deal, as I was unsure about power supplies, driver cards + motors, and would of helped me get the basics a lot quicker, and removing a lot of the guesses I took.

I just hope that some of the more experienced members will contribute and help expand the document.

Even just reading the first 2 pages has helped clarify a few things that i was still unsure about.
Now, I just need to get the mechanics designed and built, then I can start thinking about types/sizes of motors, what controllers to use, a suitable PSU and suitable software.
I'm sure with the help of this forum, I'll get there. Eventually.

thanks
moray

[m_c]

Jim, you're reply must of slipped in while i was replying to benny's post.

Your roadmap document also highlights some good points. I'll try my best to keep a journal, and get plenty of pics.

As for my ideas, I have been thinking about this for a while, however have only just purchased the plasma cutter, and can now start to think about building the CNC table.

I have my own ideas for the basic machine, including size, layout slides. But as you say, "the devil's in the details."

I won't say anymore about my plans here, as i don't want to stray too far off topic.

moray

[rustyolddo]

As I newbie, I'd like to submit my suggestions as well. I've spent hours gleaning the web for information. Benny, you are off to a good start. Basically, I knew I needed steppers and a driver board. As to Unipolar, bipolar, I didn't know. As to what size steppers I needed, I didn't know. As for software, again I didn't know. What I have discovered so far is that the chopper style driver board that I bought from hobbyCNC was a good choice. The 174 oz/in steppers were a good choice. I found TurboCNC shareware that allowed me to spin the motors. Now I need some kind of CAD/CAM and some understanding of G-Code and this seems to be my current sticking point. No one seems to make a basic CAD/CAM program cheaply or shareware for a hobbiest. Nor have I found a good G-Code tutorial. I'd gladly hand code a few programs to get the feel of it all. Mind you, I haven't fully explored cnczone, I'm working on it.

Take note software developers:

I'd like a basic CAD/CAM program without tons of overwhelming features and a steep learning curve. Something that could do a basic part like you would be able to do with a manual mill and a rotary table. I'd like this to be a freeware program to get me interested aka "hooked" on your product & it's manner of navigation then I could pay to upgrade to the full featured program. More so, I'd like to only buy the features or modules that I need as I need them and as I learn them. It's overwhelming to have all the icons and features choices as I'm trying to do something as basic as draw a square box. Seriously, this is intimidating for a first time CAD user. It should be more intuative to draw something as simple as a box or circle without reading a doc for two hours. If I want a text engraving module, or raster module, then I'll gladly pay to have that feature enabled. Same with all the wireframe and solid surface stuff. Include the tutorials as part of the package. Offer the very basic core software for free and sell me the rest. As I learn CAD/CAM I'll find the need to do increasingly sophisticated operations. As of right now, CAD/CAM software is my sticking point, if anyone has suggestions, let me know. I don't want to shell out $500+ for a software package that I may never need or master. The easier it is to learn, like turboCNC, the more enthused I am about it. I'll gladly betatest or work with a developer on this. I know that it is a considerable sticking point for other newbies like myself.

It would be nice to group all this info in one place. Have a intro to CNC type FAQ or forum where folks can build the same basic demo type CNC machine from a set of plans, cheaply using off the shelf parts. Kind of like they do for High School shop or robotic classes.
Use a wood frame, drawer slides, all-thread, cheap steppers, readily available couplers & hardware, a Dremel or a pen even and the software. Folks can sit down, lash the thing together, go ooh, ahhh and learn how it all works then move to something advanced like converting a mill or lathe or building a CNC router or plasma cutter. Right now, I'd be thrilled if I could make a machine draw a square box on a piece of paper. I continue to spend hours searching for information, currently searching for CAD/CAM software, to get more involved in CNC. I get bits and pieces all over the web but no significant chunk in one place. I'm going to do my best to document my journey and perhaps it will be a useful addition to this and other sites.

[kong]

Try Ace converter from http://www.dakeng.com/ace.html
This is as simple as it gets, you will need to work out your own tool offsets - I mean redraw yuor part in your cad program, offsetting each line by the radius of the cutter you intend to use, then it will produce the g-code for you. The best thing is, it's free, and good at what it does. Hoep it helps.

[CNCadmin]

Originally posted by rustyolddo

It would be nice to group all this info in one place. Have a intro to CNC type FAQ or forum where folks can build the same basic demo type CNC machine from a set of plans, cheaply using off the shelf parts

We have somthing like that here - http://www.cnczone.com/modules.php?name=Sections

[chuckknigh]

What I'd really like as a newbie, is something that explains each step in turn, and shows different ways of doing it (ie, for the movement - using linear slides, bearings running on bar......), and the pros + cons of each item.

Personally I'm not interested in a complete set of plans, as from past experience, this normally leads to difficulties in locating parts, and things can get complicated when you have to start modifying plans to suit what materials you have at hand. What I'd really like is a source that I could refer to when designing my own machine.

You are a very rare person, Moray. You actually *don't* want to be told what to do, in detail. The vast majority of newcomers ask certain questions, with "are there plans" being one of the most common. You seem to want to actually understand how things work, together.

Bravo.

What I really want is a site that explains all these things, but not one that over simplifies things (the description of a rack + pinion, and screw + nut in one of the opensource discussions was far too simplified, as most people who are thinking about cnc, probably already have some machine experience, and would already know these things, and personally I find it patronising reading such things as I feel as though the poster is treating newbies as complete idiots).

Actually, it was me who wrote much of that thread. You'd be surprised how "simple and basic" most of the FAQs on this board really are. What is a linear slide is one of the more common ones...what is a lead screw is another. ACME thread...huh? Go back through the archives of the "Wood router forum" posts, and you'll see what I mean. Most of them are not about machining issues...most are asking for a definition of something as basic as backlash!

You have to remember...not everyone comes to this hobby from a machining background. I certainly didn't. I'm a programmer...I come from the computer and electronics side of things. This hobby is a synthesis of machining, and computer science, with a bit of robotics thrown in for good measure. That makes for an interesting mix of people.

Since I was asked to contribute to the "motion" section, I wrote out the answers to the FAQs that I saw, the best way I knew how. It was never my intention to be patronizing...and I would welcome your help to improve it. Between the two of us, I know we can make it better! So...what are your FAQs, as a newbie?

-- Chuck Knight