CNC Noobie, need help

[NewCents]

Hello fellow CNC enthusiasts!

#1 - I would like to build a CNC mill with a large envelope.
#2 - I don't know much about CNC but am very eager to learn.

I saw the plans at crankorgan.com. In order to modify his existing plans to create a machine with a larger envelope (4'x2'x2') which plan should I purchase, or is this a bad place to start? Keep in mind I have never built a CNC machine and need a good starting point. I would love to build a smaller machine to gain some experience. I know by following his plans I would have a pretty slow machine (12" a minute). I emailed him and he said I would need an upgraded servo motor system for faster results. He was not able to help me on which plans I should purchase.

Any help appreciated!

Thank you,
Chris

[Ken_Shea]

NewCents,
It sure would be nice if all our questions could be answered in a couple of paragraphs, unfortunately they cant. There is a enormous amount of information on this site, you need to spend some time reading as much as you can here. There seems to be a lot of support in starting with a small CNC and then building a larger machine with what you have learned. Personally, I could not do that but it does make a lot of practical sense. I think most also agree crankorgan's plans are a great starting point. You do not always need servo's to go fast, what ever fast is

Best to you.

Ken

[chuckknigh]

I wholeheartedly agree on building small, first. And, let me just add to it -- build CHEAP, first. Don't spend a lot of money on it, since very little of it will be reusable for a big machine. Just get something moving.

Now, having said that, DO spend money on some driver boards...those can be transferred over to your big machine. DO spend money on your motors, if you choose to...those can be transferred over...but small motors can be had so cheaply, that this one is just a "maybe."

The bottom line is that you should just get something going, under computer control. All of us who've built "good" machines the first time, say that it was not the best way to do it. We learned so much by the experience, that we wanted to (and often did) redesign the machines halfway through. MANY of us have moved on to machine number 2...and a few of us have more versions than that!

You don't necessarily need a set of plans to do this...and especially if you intend to heavily modify them. Read this forum, and the "Open Source" forum...you'll eventually have a "eureka" moment, and you'll get it. At least that's how it happened for me.

As for "upgraded servo motors," I would tend to disagree, if John suggested servo motors. There are 2 kinds of motors that can be used for this project...stepper motors and servo motors. Unless you have the need for extremely high speed movements, and optical fedback...that kind of thing, I'd just go with steppers. The motors *and* the electronics are usually cheaper for steppers, and that's what most of us use.

Just remember...engineering is a balancing act -- we'll be happy to help you figure out the right balance for you. In the meantime, ask questions...LOTS of questions. And read a LOT.

So, what's your background? Machinist? Computer programmer? Modder? Something else?

-- Chuck Knight

P.S. Though I've not seen them, John's plans, according to all reports, are exceptionally good. They have resulted in more working machines, than any other planset I'm familiar with. In fact, John is probably the person who most helped bring CNC to the home workshop...heck, even those of us who've not built his plans even admit to being inspired by his designs!

P.P.S. 4 feet by 2 feet by 2 feet? The 2 foot vertical dimension is going to be a challenge to keep stiff...it's a 2 foot long cantilevered arm, with some potentially significant forces applied to the end of it. Yours should prove to be an interesting project. What do you intend to do with it? You've got me curious!

[NewCents]

THANK YOU SOO MUCH GUYS!!!

Ok here's the closest thing I could find to what I'm trying to accomplish:
http://www.machinecnc.com/cnc_router.html

He says he modified the Routezilla II plans found at crankorgan.com. I am going to go this exact route. The envelope on his machine looks almost perfect, I just wonder how much the z-axis can be extended? Looks like the z-axis is at 9" on his machine, wow!

As far as my background I always wanted to be an engineer but settled for a BS in Computer Science.

Thanks again for responding so quickly!

Chris

[Ken_Shea]

Going higher on the Z brings in a lot of factors, heavier and more carefully considered construction, consequently more powerful motors to move the added weight, greater load on the rails requiring better rails and bearings. I am not criticizing the gas pipe in any manner or the style of bearings that ride on them but if at all possible upgrade these to what your budget will allow, if gas pipe is it then by all means use that. Much better options are available for not a great deal more money. Here is a link for very affordable linear rail and bearings.

http://www.vxb.com/miva/merchant.mv?...tegory_Code=LM

Ken

[Patrick2by4]

hey chris,
the author of that machine said he had too many problems with the machine he built and made a second machine, see what he wrote about the original machine.
http://www.machinecnc.com/router__2.html

[NewCents]

Ohhh no. I didn't realize he was talking about that particular machine, I thought he was talking about one he hadn't posted on his web site or something. Well this changes everything. What if I followed something along these lines instead:

http://www.everbriteoem.com/CNC.HTML

I wouldn't have two movable surfaces at the bottom as this machine shows, but one large one. It looks like an extremely large version of the "7th Sojourn" at crankorgan.com. I'm only comparing it to John's plans because I don't have any experience in CNC and would like to purchase these plans as a start. Would 7th Sojourn be a good machine to modify to get to a large envelope?

Thanks again guys!
Chris

[Patrick2by4]

John's plans are a good place to start. But once you start altering the original specs, you are have to make corresponding changes in motor size, rail size, etc... Look at some of the projects in this site and get a good feel about how a cnc machine works, the problems people run into, so on... You'll have a better machine in the end.

[chuckknigh]

OK, let's start with your intention for this machine. What do you intend to do with it? If you're carving statues out of solid blocks of ebony (almost like cutting metal, or stone), you'll need a different design than if you're cutting airplane parts from balsa. If you're doing inlay work, your precision will need to be higher, than if you're cutting out plywood yard signs. Different machine tolerances, for different uses...

Let's pin down your requirements -- then we'll help you identify the types of components you need. It's obvious that neither the "routezilla" nor the "7th sojourn" planset is going to work for you, unmodified...let us help you with the design. But, to do that, we need more information.

BTW, why do you need a 2 foot Z clearance? That seems HUGE.

-- Chuck Knight

[Cliff_J]

Chris - I've purchased John's plans, the 'Morph' is the one I purchased. It doesn't have the angle-iron roller bearings but a slightly different design. His plans are decent and it'd be worthwhile for you to build one of his machines spending the $50-100 and get the machine up and running. You will learn enough from the machine's weaknesses to write your own course on building a CNC.

A lot of the CNC world is over-focused on super-high precision movement. John decided that a lot of applications have no need for extra precise movement. Bravo, this is quite true and he fits that niche. But I was on my 3rd revision before I got enough repeatability with my 'little' router to cut styrofoam to a level of precision that's acceptable. Any tougher materials will increase the machine requirements and the plans need to be accomodating.

Let us know what you're planning on cutting. The guy with the 4'x8'x6" CadCut plans made a foam plug for a boat hull in layers of foam with what looks like a 6" router bit. Very difficult to find a deeper bit and even commercial machines that exceed this by much. For me, this is a reason I think that 6" is a good practical limit since gouging the piece with the router's collet is not a fun experience. Take a look at what he did.
http://www.inshorepowerboats.com/cnc...cncrouter2.htm

Cliff

[NewCents]

Ok, this is some great information. I looked at that web site Cliff_J. The boat hull plug made out of layers of foam is exactly what I would like to do. In an attempt to keep the number of layers used to make the plug down to a minimum, I would like to increase the z-axis for my application. I followed this link on the inshorsepowerboats.com site:
http://www.data-cut.com/Page2.html

Looks as though the envelope for this Data-Cut machine is 49"x30"x10". I wonder how much further the z-axis could be extended on this machine.

Chuckknigh - I plan on milling foam and wood. I will be creating plugs such as the boat plug seen on the web site Cliff_J posted.

Again thanks for all the help! This forum is wundervoll.

Chris

[Cliff_J]

Yeah, the only thing is I wished I'd found the forum a little sooner, would've made things easier for me. But then there isn't that satisfaction that comes from coming up with a solution after knocking one's head against a barrier for a while...

Again, the only reason I've dropped any plans for more than 8" of z-axis travel on my machine is I cannot find a router bit that can accomodate what I need. To explain what I mean, imagine a kids wading pool and lets say you wanted to route that from a giant block of foam. Even if the walls are only 10" high, if they aren't tilted back enough from vertical than your router will smash into the sides of the walls when it tries to route the last bit of depth because the bit isn't long enough to do it by itself. For me, I've dropped such ideas until I can build my business a bit and have it pay to build a 5-axis machine to accomdate monster depth requirements.

Also, any time you extend things, the forces/moment increases and thus flex may introduce more errors.

Best bet is to email/post to the people offering the plans you're ideas and ask them how well they feel their machines can work with your criteria. They will know the most, and I believe they both have their own forum here to answer such questions.

Good luck.
Cliff