Looking for educational direction

[cote442]

I'm looking for some advice. I'm as green as they come but I am going to get there. My main goal is to be able to do 3d wood work with a cnc. I'm in the process of looking for a cnc machine 4x8. I'd like to be able to use Artcam with it. I'll be straight out honest. I might sound a little silly with my questions. I keep hearing of this Mach 3 program. Do I need that first than Artcam? Is there specific things I should be looking for on a high precision cnc machine (what specs)? Can any one point me in a good direction for reading. Are there certain books I should shove my nose in first? I ask all these questions because when I research them it feels like I'm going in a circle with no clear answers. If anyone can give me even a whisker of advice I'd appreciate it so much. I'm eager to learn

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[Jim Dawson]

You are asking great questions.

The path from an idea to a finished project has multiple steps. First you have to draw the part in some kind of Computer Aided Drafting (CAD) program, then you run it through a Computer Aided Manufacturing (CAM) program, then apply that output (G-code) to a Computer Numeric Control (CNC) program that actually runs the machine.

I think ArtCam will handle both the CAD and CAM functions. ArtCam outputs G-code that a CNC program can understand. But you still need the CNC program. Mach3 is one option for a CNC program.

First you need to define what ''high precision'' means to you and decide what is an acceptable level of error. No machine is perfect, and the cost of the machine goes up as function of roughly 1 / the square of the precision. 0.01'' accuracy is relatively inexpensive and in the range of most hobby class machines, many are a bit better. Consistent 0.001'' accuracy is going to be expensive and is in the range of heavy industrial class machines. Now it's a matter of balancing your budget against the precision that you want. I usually describe it like this: Accuracy, Speed, Cheap; choose any two.

Now you have to decide what drive system you want on the machine, Open loop stepper (least accurate, least expensive), closed loop stepper (better, slightly higher cost), full on AC servo (most accurate, most expensive). Ball screw drive is generally more accurate than rack & pinion or timing belt drive.

There are two main type of machines, moving gantry and fixed gantry. In the case of the fixed gantry machine, the table moves in at least one axis rather than the gantry. These are generally more rigid machines and thus more accurate, but require larger axis motors and are more expensive. They also take up more floor space, an 8 foot machine would be about 14 feet long.

The higher end machines normally come with their own CNC software. Many hobby class machines do not come with any CNC software, some are supplied with a trial version of Mach3, no computer, but are ready to connect your computer. Mach3 has a lot of online support through user groups and forums like CNC Zone.

I hope this helps get you started.

[cote442]

Actually that helps quite a bit. My budget is probably the issue. I'm looking at 10k. I was looking at this CNC ROUTER 4 x 8 | eBay but doesn't seem to have a ton of info with it. I wanted to dive into something with a 4th axis so I could router column posts. This seemed to look like my best middle of the road option. I'm figuring this would be one of those .01 accuracy systems. Which in my mind seems reasonable enough. accuracy and cheap would be my main concerns. Speed really wouldn't matter (I think). I'm really not even too scared to build my own. I have access to metal at a reasonable price. Plenty plenty of floor space so I think its doable. I've been thinking making my own would be more benefical to me just so I'd be educated on exactly what did what. Your response though has giving me a go in the right direction. I thank you

[Jim Dawson]

That machine is open loop stepper driven which is fine. NEMA 34 motors. Comes with the Mach3 demo version, just buy the license ($175) for it and it unlocks the program. Looks like vendor does all the setup on Mach3 so that is easy. It is made in North America, so you have someone to talk to if there are problems. The price seems OK. Overall not a bad looking machine and probably a good value.

I would want to know what those guide rails are made of, looks like a wear item. The aluminum cross tube on the gantry looks a little light to me and may resonate in use. It looks like there may be only about 6 inches of Z clearance, this could be a problem for running columns on a 4th axis. It is possible that the table top could come off and you could set the 4th axis lower than the existing table top.

[Biggs427]

... Open loop stepper (least accurate, least expensive), closed loop stepper (better, slightly higher cost), full on AC servo (most accurate, most expensive). ...

If the open loop stepper is sized correctly and have the proper drive, it could be as accurate as the closed loop ones. From what I know, a 1.8deg/step stepper always have 200 steps / turns with or without encoder.

If a system starts to miss steps, it is because something went wrong.

[Jim Dawson]

If the open loop stepper is sized correctly and have the proper drive, it could be as accurate as the closed loop ones. From what I know, a 1.8deg/step stepper always have 200 steps / turns with or without encoder.

If a system starts to miss steps, it is because something went wrong.

For relatively low speed, lower performance applications I agree. Closing the loop is needed higher performance applications, and not knowing what the OP's requirement really was at the time, I threw it all out there. The OP was requesting information about ''high precision'' applications. For the OP's actual application, clarified in a subsequent post, open loop steppers would be fine.

[KH0UJ]

Main purpose of the 4 axis 4ft X 8ft CNC machine sir? what materials projected to be cut or carved? (2D 3D), in that way we know the boundaries on what you really want, bigger-badder-faster = higher price

[ger21]

If the open loop stepper is sized correctly and have the proper drive, it could be as accurate as the closed loop ones.

I'll argue that it should be as accurate. If it's not, the machine is useless. 99.5% of all the machines you see here use open loop steppers, and 90-95% of them don't have any issues.
A big problem that people have, is trying to extract every bit of performance from their systems, whereas a commercial machine might have 25-50% reserve power to make sure the steppers can do their job. If people run their machines well within the limits of their motors, then they wouldn't have problems.

I was looking at this CNC ROUTER 4 x 8 | eBay but doesn't seem to have a ton of info with it.

If you look at the pictures, it looks like the machine is using some type of plastic rollers running on aluminum angle, or extrusion.
I'd say this machine is not much better than a $2500 machine.
Take a look at the Pro series from CNC Router Parts. Probably 50x more rigid, more powerful, better performance. For right around your $10K budget.

[wizard]

My first thought is that this machine is a bit on the expensive side for what you get.

Actually that helps quite a bit. My budget is probably the issue. I'm looking at 10k. I was looking at this CNC ROUTER 4 x 8 | eBay but doesn't seem to have a ton of info with it. I wanted to dive into something with a 4th axis so I could router column posts.

While it might be too early to think about this sometimes it is better to build a custom machine to do something like posts. We would need a better idea of your needs here but obviously you need to get a move versatile machine into your shop first. It would be helpful to know what sort of venture this is, for a hobby, new business, and established business & etc.

This seemed to look like my best middle of the road option. I'm figuring this would be one of those .01 accuracy systems.

Honestly I'm not getting good vibes about this system, that could be me reacting to a very poor eBay posting but my impression is that you aren't getting much for the asking price. That is being kind I could be far more negative but I won't go into detail here.

Which in my mind seems reasonable enough. accuracy and cheap would be my main concerns.

You really need to nail this down solidly because you could throw away a lot of money on a machine that doesn't meet your needs. Beyond that accuracy isn't always the most important feature in a machine, repeatability is often far more important.

Speed really wouldn't matter (I think).

Again it depends upon your goals but speed in most cases is important, how important varies a bit but if you have aspiration for commercial work you will want faster over slower.

I'm really not even too scared to build my own. I have access to metal at a reasonable price. Plenty plenty of floor space so I think its doable.

You don't want to underestimate the effort required. However DIY can often save you a lot of money over buying a turn key system.

I've been thinking making my own would be more benefical to me just so I'd be educated on exactly what did what. Your response though has giving me a go in the right direction. I thank you

There are certainly benefits to DIY a router build. How feasible this would be for you I can't say. One thing to consider is that the more shop equipment you have the better off you will be going DIY. I'm not sure doing a full sheet machine for your first attempt at DIY machine tool building is a good idea, it very much depends upon your personality and the time you have available.

Personally I'm a big fan of building with steel, this simply due to cost considerations for the raw materials. In any event before you go to far I highly suggest reading the stickies and then going through some of the build threads that are here.

[wizard]

I'm looking for some advice.

Advice is free here. The problem is you often run into conflicting advice

I'm as green as they come but I am going to get there. My main goal is to be able to do 3d wood work with a cnc.

Can you define that a bit more for us?

I'm in the process of looking for a cnc machine 4x8.

That is a big machine in might be overkill for a lot of what I see as 3D routing.

I'd like to be able to use Artcam with it. I'll be straight out honest. I might sound a little silly with my questions.

Questions are never silly, sometimes the answers are but that is another story.

I keep hearing of this Mach 3 program.

Mach 3 can best be described as a G-Code interpreter. G-Code is the raw set of instructions that tell a machine what to do physically and usually reside in text files, created either by hand or with a CAM (Computer Aided Manufacturing) program. Effectively Mach 3 is the last bit of software, in a chain of apps, that ends up realizing deign.

Mach 3 or 4 now, are just one of dozens of solutions to driving the physical machine. There is LinuxCNC, GRBL and a host of others.

Do I need that first than Artcam?

You will likely need a "CAM" program maybe even more than one. There is likely hundreds of CAM programs out in the wild, both free and commercial. Which one you will end up using depends upon what you are trying to do.

Is there specific things I should be looking for on a high precision cnc machine (what specs)?

I don't generally think of CNC routers as high precision machinery. Soooo not to rub anybody the wrong way but if you are expecting to achieve high precision you will be investing lots of money, time or effort to get there. For the most part CNC routers are not miling machines. That is an important realization.

In any event things to look for:
1. steel frame work
2. profile bearings
3. Rigidity is everything! However the larger the machine the harder it is to achieve a truly rigid machine.
4. This is a machine tool, invest in a real control cabinet for the controls. This a pet peeve of mind, you really want the controls out of the shop environment and in a proper electrical cabinet.
5. Performance cost money but so does time. I'd buy as much performance in the controls area as you budget allows.
6. Don't buy your controls before the machine designs is settled.

Can any one point me in a good direction for reading.

The stickies in this forum are a very good start. Try LinuxCNC as they have some good info on their Wiki. Step Motor Controls, Stepper Drives, Servo Motor Controls | GeckoDrive has some good info.

Are there certain books I should shove my nose in first? I ask all these questions because when I research them it feels like I'm going in a circle with no clear answers.

There won't be absolutely clear answers. To come up with the right answers for your particular need requires that you learn enough to make the decisions as to what you need. Yes it is circular because as you learn more you come back to realizing that some of your previous answers might have been less than optimal.

In any event if you really want to learn see if there are any local colleges or private schools offering training in the various machining related technologies. CAD/CAM for example is often an entire Course all on its own. Often this isn't easy if you have a lot of fires that need tending but if the school has a said program it is one of the best ways to get grounded in the basics.

If anyone can give me even a whisker of advice I'd appreciate it so much. I'm eager to learn

Take your time! Seriously don't jump in and burn off a ton of money until you have a good grasp of the basics.

The other thing is be aware that the cost of the machine itself is only part of the equation. You still need to develop the rest of the machinery required to keep a shop running. part of the machinery is a computer and software, likely software that will cost you money. Given that you can get started with CAD/CAM almost instantly by downloading some of the Free CAD options and maybe some CAM options. Combine that with software that emulates a G-code interpreter and you get get started with learning software on a virtual machine.

[cote442]

Thanks Wizard and everyone,

Very very helpful. I'll be using these forums quite often in my little journey here. More silly questions. I have access to two 5x10' cnc machines at the moment. These kind of just fell into my lap. They are probably from the 80's though. My question being are these easily upgradable? I haven't seen them yet. From what I hear they are buried in the snow (which doesn't seem promising). I won't be able to wander out there to see for another month.

As far as having tools to do anything....I seriously have just about every tool under the sun or access to them. Also have availability to a plasma cnc machine at my local sheet metal shop but the old man barely knows how to use it. I do have an employee that is graduating this year for cnc machining but I fear that his education might already be a wee bit outdated.(community college)

I'll read as much as I can when I can here and slowly come into it. I have roughly a year to learn as much as I can before I'd really like to start using it. It would be used for business but speed isn't key.

[wizard]

Thanks Wizard and everyone,

Very very helpful. I'll be using these forums quite often in my little journey here. More silly questions. I have access to two 5x10' cnc machines at the moment. These kind of just fell into my lap. They are probably from the 80's though. My question being are these easily upgradable? I haven't seen them yet. From what I hear they are buried in the snow (which doesn't seem promising). I won't be able to wander out there to see for another month.

Normally I would say a commercial machine, at the right price, is always worth rebuilding. However if they are so crapped out that somebody threw them into a snow bank there may be little there worth salvaging. The other consideration is that there is a very wide range of what would be called commercial machines.

The only thing you can do in such a situation is to check them out. They may only be good for their scrap metal value.

As far as having tools to do anything....I seriously have just about every tool under the sun or access to them. Also have availability to a plasma cnc machine at my local sheet metal shop but the old man barely knows how to use it. I do have an employee that is graduating this year for cnc machining but I fear that his education might already be a wee bit outdated.(community college)

This is great actually as many struggle to put together kits, due to the lack of machinery, much less try to do a DIY machine from the ground up. Note you will need tooling suitable for metal working in many cases.

Community college program can only really offer up the basics. Like any machine tool you build up your skills and capabilities to use the machine over time. This isn't much different than learning to use a table saw to a high degree of efficiency. The only real difference is that you are often using various bits of software to get the job done. Some of this software though has a very steep learning curve, you are basically learning to use it for the rest of your life.

I'll read as much as I can when I can here and slowly come into it. I have roughly a year to learn as much as I can before I'd really like to start using it. It would be used for business but speed isn't key.

If at all possible I'd suggest taking a few of those community college classes if they are offered at an acceptable time. The other alternative is to go with the training offered by the various software companies like AutoDesk, the hardware companies like Tormach, Haas and etc. Basically you have three groups of software to master. First there is the machine controller that processes G-Code and may have many features beyond simply doing that. Then you need to come to grips with a CAD program such as SolidWorks (possibly more than one). Third you need to become proficient with a CAM package or two (some of your CAD programs these days do integrate CAM but you still may find a need here). It should be noted that larger shops often have people specialized in these software groups.

It is a lot to learn and frankly it is easy to 'loose' it. If you got an employee about to leave a college level program you really want to get him involved in whatever that education was focused on. Because one of two things will happen, he will loose anything he might have skill wise or he will go to work somewhere else.

[Jim Dawson]

Thanks Wizard and everyone,

My question being are these easily upgradable? I haven't seen them yet. From what I hear they are buried in the snow (which doesn't seem promising). I won't be able to wander out there to see for another month.

Easy to upgrade is kind of like ''how high is up?'' It really depends on your experience and background. If the machines are in good mechanical condition then it should be pretty easy. I could do a complete ground up controls retrofit in about a week, but I do this stuff for a living. Your mileage may vary. My biggest concern is that they are sitting outside, not worried about the electronics, but how much rust and crap is in the mechanics, in addition to normal mechanical wear. If they were bought new by the community college, then the wear should be minimal compared to a machine that was running 5 days a week in a manufacturing operation.

Also have availability to a plasma cnc machine at my local sheet metal shop but the old man barely knows how to use it. I do have an employee that is graduating this year for cnc machining but I fear that his education might already be a wee bit outdated.(community college)

All school does is give you the basics, you still have to learn on the job. All of the machines are about the same and G-code hasn't changed since MIT developed it many years ago, but each has their own way of doing things. So you have to learn how to run the specific machine you are working with.