The right taig for ME?

[granth3]

Hello everyone!

I have finally decided that a turn key cnc taig is what i'm looking for. Now the question is what one?

I have read as much as i could to not re-ask too many questions.


There are a few companies that sell "turn-key" kits.

So far i have looked at:
super-tech
Deepgroove1
micromill



Some of the terms used have started to confuse me. I know that stepper and servo are 2 totally different systems. When i was doing some research i found steppers that were controlled by servos?


Taig-3000-LBMU is $2195 - stepper's
Taig-3000-LBGS-P $3490 - servo's?

I am going to be making 2d molds for resin casting but in the future i would like the ability to get a 4th axis. From the picture of the cheaper/stepper cnc set up it seems that the control box is only wired for 3 axis.


I know there are a million threads regarding accuracy servo/stepper. For those that have spent the $1200 extra was it worth it?


Anyone in the Orange County, ca area have a cnc taig i could check out?



Thanks in advanced for your help,


-Grant (current noobie, future expert )

[noisillator]

The difference between steppers and servos isn't accuracy, per se. As long as a stepper motor is operating correctly and doesn't encounter an obstruction, it performs just as well as a servo. However, if the stepper system jams or misses a step for some reason, the controller will continue on as though nothing has happened. It never knows that the motor is no longer in the correct position. That aside, I've been using a stepper-based system for about a year and a half. It's never missed a step, and accuracy is limited by the mill itself, not the steppers.

Sorry, can't advise you on the various turnkey systems. I bought a CNC-ready taig from Nick Carter and picked up the various pieces from the respective vendors. I highly recommend the Gecko 540 4-axis controller.

Jack

[strohkirchw]

What is your budget exactly?

[rowbare]

also take a look at soigeneris (google them). Jeff Birt is a frequent poster here. He has a very nice controller setup.

bob

[granth3]

Strohkichw:
My budget for the turnkey 3 axis is in the ballpark of 3k


rowbare:

Thanks! I have actually looked at that site many times. I don't know what it is with these small cnc companies but there sites are all GARBAGE!!

On soigeneris under products, the machines are on the 2nd page. Once i click that all that is available is "[$ProductListNoResults]"

[Jeff-Birt]

The problem with us small CNC companies is that we don't have an IT staff dedicated to just building a slick website. This is still a fairly new web site package for us and we add/update things all the time. I agree there are many rough edges now. Currently though we are in the process of moving it to a dedicated server so nothing is being added while the hosting company is getting everything moved between servers for us. Also, being a small company we tend to concentrate more on providing personal service to customers, I imagine other small companies do the same. Our phone number is listed, as well as my personal email address. Any reputable company will do the same.

As to your question regarding servos/stepper. A servo motor is a motor that has an encoder to keep track of its rotational angle. A servo must have an encoder/feedback. The secondary advantage to having feedback is that if the motor is too far away from were you tell it to go it can tell you by signaling an error. A stepper motor is made to move is discrete steps so no feedback is needed. You can add an encoder to a stepper as a means to keep track of where it is and provide a similar error output as the servo but it is not required.

Servo motors tend to have a flatter torque curve, the torque remains more constant over the RPM range while steppers are a constant power output, the torque falls with an increase in RPM. For larger machines this difference alone can make servos much more attractive.

On a small machine like the Taig you'll have equally good service from either servos or steppers. Neither option will change the accuracy of the machine. For a servo its step resolution (number of divisions of movement in one rotation of motor) is determined by the number of slots on the encoder, for a stepper motor it is determined by the step angle (most are 1.8 degrees, or 200 steps/rev) and microstepping (200 steps/rev * 10 microsteps = 2000 steps/rev). Step resolution is NOT the same thing as accuracy. Both steppers and servos will only be 'around' where you tell them to go, never dead on it.

With either set up you won't have better accuracy than the underlying mechanics and for this size/type of machine it is hard for me to justify servos. Contrary to popular belief: a stepper motor will never loose a step unless you over load it. With a stepper/encoder or servo set up overloading will cause the same issue.

I've posted a few videos on youtube showing my 'tiny' steppers and control driving a Taig 2019CR-ER that you might find interesting: [nomedia="http://www.youtube.com/watch?v=RzrBcXCNDhU"]YouTube - 90 IPM SS[/nomedia]

[strohkirchw]

To expand on your original question a little more, I would probably cross Deepgrove and Supertech off your list. If you want a true turn key setup with potential to add a 4th axis then neither really work well especially considering your budget. The Supertech doesn't use the G540 board and is 3 axis while the Deepgrove is cheap but not exactly turn key. Your best bet is to call someone, perhaps like Jeff, that has a well done package setup to begin with and can expand on it for your needs. That way you don't have to mess with adding relays or wiring home/limit switches on your own, they are done for you already.

[granth3]

Jeff,


Thank you for your explanation, you answered a lot of my questions. My main concern is accuracy. I know a machine is only as accurate as its operator but I would like a good place to start.


"Both steppers and servos will only be 'around' where you tell them to go, never dead on it."

Is that because the machine build? And how much off are you talking?

I am a total noobie and I appreciate the time everyone is taking to help me with these questions.

-Grant

[dlaery]

I bought a "turnkey" CNC Taig mill from DeArmond Tool. Dan was very helpful in getting me started. You can buy the 4th axis for this. I am not a machinist but have worked in a machine shop (sounds like a Holiday Inn commercial) for a short time with manual mill, lathe, etc..., so the learning curve for CNC for me was pretty big. I am making hinged hand held molds (aluminum) so accuracy in lining up the 2 halves has been one of the many challenges. Finding work holding is harder with the small mill. I had to make most of my fixtures. But with experience I think the Taig mill is accurate if you know/learn how to use it. Other things are learning the cad software, cam software and the machine software. I have no expericene with the other machine/compaines except when I worked at the machine shop I learned how to use the Super-Tech Supercam software which is good for what we used it for, 2d stuff plasma cutting. The Mach 3 is what came with my machin and I think I like it better for 3d stuff running my machine. If I was doing 2d plasma stuff again, I would rather use the Super-Tech Supercam.
Here are some pics of one some of he molds I have made with the Taig.
Picasa Web Albums - David Aery - Molds

[granth3]

David,

Thank you for your info! Your parts look great!! I was actually wondering about fixtures. I have seen a few companies that make some pretty cool fixture plates.

Thanks,

-Grant

[Jeff-Birt]

My main concern is accuracy. I know a machine is only as accurate as its operator but I would like a good place to start.

"Both steppers and servos will only be 'around' where you tell them to go, never dead on it."

Is that because the machine build? And how much off are you talking?

Let's look at the case of a stepper motor, lets say a stepper can be +- 1/2 step off. On a Taig with 20 TPI screws that is:

1/200 / 20 = 0.00025"

In reality it is not really that meaningful. All lead screws will have some backlash. You can get the Taigs adjusted down to less then 0.001", but I suspect that is far more accurate them 99% of folks would need. Other sources of inaccuracy are tool deflection, tool wear, the metal expanding as it gets warm, etc.

[awerby]

Taig/Microproto DSLS 3000, which is a turnkey system (you just have to provide a suitable computer). There is an advantage to getting a system built by one company, as this is (Microproto is the CNC arm of Taig tools) instead of pieced together from various manufacturers, since you'll get knowledgable support with no passing of the buck. The nice thing about the DSLS 3000 is that it monitors position and shuts down if it gets more than a tiny bit off. This can save a part that you've got many hours of work into. The Gecko 540 is a nice controller, especially for the price, but it doesn't do that. If your achieved position is different from the commanded position, an open-loop stepper controller like that will never know, and keep merrily chugging along, even though it's wrong.

Andrew Werby
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