[mlg]

Hi guys: I'm looking to get into CNC. I have limited experience machining things by hand and no prior experience with CNC. I'm pretty handy with computers and electronics though.

I would like to get (or build) a benchtop CNC mill. After looking at different mills, I realized I simply don't know enough to choose one. Hence, I would appreciate some advice from folks here who are more knowledgeable than I.

What I'm looking for is accuracy above all. I would like to machine small parts accurate down to 0.001 inch in all dimensions (ideally), sometimes in very complex shapes. I don't care how long it takes, as long as the machine can run unsupervised. I don't need power such as (eg) to make heavy cuts in steel etc. I will probably work on mainly plastic and (soft) aluminum, very rarely steel. The largest part I foresee working on is roughly 8 x 2 x 2 in (and typical sizes are much smaller, 2 x 2 x 2). I'm not adverse to putting together a CNC retrofit kit on a non-CNC machine, or wiring my own controller/steppers/electronics. I'm not looking necessarily for something that works out of the box, but I would prefer to not have to make my own (eg) motor mounts, or have to modify castings, polish ways, etc etc. I would like to keep this under a $2k budget (excluding tooling).

So far, I have looked at: Sherline 5400-CNC, Taig 2019CR-ER, Sieg X1/X2/X3 (micromill/minimill) with respective cncfusion kits (there is a HF store right next door to me), possibly Rong Fu round column with some kind of kit (?). For the CNC part I'm looking at kits by Keling, either the G540 + 3 steppers, or 3 G320X + 3 servos. The software will be EMC. There are a few factory-built CNC machines I looked at too: Taig 2027ER, LittleMachineShop 3501/3503, MaxNC 5/10/15, ServoImpact, Prazi (used), etc, but most of those are way out of my price range. I've seen decent deals on a used CNC Sherline, maybe ~$1000 (with steppers and controller); haven't really seen the same for a Taig.

My impressions so far are that anything bigger than the Sherline/Taig/X1 is probably more power than I actually need (for now, anyway and that retrofitting an X1/X2/X3 is probably somewhat challenging from someone with no prior experience.

What I *don't* know is how does the accuracy of the smaller mills compare to the larger mills? How does (eg) a Taig compare to an X3 out of the box? How bad is the backlash on each of these (I'm guessing this would be the main source of error for what I'll be doing), and how hard is it to eliminate? (and how do I eliminate it anyway?) Do I *need* servos? (or can I run steppers at a low speed and *never* skip steps in a long program?).

So, what do you all think? Get a Taig, put servos on it and call it done? Play with an X3 refit? Something else?

Thanks!

MLG

[yantra3d]

Have you by chance checked out Widgitmaster's Mini-routers? You might consider adding it to your list of candidates. It sounds to me like it would be just what you need.

It can be a lot to take in at first but soon enough you'll have the confidence to make the right purchase. At least you already know what you are wanting to use it for and that narrows it down considerably.

Good luck on your search...

[philbur]

If accuracy is your primary criteria then your main issues are:

1) Good ballscrews and the mounting of, all without backlash.
2) A spindle setup with good bearings and preload (in your case also with high rpm - say over 4000 rpm)

Everything else is incidental.

Phil

Have you by chance checked out Widgitmaster's Mini-routers? You might consider adding it to your list of candidates. It sounds to me like it would be just what you need.

It can be a lot to take in at first but soon enough you'll have the confidence to make the right purchase. At least you already know what you are wanting to use it for and that narrows it down considerably.

Good luck on your search...

[Jeff Davis]

Let me start by saying I feel your pain.

I cnc'ed a X1 about 4 years ago and recently did an X3. The people who hang out in this forum are a great source of help and information. They helped me a bunch on my X3 conversion. They can provide you a good sounding board to make sure you are not just tossing money for nothing.

The X1 and X2 can be converted within your budget. The X3 will be just a bit over depending on how much other stuff such as computer/ cables and other items you will need to buy. Mine came in at about $2,700 for the mill and the conversion.

If you have to stay in budget I would recommend the X2/premade cnc hardware kit with ball screws/ and a highspeed spindle conversion. You described small parts, I am assuming that you will also be using small end mills. The little end mills need more speed than the stock machines like to deliver. Of course you also need the motor and drive package.

The X1 is off the table with only a work area of 6" X 4". for decent accuracy you would also want ball screws and at the moment I don't remember if anyone is making a X1 conversion kit with ball screws. If there is someone please pop it up!

Doing the conversion is not that difficult with the premade kits. Good luck with your build!

Jeff

[yantra3d]

I just noticed that you were looking for something that handle steel. If I would have caught that part I wouldn't have recommended the mini-router. Sorry about that!

[rc-monster mike]

The Taig mill fits your budget and size envelope, and is almost certainly more accurate than any of the "X" mills out of the box. With proper adjustments, it can hold .001" in stock form(cnc of course). It has a larger work envelope than the x1 or x2 as well(table travel anyway - it is shy in z travel). Small parts usually means small tools, too - the Taig spindle can get 10k rpms(more than 3x a stock "X" machine spindle and 2x most modded "X" machine spindles). Taigs with an ER16 spindle and Gecko 540 controller sell for under $2k on EBay pretty much any day, too.
I don't know how well a Taig can handle steel(I never cut steel with mine, but it did a good job with Aluminum), but with small tools and proper feed rates, I suspect it would do OK.
The downfall of the Taig is that it doesn't have ballscrews and a ballscrew conversion would be pretty tricky. The leadnuts are adjustable and the leadscrews are accurate, though. I used to adjust mine after every few hours of machining(never let it get over .001" backlash).

[Crevice Reamer]

Hi MLG. Welcome to the Zone!

The Taig will have the resolution plus high spindle speed you will need for small cutters. I would recommend the almost-ready-to-go $1700 Deepgrove1 Taig/G540 for you.

http://deepgroove1.com/cncmill.htm

You might also want to consider their 5 Axis trunnion table.

Some of this basic CNC info may help you:

http://crevicereamer.com/Page_2.html

CR.

[rowbare]

The Taig with a G540 setup gets my vote too. Once you have the electronics setup, you can be up and running in a couple of hours. Xn conversions are hobbies in and of themselves. You would certainly learn a lot doing the conversion, but if your goal is to make parts they aren't necessarily the best option.

If you don't want to put together your own controller box, http://soigeneris.com/default.aspx and http://www.camtronics-cnc.com/index.asp sell assembled controllers with various options. Both Jeff and Dan are active on cnczone and have good reputations. Jeff is also a Taig dealer.

good luck!
bob

[mlg]

Small parts usually means small tools, too - the Taig spindle can get 10k rpms(more than 3x a stock "X" machine spindle and 2x most modded "X" machine spindles).

Very good point! I never thought of that. 2500rpm in the X mills is probably not ideal for plastic with a 1/8 ball mill which would be most of the work I foresee doing. I've been doing some work in the same material by hand with a dremel cranked up to 15k rpm or so. Hmm.

The downfall of the Taig is that it doesn't have ballscrews and a ballscrew conversion would be pretty tricky. The leadnuts are adjustable and the leadscrews are accurate, though. I used to adjust mine after every few hours of machining(never let it get over .001" backlash).

Every few hours!? Ow Is this an adjustment you can do in the middle of a job? What if the axes are preloaded with pulleys as DHK posted here?

[mlg]

Hi MLG. Welcome to the Zone!

The Taig will have the resolution plus high spindle speed you will need for small cutters. I would recommend the almost-ready-to-go $1700 Deepgrove1 Taig/G540 for you.

CR.

CR and everyone else who replied - thank you very much for the helpful advice!

Yes, I am inclining towards a Taig, based on spindle speed and out-of-the-box accuracy. Sometime later, I may want to get a second, beefier-but-less-accurate mill and do my own cnc refit on it, using the Taig to make mounts etc (gotta love bootstrapping). But for my current needs and level of experience a Taig sounds just right.

My only remaining question is... steppers or servos? Could someone comment on that? What I would like to know is, basically, can steppers run without any missing steps for a long time (10's of hours) at low speeds (a few ipm) and with very little load? (basically, while doing a finishing pass or "dusting" a few thousandths off a part) If there *any* reason to prefer steppers other than cost? (ie, would steppers actually be more accurate in any situation?)

Thanks,
MLG

[Crevice Reamer]

My only remaining question is... steppers or servos? Could someone comment on that? What I would like to know is, basically, can steppers run without any missing steps for a long time (10's of hours) at low speeds (a few ipm) and with very little load? (basically, while doing a finishing pass or "dusting" a few thousandths off a part) If there *any* reason to prefer steppers other than cost? (ie, would steppers actually be more accurate in any situation?)

Good steppers with efficient and reliable drivers (Like G540) are more than good enough. With proper PSU sizing to motors and proper tuning in Mach3, they will NOT miss steps.

Mariss has already answered your question:

http://geckodrive.com/support.aspx?q=10002

Buy the DG1 and start making chips.

CR.