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View Full Version : Is Taig pulling my leg?



c131fr
04-17-2004, 07:39 PM
I am a newbie in its truest sense. I have been using CAD software for years, but all I do is design the part, save it to disk, and give it to the machinist.

I want my own CNC machine to mill parts out of stainless steel. The parts will require a 4 axis machine, but are fairly simple. I am not rich, and this will be for my hobby, but I must make my parts out of stainless steel, unfortunatly. I have access to some pretty spiffy CAM software, and I'm told that it will generate my tool path for me, and all I need to know is my tool size and material to be milled (for rate, etc.)

Taig claims their machine will mill stainless with no problem. They say I need to buy a 4 axis from somebody else, but when I do, I can put a part in before I go to sleep, and by morning it will be completed with an accuracy of .0005 all the way around.

I posted a pic of the part. It's a fan disk for a very small turbine engine. An expert machinist who works with me stated unequivically that this part only requires a vertical mill with a forth, rotary axis.

I see folks here machining plastic, wood, and aluminum, but not much talk about steel. I am not interested in mass producing parts. I don't care how long it takes. But before I slap down two or three grand on a 4 axis Taig setup, I want to know from a non biased expert (you guys) if their machine is up to that task. If it isn't which one is?

Thanks in advance. I really appreciate you reading this long post.

c131fr
04-17-2004, 07:41 PM
Okay, maybe I didn't post a pic. How do I do that???

Cold Fusion
04-17-2004, 07:57 PM
Cnczone doesn't allow big pictures. Just email it to me and I will host it for you.

Cold Fusion
04-17-2004, 08:36 PM
http://www.coldfusionracing.com/CNC/disk12.jpg
http://www.coldfusionracing.com/CNC/disk23.jpg

c131fr
04-17-2004, 08:43 PM
You're a gentleman and a scholar Cold Fusion. Thank you very much.

As you can see from the close up, this part was CNC milled. The piece is 6" in diameter. This particular piece is made of titanium, however I'm poor and will prabably use stainless. The parts I want to make have slightly different angles and sizes of the blades, but the basic configuration is as shown.

Well, anybody know if the Taig machine is up to this task? If not, is there a hobby cnc mill that is? Thanks!

Cold Fusion
04-17-2004, 08:51 PM
No problem C131fr. I'm happy to help anything from this board (all of whom have been extremely helpful when I was first starting).

JOE65
04-17-2004, 11:55 PM
From the look of the machine specs your a little short on y travel

I.m not sure how this could be over come?

MACHINE SPECIFICATIONS:
Maximum Travel Speed: 30 in/min.
Maximum Travel: X = 9.5", Y = 5.5", Z = 6.0"

JOE65
04-17-2004, 11:57 PM
Maybe your 4th axis overcomes this??

Jcadwell
04-18-2004, 12:20 AM
I've got a taig. I don't think .0005 is quite accurate. Mine works well to about .001. Twice as much. I could tighten the nut down more, but you get to the point where the included steppers either can't run the machine or you tear things up because the motors are working harder. Because all of the Taig's adjustments increase friction of sorts (the ways have a tapered piece that tightens or loosens and the leadscrew nut has a brass screw that opens and closes) you run into issues as you try to go faster and with higher accuracy. I find that I can get 15 IPM on all axis with repeatability of about .001. If you were to go with a ballscrew you could be significantly faster with the right motor.

I would buy Taig's CNC ready machine and add your own motors and drivers. You will be ahead in the long run. Taig's motors are unipolar, and the included drivers are phase drive, not step/direction, which limits your driver software options.

I would buy Geckodrives and bigger unipolar steppers.

The only other beef with the Taig is proprietary collets. They limit you to a 5/16 tool diameter, which means you can't use 3/8 tooling which is VERY standard. You can work around this, but you need a lathe. Buy a bunch of taig's spindle blanks and you can bore tool holders to whatever size you want. I have a fly cutter with a 1/2" shaft in one and it works great.

The spindle motor as supplied is on the weak side. (1/10 HP) The speed drive is adjustable by pulleys and my motor won't start the spindle every time at the fastest setting. Once it is moving it isn't a problem. For the slow spindle speed you would want it isn't a problem.

The taig will cut steel without any problems. Just go slow. You will probably also need a reflow coolant system to do that.

I wouldn't hesitate to buy another one if I had a need. It is a sturdy machine, and I haven't had any problems with the actual operation. I would build my own control system around their CNC ready mill if I could do it again.

teilhardo
04-18-2004, 06:40 AM
I'm trying to make turbine blades to on my taig. see my website for details. i was optimistic when I first got the mill too but it has proved to be a pretty daunting task. maybe both of us together can figure out how to get a taig mill to make SS parts!
-Tei

kong
04-18-2004, 07:09 AM
i have just got rid of my Taig lathe, since it was too wimpy. Depth of cut was tiny, I only turned mild steel a couple of times, butthe finnish was poor. Obviously lathe and mill and different machines, but a lot of parts are the same. If I had my time again, I would not have bougth the Taig, and would have gone for a bigger machine instead. I reckon you should takle a look at www.homecnc.info and check out his cnc-converted mill.

c131fr
04-18-2004, 10:12 AM
Originally posted by teilhardo
I'm trying to make turbine blades to on my taig. see my website for details. i was optimistic when I first got the mill too but it has proved to be a pretty daunting task. maybe both of us together can figure out how to get a taig mill to make SS parts!
-Tei

I see you cut out your diffuser. Very nice work. It looks like the clearance between the compressor and the diffuser is a bit too generous though. Is that just an optical illusion?

I actually have build several turbines before. Did you see Junk Yard Wars when they made jet trikes? The one with the afterburner was my design. The guy who built the engine, Chris Krug, is a good buddy of mine.

Do you plan to spin your casing? I found a place that sells a 6"X6"X1" plate of Inconel for $115.00. They say it machines like any other stainless. I planned to cut my turbine into it. Inconel ratains 75% of its strength at 1500 deg F, and thus doesn't require supplimental cooling. Pretty neat stuff.

After looking at the homecnc.info site, I gotta tell you, making your own really looks like the way to go. I don't know. I kinda like the fact that the Taig is pretty much ready to go.

Well, thanks for all the input, and I welcome more if care to give it. When I do make my decision, I'll fire up a web site so you guys can see what I'm up to and maybe lend me a hand. Thanks again.

ESjaavik
04-18-2004, 03:25 PM
Check that the kind of stainless you want to machine is not work hardening. Then you cannot just downscale your cut. It will just harden the steel and then that's how far you got. I understand you have machinists in your company, ask them for the full story on tiny cuts in work hardening materials.

c131fr
04-18-2004, 03:36 PM
Originally posted by ESjaavik
Check that the kind of stainless you want to machine is not work hardening. Then you cannot just downscale your cut. It will just harden the steel and then that's how far you got. I understand you have machinists in your company, ask them for the full story on tiny cuts in work hardening materials.

Okay, thanks. I'll ask, but have you got any suggestions? The only thing this part will be doing is compressing air, so it doesn't have to be terribly rigid. Most production pieces of this size are made of titanium, but that is mostly for weight. Is there a metalurgical table somewhere that lists hardening properties?

Thanks again.:)

JFettig
04-18-2004, 06:22 PM
I really have a lot of doubts in that machine, first of all, the spindle motor. not nearly enough for anything more than aluminum(unless you take tiny tiny cuts) but stainless, thats even worse than regular steel.

I would suggest you looking into a much bigger machine, you will be glad you did. If you check out the machine at homecnc, thats what I would be looking at if I were you. I wish I had the space and all for one rather than my homier mini mill retrofit.

$2000-$3000 is a lot for one of those little mills, I did my complete conversion and everything for under $2000 and got a much better machine than one of those aluminum taig mills. I have run a sherline at school once apon a time, and that was horrid.

If your really set on one of those mineature things, check maxnc. I dont know if they are better, but its just another option.

Jon

TyRex
04-18-2004, 07:05 PM
True, but the minis and the one on Homecnc are only 3 axis......while he needs a 4 axis

c131fr
04-18-2004, 07:23 PM
Originally posted by TyRex
True, but the minis and the one on Homecnc are only 3 axis......while he needs a 4 axis

I talked (emailed) Jeff Davis and he thinks that a 6" rotary table I found could be used as my 4th axis. I'd have to convert it, or course, but I think I can do it. I'm thinking of really doing something radical. Look for future posts. :idea:

JFettig
04-18-2004, 09:39 PM
yes, you have it right, you need to add a rotary table, either a cnc one or retrofit it. I think that will be one of the next addons to my cnc.

Jon

marjamar
04-19-2004, 01:19 AM
We just bought a Taig mill CNC ready. I put USDigital MS23 steppers on it and got a DenverCNC 4 axis driver. The driver was to low on current, so I have to put together a gecko system. I'm looking at using a 300 watt 48v power supply as I will also be using a rotary table.

We also bought a shurline CNC ready mini lathe to do whatever else was necessary that the mill couldn't do or do as well as a lathe would.

Still setting up and testing, but using the mill the little I have so far, it seems to be very accurate, better then 1000ths of an inch I would say.

-Rodger

bean7795
05-05-2004, 09:04 PM
inconel is a lot like 340 s.s. but kinda sticky on a lathe but when you machine it watch for heat it will melt carbide emills down in a hurry if you let one get a little to dull and keep running it

bean7795
05-05-2004, 09:05 PM
correction 304s.s. not 340

Graham S
05-28-2004, 01:31 PM
Am I being daft but aren't those blades very thin indeed, how do you machine them without deformation?

DHK
07-09-2004, 02:27 AM
I've used a Taig CNC mill extensively in the past and currently have another one I'm rigging (using a different CNC setup than the factory models). As much depends on the endmill and feedrates used as what is being cut (in your case inconel?). Harvey tool has some nice miniature crystalline CVD diamond and amorphous diamond endmills which will fit the Taig mill (www.harveytool.com). These can substantially cut down on temperatures when cutting so you won't work harden stainless. One of the main reasons for selecting a smaller desktop is that they can spin at 10,000 RPM all day. In fact, Taig runs their spindles in at 10,000 RPM for a whole day before they ship them (their bearings are rated for 15,000 continuous). A larger machine won't be happy at those speeds for extended periods of time. A contractor friend used to run his large Fadal at 10,000 for small parts and he ended up replacing his spindle. While it was running at 10,000 RPM it made an unhappy "screaming" screech. The Taig mill, on the other hand, was very quiet -- just a fan-like humming sound. I ran the Taig very hard -- often at 10,000 RPM for 24 hour periods.

Backlash is the primary limitation on accuracies on these small machines. One way to zero out all mechanical backlash is to use simple pulleys and weights to preload the X and Y axes. You'll need about 7 pounds on the X and Y. I'll be rigging up a Taig with weights soon -- perhaps I can post pictures on this 'board when I'm done. The Z axis has zero backlash because it is already "weighted" by the weight of the spindle and motor. I never had any problems with the CNC drive on the Z axis. With a 20:1 feedscrew, 7 pounds of weight adds a trivial amount of back-torque. The stepper motors used on the factory Taig CNC mill are very strong (they'll bend a 5/16 endmill right over). They do run warm and I never had problems with lost steps. I'll be equipping the Taig that I'm currently rigging with a DC servo drive system from Imsrv (www.imsrv.com). This will result in greater accuracies and much cooler (and quieter) running. Steppers can be irritatingly noisy. I've already got the imsrv servo system up and running. The DeskCNC CAM software used with the imsrv system uses a serial port and has no problems running in Win2K. My biggest gripe about the desktop mill parallel port stepper software was the need to run in DOS mode. A few such software packages claimed to run in Windows, but these often generated errors and were happiest running in DOS mode.

A larger mill will carve out stainless faster and with common tooling. But, there's something to be said for a nice and quiet desktop mill which you can run all day. I'd caution that when cutting stainless always wear eye protection, especially with a non-enclosed mill. Some varieties of stainless are non-magnetic -- and a few slivers/flakes in the eye can take a lot of flushing to remove. I unfortunately know this from direct experience...

-D

mgamber
07-09-2004, 02:58 PM
See Mach2 for Windows based control software.

Meltdown
07-09-2004, 09:53 PM
DHK

I also have the servo's from imsrv. They are nice but the problem i'm having with them is the backlash in the gears. I thought about buying some ball-screws but didn't because with this gear backlash in the servo's it would defeat their purpose. I'm looking into how to improve that without shelling out for expensive planetary gears. Any thoughts on this would be most welcome ;)

metlmunchr
07-10-2004, 02:37 PM
Re the cutting of Inconel.........I don't know which Inco alloy you're looking at using, but 718 is a common one for use in jet engine parts. The guy who proposes to sell you a chunk of inconel with the advice that it machines "just like any other stainless" is being just a tiny bit less than honest IMO.

Milling 718 is similar to SS in that it needs slow speeds and heavy feeds, but my limited experience with it also says it takes about twice the power to drive either the spindle or the axis as compared to 304, and using light feedrates to compensate for lack of power is an option that simply does not exist. It only makes a bad situation worse. Razor sharp tools help more than anything else. T-15 HSS endmills often work better than carbide on these materials. T-15 has good red heat hardness, and can take and hold an edge that's next to impossible to get on carbide. Avoidance of heat generation, or the use of flood coolants will have little effect on whether the stock work hardens. Work hardening occurs due to the rubbing action of the tool against the stock, so that's what has to be avoided. It might be worthwhile to check with Carpenter Technology and find out whether they produce any relatively free cutting high temperature stainless alloys that could be suitable for your parts. Materials like this are generally available in small quantities, since no one can afford large quantities of them :D

DHK
07-10-2004, 06:59 PM
Meltdown,

The Pittman DC gearmotor servos used in the Imsrv system (part# GM9236C534-R2) do have a bit of backlash in them. Using DeskCNC, you can select the "Abrupt" style backlash compensation to consistently remove this. I think this is done in the 2.067 and 2.070 versions by unselecting the "Metered" backlash compensation box in one of the configuration menus. The Taig Z axis, despite the weight of the motor and spindle, doesn't have any static back-torque on the feedscrew (which would eliminate the slight rotational backlash in the servomotor gearbox). I think even if one used a much better lubricant (Taig recommends ATF -- auto trans fluid -- as the lubricant) you probably couldn't achieve static back-torque with a 20:1 feedscrew with any reasonable amount of weight loading. Ballscrews may well be different. Preloaded axes with ballscrew drives may have enough static back-torque to eliminate the servomotor gearbox backlash. But, this might also continually stress the DC servomotors to remain in any static position (my experience with ballscrews is limited). I think the important part about servomotor gearbox backlash is that it remains consistent irrespective of axis position. Software backlash compensation, of the simple abrupt type, should render this backlash negligible.

By the way, you can get these servos as N.O.S. surplus from www.servosystems.com for around $49 each. They're the exact same Pittman part (GM9236C534-R2) used by Imserv in their system. The only difference is that the "flat" on the output shaft hasn't been machined/ground on them. I figured that Imsrv did this as Pittman makes no mention of a flat on the output shaft for this part number. I picked up a set of these units myself -- nice to have as spares as the brushes on these motors do not look to be user serviceable.

-D

Meltdown
07-12-2004, 05:31 AM
Thanks DHK for the servo link! I will get me some extra servo's just in case. You're right on the constant backlash in the gears. The problem i'm having is that with with the screws i use the backlash is constantly changing. The only cure will be ball-screws i guess. After that the gear backlash should be constant and manageable in the software . Now how to find affordable 12mm ballscrews is another matter :eek: