Turn key ball screw based CNC Taig -> Can I buy it?

[Rohan2008]

Hi everyone,

I am looking to purchase a benchtop CNC mill strictly serious prototyping stuff
Materials: Nylon, Derlin, Teflon, Derlin AF & aluminium

Usage:
Precise vnc (turning, facing, parting, grooving) operations by sticking in the part into the spindle. Make small plastic gear boxes to get an estimate of how fast I can make precision parts using some techniques I have in mind (of course, I am a CNC newbee).

I prefer threading as well, but I am afraid I would be needing a servo based spindle instead of the standard dc motor spindle.... this is a different story altogether..
Diameter of parts -> 1/4 “ to about 2” … I can get them to the correct diameter before sticking them to an appropriate ER collet.

I live on the 2nd floor of an apartment; The machine MUST be under 200lb/ $2-4K. I am not interested in a DIY kind of stuff (no time). I am looking for something that is “out-of-the-box” turnkey solutions so that I can focus more on what I would like to do rather than how to make a CNC work.

I like CNC taigs that deepgroove and microproto offer, but I am not able to digest the fact that their $2XXX products don’t have ball screws…? Do deepgroove or microproto customize their taigs with ballscrews if I place a special order...? Money is not an issue for me unless we are talking about serious dollars. Does anyone have experiences with special orders at deepgroove and microproto?
Is there a way to attach ball screws to a taig; I hate backlash? Don’t these http://www.homeshopcnc.com/Ballscrews2.html fit a taig? if I purchase ball screws from here and attach them to a deepgroove taig, will it work without too many adjustments? Is there a way to configure the mach software as soon as we install ball screws with a different pitch? What are the steps I need to execute to make a taig ball screw enabled? I have read several prior posts on this topic, but I really don’t want to get into this install ball screw mess unless I don’t have a way out.

One school of thought is, why not go with townlabs TL518ER since I will be machining aluminum and plastics, but I am more lured toward the Taig popularity. Repeatability along with good accuracy are what I am looking for. Any suggestions are highly appreciated.

[sp1nm0nkey]

Ball screws for machines in that price range are likely to be rolled and not ground, and thus not much better than lead screws. Even the townlabs website admits up to 0.003" backlash for ballscrews (w/o preload), which really you can do better than on a Taig.

The problem with ball screws on a machine that size is they backdrive, so you need more powerful motors, meaning everything gets more expensive. On the other hand, you can drive the hell out of smaller stepper motors with a good driver like the one deepgrove1 provides. I can get 80 IPM rapids on my Taig, very low backlash, and I cut titanium and stainless without a hitch. I don't miss steps either.

Yes it's not terribly elegant but it works very well.

[Jeff-Birt]

'Ball-screws' tends to be more of a advertising buzzword than an actual benefit many times in the lower cost bench-top CNC world. You not only need to be concerned with backlash but the accuracy of the thread pitch over the length of the screw. It does you no good to have 0.0001" of backlash if the thread pitch is off 0.010" over 12" (just made up numbers to illustrate the point.)

With the standard screws on the Taig you can get 0.0005"~0.001" backlash if you take care in adjusting the split nuts (it is really pretty easy to adjust them once you figure out how).

In reality you'll see more inaccuracies in your machining from tool deflection, tool wear and incorrect tooling choices than from backlash. Learning how to create your Gcode and choose the correct tools to minimize such problems will produce superior quality parts.

[awerby]

Hi everyone,

I am looking to purchase a benchtop CNC mill strictly serious prototyping stuff
Materials: Nylon, Derlin, Teflon, Derlin AF & aluminium

Usage:
Precise vnc (turning, facing, parting, grooving) operations by sticking in the part into the spindle. Make small plastic gear boxes to get an estimate of how fast I can make precision parts using some techniques I have in mind (of course, I am a CNC newbee).

I prefer threading as well, but I am afraid I would be needing a servo based spindle instead of the standard dc motor spindle.... this is a different story altogether..
Diameter of parts -> 1/4 “ to about 2” … I can get them to the correct diameter before sticking them to an appropriate ER collet.

[Doing this would be a lot easier with a lathe than with a mill. While it's possible to do some basic turning by putting round stock in the mill spindle and fixing a tool to the bed, you will soon run into pieces you want to make that can't be done this way, for instance things that protrude far enough from the spindle to need support from a tailstock.]

I live on the 2nd floor of an apartment; The machine MUST be under 200lb/ $2-4K. I am not interested in a DIY kind of stuff (no time). I am looking for something that is “out-of-the-box” turnkey solutions so that I can focus more on what I would like to do rather than how to make a CNC work.

I like CNC taigs that deepgroove and microproto offer, but I am not able to digest the fact that their $2XXX products don’t have ball screws…? Do deepgroove or microproto customize their taigs with ballscrews if I place a special order...? Money is not an issue for me unless we are talking about serious dollars. Does anyone have experiences with special orders at deepgroove and microproto? Is there a way to attach ball screws to a taig; I hate backlash? Don’t these http://www.homeshopcnc.com/Ballscrews2.html fit a taig? if I purchase ball screws from here and attach them to a deepgroove taig, will it work without too many adjustments?

[MicroProto is Taig's CNC division; "Deepgroove" is an Ebay Taig reseller who furnishes them with an aftermarket controller that's not supported by Taig. There is no ballscrew option available for the Taig; it's built to accomodate the (actually very precise) acme screws it uses, but there isn't any room for ball-nuts. To install them, you'd need to remove a lot of material inside the mill's slides, which wouldn't be a good idea. It seems like you haven't actually priced precision-ground ball-screws, or you wouldn't be surprised that they aren't offered on a machine that retails for about $1000 (or $2000+ with CNC included). This link, should give you an idea:
http://www.automation4less.com/store...s.asp?cat=1245 - digest it...

The rolled ballscrews you pointed to will give you less accuracy than an unmodified Taig has. This type of ballscrew was designed for linear-motion applications like opening garage doors, not for precision machining, which requires a much higher standard of accuracy. Backlash isn't the worst thing to deal with; it's a regular thing that can be compensated for; their thread "drunkenness" of about +/- .002" per foot is a lot more difficult, since it occurs randomly throughout the screw.]



Is there a way to configure the mach software as soon as we install ball screws with a different pitch?

[Assuming you managed to do that, reconfiguring the software would not be difficult.]

What are the steps I need to execute to make a taig ball screw enabled? I have read several prior posts on this topic, but I really don’t want to get into this install ball screw mess unless I don’t have a way out.

[That is smart. People every so often launch into a Taig ballscrew retrofit project; we hear a lot about it at the beginning, but then they seem to drop out of sight...]

One school of thought is, why not go with townlabs TL518ER since I will be machining aluminum and plastics, but I am more lured toward the Taig popularity. Repeatability along with good accuracy are what I am looking for. Any suggestions are highly appreciated.

[I don't have any personal experience with that machine, but it uses rolled ballscrews, not precision-ground ones, and doesn't promise zero-backlash or publish any accuracy or repeatability figures. You might enquire about those things if you're considering buying one.]

Andrew Werby
www.computersculpture.com

[Rohan2008]

Thanks so much for the info.

'Ball-screws' tends to be more of a advertising buzzword than an actual benefit many times in the lower cost bench-top CNC world

.

Ball screws for machines in that price range are likely to be rolled and not ground, and thus not much better than lead screws. Even the townlabs website admits up to 0.003" backlash for ballscrews (w/o preload), which really you can do better than on a Taig.

Hmm… I didn’t see this ‘type of ball screw’ issue coming. I learned how to deal with backlash through the old school and I am fairly confident; except for a few horror stories: combination of backlash in the lead screw, backlash in the dials and “operator fatigue”. Backlash is sure to stay for some more time in my life

I am used to making parts that have tolerances of around 0.005” (Bridgeport & sharp lathes) and I would like to continue it. I typically take rough cuts of about (on manual machines) 0.030” @ 8-9 ipm (IPM is puny compared to CNCs) on 1080 steel and about 0.070” @ 12ipm on aluminum. With this, I go for as many passes as needed to a final finish cut of about 0.002 or a 0.001… this is how I typically get to 0.005” tolerance. [As said earlier, I will be cutting mostly 6061, nylon, derlin & derlin AF]

Question 1
I just want to relate this to Taig. What kind of depth cuts and feed rates can I safely use with the CNC Taig on 304s, 1080, 6061 and titanium so that I can comfortably and repeatedly get to 0.005” tolerance? (I have taken a class in CNC but I don’t have hands on experience with CNC way of doing things).

Question 2
As I understand backlash I need to adjust the split nuts (as jeff pointed out), I can reduce backlash to under 0.001” and so, if I contour a circle, I will get a fairly consistent circle with a circular runout of less than 0.002”… which is enough for my applications. On top of this, I assume that we can do this compensation in the Mach software? What are your experiences with circular contours on a Taig?

Question 3
What is the typical backlash that one would get on the taig/sherline 4th axis rotary? I want to form mill some gears with precision cutters. How serious is the 4th axis backlash and how acute is it’s effects on gear cutting through form milling? Although form cutting is itself not that accurate, I will try to use a cutter that is VERY specific to a particular dimension in order to maintain some accuracy.

Thanks for all the wonderful suggestions!

[sansbury]

As a side note on the threading question, you should be able to do that with the regular spindle motor. Mach3 and, I think EMC2 as well, can single-point thread using what's called an index pulse encoder, which can be done for short money, and also functions as a spindle tachometer.

[Jeff-Birt]

Rohan2008, I just realized that most of your followup questions went unanswered.

A1) Feed rate and DOC is entirely dependant upon material. For instance in 6061 T6 with a two flute 1/16" stub mill I can feed at 11 IPM with 0.035" cuts with very good results; no need for a cleaning pass when cutting out operator panels and the like. For stainless you'll want to use a 4-flute bit, possibly TiLAN coated and feed at perhaps 1/3 at what you would do in Aluminum. This could vary wildly with different stainless alloys so there is no one answer.

A2) On a well adjusted Taig mill my circles come out circular. If it is parts requiring a precision fit than I'll do a finishing pass at the full depth of cut. If you need a precisely bored hole a boring tool may be a better way to go.

Open loop backlash compensation is a mixed bag. It requires all axis to stop when one axis changes direction. So it will make 3D relief work agonizingly slow. For other types of work you have to consider that the cutting forces will tend to push the table about if there is any backlash. So when the control blindly compensates for it it might just be compensating the wrong direction.

The feedback I have had from other folks is that they have found it use full when engraving and when doing high precision drilling. For other uses tool deflection tends to be more of an issue and a well thought out machining strategy produces better results. (Finish pass after a rough cut, etc.)

A3) I have not measured the backlash on the rotary axis, but I'll do that some time and report back. There is an adjustment for backlash on the unit though. Also, when gear cutting you'll only be turning the table one direction which eliminates any possible problems with backlash.

[fly_boy_bc]

"in 6061 T6 with a two flute 1/16" stub mill I can feed at 11 IPM with 0.035" cuts with very good results; For stainless you'll want to use a 4-flute bit, possibly TiLAN coated and feed at perhaps 1/3 at what you would do in Aluminum."

What RPMs?

I am also a brand new Taig/Microproto 4 axis owner and I have been thinking about this subject at length. I have come up with a few reassuring thoughts.

First is the point that a previous poster has already mentioned. Ball screws probably would not be as accurate as the system employed by Taig. (what do I care HOW accuracy is achieved?) and the system is easy to keep adjusted. When the nuts get too worn replace them and you'll do fine.

Next is the two uses a bench mill is put to namely low accuracy work like control panel cutting and engraving and small part production/modification. Usually (and probably exclusively in my own case) the highly accurate work will be preformed in a 2.5 D environment. In this case all you have to do is let the fancy software do all the roughing/shaping/replacing a forge and either produce code that will do your critical passes the way a machine operator would do them or even do many of your "critical" operations with the mill under manual control!

I really can't think of too many things that need to be both "fully 3D" and "highly accurate" at the same time in the same operation. In other words, Cut your 1/16 scale V8 engine block in one operation in 4D if you must but when it comes time to bore the cylinders and grind the heads do THOSE operations in 2.5D or even by hand (Jog) Just like you would if there were no CNC. Backlash? What backlash? Remember on a manual machine you can do perfectly accurate work despite RIDICULOUS backlash.

All that being said a properly adjusted Taig can produce a perfect inside thread using a single point cutter so how badly out of round is your engine cylinder going to be even if you don't use a boring bar? Don't know but probably good enough for 99% of us. And if you need better go with the bar and head.

Gary B in BC starting to "get" CNC

[Rohan2008]

Jeff & Fly_boy_bc, thanks so much for your time. I intend to write G-code by hand since VNC maching on a normal mill is not supported by standard CAM software. Also, I am comfortable programming things myself rather than some CAM software generate g-code for me especially for operations such as turning, facing, grooving etc.

based on what you are saying, I think I shouldn't rely on mach3's to do my backlash compensation job. I should use the old school tricks that I learned in my machine shop and produce Gcode accordingly.

All that being said a properly adjusted Taig can produce a perfect inside thread using a single point cutter so how badly out of round is your engine cylinder going to be even if you don't use a boring bar? Don't know but probably good enough for 99% of us. And if you need better go with the bar and head.

Gary B in BC starting to "get" CNC

This is totally "unknown" to me: can you do single point threading using a taig mill? How... its spindle speed is not constant. How does Mach3 know where to start the thread? I looked at some videos on youtube, so, do we need to put a feedback look to the mach3 software? If this can be done, can I machine worms for a worm gear... of course, I would like to use acme thread profile for the low RPM, low torque worm gear that i have in mind.. Any suggestions here would be VERY helpful because I am about to buy a machine and I love to have this feature on that machine. So, in order to single point threading, what feature do we need in the mill. How can we equip a taig to do single point threading?

[fly_boy_bc]

When you say VNC machining do you mean from a firewalled server? Otherwise I have no idea what that is. If it is a typo and you meant CNC I am even more confused when you say there is no support for a "normal mill".

As far as threading I believe all you need is a timing/registration setup for the mill spindle. Very simple to wire up and there are several "projects" on the web that claim success. I have not tried it yet but I have also seen laser alignment systems and webcam adapters for zeroing and measurement.

It all works just like the big boys with hardware that comes from the junk box and the dollar store.

I will try to find the threading project since I want to implement it as well. Perhaps we can help each other in getting them up and running.

I still don't even have limit switches or cooling.

[Rohan2008]

Here are some videos:

http://en.kendincos.net/video-npjhjj...g-acetal-.html
[nomedia="http://www.youtube.com/watch?v=0d2AcT_rJig"]YouTube- Taig Mill Turning with lathe conversion[/nomedia]
[nomedia="http://www.youtube.com/watch?v=wViMFtxauOQ&feature=related"]YouTube- MILL2LATHE converts your CNC mill to a CNC lathe![/nomedia]

This is more like, you stick the part in the spindle and do lathe operations. Thats a pretty cool operation... try it out.

As for me, I am yet to buy my machine and I am getting overwhelmed right now with what I want vs what I need to get what I want…. aaaarrrrgggghhhhhhhh….

[Rohan2008]

When you say VNC machining do you mean from a firewalled server?

Too much of programming is getting confused: VNC & VMC :-(