[jalessi]

Serge,

There is no doubt the Syil X4 is built with high end ball screws and is much more stout.

I am not discounting the quality of any of the other machines that have been mentioned.

They are asking $6,450.00 for the Syil X4

http://www.toolmach.com.au/home.php

Still after all is said and done there is a $4,000.00 price differential.

You can replace the Taig lead screws for $24.00 each verses $4,000.00

Thats a lot of banana's.

Jeff...

[acondit]

The statement that caused all the problem was I simply pointed out that as a concept there are definite valid engineering reasons for smaller machines, and offered to go into depth. That is what isn't being accepted here, (that and mainly someone claiming to have some information Hoss doesn't.)

Please, instead of ranting about how your reasoning isn't being accepted, just share what you consider to be the valid engineering reasons. I for one can make no judgment on your reasoning (for or against) until you share it. We might learn something and who knows, we might even be in general agreement.

Alan

[sansbury]

Leaving aside all the dirty water, let's leave VMCs that cost more than some peoples' houses out of this. It's like comparing a Ferrari with a Fiat. A lighter car is usually faster and more nimble but the Ferrari has so much more power and refinement the rule doesn't apply.

I've always been under the impression that the rule was more like "use the smallest machine that's big enough for the job" than "bigger is better." Mass is costly but confers a lot of advantages if you pay the price. The high end is quite high when you have servo motors that generate torque measured in pound-feet the way we use ounce-inches

[sergizmo]

Serge,

There is no doubt the Syil X4 is built with high end ball screws and is much more stout.

I am not discounting the quality of any of the other machines that have been mentioned.

They are asking $6,450.00 for the Syil X4

http://www.toolmach.com.au/home.php

Still after all is said and done there is a $4,000.00 price differential.

You can replace the Taig lead screws for $24.00 each verses $4,000.00

Thats a lot of banana's.

Jeff...

I agree with you Jeff. If non production work (prototyping, really small runs) of small/medium sized parts in brass/aluminum/plastic are to be done, the Taig is the most economically sound option. A big savings on the initial purchase, cheaper replacement parts, less electricity used, etc...

It's not just replacing the leadscrews or nuts though. Keeping the nuts properly adjusted can be a PITA. I'm not sure about the Taig, but on the Sherline it certainly is. With ballscrews it's a little grease every 500 hours or so.

So...
In favour of Taig
+ Cheap initial outlay
+ Several CNC configurations available
+ Small footprint, can be put anywhere
+ American made, quality construction
+ Lots of affordable accessories available
+ Cheap replacement parts
+ Easily moved by one person
+ High spindle speeds for engraving or small cutters
+ Tons of internet support and info
+ Low electricity usage

In favour of X4
+ Longer travels
+ More solid, rigid and sturdy
+ Ballscrews
+ Faster rapids
+ Variable speed (No pullies to move)
+ LCD display with coolant and spindle control
+ More spindle HP
+ Limits installed
+ R8 taper
+ Easier/faster lubrication

That's all I can think of but there are probably some things missing.

Serge

[jalessi]

Serge,

Well said, your post is eloquent.

I agree with you 100 percent.

Jeff..

[jalessi]

Sansbury,

Your analogy is very articulate and refreshing this evening.

Jeff..

[Stepper Monkey]

just share what you consider to be the valid engineering reasons. I for one can make no judgment on your reasoning (for or against) until you share it. We might learn something and who knows, we might even be in general agreement.

Alan

Thank you. I have no problem at all with spirited discussion, but hastily constructed straw man attacks before I even get to make a point are bothersome. I actually rather welcome dissection of ideas AFTER I have made them...

I stated before I was going to post a number of related engineering points, and perhaps that is an idea for a different thread should the discussion become productive. For now I will touch upon just the one I alluded to earlier and we will see how it goes;

When working with very small tools, a high speed spindle of some form is obviously necessary. I think we can all agree that is a given. With any small machine, whether it is like a Minitech, Roland, Model Master, or similar that have one mounted as stock, or a Taig or similar that can have one mounted on the dovetail in place of the general purpose headstock as opposed to mounted to it, there is one common underlying design consideration - mass reduction. There are reasons some of the small spindles like the NSK micromotors that seem so brutally expensive for thier power output - they are very light for their power output.

With a high speed spindle we have covered speed. That is half of the speed/feed equation. The other half is far more difficult.

Proper feed rate is just as important. I think we can all agree there as well. If you look at any small item with texture or fine sculpted detail, such as is found in cutting molds for jewelry, small model parts, coin stamping dies, sculpted items, etc., you will see that if you trace an imaginary toolpath line over it for even half an inch, there can be areas with as many as 10 or 20 or more elevation changes. At the proper calculated feedrate for the tools this means that the Z head not only has to make a large number of small motions, it has to stop and change direction sometimes at a rate of 10 or 20 direction changes PER SECOND to travel at the right feedrate. Think about that for a bit.
Rapids and top IPM is irrelevant here, as you will never see anything but a few milliseconds of the accel curve before the decel curve has to start. You only get around maybe an average of 50 milliseconds give or take for the whole move before the next one starts the other way. Mass is everything here as oscillating a Z head at 20hz is no mean feat no matter what. Not just getting it going but rapidly stopping it as well. Of course, if the Z head isn't up to moving that fast the other axes will by definition slow down to keep in sync so the cut still continues. This is why a machine capable of much slower rapids can just as easily out cut a machine with much faster rapids sometimes. Their top speeds are irrelevant. Z mass and related moment and G forces are what is the limit. Total machine feed speed here is limited entirely as a function of the Z's rapid movement potential in the first few milliseconds of the accel curve.
At first you would think that this just simply means that a cut would just take much longer on a more massive head, and it would, but what it really means is that as the machine slows down for those movements in high-detail spots feed speed randomly changes in the middle of the cut! If you think thats bad for tool life with larger endmills, try it with little ones. And unfortunately the limit for the whole piece then is the most detailed area of whatever you are cutting. There is no such thing a a dull or loaded tool at these sizes and speeds, just a little >snik< and another $25 mill has it's tiny little tip bouncing across the workpiece the instant it starts to load, heat, or dull. Radically changing your feedrate mid-cut is never a good thing. This is as true in wax as it is steel, lots of snapped tools and possibly ruined cuts either way. If you've ever had a little mill snap and looked at the piece under a loupe or comparator, you'll see it usually tends to go on an elevation change for just this reason. It makes sense to think it snaps on a downward (because of the plunge), but if you look at enough of these failures up close you'll see quite a large number of the failures actually happen while the bit is going UP too, for just this very feed change issue.
A related issue is also the rotating mass. The smallest and shortest screw up to the job is a necessity. Inertial moment of the motor is as well. Now that we have determined the Z should be as light as possible, think about how the infamous 'flywheel effect' (inertial moment) comes into play. If you think adding a handwheel to an axis might be bad, try getting a rotational mass that is a very significant percentage of your driven mass! We tend to ignore this number in most of what we do, but this is why rotor inertia is so clearly listed on any motor manufacturers spec sheets - sometimes it is important and here is one of those cases. Both of these reasons are why even if you could replace the headstock of a larger machine with a light spindle it still would not be optimal at all. The heavier screws and related rotational mass is too high, and even the extra power of larger motors doesn't help here as the rotor inertia tends to increase out of proportion to the power as the motors get over a certain size.

In summation, getting the right feed speed is a headache, and it all comes down to the Z performance. A light Z assembly wins over the same spindle mounted on the side of a heavy headstock assembly every time for this, the only exception being for generally flat cutting like a circuit board or engraving where Z travel speed doesn't matter and a big machine with a side mounted spindle is at least as good as a small one.
Specifically, a machine to do this type of job well has far more than just the spindle needed - it needs screw pitches sizes and lengths, motors, power supplies, carriages and more that are designed differently than a big machine has. Spindles aren't all of it.

------------------------------------------

I thought I might point out that for those of you with big machines who want to cut these types of jobs without losing hundreds of dollars in tooling and many grey hairs per square inch figuring out all of the above, I have a proposal that may get you cutting on par with even the best small machines. Then you likely will truly be able to do everything well with a full sized unit!

Unlike the above data, I have no experience with this, its just an idea so bear with me, but it goes like this;

My idea is that since the Z is the killer here, if you were to simply mount not just a spindle to the side of your Z head, but instead mount one of those cute little lab grade unitized linear stages that come up cheap on Ebay all the time. I have nabbed some that only weigh a couple of pounds, have two or three inches of travel, little ground ballscrews, and even glass encoders and way covers. With that little travel no one ever bids much on them.
If you were to then mount a high-speed spindle to it, lock your regular headstock in place at the right height, and drive the little slide as the Z axis, you may well be golden. If someone tries it let me know. It might work out very well. Thought about trying it a while ago for my X3 but wrote it off for me as pointless as I already have too many small machines that already do that job, but the idea of a true all-purpose machine is pretty intriguing though.

[Stepper Monkey]

Sorry that was such a long post. It really barely covers even that one concept, especially the related drive aspects, and there is so much more just to that it could fill a book. It fills several textbooks somewhere I'm sure, likely much more clearly written.
I hope I got the basic concept across though, even in a somewhat incomplete sense. A lot more will hopefully just become more apparent to all when this concept is integrated with some of the other basic aspects of design that we are already generally familiar with.

[bilinghm]

Thanks Stepper Monkey,
Well written, very interesting, and undoubtedly correct.

[jalessi]

Stepper Monkey,

I have personally seen what you are talking about.

When doing a detailed rotary job, the Z axis starts bouncing and because of the weight and the lack of rigidity the whole Z axis starts almost a harmonic like vibration or oscillation.

Instead of the Z axis cutting it starts acting like a wood pecker and the cutter gets killed in the process.

You have made a very good point, much better than name calling by the way.

Jeff...

[Harryman]

Ummm, Hoss?

Stick to Geology, skiing and jewelry Harry, leave the machining advice
to those of us that are actually experienced professionals with real equipment or
enthusiastic hobbyists that are savvy enough to share their ideas with pics and videos.

I think you have me confused with someone else, I hate being dragged into a rant I'm not involved in.

Thanks for checking out the website though.

[jalessi]

Harry,

Someone needs to take the heat, better you than me.

Nice web site by the way.

No hard feeling, I hope.

Jeff...

[jalessi]

Gentleman,

Just a little note about eating crow for along time.

Its ruff when you make a post that cant be deleted once someone else "quotes" it.

The saga continues...

Jeff...

[hoss2006]

Yes, nice theory, have you shown proof?
NO.
You can guess about how a larger machine might work
but that doesn't make it fact.
Have any of you jewelers actually tried using a larger machine to make
your molds?
If you only had an X4, I bet all of you could manage to figure out how to get
them done on it in the same time (plus or minus a few microseconds)
without snapping your bits if you use your equipment properly.
I'm hearing a lot of theories but not actual real world experience on the matter.
The Taig obviously is a good fit with you jewelry guys but there are only a handful
of you here compared with the rest of us that need a mill with some heavier duty capabilities.
As Stewbaru stated in his initial post

I am looking for a 4 axis machine, for working aluminium, and steel to 1/4" with a 1/16" cut.

I don't see why you guys insist on trying to talk a guy into buying a Taig which will not
meet his needs compared to the X4 no matter the number of theories put forth.
Bigger IS better for some things (mills, boobs, paychecks) but not everything (egos, bellies, debts)

Umm, Harry er millingjeweler er stepper, There are plenty of aliases here on the zone,
the anonymity makes it easy. Hoss could just be one of MY alter egos, hmmmm.
P.S Jeff, I don't eat crow here in the backwoods, opossum is tastier.

[jalessi]

Hoss,

We all agree that a bigger machine is better for many tasks.

Possum may taste better, ask a moderator to check Stepper Monkey and Harryman's IP address.

I believe you might be in for a lifetime ration.

Jeff...

[jalessi]

Hoss,

We are talking about alternatives, budgets, sharing ideas and a little drama too.

Stepper Monkey did suggest the X4.

I have suggested larger machines also, however the Taig is a viable small alternative that is being defended because it will do the job even though its small and has limitations.

One of the "Jewelers"

Jeff...

[hoss2006]

I believe you might be in for a lifetime ration.

Jeff...

Not hardly,
writing styles and personalities come thru no matter which username they logged
in with, it's apparent when you take notice.
Some make it easy by continuing an ongoing conversation as a different user,oops.

It's a fun little mental game to play on here when it's just more of the sameold sameold.
A little Sam Spade.
ooh, found a new alias.
You can trust the upfront ones with websites with 'About Me' pages.
I did logon as hoss this time i hope

[jalessi]

Hoss,

You have to be kidding, They are both on the Zone right now however they are viewing different threads.

Are you saying that he has gone through all the trouble to log in to the Zone on two separate computers and on two separate threads just to defend a issue with you?

"One of the Jewelers"

Jeff...

[hoss2006]

"One of the Jewelers" , did I give you a new signature?
I've done the same thing. I have 3 computers in front of me,
what's so strange about that?
I might have a ghost on this thread right now.
spooky.:bat:
I could actually be having this conversation with myself, "jeff"
The things we do to amuse ourselves.
I'm getting bored though, I need to get ahold of Keling about a motor.
Hoss out

[jalessi]

Hoss,

I concede and agree your Hoss conspiracy theory must be correct.

"One of The Jewelers"

Jeff...