is it me or can you see the backlash in the number
I have finally done some engraving using the Syil 4th axis as supplied together with the X4+.
This follows a lot of work I have done to the basic components of the 4th Axis, this work included adding a needle thrust bearing to the underside of the worm wheel, removing burs from all the worm wheel teeth, lapping the worm and wheel to remove the tight spots and adjusting the worm to mesh with as little backlash as possible without locking up.
The attached photo's are 360 graduations arround a 50mm diameter index ring marked at 10 degree increments.
is it me or can you see the backlash in the number
The opinions expressed in this post are my own. -Les opinions exprimé dans ce messages sont les mienne
There is still some backlash as is evident in the photo's, however with the naked eye it is difficult to pick out.
The photo's are closeup and magnified somewhat.
I have resigned myself to the fact without totally re-designing the worm and wheel setup, it is not possible to reduce backlash totally. As I have said in previous posts this 4th axis is not fit for the porpose it has been sold for.
-copy of post 05-12-2009
There has much criticisum of the 4th axis table supplied by Syil, some saying due to the backlash the table is incapable of accurate work, also some very complex solutions to the percived problem. But I wonder how many are aware of the adjustments on the unit, as Syil products come with little or no documentation and what state they leave the factory is questionable ( remember crimps ) it is therefore a good idea to adjust the rotary table prior to use.
With the unit clamped to the mill in the vertical mode losen off the two recessed hex grub screws on the top of the base casting, the worm is mounted in an offset coller so as you rotate the coupling housing clockwise the worm ingages into the table gear and vice versa. Rotate the worm anti clockwise to dissingage and then rotate the table by hand to establish any play, in the base is a threaded ring secured by a screw, losen off screw and turn ring thus locking table, now back off ring untill it turns freely without any play and tighten screw.
Now turn motor housing to engage worm tight then just back off again, and tighten grub screw, you can make this adjustment with the motor running to prove its not to tight to run freely. If the motor housing is now not square with base lossen off the two cap screws and adjust to suit.
Regarding backlash ,those of us who learned their engineering on conventional
mills and lathes knew no different, as long as the table screw is turning in the same direction there is no backlash, as the name implies it only occers when the screw changes direction, so ergo if you run your 4th axis in the same dirrection to cut your part you will not encouter any backlash.
There are many posts on this site by people asking for advice on what machine to buy, nobody has invented the perfect machine tool ,they all have there sortcomings, Syil gets its justified share of criticisum ( and I have made my feelings known ) but in the right hands this value for money tool is capable of accurate work. I recently made some small gears useing the 4th axis, and they run very well.
That is a nice part Martin.
One suggestion I have as a 4th axis user, NOT a Syil user.
It is more of a nuisance, but for higher accuracy requirements, a programming workaround would be to index the 4th maybe 10-20 degrees at a time and use 3 axis machining strategy. Assuming the 4th has a brake you will only have to contend with the XYZ backlash this way.
I fully understand the process of adjustments, I served an apprenticeship in the UK in the 60's as a machine tool fitter, I have built milling machines where bedways required scraping, made taper gibs etc. I have maintained CNC machining centres etc. At 61 years old I consider myself as being quite experienced.
The problems with the Syil 4th axis are firstly, the worm wheel is not a true concave worm gear, it is a simple helical gear, in addition to this the teeth are running slightly excentric to the bore, making it impossible to adjust for zero backlash over 360deg revolution. I have lapped the teeth with the worm in an effort to reduce the runout in the wheel diameter.
The second point is the worm shaft is only supported at one end, this allows lateral movement in the worm shaft which increases friction, consiquesntly stalling the stepper motor, resulting in scrapped component.
There are other points which which are not, as I would consider to be general engineering practice.
I fully understud what I was buying for the price I payed, the machine in general is very good, but this particular item is a manual rotary table where the hand wheel has been replaced with a stepper motor, and it's not working!!!
I now consider the matter closed, it is something I will live with, as they say "just get over it"!!!!!!
Or... we can try to find a better rotary table and suggest the improvement to syil
Im sure there are room for improvement at the same price levels.
I looked at this sometime ago. I'm not sure what is out there that would fit the mill, but there are a couple of different designs of zero backlash worm drives. Some have a split worm, some have a funky geometry.
I never follow up enough to get pricing though.
I thought a split spring loaded worm wheel would be simpler.
Professional units just use brute force.
They have a drag brake, strong enough to resist all cutting loads, a shaft resolver, and a brutal servo motor that just ignores the drag brake.
Bingo. No backlash. Servoed it all out. It can be made to work even on the so-so Syil one, but the motor would need some hormones, and an expensive shaft encoder, to say nothing of the servo drive for the electronics. That's a project on it's own.
Super X3. 3600rpm. Sheridan 6"x24" Lathe + more. Three ways to fix things: The right way, the other way, and maybe your way, which is possibly a faster wrong way.