Cool tables and spindle ordering fun #6 - Brakpan, S.Africa

[Gerald D]

The Chiaravalli catalogue lists up to 127 tooth gears (129mm diameter for module 1)....maybe that would be the limit that Nusaf stocks, but I am not familiar with these sizes of gears and who stocks what. Why don't you try a MDF gear first and then maybe nylon or alu.? If the gear wheel is that big, the load on the teeth will be relatively light.

Yes, the pressure angle is 20 degrees.

[Kobus_Joubert]

Found this little program ...only about 900k size.. http://www.hexagon.de/zar1_e.htm ..... Are there any clever people out there that can design me a module -1 gear about 300mm diameter and supply me with a DXF file please.
There are so many parameters I don't know if I am Arthur or Marther in this thing..

[hennie]

Ok I am now confused,what if you turn something with a 100 mm dia and you have a 300 mm dia gear on the end stock doesn`t the software lets say the new upgrade of v-carve5.5 and mach works it out for you ?Can`t one hook the motor direct to the shaft ?

[Kobus_Joubert]

Nee man...a 100mm or 300mm... or 30mm piece will not be the problem. Once calibrated via Mach and V-Carve this thing will be TUNED. The big gear is just to give it some more Torque. Am I right Gerald.

[hennie]

Ok, why need more torque if you are not going to turn at speeds that one would usually turn a project.The way I see it is that your motor that you are going to use have more than enough power to handle anything you throw at it and you also have a cutter that has its own power to cut.

[Gerald D]

The bigger the diameter of the workpiece, the more torque you need. When you have a 300mm diameter log in there, you are really going to need that 300mm gear wheel.

[hennie]

So one could use a motor with a 5:1 gearbox and hook it straight up and it should do the same thing?Or have the motor with the 5:1 gearbox and a belt hooked up with the 300 mm dia gear turning the 300 mm log?My logic tells me that when one turns a 300 mm log I am going to use the slowest speed on the machine and when I cut a smaller dia 50 mm I would up the cutting speed.When one starts cutting and the project still looks like a log it needs the torque but once lets say the log is the same dia of 290 mm it would not use the same amount of torque to stop and start movement as it is balanced and round on the full length of the log.If one cuts a barley twist over the length of the project one would not cut it in one pass maybe cut it in 3-4 passes of 2.5 mm at a time.What is that formula for working out the rpm`s ( sorry can`t remember it )

[Gerald D]

A 5:1 reduction will allow you about 5" max diameter unless you are happy to use smaller cutters and passes (lighter loads).

If you look at your flat table and the normal rack, the system behaves as if the rack is screwed to the job. To move the cutter 16 inches in the x-direction, you need 16" of rack and say 16000 step pulses. Now, take that 16" and wrap it around into a cylinder....a 5" cylinder and the rack becomes a 5" diameter gear. The cutter won't know that the table isn't flat anymore, and you can use your same feedrates, pass depths etc. Same goes for a 12" job with 12" gear - the cutter still thinks it is a flat table.

But, if you have a 12" job with a 5" gear, there is now a very big surface and too few steps coming from the drive pinion.

[bradm]

A random thought: certain types of timing belts, like HTD belts, mesh well with themselves. So, you could potentially cut a large disc, glue a piece of timing belt around it, and create an extremely large pulley. Combine that with a small pulley on your stepper motor, and you are pretty much ready to go.

[hennie]

Got it,Thanks

[Castone]

See if you can find a fly wheel off of a small car. Make a MDF or alumn backer plate for it then take the gear from the starter mount it on your stepper motor and spring load it to mesh the two together. It would be about 12" in Dia .

[Kobus_Joubert]

Good idea Brad... always another way to skin the cat. I am willing to try it if nobody can produce me that DXF as I asked in post # 572

[Gerald D]

Good idea Brad.

[Gerald D]

Leo, your idea is not bad either

[hennie]

Or take the timing belt as is and flip it inside out and cut a disc to fit on the inside of the belt without cutting it for the big gear.How will nylon work for cutting gears?

[smreish]

Leo, Creative - I like it.
Brad, also, very creative! Just think, you could theoretically make a quick disconnect plate and have multiple drive pulleys. Cheap and effective. Nice.

Greg thinking gentlemen.

Sean

[Kobus_Joubert]

Finally decided to give all the GOOD ideas a miss and go for the Module -1 gear where my existing stepper will drive directly onto.

The biggest that they make is 120mm or 120 teeth...thought what the heck lets experiment and try it as I plan to start turning small things most of the time....I don't like to waste good wood....

Was not that expensive R120.64 plus tax for the gear....but when I looked at it , it was just a plain flat gear and no indication how to fix it to the shaft. The technical chap said that I needed a POWERLOCK locking Element....price R 109.93 plus tax and R 35.00 plus tax to machine the centre to accomdate the 18mm lock. Well with a spare 27 tooth pinion at R26.69 the total came to R 333.18. Not too bad I suppose.

DSC00988.JPG

The problem now is that this locking thing has 2 sleeves that pull against each other. It was bought as a 12 x 18 lock meaning 12mm I/D and 18mm O/D. So I had the lathe shaft turned down to 12mm

Now I cannot get the thing to lock tightly around the shaft....even with a bit of shimming I cannot get it to clamp securly around the shaft. Anybody with experiece on these tipe of locking elements. Should I have made my shaft 12.5mm ?? any Ideas.
Thanks
Shaft_Hub_Key_Less_Locking_250x250.jpg

[Gerald D]

I am quite familiar with those locks in 40 x 80 size, and they grip very well, if you tighten the heck out of the screws.

If yours is not working, take it back, with a allen key and tell them to fit it for you. The shaft would be allowed to be about 0.01mm under 12mm.

[Kobus_Joubert]

I think that there is a problem with this one that I got...even the allen screws and not 100 % square to the base... looks like it was made locally. The gear is perfect...imported from Italy I believe.

I nearly welded the thing too the shaft this afternoon.

[Gerald D]

That reminds me, I was also given local junk at a time, and took it back for some decent quality. The tapered surfaces were too rough to slide and tighten up.

[Kobus_Joubert]

The company apologised for the local junk. We checked all of them and eventually had to settle for the smaller unit. This one looked more professional and they turned my shaft down for free to fit...they also had to change the 120 tooth gear and did a new hole in this one as well. I tightened the unit to max ,but if I really put some effort into it, can cause it to slip. Will put some Loctite on this shaft and also on the chuck side shaft.

Tonight after supper started with the bracket. Will try and finish it off tomorrow after work.

Don't worry, will paint the lathe BLUE when all is done.

DSC00991.JPG

[Gerald D]

Thinking of it now, a 12mm shaft feeding into a headstock for an indexer is very small. You are probably going to have a some problems with slippage or it breaking off. Remember, we have problems with our pinions on our motor shafts . . . . . that big gear is going to have 5 times more torque to transmit.

[Kobus_Joubert]

Thanks for the warning Gerald. Will use it as is for now until it breaks, then maybe put a taper flange thing on. I can still cut the thin part of the shaft off and move the gear a bit closer to the headstock. Lets see how long it lasts.

[Castone]

Looking good Kobus

[Gerald D]

If you are using an x-motor to drive that 120 tooth module 1 gear, an x-distance of pi X 120 will equal one full revolution (376.991mm).....that is really quite good for a quick, cheap, backlash-free indexer.

[dragonfinder1]

Here is a gear form Rush gears. It's 8.1" Diameter 160 tooth. Would that be large enough? 8:1 ratio direct and 24:1 with a 3:1 transmission, that should easily break a 12mm shaft

www.rushgears.com

[Gerald D]

Dave, be careful of going to a very high ratio - it will make for a very sloooowww indexer when turning small work. Ideally you need to be able to change ratios according to the task at hand.

[dragonfinder1]

Actually I believe the ratio is still close to 3:1 with that gear. For me 24" ( 610 mm ) is 152 teeth. I think the problem is when the work is not the same size as the gear, and I think that is what you mean when you say we need to be able to change ratios according to the task at hand. What happens when you start out at 200mm and now the work is 150mm? I guess that's why the soft ware to operate the indexer is so expensive.

[Gerald D]

It's like driving a delivery truck :- When the truck is fully loaded early in the day, you are mostly going to use the low gears. As it gets lighter through the day, you use the higher gears. There isn't one single gear that will be good for all loads. If the gear is too low, the engine revs can't keep up.....if the gear is too high the engine might stall due to overload.

[Kobus_Joubert]

Well I am glad to show you what I did. My indexer is running..still to finish small things, but there is movement.

What I did:

Used my old wood lathe....just cut the legs down
Fitted a 120 tooth Module 1 gear to the headstock.
Removed my one X-axis stepper and mounted it on the indexer.
Made up a 4 meter extention cable to extend this X-axis cable to the indexer.
Set up another Mach-3 profile.
In this profile removed the slave on the X-Axis
Disabled the X-Axis
Enabled the A-Axis and gave it the Direction and Step ports of the old X-Axis.
Ran the calibration of the A-Axis in Mach and it's all done.

To revert back to the normal X-Y-Z cutting...
Remove the indexer stepper and put it back on the X-Axis
Start Mach-3 with my Normal Profile and cut away....Easy..., but if somebody in South Africa is going to import MotionKing steppers, I would like to get another 9801, then it is a matter of unplugging the X-Stepper. Put the extention from here to the indexer. Start Mach-3 in the indexer profile and away I go.

DSC00993.JPG

Extending the existing X-Stepper wires to the indexer.

DSC00994.JPG

Look at the video of a simulated 4 flute done on the indexer.

http://www.youtube.com/watch?v=5AeVX52iSOo

I am not happy with the thin shaft, but will fix that up. Also to tidy everything and paint it BLUE...