4th axis

Newton said:
Ho ho, I did not know that CH made these setups...:confused:
Could it be knocked in a beefy stepper in there in stead without any backlash ?

Guess I have to drop CH a email then..

K
Click to expand...
Get a SERVO in there. :thumbup:
I'd mount a stepper directly.
Collet closer maybe or ER collet instead of chuck.

Yeah, I did not know I could build a turner from CH's goodies either.
Chris, I want free crackerjacks for this free ad.
 
Are you guys on the same page? Kent is looking for an inlay setup, I think, and Joey is showing a taper setup. These are not the same creature are they?

Jim.
 
Mc2 said:
Kent, the face of the rotary has a hole drilled and tapped into the center. The table should come with an adaptor that screws into this hole and is threaded on the other end for the sherline or taig chucks. The chuck would have to be ordered in addition to the table but adaptor should be included. I am as well interested in milling a wrap around inlay. This is my reason for purchasing bobcad 23. By the way Bobcad has of yet been un-able to tell me how I can do this. I will most likely have to cheat. As far as the backlash goes I am going with Dick on this one. 6 thousanths of a degree is nothing to worry about. This is why though I would make sure that the table was already setup with the cnc coupler as the manual table can have this added. When it is added it will have extra backlash. Can you tell me what controller you will be using with the table?



Jim.
Click to expand...

I have a DSP setup on my CNC which was supposed to be 4th axis ready. This was however a fairly "hairy" thing where the actual functionality was way to basic. So I'm looking in to rebuilding the controller with a Mach3 support and possible the "Smooth stepper" USB interface. The other option is to go for "The Brain" - which might be a better setup since it's expandable with feedback/encoders but it's still in "beta mode". However some very cleaver guys behind that product.

I have at the moment 5 large stepper drivers (Gecko similar) which goes to a breakout board - and then to the DSP controller.

The idea is to rip the breakout board BB out and control the steppers from "The brain"/"Smooth stepper" and directly to the stepper drivers directional and pulse inputs.. Almost there now :)

4th axis SW is in the box. OneCNC has it all and so much cheaper than the other "take a mortgage on you're house to pay" type of SW.

K
 
Mc2 said:
Are you guys on the same page? Kent is looking for an inlay setup, I think, and Joey is showing a taper setup. These are not the same creature are they?

Jim.
Click to expand...

I understood that Joey had that running for tapering but if the chucks and the rest is good enough I guess it's just to add a stepper and start rotating in each direction.
It's the same as Sherline I guess with a tailstock but on a small alu bed and a DC motor in stead of the stepper ?

K
 
JoeyInCali said:
Correct.
Maybe do a 1 to 1 pulley system and use the stepper to index and spin ( 360 degrees times 150 rpm? ).
Ebay alert!
http://cgi.ebay.com/Rotary-4th-Axis...3286.c0.m14&_trkparms=66:2|65:3|39:1|240:1318
Click to expand...

Cool, there we have that directly driven version. But torque would be very low I guess, so milling while moving is most likely not it's every day dinner.

Guess a much beefier stepper could help ;)
Edit: Had a look at shopboots home page and they seem to have done some decent 3D work... Hmmm

Kent
 
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I am not sure why you need such high holding torque? In cues, we are using very small end mills turning at very high speeds, so there is virtually no load. If there was much load, then we would have to hold the cue itself from deflecting to the side because it would bend.

I have done very little inlay work with cnc, but when I did it, I just had a 270 ounce stepper attached directly to a Taig lathe chuck. If I was going to do much of it, I would want to go the timing belt route with a 2 to 1 ratio and a 425 ounce stepper. I would think that would be plenty strong enough. I don't think you would have much backlash as long as the belt was tight. MC2, did you have belt tightness issues? Is that were the backlash came from?

Like I said, I have not done much inlay work, just ALLOT of shaft turning!


Royce Bunnell
www.obcues.com
 
RBC said:
I am not sure why you need such high holding torque? In cues, we are using very small end mills turning at very high speeds, so there is virtually no load. If there was much load, then we would have to hold the cue itself from deflecting to the side because it would bend.

I have done very little inlay work with cnc, but when I did it, I just had a 270 ounce stepper attached directly to a Taig lathe chuck. If I was going to do much of it, I would want to go the timing belt route with a 2 to 1 ratio and a 425 ounce stepper. I would think that would be plenty strong enough. I don't think you would have much backlash as long as the belt was tight. MC2, did you have belt tightness issues? Is that were the backlash came from?

Like I said, I have not done much inlay work, just ALLOT of shaft turning!


Royce Bunnell
www.obcues.com
Click to expand...

Thank's Royce.

Well, I was hoping to "take all those flies in one bang" and make my wife happy as well. Se is educated as a dental technician and would like to make 3D stuff. Much would be for molds (which requires no torque) but then she saw this video and tripped : "Can we do like that" ? :D
http://www.cnc-router-routers.com/html/drehtisch_cnc_router_routing_e.html
Scroll down on the page.

You know girls - what ever "sparkles" like some fancy metal - result - "Me want...". Almost like the Crows he he. Hope my wife never figure she should go up here and read. I could be in for a "One week'er" :D

The unit used in the video has 20Nm holding torque and backlash is 3 minutes (which I don't know how much is in degrees).

Kent
 
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RBC said:
I am not sure why you need such high holding torque? In cues, we are using very small end mills turning at very high speeds, so there is virtually no load. If there was much load, then we would have to hold the cue itself from deflecting to the side because it would bend.

I have done very little inlay work with cnc, but when I did it, I just had a 270 ounce stepper attached directly to a Taig lathe chuck. If I was going to do much of it, I would want to go the timing belt route with a 2 to 1 ratio and a 425 ounce stepper. I would think that would be plenty strong enough. I don't think you would have much backlash as long as the belt was tight. MC2, did you have belt tightness issues? Is that were the backlash came from?

Like I said, I have not done much inlay work, just ALLOT of shaft turning!


Royce Bunnell
www.obcues.com
Click to expand...

That's how I have built my last 2. Directly linked was actually fine on some but then I started running belt drives which gives the option to vary drive ratios to match the project. I need that since I do more than mill wood. :) For cues and like 1/16" at most bits , I can't imagine needed any more torque than direct can provide.
 
RBC said:
I am not sure why you need such high holding torque? In cues, we are using very small end mills turning at very high speeds, so there is virtually no load. If there was much load, then we would have to hold the cue itself from deflecting to the side because it would bend.

I have done very little inlay work with cnc, but when I did it, I just had a 270 ounce stepper attached directly to a Taig lathe chuck. If I was going to do much of it, I would want to go the timing belt route with a 2 to 1 ratio and a 425 ounce stepper. I would think that would be plenty strong enough. I don't think you would have much backlash as long as the belt was tight. MC2, did you have belt tightness issues? Is that were the backlash came from?

Like I said, I have not done much inlay work, just ALLOT of shaft turning!


Royce Bunnell
www.obcues.com
Click to expand...


Royce, you are correct. Now that I think about it, I was interested in cutting alluminum and other non wood items when I was shopping for one. The shereline worked out so well that I purchased another. I have been very happy with these little guys. I may now just be biased.

Jim.
 
Mc2 said:
Royce, you are correct. Now that I think about it, I was interested in cutting alluminum and other non wood items when I was shopping for one. The shereline worked out so well that I purchased another. I have been very happy with these little guys. I may now just be biased.

Jim.
Click to expand...

Now I remember the reason I chose the sherline. I didn't think I would get the holding power I wanted when cutting in points. Also, I wanted to be able to cut points in at odd angles for example a prong with seven points. If you go direct drive on the chuck with a stepper, you will loose alot of resolution.

Jim.
 
Mc2 said:
Now I remember the reason I chose the sherline. I didn't think I would get the holding power I wanted when cutting in points. Also, I wanted to be able to cut points in at odd angles for example a prong with seven points. If you go direct drive on the chuck with a stepper, you will loose alot of resolution.

Jim.
Click to expand...

I've been using the Sherline for about 6 or 7 years now and am very happy with it. I have the stand alone with it's own controller built in so I can either just punch in how many equal increments from 1 to 999 or in .006 of a deg. or just hit a button and slave it to my normal operating program. Very stable and easy to use.

Dick
 
specification difficulties, Minutes and so on..

I have been reading on this now and trying to correlate some of the
information could some times be a challenge...

Some use arc minutes some arc seconds and some mm or "..

Just so I'm not on the wrong tracks :

1 degree :1/360 = 17.45mRad
arc minute: 1/60 degree=290.888uRad
arc second: 1/60 of arc minute.

So when a vendor has accuracy of "5 seconds" and the other "100 arc seconds"
I guess we meant that the "5 seconds" is better than the "100 arc seconds" assuming the manufacturer actually mean "5 ARC seconds"?
Or I'm I totally on the wrong track here where just "seconds" means something else?

Same with backlash ;
One has "3 minutes", the other has "Repeatability 1 arch seconds", the third has 0.01mm after adjusting and Sherline .0001" (.00254mm)

Kind of frustrating so to figure which is best in this respect I'm trying to sort these things out. Any one which is well known with these figures ?

Thank's
Kent
 
rhncue said:
......The stepper motor locks the rotary table in position once the movement has been made and the Sherline has 28,000 steps to a revolution. That comes down to .006 of a degree resolution. .....
Dick
Click to expand...

Dick,

I guess you are then running half steps ?

Playing with the numbers, a Sherline is 100mm Diameter.
That gives 0.27mm/degree or a resolution of 0.001785mm milling @ a
diameter of 100mm (decreasing with diameter)

The bearings used has a run out of 0.00254mm(0.0001") and then I guess
the worm gears production accuracy's comes in to play together with the holding device.
Backlash should therefor be expected > 0.00254mm.

I'm expecting that you would not be able to mill with the accuracy you have
even if the stepper's setup gives you that on paper ? Specially if you are
milling on a even smaller diameter where the backlash would be hugh compared to the potential resolution.
Or I'm missing something vital here ?

Was just wondering since I have "redone" the math on a commercial 4th axis 100mm.
It claims rotational accuracy of 5 Arc Sec which if I'm doing
the numbers correct means 0.000385mm @ 100mm.

100mm
------------ * 5 Arc Sec=0.000385
360*3600

However, backlash is stated to be 0.05mm but could be trimmed down to
0.01mm when fully set up???? Is it just me who finds this strange ???

Kent
 
Newton said:
Dick,

I guess you are then running half steps ?

Playing with the numbers, a Sherline is 100mm Diameter.
That gives 0.27mm/degree or a resolution of 0.001785mm milling @ a
diameter of 100mm (decreasing with diameter)

The bearings used has a run out of 0.00254mm(0.0001") and then I guess
the worm gears production accuracy's comes in to play together with the holding device.
Backlash should therefor be expected > 0.00254mm.

I'm expecting that you would not be able to mill with the accuracy you have
even if the stepper's setup gives you that on paper ? Specially if you are
milling on a even smaller diameter where the backlash would be hugh compared to the potential resolution.
Or I'm missing something vital here ?

Was just wondering since I have "redone" the math on a commercial 4th axis 100mm.
It claims rotational accuracy of 5 Arc Sec which if I'm doing
the numbers correct means 0.000385mm @ 100mm.

100mm
------------ * 5 Arc Sec=0.000385
360*3600

However, backlash is stated to be 0.05mm but could be trimmed down to
0.01mm when fully set up???? Is it just me who finds this strange ???

Kent
Click to expand...

Kent, you've lost me. What I do know is that there is 28,800 steps to a revolution and the backlash in the gear train is adjustable. For more detailed information you can go to this site:

http://www.sherline.com/8700inst.htm

Good luck in your endeavours.

Dick
 
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