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Author Topic: Use Spindle Feedback in Syn Modes ? Experiences  (Read 7706 times)

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Offline Fastest1

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Use Spindle Feedback in Syn Modes ? Experiences
« on: December 15, 2009, 10:07:28 PM »
Anybody understand this? The wording seems like it would be obvious but is it? I swear I have run threads both with and without it checked with similar if not better results without it checked. If it is checked, I uncheck spindle speed averaging as they would seem to conflict in the threading scheme, again I could have some flawed understanding of what is necessary. And today in a lapse where I had been using the manual speed control, I forgot to switch it back to automatic speed control on my spindle, hit cycle start and somehow the tool still hit the right place on each return pass at least 5 times before I realized my error. You know if I had a list of all the things to reset, change, plug back in, I couldnt see the machine.  ;D
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)

Offline Hood

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Re: Use Spindle Feedback in Syn Modes ? Experiences
« Reply #1 on: December 16, 2009, 02:28:53 AM »
Well I am extrememly surprised you got a good thread with it unchecked. Normally you would see a stepped like leading edge to the thread.

Hood

Offline RICH

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Re: Use Spindle Feedback in Syn Modes ? Experiences
« Reply #2 on: December 16, 2009, 05:37:32 AM »
Like Hood, I am also suprised. You should use always have spindle feedback checked. That provides for monitoring of the rpm while doing actual threading. Spindle speed averaging took the  rpms and adjusts the next pass based on an average of the monitored rpms. If there was not much change in the rpm then you may get away with it. Don't fool yourself, as the spindle rpm changes even when not under load, and you don't have the equipment to  measure it.
Not having those checked you will find that you have lead error or run into problems. If you do find you have lead tolerance issues it's your lathe system and not MACH. Testing shows the software can meet the criteria shown in figure 4.4.5 in threading on the lathe write up. The accuracy of the software exceeded my measuring capabilty.
RICH 

Offline Fastest1

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Re: Use Spindle Feedback in Syn Modes ? Experiences
« Reply #3 on: December 16, 2009, 07:58:50 AM »
I agree in theory. I was shocked at the results and as usual it was an accident. I was merely changing settings trying to figure out why speeds didnt match indicated speeds and proceeded before correcting the setting. That is exactly why I posted this. I might try to replicate it but damage usually occurs when I do things on purpose. So for correct threading I can see where spindle feedback would be a necessity however is speed averaging also to be checked? Seems like averaging would defeat the compensation that the feedback was provided for. What is up with the first pass? It starts in segments and then smooths out over the next few passes. Very interesting to hear and watch and to see a decent thread being cut. I am hypnotized watching it perform. The mathematical idea that you could match linear and rotational travel to a single point at 400-500 rpm is incredible.
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)

Offline Hood

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Re: Use Spindle Feedback in Syn Modes ? Experiences
« Reply #4 on: December 16, 2009, 08:19:52 AM »
What is up with the first pass? It starts in segments and then smooths out over the next few passes.Very interesting to hear and watch and to see a decent thread being cut. I am hypnotized watching it perform. The mathematical idea that you could match linear and rotational travel to a single point at 400-500 rpm is incredible.

Not sure what you are meaning by the first pass bit.
Heres a vid of my lathe doing the first op of the pullstuds I made for my Beaver Mill, not sure you will hear much though ;D http://www.youtube.com/watch?v=8J9q0NqoHhg
The material is EN24T and the thread was 16mm x 2mm pitch.
I also have a video posted of the full operation of the pullstud with the Computurn  lathe and Bridgeport but its at much slower speeds as it was before I got the smoothstepper.

The pic below has the original pullstud for the mill on the right, the left is the ones I made and below is one of the ones I made for Brett (Chaoticone)

Hood
« Last Edit: December 16, 2009, 08:21:39 AM by Hood »

Offline Fastest1

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Re: Use Spindle Feedback in Syn Modes ? Experiences
« Reply #5 on: December 16, 2009, 08:57:22 AM »
Hood, great work as usual. When I first start the simple threading wizard, the very first pass does a 3-4 segmented pass. I hear the steppers slow down and speed up. It does this only on the first pass and each pass after that smooths out and speeds up til S value is acheived. Usually 3-4 passes til up at full speed. The threads are very evenly spaced and appear very good. I have no knowledge or tools to verify quality of thread. I do know the nut fit better with less play than the bolt I copied the measurements from. I bought the bolt for .67 cents, I told my wife mine was better so I am going to charge .68 cents and claim it is American made. I do have some surface issues that might be the aluminum (home depot) I am using. I will have to try some different stock.
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)

Offline Fastest1

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Re: Use Spindle Feedback in Syn Modes ? Experiences
« Reply #6 on: December 16, 2009, 09:12:43 AM »
Hood, 2 more questions. What is a pullstud for? (I am guessing it is for a drawbar). Second now that I see your toolchanger, I have a new idea for my rotary table that is sitting on the mill table LOL. On my little lathe that could probably work as well as anything else I have seen. Just a round plate to bolt to the table with slots cut or broached with set screws. Too easy. Well I say easy but the rotary table (Sherline too) is bigger than the entire lathe table but I am going to look. It might be a good idea for my next lathe.
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)

Offline Hood

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Re: Use Spindle Feedback in Syn Modes ? Experiences
« Reply #7 on: December 16, 2009, 09:53:13 AM »
Your first pass doesnt sound right at all, the motion should be constant and the speed should be up to its max before the thread starts. How much of s start are you putting on the Z? If your steppers have fairly slow acceleration you will maybe need to increase the Z distance so that it has time to get to speed before the cut starts.

Yes the pullstud is for the mill, instead of a screw drawbar like on a manual mill mine has a hydraulic operated drawbar that has jaws on the lower end, they open as the bar is pushed down, go over the pullstud and then the drawbar raises again and the jaws close round the pullstud and pull the collet holder into the spindle taper.

You will need some form of brake or pawl on the changer to make sure there is no movement when the tool is in position as even on a small lathe the cutting forces will be fairly large, especially in threading. I also have a front toolpost on the lathe, you should see it in the video, I am about to replace with another turret that I got, looking forward to it, just need to find the time.

Hood

Offline RICH

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Re: Use Spindle Feedback in Syn Modes ? Experiences
« Reply #8 on: December 16, 2009, 10:36:15 AM »
"So for correct threading I can see where spindle feedback would be a necessity however is speed averaging also to be checked?"

YES ( checking it should do no harm and i need to go back and find some specific info on it . There is only 450 pages of stuff on threading, so don't hold you breath while i look ).

"What is up with the first pass?"Do you mean what happens during the first pass? That is explained in section 2.1 of the write-up.
RICH

Offline Hood

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Re: Use Spindle Feedback in Syn Modes ? Experiences
« Reply #9 on: December 16, 2009, 10:40:21 AM »
Rich, I always just thought averaging was used only for the display in Mach so that you dont see that jumping about if you have variations such as you may get with a vee belt that is unevenly worn but maybe not.
Hood