Sieg SC4 (LMS 3540) doesn't stop quickly enough

So, just to summarize, my machine is not faulty; the SC4 is supposed to work like this. Is that correct?

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So, just to summarize, my machine is not faulty; the SC4 is supposed to work like this. Is that correct?

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The green "stop" button on mine works exactly as you described in post #9, including the ~7 second acceleration time from zero to 2000 rpm. But, as said before, there is no delay with the red Emergency stop button, even during acceleration.

Tom
 
No problem. Glad I could help.

Tom
 
This is completely normal. I agree, it should stop instantly when you hit the stop button. I dont like to have to use the emergency off button because it resets your speed. What until you get a 5” 4 jaw or a 5C collet chuck. It takes even longer to accelerate and stop.
 
So, perhaps I've taken this a bit too far, but..... The foolish design of the electronics on this lathe got the better of me. In the summer I ordered a VFD and a 3 phase motor, and I gutted the lathe and put all of the stuff in a box. Now I have a simple pot to control the speed, a three position switch for forward, stop, and reverse, a big red panic button and a rpm meter. If I turn the speed pot up to full, throw the direction switch to forward and immediately back to stop, the lathe stops almost instantly. It doesn't ramp up to the target speed before agreeing to stop. It stops, right now. Just like it should have been designed to do originally. I've done some threading on it recently, and it has been a much less stressful experience. I have to say that pulling out the electronics, installing the new motor and the switches was a lot more work than I expected. I probably should have expected it, but that's usually the case with the projects I tackle. The VFD was a huge learning curve, and I have a degree in computer systems engineering as well. It works (mostly) how I want it to, but I honestly don't truly know why the settings I chose gave me the results I have. If I was going to do this again I would buy a bigger VFD and motor than I need, and I would ensure the VFD has SVC (which mine doesn't). However, it works well, it operates safely and it makes much more sense to me.
Here endeth the lecture. Amen.

Thank you for all of your comments and feedback.

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You just kept this thread alive, well at least for me ! This mod sounds awesome. I have always thought that this Lathe had a good amount of power for it’s size but it did have the downfall of not stopping when you tell it to. It really hasn’t bothered me much because I plan my methods of threading and other opperations around it, but this motor and VFD upgrade sounds awesome. Can you post some pictures of it and tell us more about it ? I am always into upgrading and making my SC4 better such as tapered roller bearing on the back Side of the spindle, tapered gibs on the carriage and a solid toolpost. Lately I have been wanting to add a brake to the lathe just so I can thread closer to a shoulder. A BMX 120MM disc brake rotor and caliper can be had dirt cheap. I would just have to figure out how to mount it and whether or not to disable the motor braking when the pedal is used.
 
Well she sure ain't perdy, but she's mine. Don't judge me, k? I'm no Stephan Gotteswinter or Robin Renzetti. You will see that clearly enough. Over the next few days I'll try to take some pictures and videos and write up a bit of an explanation of the good and bad bits. I'm still a bit chaffed that any of this was really necessary. I doubt the smaller Sieg lathes have these "features", the SC6 and 8 look much more like industrial machines, and even the milling machine I have works like it should. So why.....?
Any way, I'll post something that I hope will be interesting.

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Don’t worry, I don’t compare anyones work to anyone else’s.
The SC6 and 8 share a good amount of parts with the SC4 believe it or not. Some parts appear totally different and some are just slightly modified from the SC4 or the other way around. I do wish the SC4 had a heavier tailstock that had a wider span on the ways. I’ve thought about filling the recess with lead and rebiulding the base of the tailstock from a larger piece of cast iron that I have. Definnitly next on the to do list is to add a ball bearing to the tailstock quill and add a larger handwheel
Well she sure ain't perdy, but she's mine. Don't judge me, k? I'm no Stephan Gotteswinter or Robin Renzetti. You will see that clearly enough. Over the next few days I'll try to take some pictures and videos and write up a bit of an explanation of the good and bad bits. I'm still a bit chaffed that any of this was really necessary. I doubt the smaller Sieg lathes have these "features", the SC6 and 8 look much more like industrial machines, and even the milling machine I have works like it should. So why.....?
Any way, I'll post something that I hope will be interesting.

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