[4]

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

[3]
[10] Like what you see?
Click here to donate to this forum and upgrade your account!

Four Corners

New Member
Registered
Joined
Mar 13, 2017
Messages
26
Likes
11
#1
I have a Sieg SC4 from Little Machine Shop. I've contacted them for help, and I'm sure they will, but I always like several opinions. In the link below you will see that my lathe takes a long time to respond to the stop and direction buttons. At full speed it take around seven seconds before the lathe stops or changes direction. This is dangerous for so many reasons. Is mine the only machine that does this

https://photos.app.goo.gl/gdKQGp9XXseL9GTa2

Sent from my Pixel 2 using Tapatalk
 

darkzero

Global Moderator
Staff member
H-M Supporter - Gold Member ($25)
Joined
Nov 27, 2012
Messages
3,033
Likes
1,896
#2
Looks normal to me. Don't know if that's safe to do but I wouldn't feel comfortable forcing spindle direction like that. Being electronic I assume precautions are built in but still.

Many non-electronic drive, belt & gearhead lathes take much longer than that to slow down/come to a complete stop. Bigger the chuck the longer it will take also. Sounds like a VFD with braking or a mechanical foot brake is what you want but even then it's not recommended to stop the spindle instantly all the time.
 

DAT510

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Oct 20, 2016
Messages
310
Likes
193
#3
I don't have a Sieg Lathe, but I do have a Sieg SX3 Mill. I've noticed during startup/ramp-up the "stop" button has no effect until it reaches operating speed. The "emergency stop" button works regardless. Once up to speed, the stop button is immediate. My thought was, the controller has a very simple processor and the way the controller is programmed is only one operation can occur at a time. Meaning the next operation can't start until the first is finished. In my case Ramp-Up, then the stop command. It startled me the first couple of times it happened.

Hope this helps.
 

4ssss

Active Member
Registered
Joined
Apr 25, 2017
Messages
451
Likes
262
#4
Throw an anchor out.
 

higgite

General Manger - Proofreading Dept.
H-M Supporter - Gold Member ($25)
Joined
Aug 15, 2013
Messages
829
Likes
872
#5
Four Corners,
It’s hard to tell exactly what’s going on in your video, but I think what you are experiencing is the stop button doesn’t work while the spindle is automatically accelerating back to its previous speed when you restart after using the stop button or when you reverse direction with it running. However, the E-stop button will immediately shut it down quickly at any time, even when the stop button won’t. At least, that’s how my LMS 3540 (Sieg SC4) works. Sounds the same as Dat510's SX3. I haven't tried it on my LMS 5500 (SX2.7) mill, but I'm guessing it works the same.

Darkzero,
I hear what you're saying about reversing polarity at speed, but the controller on these machines doesn't reverse the contactor until the spindle has slowed to zero.

Tom
 
Last edited:

T Bredehoft

Active User
H-M Supporter - Gold Member ($25)
Joined
Dec 27, 2014
Messages
2,691
Likes
2,076
#6
My little Atlas Clausing MK2 doesn't have any electronic braking, I use my hand on the chuck. Works a treat.
 

darkzero

Global Moderator
Staff member
H-M Supporter - Gold Member ($25)
Joined
Nov 27, 2012
Messages
3,033
Likes
1,896
#7
Darkzero,
I hear what you're saying about reversing polarity at speed, but the controller on these machines doesn't reverse the contactor until the spindle has slowed to zero.

Tom
I assumed that the controller would do something like that as I mentioned. Perhaps I'm missing what the OP is asking. Whether if the buttons don't seem to respond as fast as he would like of if he thinks the spindle is not stopping/slowing down fast enough when pressing stop. If the latter, doesn't look abnormal to me.
 

mksj

Active User
H-M Supporter - Gold Member ($25)
Joined
Jun 12, 2014
Messages
1,892
Likes
2,309
#8
Your are limited in braking speed in particular with lathes due to the momentum in the system. The SC4 uses a smallish DC motor and it is probably limited as to braking capacity depending on the design of the controller. Some DC controllers (like KB Electronics) you can set these parameters with pots, some have forms of dynamic braking vs. regenerative, but I would assume the SC4 uses a rudimentary design. If pushed to harder braking (assuming it is adjustable) it might damage other components not rated for the higher dissipation. There are two pots on the control board, but no information as to what they do.

Faster stops are desirable in an emergency situations, but short of a manual foot brake or electronic braking with a braking resistor, lathes take many seconds to stop. As far as switching directions, as others mentioned (and what I am familiar with VFDs) is that the controller needs to cycle down to 0 RPM per its programmed rate and then change direction. The control systems/VFD programming for systems I build, an E-Stop or limit stop reverts to fast braking, but this is using a large braking resistor and even with this it can be tripped into a free run stopping from maximum speed.

You might watch this video which shows start/stops and speed adjustment of the SC4 and compare with yours. It does seem to stop in 3-4 seconds from speed.
 

Four Corners

New Member
Registered
Joined
Mar 13, 2017
Messages
26
Likes
11
#9
Firstly, I would like to thank you all for taking the time to respond. However, it seems that I didn't properly describe the problem that I'm having. I understand that because of the momentum of the chuck spinning it takes a small amount of time for the lathe to stop. But that's not what I'm talking about here. My problem is that the lathe doesn't respond to the stop command until after the target speed is reached. In the video you can see that I press the start button and then immediately press the stop button but the lathe continues to accelerate for about 7 seconds. If this is the way the machine is supposed to work then I don't understand why it was designed this way. It's quite dangerous, I would say. Any more thoughts on this would be greatly appreciated.

Sent from my Pixel 2 using Tapatalk
 

higgite

General Manger - Proofreading Dept.
H-M Supporter - Gold Member ($25)
Joined
Aug 15, 2013
Messages
829
Likes
872
#10
Firstly, I would like to thank you all for taking the time to respond. However, it seems that I didn't properly describe the problem that I'm having. I understand that because of the momentum of the chuck spinning it takes a small amount of time for the lathe to stop. But that's not what I'm talking about here. My problem is that the lathe doesn't respond to the stop command until after the target speed is reached. In the video you can see that I press the start button and then immediately press the stop button but the lathe continues to accelerate for about 7 seconds. If this is the way the machine is supposed to work then I don't understand why it was designed this way. It's quite dangerous, I would say. Any more thoughts on this would be greatly appreciated.

Sent from my Pixel 2 using Tapatalk
As I said in my previous post, the spindle comes to a stop very quickly if you press the red E-stop button, whether the machine is accelerating, reversing, steady state or whatever. I don't have a problem with that, but some might.

Tom
 

Four Corners

New Member
Registered
Joined
Mar 13, 2017
Messages
26
Likes
11
#11
So, just to summarize, my machine is not faulty; the SC4 is supposed to work like this. Is that correct?

Sent from my Pixel 2 using Tapatalk
 

higgite

General Manger - Proofreading Dept.
H-M Supporter - Gold Member ($25)
Joined
Aug 15, 2013
Messages
829
Likes
872
#12
So, just to summarize, my machine is not faulty; the SC4 is supposed to work like this. Is that correct?

Sent from my Pixel 2 using Tapatalk
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
 

Four Corners

New Member
Registered
Joined
Mar 13, 2017
Messages
26
Likes
11
#13
Thank you Tom. Much appreciated.

Sent from my Pixel 2 using Tapatalk
 

higgite

General Manger - Proofreading Dept.
H-M Supporter - Gold Member ($25)
Joined
Aug 15, 2013
Messages
829
Likes
872
#14
No problem. Glad I could help.

Tom
 

9t8z28

Active Member
Registered
Joined
Aug 16, 2016
Messages
233
Likes
86
#15
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.
 

Four Corners

New Member
Registered
Joined
Mar 13, 2017
Messages
26
Likes
11
#16
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.

Sent from my Pixel 2 using Tapatalk
 

9t8z28

Active Member
Registered
Joined
Aug 16, 2016
Messages
233
Likes
86
#17
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.
 

Four Corners

New Member
Registered
Joined
Mar 13, 2017
Messages
26
Likes
11
#18
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.

Sent from my Pixel 2 using Tapatalk
 

9t8z28

Active Member
Registered
Joined
Aug 16, 2016
Messages
233
Likes
86
#19
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.

Sent from my Pixel 2 using Tapatalk
 
[6]
[5] [7]
Top