Foot Brake For The Pm 1340gt

Randbo

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I'm so used to a foot brake on lathes, that I decided to see what I could come up with for the 1340GT. I had a couple of foot switches laying around work so I incorporated it into my lathe. I just rewired the microswitch inside the foot petal to NC. Then I just wired it in series with my E-stop. Now I can just rest my foot on the petal and stop the lathe at a moments notice, freeing up my hands. I'm curious has anyone else tried or done this? I'm sure some of you have. Thought I'd post it for anyone who was looking for something like this.

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Nice solution and added safety feature, probably better than trying to hit the E-Stop. On machines that have had mechanical brakes and were converted to a VFD system, I have rewired the foot brake switch into the VFD for electronic braking. Also have done this on some machines that have a trip wire type system. I had thought of using something like a dead man switch that would require it to be depressed to operate, but one tends to move around a machine a bit so probably would not be too good. On the PM1340GT I had thought of adding an electronic foot brake between the cabinets, but I am fine without it. Having an electronic stop that reverts the system to 1 second braking also helps.
 
Nice solution and added safety feature, probably better than trying to hit the E-Stop. On machines that have had mechanical brakes and were converted to a VFD system, I have rewired the foot brake switch into the VFD for electronic braking. Also have done this on some machines that have a trip wire type system. I had thought of using something like a dead man switch that would require it to be depressed to operate, but one tends to move around a machine a bit so probably would not be too good. On the PM1340GT I had thought of adding an electronic foot brake between the cabinets, but I am fine without it. Having an electronic stop that reverts the system to 1 second braking also helps.

At this point I've kept it simple. My VFD is set up on a .5 sec decel for all stops (e-stop, foot brake, fwd/rev switch) and I'm using an overkill 1000 watt, 75 ohm braking resistor that came my way for free. The thing never even gets warm. I've considered setting up various decel rates, on multiple inputs, based on various situations. At this point I've decided that is unnecessary for my use.
 
At this point I've kept it simple. My VFD is set up on a .5 sec decel for all stops (e-stop, foot brake, fwd/rev switch) and I'm using an overkill 1000 watt, 75 ohm braking resistor that came my way for free. The thing never even gets warm. I've considered setting up various decel rates, on multiple inputs, based on various situations. At this point I've decided that is unnecessary for my use.
I apologize for the 2 year old necro post. I have a 1340gt on order and just wondering how this has worked for you after a couple years with it set up this way. Have you found the .5 sec stop to be rough at all on the gears, bearings etc? What size chuck are you running with that half second stop?
 
So far it has been working absolutely flawlessly. The chuck stops faster then any manual brake I’ve used, but isn’t jerky and extremely smooth. There isn’t any signs of excessive load on the gears or power train. Starting the lathe probably puts just as much load on the system as braking for the way I have it set.
I’m running multiple chucks with this set up. 6 inch 3 jaw, 8 inch 4 jaw and 8 inch 3 jaw. I haven’t had any problems with any of them at the current settings. I have had some pretty large chunks of material in the chucks with no problems. I did have to play with the VFD settings to find the sweet spot for my liking. I can post them if you are interested.

Randy
 
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Thanks a lot for the reply Randy. I just placed my 1340gt order and its end of July before I get to start putting her in the shop and working on the VFD conversion. I will do nearly all my work with the 8" 4 jaw (about 35 lbs) and the work itself is rifle barrel chambering, threading etc. So mostly lowish speeds and not a ton of stress. I'm planning on Mark Jakobs proximity stop and wondering about the .5 second stop when threading. Though he says a 1 second stop is still plenty. Once I get it all installed and get into programming I may take you up on the parameters. I'm at least a couple months out from that though.

-dave
 
Thanks a lot for the reply Randy. I just placed my 1340gt order and its end of July before I get to start putting her in the shop and working on the VFD conversion. I will do nearly all my work with the 8" 4 jaw (about 35 lbs) and the work itself is rifle barrel chambering, threading etc. So mostly lowish speeds and not a ton of stress. I'm planning on Mark Jakobs proximity stop and wondering about the .5 second stop when threading. Though he says a 1 second stop is still plenty. Once I get it all installed and get into programming I may take you up on the parameters. I'm at least a couple months out from that though.

-dave
 
Congrats on the new purchase.
It’s been a decent lathe for me. Honestly I wish I’d have gone with a larger lathe (casting) but I’m able to do most of what I need.
I’ve done a few modifications to the lathe but honestly have never seen a need for a prox. stop. I can machine or thread right up to the chuck or end of the tool without any issues or concern. I don’t want to criticize anyone who finds this function handy but I’ve just never seen the need for it. Keep me posted on your new lathe and modifications!
 
A lot of different factors and depends on the relief groove when threading and the speed that you thread. Typically I thread at around 250 RPM which is too quick for one to consistently disengage the half-nut on every pass. My relief grooves are the thickness of the thread cutting insert, so I can thread up to a shoulder or internally to a blind cap. I also do not disengage the half-nut for threading so doing metric threads is easily done. Being a bit older and not using the lathe daily, my hand eye reflexes got it down to 9 out of every 10 threading passes I got right, and then I would break my insert. Internal threading to a shoulder was not as successful.

On braking, you can dial down the braking time to whatever you want but the electronic braking only has so much ability to generate a given stopping force. On the smaller lathes the 1.0 second stopping time is about as low as you can go without risking a VFD fault (over voltage on the buss), but this is a factor of speed and chuck weight. The size of the braking resistor has no bearing on braking time so you get the same braking times whether you have a 250W or 1000W braking resistor, I use a 500W but never had it even get warm. Braking your lathe at 1 second or under all the time I think is a bad idea, why put undue stress on the lathe and gear sets, something is going to break or wear out sooner. The VFD has programming for two different acceleration and braking rates (1 stage or 2 stage), I set up all my VFD systems to allow the user to choose the rate (typically 1.0 and 2.5 seconds), but also that any trigger/fault overrides the braking rate switch to the shortest possible time. Some of us run heavier (80lb) 8" chucks and at speed these will trip a VFD error when run at speed, 1 second is about the max. and on a few systems (and larger lathes/chucks) we have setup slightly longer braking times when running above 1000 RPM. So YMMV.

In the video below threading at ~250 RPM into a blind cap the chuck will stop in the same exact position on every pass (typically 0.0002") using a proximity stop trigger.
 
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