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Automatic bandsaw problem

Pysiek

Aluminum
Joined
Aug 26, 2010
Location
Illinois
We bough a HBS-12A (I know old) automatic band saw with roller feeder. It was working fine for few weeks and then this problem occurred. It will not push the material in auto mode. What happens is it will finish cutting hit the switch and bandsaw head will lift and stop then start descending slowly and cutting but material have not been pushed to limit switch so basically it's cutting air. But if we press the feed manually with button it will feed the material. What might be the problem? This machine uses basic electronics. And it won't happen all the time. Sometimes it will cut fine for an hour and then quit feeding material.
 
Check the "out of stock" limit switch .

It works if we push it manually. Let me explain the switches on the saw. Please take a look at the image. This is not our saw. I found this image online.
There is a "stock limit switch" which you adjust to the length of piece being cut. Next there is a "head down switch" which let the relay know the head is down so the cut is done. And the third switch is a "stock switch" which makes sure there is a stock loaded in the feeder.
Now I will try to explain the best how it works. You load the stock in feeder. This way stock switch is activated and saw works fine. Otherwise it will not work at all. Now you turn the main panel switch to "AUTO". Press "stock forward" button and feeder feed the stock till it hits the "stock limit switch" then saw start to go down and cutting. Once it finish cutting , cut piece fell off the "stock limit switch" and saw head hits "head down switch" and now head lifts till it reach height set up by knob on the control panel. (there is a mercury switch behind the knob that is responsible for this). Once the head reaches it's height feeder should push the stock forward again till it hit the limit switch. But it's not happening on our saw anymore. We have to use a manual button to push it forward.
Jet HBS-12A SWITCHES.jpg
 
Sounds like it's not getting the signal that the head is up.

When it stops, have you tried lifting the head by hand to see if it resumes the cycle?
 
Sounds like it's not getting the signal that the head is up.

When it stops, have you tried lifting the head by hand to see if it resumes the cycle?

The problem is when the head goes up and reach the adjusted height it will resume the cutting cycle (go down slowly while blade is running) even without the stock being pushed forward. So the head is getting a signal (from mercury switch) but some how the feeder don't. And it's not always. Like I said sometimes it works fine for half hour and then stop again.
 
The limit switches are simple animals. Break out the DMM, and test the switch while working, seeing if it is N/O or N/C. Next, test same switch when feed is not working. Boom, done.

Intermittent issues usually come down to sketchy wiring (i.e. intermittent connection form broke wire), or corrosion, albeit rust, coolant, old age/wear, or the dudes french fry and apple pie crumbs.

The switch is two wires, yeah? If so, figure out nc or no, and just jump the wires to see if it works.
 
The limit switches are simple animals. Break out the DMM, and test the switch while working, seeing if it is N/O or N/C. Next, test same switch when feed is not working. Boom, done.

Intermittent issues usually come down to sketchy wiring (i.e. intermittent connection form broke wire), or corrosion, albeit rust, coolant, old age/wear, or the dudes french fry and apple pie crumbs.

The switch is two wires, yeah? If so, figure out nc or no, and just jump the wires to see if it works.

Every two wire switch works fine. Not sure how to check that mercury switch. How about the relays? Is it possible it's getting stuck or something?
 
The problem is when the head goes up and reach the adjusted height it will resume the cutting cycle (go down slowly while blade is running) even without the stock being pushed forward. So the head is getting a signal (from mercury switch) but some how the feeder don't. And it's not always. Like I said sometimes it works fine for half hour and then stop again.
Gotcha- I missed that part.

In that case, it sounds like the stock limit switch may be the culprit. One would think that the head should not come down in auto mode if that switch is open (assuming a NO switch), since the stock is not in position.

If the switch is sticky and remaining closed, the head hits the all the way down position, lifts, and the controller thinks the material is in the right position so it resumes cutting.
 
Gotcha- I missed that part.

In that case, it sounds like the stock limit switch may be the culprit. One would think that the head should not come down in auto mode if that switch is open (assuming a NO switch), since the stock is not in position.

If the switch is sticky and remaining closed, the head hits the all the way down position, lifts, and the controller thinks the material is in the right position so it resumes cutting.

Yes it makes sense. So why it allows me to do it manually? Also I can hear the switch click when the piece release it.
 
Double check your limit switches. Make sure you can hear the click when you activate the arm, and again when you release it. The microswitch inside usually works, but the arm pivot can get rusty or gunky and either not trip or not release the microswitch. After that, troubleshooting electrical problems are #1, connections, #2, connections, #3, connections, and #4, everything else. If you can fix it with a hammer, its not really electrical.
 
Yes it makes sense. So why it allows me to do it manually? Also I can hear the switch click when the piece release it.
I don't know that saw, so I can only speculate. But the logic in manual cutting is different than in auto cutting. IOW, if you are just cutting one piece, there isn't any reason to require the stock stop limit switch to be part of the process. You just position the material and make the cut.

If I was programming the modes on that saw, I would not require all the logic of the auto mode for manual operations.

I'd put the voltmeter on that switch and make sure it's working right.
 
I don't know that saw, so I can only speculate. But the logic in manual cutting is different than in auto cutting. IOW, if you are just cutting one piece, there isn't any reason to require the stock stop limit switch to be part of the process. You just position the material and make the cut.

If I was programming the modes on that saw, I would not require all the logic of the auto mode for manual operations.

I'd put the voltmeter on that switch and make sure it's working right.

We cut a 12 ft stock pieces to 5" long pieces. We bought this saw to be used in automatic mode all the time. Also there is no programming on the saw. Everything is controlled with relays and switches.
 
Double check your limit switches. Make sure you can hear the click when you activate the arm, and again when you release it. The microswitch inside usually works, but the arm pivot can get rusty or gunky and either not trip or not release the microswitch. After that, troubleshooting electrical problems are #1, connections, #2, connections, #3, connections, and #4, everything else. If you can fix it with a hammer, its not really electrical.

If they click it's mean they are good?
 
We cut a 12 ft stock pieces to 5" long pieces. We bought this saw to be used in automatic mode all the time. Also there is no programming on the saw. Everything is controlled with relays and switches.
Even if there is no PLC, there is still logic. You don't want the head coming down if the vise is not clamped, you don't want both vises unclamped at the same time, etc.

It's just being done in an analog manner- switch closes, activates relay, cycle advances to the next step, etc. The point where it breaks down is your clue where to look for the faulty switch or relay.

If the relays and or switches are the same, you can swap one out with another and see if the behavior changes- sometimes that helps to isolate the faulty component.
 
You don't want the head coming down if the vise is not clamped, you don't want both vises unclamped

I've got the same POS.. No viseS, single vise, it doesn't unclamp, it has rollers that roll the stock through,
which can make it a pain in the ass on lumpy hot rolled garbage, or stock sawn out of plate..

Mine has never worked in auto mode.. Never really tried to get it to work in auto mode.. I just
needed a bigger saw, and it was available local at a price I was willing to pay.

I haven't even used it in a while, but when I did, the thing was a constant battle to keep
working.. There are a ton of contacts and relays and switches, and they were always getting
burnt or corroded..

The only advise I have is to chase the logic and look for burnt, or corroded contacts and
loose wires.. If you take it one bit at a time, its fairly simple... If you draw out the
logic in a diagram you can usually pin point the problem pretty quick.. Sorry I can't
be any more help (if at all), I haven't had my head into that thing in a long time.
 
AS mentioned above, when the switches[or related relays] get stuck into an inappropriate state, odd things happen. Like if the up and down switch both show closed at the same time, who knows what is going to happen.
 








 
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