Thread Sensor Assembly - One Works Well, One Not So Well

[levelbest]

Hey Tech Friends...

I have two machines roughly the same vintage (2003) that are same in almost every respect - except the readings for actifeed when sewing the same design.

Both have the upgraded Thread Sensor Assembly that replaced the original (I did that a year or more ago).

I've made things as equal as I possibly can sewing on the same type of garment, same bobbin spider walk, same oiled hook. I've cleaned both machines out, greased at the same time etc.

Yet, Machine 1 sews beween 1-4 on actifeed while machine two sews between 3-8. Of course, machine 2's sew quality looks better. When I set the minimum Material Thickness on Machine 1 to 3, it goes then between 3-5 and the quality is pretty much the same as machine two (so at least we can use it).

So, the million dollar question - what should I check at this point. I thought I might have overtighened the two screws that attach the thread break sensor but they seem fine.

Where to go from here (other than ordering a replacement Thread Sensor Assembly)? It feels like the end of the week because I can't pull any answers right now.

P.S. Just in case you were thinking - did this just happen - what changed... Machine 2 has always sewed out just a little better and I've never bothered to mess with it. What is it about the handymans house being the last to get fixed? My brilliant wife today was the one who noticed that the Material Thickness was running different between the two. I think we just had a design today that made everything a little more obvious. It's not that the first machine looks bad - it's just that the second looks BETTER Thought I'd finally try to put this issue to bed.

[Aaron]

John,

Im no tech but I have 3 reds and 3 grays and my reds (haven't payed attention to the grays)seem to run different MT's on the same designs and sometimes they will sew differently like you are talking about. I usually just set the lower limit to the same on them but even then sometimes I will stop sewing certain designs on both machines because the logos do look different. I guess I would be interested to see what answers you come up with here.

[Rod or Sharon]

John,

Given that every machine is just that, a machine and has multiple moving parts, there are numerous combinations of things that can make one machine sew just a bit differently than another. the information below is going to assume that the thread break sensor is in good operatng condition.

I have found that for the auto activ-feed to work better, the bobbin tension needs to be tighter than a "spider crawl" as you put it.

Remember in a previous post, the workings of the thread break sensor is dependent on pressure exerted by the thread pulling up on the thread break sensor at the top of the stroke of the takeup lever.

Inside the machine behind the needle plate is a round disk with a contoured face on it. This is the takeup lever cam disk. If this disk has not been kept lubricated, then wear will occur at a more rapid rate than it is designed for. I have said many times on this forum that it is best to not wait for the pop-up timers to lubricate certain parts of the machine. Those being the takeup lever cam disk, the needle bars, the reciprocator, pinch and thread feed rollors and the rotary hook.

If the takeup lever cam disks wear at different rates, between machine one and machine two, then the upper stroke or travel of the takeup lever will vary, which in turn will vary the amount of tension being applied to the thread break sensor. If this does happen then auto activ-feed readings will also vary somewhat. So tightening the bobbin tension on one machine just a bit tighter may be all that is necessary.

There are other reasons to be sure....but hope this lends some light on one important issue concerning the thread break sensor and the importance of proper lubrication......

Rod Springer
Amaya Tech & Trainer

[levelbest]

Hi Rod:

Thanks for the reply! The cam is well lubricated on both machines (as the other parts you mentioned). Tech training has me watching out for that sort of thing I agree completely.

On the spider crawl... I guess I use that term "loosely" but with actifeed, run the bobbins more tightly. So, it's not really a spider crawl anymore.

My big concern is that without setting a lower thread feed limit, machine 1 is sewing worse than machine two using actifeed. Honestly though, we have gotten into the habit of setting the minimum MT, so I guess it's not a huge issue, but still one I was curious about solving.

I'm going to swap out the sensor with a new one to rule that out but I'm still open to other thoughts.

[levelbest]

Hugo posted this directly to the list, so I am going to post it here on the web side of things so everyone can see...

"John,

You can also check the gap in your feeder gears as well as the gap on the take up lever gears.
Another thing that comes to mind is the x cable tension, X-carriage bearing load, y rail belt tension and y motor belt tension.

You can always swap the sensors on the machine and see whether they react differently

Do all this while you are hopping and skipping and running in place!

Hugo"

[Hugo Torbidoni]

John,

Was wondering what you found on the thread sensor/sew quality issues you were having?

Hugo

[levelbest]

Melco said they were going to send a thread sensor out - so I am waiting on that. Right now, my wife is in the middle of a big production run and I didn't want to get in her way when she was using it as is right now (sewing just fine otherwise with minimum MT set). You know, the making money thing comes first!

I'll report back by Thursday. Probably will be looking for more of your insight then Hugo!

Thanks for checking in on me.

[levelbest]

Ok, here's the results.

It was the sensor. More specifically I believe the sensor board soldering joints where the wires from the sensor bars connect. These are tiny guage wires connected to the board and I believe that there was either an intermittent connection or that the red wire on the left side had totally been severed. Seems like in this state, it was still able to pick up something, but it was not as sensative as it should be.

So, putting a new board and sensor bar on has completely solved the issue and big red one is sewing as good as new.

Given the size/guage of the wire and vibrations the machine experiences when sewing, I guess I shouldn't be shocked that this could be a point of failure. Now, if I was handy with a soldering iron, I could have probably fixed the issue. May give it a shot and keep it as a spare - though my skills soldering aren't the greatest!