Brother Bas 342Gx Underneath Stitching Problem.

[Yanni]

http://www.youtube.com/watch?v=aT2qWOzcIVc

We have one of these Brother automatic sewing machines in our factory and it tends to do what you see on the photo in the beginning of some stitches.

It seems that the thread doesn't make a proper loop.

The way it starts is 2 stitches forward, then three back and then forward to lock the stitch.

I have tried decelerate the program to stitch slowly, changed the thread tension and still can't figure out why it does it.

It's usually on single layer leathers only, if it's more than one leather then it doesn't really do it.

I understand most of you guys are using manual cylinder and flat beds but could someone with perhaps a bit of experience in these machines guide me to the right direction.

Thanks

Edited March 30, 2014 by Yanni

[gottaknow]

The proper sewing of any programmable machine begins with the adjustment of the stitching foot. You say it sews fine on two layers of your work, but not one. Loosen the foot and lower it exactly the same amount of the layer of leather you aren't sewing. It appears from your photo that the leather is flagging (rising up slightly with the single ply of leather) and your thread loop formed on needle rise is collapsing or not forming at all. This is common on this style of machine. We use the Mitsubishi PLK series of similar machines. They all have this in common. Your machine is simple skipping stitches because of improper foot contact with the material being sewn. The foot may have slipped up just enough to create this condition. The same thing happens on regular sewing machines when the foot doesn't make sufficient contact when the needle is rising and loop forming time. These machines are also sensitive to burrs on the hook point. Make sure it's sharp with no burrs. A bit of 600 grit emery paper rubbed ONLY off the tip of the hook point with fix this. Hope that helps.

Regards, Eric

[Yanni]

Thanks for your help Eric,

The problem is that this machine is 4 weeks old and unlike the PLK machines this one has the presser foot height adjustment on the software.

So you basically program the foot to raise in increments of 0.1mm anywhere you like on the program.

You don't do it manually.

This way you can stitch both single and double layers of leather on the same program.

I have tried lowering the foot to almost 0.2mm above the leather, slow down the speed during the beginning of the stitch but still it does that.

I'm wondering if I do the initial stitch locking wrong.

It always stitches from left to right starting with:

A. 2 3 4(forward)

B. 3 2 1(back)

C. 2 3 4 5 6 7 8 9 10 (forward) etc...

with 1 being the hole furthest to the left.

I will try to reverse the sewing order as sequence A moves the jig away from the hook to see if it makes anything better and also I will increase the number of stitches forward before moving backwards just in case this is what causes the loop not to form.

Any other thoughts much appreciated as it's only one jig that causes this problem.

[gottaknow]

The machine should start sewing regardless of which way your programming takes you. If you say it's just the one jig, is the foot rubbing against the jig at all in the start area? Something is causing a "flag" skip where you're starting. The needle guards on the hook are going to keep the needle where it needs to be at loop taking time. I assume the machine uses a shuttle hook and not a rotary hook. Can you run your machine in "test" mode (one stitch at a time) and observe the action of the foot? Do you have other jigs that start on single ply?

My other thought is that your needle bar is just a tiny bit too high. On a single ply, you're going to get a smaller loop formed due to the fact that the material is pinching the thread less on needle rise. Try lowering the needle in the holder, perhaps 1mm to start with. If you are getting a smaller loop, your hook could be going under your loop. If it starts to work, simply lower the needle bar whatever amount you dropped the needle in the holder.

When you have an issue like this, think first about what your needle thread loop is doing. Regardless of what kind of machine you have, it's all about the needle loop and how and where it's forming in relation to your hook. It sure looks like your material isn't being held firm enough and that it's moving up and down with the needle just enough to not form the loop properly. One way to test that is to load your material with the jig in place ready to start. Take the needle out of the holder and use a small vise grip to hold it. Press the needle down through the material through the throat plate about 5mm. Now move the needle up and down and watch your material. If the material moves up and down with the needle, there's too much space and your material isn't being held secure enough. My programmable Brother bartack is really picky about how the fabric is clamped. Good luck.

Regards, Eric

[Yanni]

Thanks again Eric,

I lowered the needle bar a bit as you suggested but made no difference whatsoever.
My only guess as it happens most of the time but not all the time, is that the two rectangular pieces on JIG01 are very low down on the jig as the engineers tried to fit too much on
one jig. It's a 600 x 300 sewing area. As they are fairly down on the jig the top lid of the jig if it's not closed very tightly it allows some movement of the leather inside and thus the mess underneath.

If you see JIG02 has an identical start and it is perfect every time but the sewing line is further up on the jigs thus keeping the lid of the jig shut more tightly.
That's again my guess which I will have to try again on Monday when back in the factory.

I'll get there in the end....I'm not sure whether I have been extremely unlucky but every single machine whether it's an eyeletter, cutting press or rivetter everything I bought had some kind of issue that
had to figure out how to solve it...for most of them the engineers did not have a clue how to fix them initially!

[gottaknow]

From the looks of your first picture, I suspected the fabric wasn't being held down tight. Whether it was the foot too high or the clamp not holding the material firmly the results look the same. If it were me, I would build up the area around the trouble spots. I don't know what they make your jigs out of, but a permanent fix would be to build up the area a little at a time until it stops. I use regular masking tape to do this so I know where to make permanent changes.

Over the years, (34 to be exact) I've seen a lot of design flaws that have to be corrected at the factory level. A classic example is the Juki 5410. We bought 25 of these about ten years ago. They are a really decent needle feed machine. However, the submerged oil pump is driven by a shaft off of the top shaft. In some machines, the oil tube coming off the top of the pump is too short and rubs against the spinning shaft that drives the pump. Over time, it rubs through the tubing and the only source of oil to the top shaft is cut off. It's an easy fix, but I had one bearing seize up so I tore down each machine. About half had the issues.

Other than this jig issue, how are you liking the Brother? I need to think about replacing my Mitsubishi's in the near future.

Regards, Eric

[Yanni]

Hi Eric,

The brother machine is fantastic, has one of the easiest timing settings you can get on a machine with three screw adjustments your timing is perfect.

We have jammed it badly, broke needles, presser foot, then you turn it off an on and you are back and running within seconds.

If you buy one of these make sure you buy the Brother PS-300B software, paid £300 for it but worth every penny as you will need to make minor adjustments depending on leather thickness,

mainly on the presser foot. You can go through multi layers of leather and then back on single ones without any problems.

I also bought a 2-step tension device that can bring extra tension in and out of the same program to perfect the stitch.

I found that the thread tension is different when the machine is sewing in the two opposite directions so the two step tension is a great tool.

The guy who operates the our machine was working with PLK ones that they were loading the programs on floppy disks!

This one takes a CF card and I have bought an extension and converter from a CF to Micro SD so that I do not damage the internal CF reader and can take the micro SD card and read it on my laptop.

Any more questions...let me know..I just placed an order for another one, this type a copy at £23K but it comes with built in programmer and USB connection not CF card.

[gottaknow]

Thanks for the information Yanni. My PLK's use flash programming via eprom. They still work surprisingly well given their age. They are limited somewhat by the clamping system as you probably know. I am ordering another Brother programmable bartack which I really like. It was able to do a nice box X on 2 5oz pieces of dense suede for some welding jackets we made. Thanks again for the reply.

Regards, Eric