Bartacker troubleshooting - LK-1852

[orangecatpacks]

This seems to be the best source for industrial machine advice online, thanks for any advice you can offer!

I have a used Juki LK-1852-5 (28 stitch) and have been struggling with an issue that I can't find any good examples of online.

The machine is set up with v45 bonded nylon top and bottom and I'm sewing mostly at the upper limits of the width.

The issue I'm encountering is that the machine will skip the first couple stay stitches before the thread catches and starts forming stitches. The rest of the stitch forms properly and seems to have good tension but the stitch skipping varies from cycle to cycle and some end up looking decidedly empty in the centre because of how many stay stitches are missing.

I've gone through the engineers manual and tried to make all the adjustments suggested but am still struggling with this issue. Hook timing is good, the needle and bobbin thread ends left after cutting are on the upper end of the recommended lengths, and feed timing is adjusted to spec with the manual. I've tried a pretty wide range of tension levels for needle and bobbin as well.

Does anyone have any suggestions of likely causes for this problem?

Thanks!

[Wizcrafts]

You didn't mention the needle size you are using. Perhaps moving down one number will stop the skipped starting stitches. If you are using a #14 needle, try a #12.

Watch the material as you begin the tacking cycle to see if it is lifting under the foot/clamp. If it is lifting that explains why there are skipped stitches. As the material lifts up with the needle, the loop under the throat plate gets dissolved before the hook picks it off. You can try countering this by placing a solid object against the starting side of the material and holding it down. Maybe even a toothpick with the end blunted.

It's also possible that there is a gap on the bottom of the foot on the starting edge. Or, try increasing the foot pressure so it holds down the material more firmly. If none of these things keep the material from lifting, place basting tape under the material to stiffen the area to be tacked.

I guess another possibility could be that the foot slot is too wide to hold down the starting stitches.

Last, try adding some slack to the top thread with the check spring.

Edit: I just read a manual for the Juki LK-1850 and it mentions different throat plates, with varying needle holes, to match the needle you will be using. If your machine was originally setup for #69 or #92 thread, the hole will be quite large when you use a #14 or smaller needle. This reduces the bottom support.

[orangecatpacks]

Thanks for the suggestions! I'll do more experimenting and see what I can manage. I've already sized down from #16 to #14 needles and that seems to have helped slightly, I'm not sure if I'd even be able to thread v45 thread through a #12 needle though! The machine isn't a heavy subclass and the needle hole seems appropriate for the size of needle. I'm using heavier thread than the machine was previously running.

The feed plate is worn though so maybe there's a clamping pressure issue. I'm sewing mostly pack fabrics which are quite rigid, corduras and laminates, so I've never thought there was too much potential for lifting but I'll try adding some foot pressure and possibly order in a new feed plate.

Thanks again!

[orangecatpacks]

Thought I'd add a final recap in case anyone searches for a similar problem and finds this thread.

My issue ended up being due to insufficient clamping pressure on the starting edge of the tack. One of the springs that holds down the clqmping feet had been replaced and happened to be on the left (starting) side of the stitch. Swapping the two springs so the stronger one was on the left immediately improved the issue and some fine tuning of tension brought things all perfectly together.

The other factors that maybe were contributing to this issue were a slightly worn and misaligned feed plate. It's a more involved adjustment to re-center it so I had avoided it, but the gap in the feed plate is shifted a little to the left, contributing to less clamping on that left end of the tack. One day I'll get around to it, but for now just upping the clamping pressure was enough.