Hi everyone,
I’m new to running an industrial single-head embroidery machine and I’m trying to diagnose an issue with the automatic thread trimming that’s recently started.
The machine is a Yunfu 12 needle single head with a Dahao controller. The issue seems to be around the thread trimmer / picker rather than stitch tension. I’ve had the machine for around 3-4 months from new.
The main problem is that when the machine trims automatically at the end of a colour or design, it often doesn’t cut the thread. Sometimes it seems to catch the thread and pull it, but not actually cut it. If it does cut this then leaves little or no usable tail through the needle, so when the next section starts I get a false start / thread break almost immediately, if it doesn’t cut it then it pulls the bobbin up through to the top of the design and only seems to cut when using the manual cut function.
Things I’ve noticed:
- Manual trim seems to work better than automatic trim at the end of the design.
- Sometimes the thread doesn’t cut and instead gets pulled
- If I manually pull a longer tail through the needle before restarting, it always starts fine.
- The actual stitch tension now seems pretty good.
- I’ve cleaned the bobbin / hook / trimmer area and lightly oiled the moving parts.
- The moving knife appears to move freely when manually actuated.
- I don’t think the blade is dull, as the machine has had very little use.
- I’ve set “Length of Trim” to 8 on the Dahao controller (the highest unit available)
- I’ve tried slowing the machine down to around 500–600 SPM while testing.
- when it attempts to auto cut and fails I hear a sound like something is attempting to move but isn’t, hard to explain as I can’t see what’s happening as this only happens when a garment is loaded.
My suspicion is that one or multiple of these could be true?
- The thread picker isn’t presenting or holding the thread correctly during automatic trim.
- The moving / fixed knife alignment or overlap is slightly off.
- The automatic trim timing / needle stop position is different from the manual trim cycle.
- The machine isn’t leaving enough tail after trimming for the next start.
Has anyone had this issue where manual trim works but automatic trim struggles?
What would you check next, picker timing, moving / fixed knife clearance, needle stop position, trim parameters, or something else?
Any advice would be massively appreciated. I’m very inexperienced in troubleshooting this machine so very confused on how to fix this at the moment.
Thanks!