Solving sewing problems by testing your machines
A seating manufacturer who recently added sewn cushions to his product line had a vexing problem. The stitcher kept stapling pieces together prior to stitching and she was very slow. She stapled because she could not pin -the material is vinyl. The consensus in the shop was that she did it because she had never sewn in a factory and wasn’t comfortable with industrial equipment. The customer wanted me to work with her to reduce pre-work and hopefully pass along a few tips since I have extensive experience working with heavier materials.
Otherwise motivated people (as this lady is) aren’t stupid and they aren’t crazy. If they’re pinning, it’s for a reason. The first step is to figure out why they are doing it, fix that thing and then they stop having to correct for an upstream problem. As I’ve explained before, the way you troubleshoot in an organized way is according to the 4 M’s -Man, Method, Machine and Materials.
The first thing I analyzed was Man. The operator was pleasant and motivated with appropriate skills for the task (she had several industrial machines at home). She was -frankly, this is a rarity- very happy the company had hired someone to give her pointers.
The second thing I looked at was Method. I gauged her handling of work pieces which was quite good under the circumstances (workstation was a problem but a story for another day) and I could not see how her handling was contributing to problems. I asked her why she was stapling seams. She said it was because the cut pieces would not join smoothly and had suggested previously that it was a pattern problem. For expediency’s sake, deleted from this recitation was the elimination of the pattern as a problem so that just left all fingers pointing at the operator.
The next step was to look at the Machine -the point of today’s entry in case I’ve lost you- which annoyed the boss because he did his research to buy a brand spanking new, top of the line upholstery machine. It’s a great machine, exactly the one they needed and one (confirmation bias noted) I’ve had my eye on to buy for my shop. But continuing on with structured troubleshooting, you test it anyway.
The cut to the chase summary is that the machine was mis-feeding quite a bit. The problem wasn’t Man or Method, it was Machine. The boss was really annoyed then and thought it was a bum machine but it wasn’t and that is yet another story I’ll skip for now.
Incredibly lengthy preambled dispensed with, this is how you test a lockstitch machine:
Cut two strips of fabric you intend to use 4″ wide by 36″. It can be longer or shorter but anything under 24″ may not be as helpful. The math is easier if the figure is divisible by 8 (just my opinion). The lengths can be either cross grain or length of grain, it makes no difference.
Then sew a basic seam as you would normally so you can assess it.
There are two basic types of feeding problems you can have. One is where both edges join evenly for the length of goods but the sewn edge does not match the original cut length. This means thread tensions may be too tight. You should make a note of how much shorter the seam side is.
The second feeding problem is if one piece ends up longer than the other. This is usually the top side. This indicates a feeding problem. Either the pressure is too high, you have the wrong feed dogs, they need adjusting or whatever. The correction of feeding isn’t the intent of this post, only the means to recognize you have a problem.
In short, that was the problem this company was having. Their Man was fine. Their Method was fine. Their Machine wasn’t. The stitcher wasn’t going to be able to sew faster because she did need to staple seams to have them come out evenly.
Since the company was new to sewing, they were unaware that frequent machine adjustments are necessary for varying materials. My suggestion was that they hire a mechanic to come in to teach them about machine adjustment.
It is a good idea to document machines settings for tension and the like for various fabric types as you come across them. If you change materials frequently, it may be good to create a form with clock dials to document settings. Remember to cut a swatch of fabric and affix it to the form and save these sheets in a folder or notebook. Stu has been doing this for a long time, hopefully he will comment with useful suggestions.