Batch, UPS and Modular (Batch pt.1)
There are three basic kinds of manufacturing process systems in the apparel industry. These are Batch -also often called “bundling”- UPS (Unit Production System) and Modular, aka lean or team sewing. I’ve described each of these at various times but this entry will be the first of a series of posts intended to define and discuss these comparatively. A manufacturing process system refers to how the inputs or WIP (Work in progress/process) enter the production stream and how they move through it.
With a nod to pedants, batching and bundling don’t mean the exact same thing but are closely related enough that they’re often used interchangeably. I mean, nobody is going to look askance if you flub those two. Batching means that a bunch of things are worked on at once, done in a batch. Baking cookies is batching (but baking one cake is not). For our purposes, a typical example of a batch process is cutting. A bunch of fabric is laid out in layers and cut out at once. Obviously, if you’re only cutting one item, this is not batching.
Typically, batching is frowned upon in lean manufacturing circles. With lean, you’re only supposed to make one thing at a time. However, as I’ve long argued with my colleagues in the lean community, batching is unavoidable in certain industries, not just apparel. Take agriculture. You can’t pull corn and coats like cars and computers. Lean isn’t as easily implemented in industries lacking the high engineering component of durable goods. Not being able to hire nine women and get a baby in a month applies to our industry both literally and figuratively; there’s a limit depending on natural cycles in industries tightly bound to nature. So, I argue to anyone who will listen that batching is unavoidable in primary industries, what lies on the lowest rung of Maslov’s hierarchy of needs. Batching will continue to be unavoidable in the construction of shelter, food and apparel production.
The definition of a bundle is a collection of cut pieces organized for sewing. Typically, bundles and their constituent parts are assemblies (or sub-assemblies) of a product. In a plant, bundles are worked on and then, reorganized for a later process. For example, a first bundle could consist of a quantity of undercollars. Once these were joined, the undercollar sets would be rebundled with top collars. Once the under collars and top collars were joined (and pressed), these would be bundled with bodices (themselves already preprocessed too) for joining and so on.
In larger plants, different people will work on the various bundles. The same person joining undercollars won’t be the same person joining the top collars. In a smaller plant though, this may not be the case. As I mentioned before, there’s some quality downsides to having different people process the same bundles (see how to prevent sewing defects).
Batch and bundling is the most traditional method of apparel production. It is also the easiest to organize and plan but that doesn’t mean it is the most cost effective. The reason is, most of the time allocated to sewing isn’t sewing at all, it’s handling. Estimates vary but some say 60% of sewing time is handling and others say 80% (hearkening to the Pareto Principle).
This is how I explained the costs of handling to Miracle last week:
One operator has a bundle. They must pick up two pieces, align them, set them to needle and then sew. The work is removed, clipped, then the items are folded (not always, depending on the size) and neatly stacked in another pile off to the side for rebundling. The pieces must be lain carefully and neatly because wrinkling must be minimized. While it is common for work to be pressed before leaving the plant, individual constituent parts usually aren’t; just the whole shooting match, “blowing” it together. The constituent parts are then passed off to another operator in their bundle which again means picking up the pieces, aligning them to needle, sewing, removal, trimming and again, reorganizing the stack for still another step in the process. In lean or team sewing, none of this stacking takes place, parts and pieces are never lain down, they remain in hand for the duration of production until completed, eliminating all of the handling time wasted that is dictated by the bundling in a batch processing system. Similarly, the very need to bundle is eliminated too. Likewise, you don’t need a floor girl to schlep bundles from one operator to another which eliminates a position. In short, eliminating a bundle system doesn’t force people to work harder or more. Rather, you’ve eliminated the necessity to do a given job or function in the process so how is that making people work harder when they have less to do? In short, much of bundling is waste. It’s a wasted process.
Instinctively, humans like batching. I think that owing to agriculture, we’re hardwired to do it which is why attempting to adopt a singular processing strategy like lean is counterintuitive, going against our natures (dependence on agriculture also explains why we like inventory, just in case). For example, if you had a six year old process your Christmas card list, even they will start batching the work by organizing each step of sealing envelopes and applying stamps in lot jobs. In other words, it’s not that managers are bad or lazy people for insisting on batch operations but it is easier. Batching is also easier to quantify and manage since the body of knowledge and heuristics is better known for this system of production.
Still, as I mentioned above, even in the leanest of companies, batching may be unavoidable for certain jobs and a company will often use a combination of these systems. For example, even a modular (lean) or UPS plant will use batching to cut the goods and sort them. Likewise, even the largest firm uses one person to sew an entire sample. Some companies can cut in single quantities but this is limited to either the smallest or the largest of enterprises. The smallest companies producing niche, high priced goods can cut in single lots manually. The largest companies, often heavily capitalized, can also cut in single plies but mostly don’t. If they have that much money tied up in a cutter, they have the head count to match and cutting in single orders won’t keep them busy. The company would need a lot of single ply cutters.
By capitalization, I mean the investment of needed equipment and plant. Maybe this should precede the heading above? Anyway, in the traditional batch/bundle operation, you have roughly one operator per machine. Being that batch/bundle operations like inventory, of course they have some back up machines in case of “famine” -in agricultural terms. Likewise, operators are similarly “inventoried”. One would have 10 double needles and 10 double needle operators, 80 lockstitch machines and maybe 78 single needle operators, one pocket welting machine and one pocket welter. The other production systems, namely UPS and modular vary from batching/bundling somewhat to quite a lot. I’ll explain the differences in an upcoming post. Hopefully you’ll have some questions that will help guide my presentation of the material. I have no way of knowing what you don’t know or whether this makes any sense to anyone so I’m grateful for suggestions.
Earlier entries on batching in product development (as opposed to production which is what we’re discussing now):
Batch product development
Batch product development pt.2
Batch product development pt.3