How do divide up your work among your saws? Chords to one, webs to another? Or do you find it easier to send certain types of jobs to your "A" saw, and other types of jobs to your "B" saw?
Before Automated Saws
Prior to the development of highly automated component saws (around 1995) the conventional wisdom suggested that two saws were best because:
1. Saws are the production bottlenecks and we need at least two saws to keep up with one 100' gantry.
2. If one saw breaks down, we won't be totally shut down.
Before 1990, there were large saws for chords and a smaller ones for webs. The web saw was more compact, meaning less distance for the sawyer to cover between blades to set them up.
The Current Landscape - Different Saw Lineups at Different Plants
Today, a relatively small number of component operations cut their pieces primarily using a single saw - either a component saw or lineal saw. One MiTek account manager I know is convinced if you are going to build your operation around a single saw, that that saw should be a component saw. Component saws are popular, of course, and have been the workhorse of the industry for many years.
In spite of this, in recent years several startup plants have chosen to begin with a single linear saw. Several ideas have driven this decision:
1. The lineal saw is better suited to a 'just in time' production process
2. Lineal saws can cut "chopped up" (high 'setup to run' ratio) work more efficiently
3. Lineal saws produce less waste
4. There is very little a lineal saw cannot cut, meaning a simple manual radial arm saw is the only "backup" saw needed. A plant with a single component saw is best complimented by a more expensive, semi- automatic radial saw.
5. In some cases, a lineal saw is less expensive than a component saw.
Most truss operations have two or more "major" saws, either multiple component saws or a component paired with a lineal saw. Let's look at the first of these two, the multiple component saws shop, first. As mentioned earlier, component saws used to be more specialized than they are today. Some were more clearly "chord saws" and others "web" saws. Today, component saws are designed to be equally proficient at either. As a result, although some plants parse their cutting lists into "chords" and "webs" and send them to different saws, many simply alternate - sending complete jobs to each saw.
If your truss operation has an older, semi-automatic saw and a newer, fully automatic component saw then sending the chords to the "old" saw and the webs to the "new" saw makes a lot of sense. Another strategy is to split the work between the two based on quantity. For example, If there are 10 ore more pieces that are identical, send them to the "old" saw, and all quantities less than 10 to the "new" saw.
The other 'multiple major saw' scenario is the component and lineal saw combo. Although arguably the "best of both worlds," there is by no means a consensus about how best to divide work between the two. Here are some of the ways people divide work between their component and lineal saws:
1. "Straight run" jobs go to the component saw, "chopped up" jobs to the lineal saw. This is a variation on the "quantity-based" strategy mentioned in the last section. The advantage here is simply keeping the entire job on one saw.
2. Chords to the component, webs to the lineal, a modern-day version of the "two saw" strategy of twenty years ago.
3. Attempt to keep the saws equally busy by implementing the "quantity based" strategy, but changing the quantity as one saw gets ahead of the other. As an example, you give your component saw all trusses with quantity over 5, and your lineal saw gets the rest. You find you component saw getting ahead, and so you change the rule and start to give the component saw all trusses with quantity over 4.
Reviewing, we have seen several strategies for dividing work among multiple saws:
1. Job by Job - I use my judgment and send some jobs to "A" and some to "B." I do this on the basis of either the type of work it is, or which saw is currently "ahead."
2. Role - Each saw plays a role, such as "Chord saw," "Web Saw," "Panel Saw," and work for that role is sent to that saw.
3. Quantity - By splitting my cutting lists using quantity of pieces or trusses, I send work with more "setups" to the quicker (to setup) saw, and work with more "runs" to the slower (to setup) saw.
Thinking through these "utilization of saws" discussion, many questions suggest themselves:
· At what point will a single linear saw be unable to keep up with a plant's work?
· Is it worth keeping an old, inefficient saw in production when the work could be done on a more efficient saw?
· Is there a way to decide with numbers which strategy is best?
We will tackle these questions in future newsletters.