MEAN MACHINES

Investments in machinery enable a company to increase its volume; investments in material handling allow the same company to reduce its labor content. You probably need both, but historically most companies justify capital projects by increased volume. Today’s labor shortage, combined with concerns about workplace injuries, may shift the focus to material handling and the concept of working smart rather than hard. Conversely, material handling equipment that stands idle most of the time is wasted money.

In existing factories this is rarely is a chicken and the egg question. Machinery is purchased first to gain output and then attention is paid to material handling. In planning a new factory you must not only think in terms of an equipment budget but also a "people budget" (the available labor pool) and then you also have to siphon off dollars to build the infrastructure for future growth; i.e., dust collection. Sometimes, you’ll even bite the bullet and invest in a material handling system that initial volume can’t justify (but will be needed for future growth) such as roller conveyors or a towline because these will define the flow of the factory. (Moving equipment later on to facilitate flow often is too costly.)

As the accompanying article  No Naked Machines states: just as clothes make the man, accessories make the machine! Try to budget up front for the necessary extras that are necessary to maximize performance. That article discusses the gains made at a panel saw by adding scissors lifts, optimizing software, laser line, etc. and although they increase the investment they substantially reduce the time to payback the entire investment.

Return on investment is only one reason to add material handling accessories. You need to get away from "mean machines". Those which when run naked require gorillas to operate and make you fear for safety and quality. When you unpack any new machine, you see the effect of lawyers at work. It's plastered with warning signs that may make you afraid to even turn it on. I'd like to add one more sign from an engineer's viewpoint. It would say:

The drawing is of a gang ripsaw. It could be any machine with lineal feed; a molder, automatic spray, or an extruder. In the simplest situation, the operator lifts tons of material a day when manually feeding a machine and his energy determines the machine pace. He is a ticking time-bomb for a back injury. The workers stacking the output are basically spear catchers because as machine speed increases it becomes impossible to judge quality. (Ripped lumber comes at them at 150 ft/min; painted molding from a flow coater at 500 ft/min.)

Here are some basic improvements:

 -- Package chains at the infeed to eliminate starting and stopping while waiting for a forklift driver to bring new material.

 -- A scissors lift to bring material up to the infeed height.

 -- Infeed alignment rollers so the operator doesn't have to muscle the board into the machine. This will also take him out of the direct line of possible kickbacks.

 -- Transfer the outfeed onto cross-feed inspection chains so the operator can examine the material while it moves at a few feet a minute rather than hundreds of feet a minute.

 -- A pull bar with a roller to reduce the effort of unloading and stacking.

 -- Don't forget to leave room for a wagon or pallet for rejects at the infeed. If you don't block out an area, the operators will put substandard material through. This material can often be salvaged and upgraded by crosscutting, but if you just run it through as is, loose knots can damage the machine or you can lose yield.

The above are of value regardless of line speed and the weight of the product. As throughput becomes more important, further refinements are necessary:

 -- Replace the scissors lift with an unscrambler (for rough lumber only), tilt hoist, or vacuum unstacker.

 -- If the product has to be inspected, an automatic turnover can be added with an ejection chute for rejects. The boards would be fed into the machine through an automatic aligner.

 -- Whenever possible, unload on the side nearest the machine's outfeed to reduce the cost of mechanization and make it easier to handle broken boards.

 -- Unload onto scissors lifts with rollers to reduce effort. Note they are paired with outfeed rolls for nonstop stacking.

 -- Combine operations, that can still be run independently, without disrupting product flow.

 

 

 -- With mechanized infeeds operations can be machine paced and not limited by operator fatigue and motivation.

 -- Eliminating much of the physical effort has changed the primary job qualification from being a gorilla to being an eagle. It enables you to recruit people with brains so you can maximize yield and quality.

Combining operations is like money in the bank. The cost of tying the ripping operation to the secondary end trimming is typically less than $30,000. You save two workers when you combine these operations. At $15 per hour per worker (including fringes) the payback comes at 1,000 hours of operation. How many hours a year can you run these machines together -- Before you jump on this as "a great idea" remember its limitations --

 -- When combining a molder and a double end trim (tenoner or component cutter), the end trim should be the first operation if the wood is presurfaced and the ends are to be square cut.

 -- When using a gang ripsaw with a single optimizer, the optimizer will take 24 hours to process what is ripped in a morning. The imbalance is too great.

 -- When the costs of quality and inventory are greater than the advantages of productivity. Imagine the outfeed being automatically transferred to a bank of chop saws, pushed for maximum output rather quality. Taking the rippings as they come out doesn't maximize your yield of parts for today's requirements. By separating ripping and crosscutting you can preselect material by grade and other factors to maximize yield and immediate needs.

The concept that I preach "Pick up a board - ONLY ONCE!" summarizes the above example but the material handling situation can be a lot more complex. A good example is the finishing line. Conveyorizing the process focuses the operator on spraying and drastically increases his productivity over the get product – pick up gun – spray –hang up gun – move product out scenario that wastes the time of a highly skilled operator. The labor savings is great but don’t forget the first-in, first out work structure added by the conveyor. Think of the opportunity to control dust which results in a cleaner product while improving the work environment. Product appearance and reduced rework due to contamination are important reasons to clean up your act and may, by itself, justify the investment.