Beware of One Size Fits All Solutions

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Issue #10231 - October 2018 | Page #33
By Todd Drummond

I am often asked about what is the best one-size-size-fits-all equipment solution to fit all the component manufacturing needs. Of course, too many equipment vendors are more than willing to offer their version of a one-size-fits-all solution. Below are three examples of when one size does not fit all.

Example One:

Linear saw versus a 5-blade component saw. Each has their strengths and weaknesses.

5-Blade Component Saw:

Strengths: Large volume cutting is unbeatable for time per piece when piece count exceeds the break-even of approximately eight pieces in a run.

Weakness: Much slower setup time than an automated linear saw for very short runs such as one-one-one. Also, the cutting angle/length accuracy is not normally as good because of lumber’s imperfections, such as crowns and twist, cannot be compensated when both ends of the piece are being cut at the same time. Small pieces, such as less than 2.5 feet, cannot be cut on this type of saw easily.

Automated Linear Saw: 

Strengths: Small volume cutting is unbeatable for time per piece when piece count is below approximately eight pieces in a run. Accuracy normally is the best because of lumber’s imperfections can be compensated when only one end of the piece is being cut at a time. Small pieces, such as less than 2.5 feet, can and should always be cut on the linear saw. 

Weakness: Large volume cutting is far slower than a component saw because there is only one blade repositioning and plunging for every cut. There is simply no way a single blade saw can keep pace with a fully automated component saw when the quantity exceeds the break-even setup plus run time of linear saw versus 5-blade saw.

Example Two:

Another example of this one size does not fit all is having a fully automated lumber retrieval system linked to an automated linear saw that pushes the cut lumber directly to the assembly table with an auto puck system. This type of setup is often touted as being the best for truss assembly to lower the cost of labor and get the most from your investment. This system is frequently being hyped as the perfected just-in-time cut and assembly system. For a greater explanation of the why this type of system is not the best, see my November 2017 article, “Is a Linear Saw Paired with Each Roof Truss Assembly Table a Magic Cure for the Best Lean System?”

Summary points:

  • Point #1 – Pairing the linear saw with each assembly table and using a chain or roller system to move the cut material to each assembly table will only reduce the labor count by 1/3 of a person or 1/4 of a person per workstation.
  • Point #2 – All the material being positioned in the center of the span, no matter the span of the truss, which would mean more walking and therefore more man-minutes per truss the longer the truss span. There is too much walking the longer the spans with this system.
  • Point #3 – Most linear saws cannot consistently cut more than what a three-person crew can assemble (called line balance in industrial engineering). More personnel equal more people to move material onto the table to assemble each truss more quickly. With a 55-foot truss, one could easily have five or even six people assembling that run of trusses. If one did add personnel to the assembly workstation beyond the three or four-person team, the linear saw’s output would be exceeded. Limiting the output of the assembly workstation is not a proper use of the just-in-time lean principle. The goal of the company should be maximizing the gross margin dollars per day and not getting blinded by reducing the number of personnel at each workstation in the hope of reducing labor cost. One can increase the number of crew and yet still maintain or reduce labor cost per unit with added efficiencies.
  • Point #4 – If more than two personnel are removing the lumber from the linear saw’s live deck system, they can be in each other’s way.
  • Point #5 – Cutting the material needed for a run of one-one-one is the realm of the linear saw. But cutting a much greater quantity run is easily done more quickly by the auto five-blade saw, so that the greater the quantity needed, the more noticeable the difference between the two types of saws.
  • Point #6 – A linear saw can reduce the lumber cut waste by batching and combining different cuts of various pieces (lumber optimization). However, this cannot be easily done when the linear saw is only cutting the trusses as the trusses are being built.
  • Point #7 – Pairing a linear saw with each workstation creates such a rigid system that, if one part of the system fails, the entire system comes to a standstill.

When does the pairing of a linear saw with each workstation make sense? It is simply when the quantity run is the lowest, such as one-one-one, and the span is not so great that it would make sense to add more assemblers to the workstation. The greater the quantity run and the greater the span, the less it makes sense to pair a linear saw with every build workstation. One configuration of equipment is simply not the best for all conditions.

Example Three:

A large roller gantry table with no walkthrough aisles to assemble all the roof trusses is not ideal in all cases. Often touted as the being the best solution in all cases for assembling roof trusses, but this is certainly not the case and should be viewed with a critical eye towards what is being assembled at the given time. 

Strengths: Greatest flexibility for the various configurations and types of trusses, able to add additional personnel to increase units per hour, and can easily be configured with more automation such as auto-pucks. 

Weaknesses: Small trusses can be assembled far quicker on a much smaller press table, very large pole barn trusses cannot be fed from both sides of the table when there are no walkthrough aisles, and ergonomically it is the worst configuration for movement of material and personnel for time-in-motion studies for many truss configurations, runs, and sizes.

Most operations need a blend of different equipment and vendors to have the very best of everything. When you are ready to have the very best system to meet all your needs, combined with the very best of true lean manufacturing principles and industrial engineering practices, give TDC a call. TDC does not receive any referral fees from any equipment or truss plate manufactures. Cost savings and net profit gains that usually take months or years can be accomplished in weeks or months with TDC.

You're reading an article from the October 2018 issue.

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