The Basics: Finishing What You Start
Fabricate, fab’ rik-at, (fabricating, fabricated). To make or fashion, to form by art or labor. That is how the dictionary defines the word. Most in our businesses think of it as taking a pipe, valve, fitting, tube, rod or sheet; and creating a flow system, store fixture, display, or sign. The individual ideas, designs, creativity and quality are the fabricator’s signature. Some similar, some clearly unique. Upon close inspection, one can even determine the type of equipment used in the process.

At the start of every new season, a very famous football coach lined up his players; rookie and veteran side by side. He held up an object for all to see and said, "This gentlemen is a football." Mr. Lombardi understood and taught that you cannot take the basics for granted. You must begin with the basics, study the basics, practice the basics, and master the basics to be the best.

So, what does football have to do with fabrication? Let me begin by saying, "This ladies and gentlemen, is a sheet of plastic." You will cut it, shape it, finish it and form it. How well and how efficiently you handle these basics will in large part, determine your success. We all know our customers are more price and quality conscious than ever before. That’s good. It drives us to become more efficient producers of better and better products. The customer is moving us toward mastering the basics.

What are the basics for a sheet fabricator? A saw, a router, an edge finisher, and in most cases a linear heater. Just as we have gone from the telegraph to the cellular phone, technology is rapidly increasing efficiencies for plastic fabricators. The latest CNC saws and routers nearly program themselves, and one day, I believe they will; or at the very least, respond to voice commands. Yet with all the technological gains, the basics remain the same (I suspect that’s why they’re called the basics). You can cut more pieces, with tighter tolerances, faster than ever… but you must still finish the edges, peel masking, bend and package.

Efficiency gains at the finishing and bending operations will make you more competitive, and ultimately, add to your bottom line. Ask yourself the following;

• Does your equipment provide the versatility to handle both large and small jobs with minimal (under 5 minutes) setup time?
• Does your bending equipment provide heat from both above and below the work to reduce cycle times?
• Does your edge finishing system polish, shape, and produce matte finish bondable edges with the same piece of equipment?
• If you completed the last job in half the time, how would that have effected your profit?

The majority of the expenses for any job relate to the time that it takes to complete the job. Another basic… Time = Money. Reduce setup and production times, acquire versatile equipment, hire, train and empower good people.

Setup/Tool Change Procedures
An often underestimated part of any production atmosphere, and one that when monitored and controlled can produce efficiency gains and add profit to the process, is the time spent between job setups and scheduled or unscheduled tool changes. This adds up quickly, and associated process costs become a double-edged sword. Not only is your process in an idle state at these times, but you are expending wage resources during the downtime. The reality is this must occur at some point during the process, but the time duration is certainly controllable.

How many times do your operators need to walk across the shop to some other area to find a tool only to return moments later for another tool necessary for the changeover? Keep spare parts, tools, and any necessary measuring instruments as close to the machine as possible. Two steps, or two hundred steps; the choice is yours.

The savings may not look like much in the short term, however, it is a bit like compound interest. You will notice only a small change in a day, but look again in 5 years and you will be very pleased with what you see.

Consumable Tooling
Saving time and money here is a matter of watchful eyes. Obviously a tool works best, and produces superior quality parts when the tool is new or just sharpened.

All consumable tools have a fairly finite life expectancy. In most instances the wear period is predictable. Once you have established the time pattern, remove the tool just before the failure point. Removing the tool from service while it is still fairly sharp will, in the long term, increase the life of the tool. Less material from the tool itself will require removal to bring the cutting edge back to optimum quality.

Different materials will cause your tooling, especially the diamond tooling, to wear at varying time intervals. Harder materials will produce longer tool life. Those of you who were scouts will probably remember that your knife would remain sharp all day if you whittled away at a piece of oak or maple. That same knife would be dull in about five minutes if you were cutting cardboard boxes.

The manufacture of diamond polishing tools for plastics is still mainly a human driven process. Much of the work is completed by hand, so there will be some variation between tools. The average life expectancy for the diamond polishing tools is approximately 45-60 hours of use between sharpening and 9-12 sharpenings before the inserts must be replaced.

Tool life for the diamonds is based upon working with clear acrylic material. You will notice a better result with cell cast materials over continuous cast or extruded materials. Tool life will be reduced by one-third to one-half on colored materials, especially smoke or black; and on any of the softer materials, i. e. impact modified, polycarbonates, copolymers, and PETG. The diamond tools will have much the same reaction as your saw and router tooling. Softer materials will create a reduction in tool life at all of your cutting and finishing operations.

Another factor to consider in your production versus quality equation is to stack or not to stack material. Obviously machining 4 or 6 pieces of 1/8" thick material simultaneously is preferable to machining them singly, however, you will sacrifice some tool life and edge quality in the process. The loss is due to the many layers of film and or paper masking through which the diamond must pass. Best results are obtained when machining no more than 5 pieces of 1/8 or 3/16", and no more than 4 pieces of ¼" material. Placing two smaller capacity machines into service can improve both efficiency and quality of your finishing operations. The smaller units will use less valuable floor space and the same operator can easily manage both units simultaneously.

Bending Sheet Materials
After all of your efforts from initial design, cut to size, and finishing, you have a great deal of time and money invested in each part. Now you must bend your creation to its final form…this is the point in your process where you clearly want error free performance.

Enter the variables of ambient temperature fluctuation, relative humidity, process variation and operator differences, and your bending operations can present quite the challenge. Of the many options from calrod to quartz, straight nichrome wire will provide the most consistency of heat over distance for your process.

Setups with nichrome wire range from over simplification (a length of wire stretched between two ten-penny nails driven into a two by four) to the extremely complex. Generally, an 18 gauge wire set into a 15mm-20mm wide aluminum reflector will provide the best results for materials up to ¼" in thickness. Support along the underside and pressure from above the material adjacent to the heating area will reduce warping and bowing. One of the most important, and sometimes least attended to aspects of the bending process is the cooling fixturing. Bends over 24" in length should be secured along the entire length of the bend. Longer bends should also be made perpendicular to the manufacturing direction of the material. Jigs should be constructed of smooth surfaced, heat resistant materials. MDF or a laminated phenolic is ideal for this purpose.

For optimum results, and efficient cycle times, heat both sides of the material simultaneously. If your current capability allows heating from one side only, it is best to flip the material over during the cycle to ensure even heat distribution through the material.

Worth mentioning – to achieve bubble free polycarbonate bends - heat from both sides, lower the wire temperature, and be patient! Always be sure your material is fairly dry to prevent blistering.

For thin materials - .010" - .062" vinyl etc. - use a Teflon® coated brass insert over the heating wire. You can then place the material directly on the insert surface, heating a narrow (1/16") area of the material to produce sharp, straight bends.

To reduce and or eliminate the "dog ear" at the bend point - block off the edges of your parts while they are over the heating area. This will keep the edges a bit cooler than the surface, and when bending, the material will tend to flow toward the center and not out of the edge.

Adding Value
We are all on a continuous search for added value. Moreover, we want added value that costs less than we gain. Of course the customer wants the greatest value for the least dollar. Often times, long term benefits are ignored in the value equation. For example, a routed and flame polished edge is quickly and easily manufactured with relatively low associated costs. What happens after sixty or ninety days at your customer’s location? Unless a flame polished part has been through an annealing process, it will craze and crack. Especially if someone has made the common error of cleaning the parts with a type of solvent other than those specifically recommended for thermoplastics.

Customers need an education. Teach them about the different processes you can use to ensure a part will look as good on the hundredth day as it did on the first day. Yes, it may cost a bit more; but why should we feel the need to apologize for pricing? Parts of a superior quality do cost a bit more and they are well worth the extra.

Above all, remember the words of Henry Ford…"If you need a machine and don’t buy it, then you will ultimately find you have paid for it but don’t have it."

Written by Darrell Bishop, Operations Manager, for Edge Finisher Company, manufacturers and suppliers of edge finishing, edge polishing, and flame polishing equipment, and linear heat tables for plastics fabrication.

For more information, contact Edge Finisher Company, 16 Stony Hill Road, Bethel, CT 06801, 800-625-5863, 203-796-7923, Fax: 203-796-7924, E-mail: info@edgefinisher.com, Web: www.edgefinisher.com.