Making Little Ones

Why Machine Plastics?

Moulding tools and forming equipment used in the various plastic moulding processes are invariably hand made one off creations. They can often take weeks and months to manufacture with a resultantly high cost. Where a plastics component is specified and the numbers to be used are not large, then machining the component becomes more economical. Not all plastics materials can be machined. The more rigid a plastic then the easier it is to be machined. The more flexible and the softer plastics are not suitable for machining.

What are the main points to note when machining plastics?

• The cutting tools used in the machining of all materials rely on the rigidity of the component being cut.
• In the case of cutting metals, the materials' natural rigidity is good. Therefore the component resists distortion when the cutter (saw,drill or machine bit) cuts the metal.
• In the case of plastics, machining tends to lend itself better to rigid materials, such as fibre reinforced thermosetting plastics materials, glass reinforced nylons, acrylic or PEEK have good relative stiffness. Less rigid plastic tends to deform and bend away when the cutter attempts to cut the component, making the achievement of fine dimensional tolerances difficult.

Advantages of Machining Plastics

• No mould costs are needed
• Ability to manufacture plastic components with short lead times
• Ability to manufacture low volumes economically
• Can trial a design before committing to tooling
• Thicker wall sections can be accommodated
• Components too large to be moulded can be machined from fabricated plastic
• The forces required to machine plastics are low
• Plastics normally machine dry
• Swarf can be recycled back into the compounding process

Disadvantages of Machining Plastic Materials

• Machining ability limited to the more rigid plastics materials
• Relative high cost of block plastic material
• High scrap (relative to other plastics forming processes) can result
• High volume of swarf to be removed can present difficulties
• High costs of CNC machine time
• Volume production by machining will require robust jigs and fixtures
• Plastics materials do not conduct away any heat generated in the machining process
• Dust producing composite plastics require an effective dust collection system

Considerations When Machining Plastics Materials

Due to the softer nature of plastics materials, the holding jigs and fixtures have to be designed with jaws which protect the plastic being machined, this can be with other plastics materials shaped to the form of the block being machined. In addition the jigs require to be robust in order to support the material being cut.

Thermoplastic Plastics Materials being machined can be cooled with an air blast providing the resultant swarf is continuous and not in chipping form. Thermosetting plastics can be cooled using a liquid coolant, but care needs to be taken in terms of plastics prone to swelling in water to ensure that machined dimensions do not change. Heat generated in the process can cause thermal expansion – this effect must be factored in as dimensions may alter on cooling.

Methods of Machining Plastics Materials:

CNC Machining
If the component to be cut has a complex shape, its profile can be programmed into a computer. A CNC machining centre can be used to manufacture duplicate numbers of components. Multiple interchangeable cutters typically used on CNC machines enable complex and varied components to be machined.

Turning
If the shape to be achieved is round, then a simple turning operation can be used. Specialist supplementary equipment attached to the lathe can extend the capabilities of the lathe's operation.

Milling
This method of machining can vary from simple milling to profile and CNC milling. Again as with lathe work, either additions to the milling machine, or the use of a more complex milling machine can extend the milling machine's capability to make more complex shapes.

Sawing
Invariably this method of machining is solely for parting off sections of plastic material from bar stock for subsequent working by other machining operations.

Die Cutting
In certain cases the use of die cutting of plastics material can produce a simple component. The process is limited to sheet material. A male and female die are used to punch out a predetermined shape. The process can be either a manual process or automated using a special machine.

Hot Knife Cutting
The softer less rigid types of plastic can be cut using a hot knife to slice through the plastic. An electrically heated wire or blade melts the plastic locally. This type of process is commonly used to cut blocks of foam and Expanded Polystyrene (eps).

Punching
Certain shapes can be cut on metal type punching presses. Like a CNC machine, they are invariably computer controlled and are multi tool bit equipped. This process is limited to the thinner thermoplastic and thermoset sheet.

Water Jet Cutting
This process is used to edge trim fibre reinforced thermosetting components, which would otherwise prove difficult to trim by other processes. The tough reinforcing layers in the material defy trimming by conventional knives and cutting equipment. The narrow cutting path and fast progess without dust or chippings are an advantage.

Separating
Acrylic and laminated sheet can be separated by means of scoring using a sharp knife and breaking about the scored line.

Laser Cutting
This process can be used for cutting and profile boring of certain types of acrylic and other plastics although not thermosetting. The process uses an industrial laser to melt the plastic often with computer controlled profile following.

Ultra-sonic Cutting
Some of the softer thinner plastics can be cut using ultra-sonic equipment. The high frequency generated by ultra-sonics in the tool, have the effect of locally melting the plastic being cut. Again, integrated with computer profile control the process lends itself to high speed automated production lines.

Stretching the Limits

For the Really Big Shew

If you had the good fortune to attend the recent (ongoing as of this posting!) SEMICON West show, you may have seen an exhibit with our most recent Grand Achievement (part of which is shown above) - an enormous functional vacuum chamber containing a robot to handle parts processes. Just how enormous are we talking here? Well, to give you an idea, those are 24" calipers sitting by the side of it there, about 30" long. The body of this, the central chamber of the thing, is made entirely of clear acrylic, 1 1/2" and 1" thick, precision machined and put together with huge, cosmetic bonds at those 20" high corners.

Was it Easy?

I don't think so! This project was brought to us by an engineer we've had an ongoing relationship with, assisting him in design and fabrication of, at times, extremely challenging parts. He wanted a show-stopper for SEMICON, a containment for his company's new robot (which containment in "real life" will be made of aluminum plate) that they wanted to to be clear for the show so folks can see what's going on in there. Did I mention that it's a VACUUM CHAMBER! As in as empty of air molecules as is mechanically doable, 29 inches of mercury's worth, and over 4 feet across. And since it's for the Big Show, every bond and surface needed to be as cosmetically correct as we could get it. AND, on a tight deadline for SEMICON.

All in Two Weeks' Work

So, after some serious head-scratching, the production team (mostly John and Scott) decided to take the job - requiring thousands of dollars of material and the creation of production techniques to do stuff we'd never done before, and where the opportunities for serious project-threatening accidents were evident throughout. While the rest of us were out over the July 4th holiday, John, particularly, was working late with this baby. John did dozens of experiments developing the methods and fixtures needed for fabrication, and step by step the chamber and it's outer boxes emerged. As delivery approached, everyone in the shop got involved with pieces of the project, and finally, it was ready to be shrink-wrapped and put on the truck! As the clients said on delivery, the chamber alone took 6 "geeks" to carry into the assembly room.

So We Delivered

A totally unique project, on time, and assuming everything went well with assembly, people are looking at it at SEMICON as I'm typing this. Not for the faint hearted...

Machining Plastics? Who You Gonna Call?

Imagine this scenario: A relatively low-volume order for machined plastic parts comes across your desk. Quality and product liability are major issues - the parts have to meet critical tolerances, and maybe even FDA standards. The best possible product has to be obtained at the lowest possible cost.

Who are you going to call?

It might be easiest to contact a sheet, rod and tube distributor, but at some risk. The distributor would probably know the materials, but may be completely unversed in machining.

Another possibility would be a metal machining house. The source would likely be expert in machining, but would they know the materials well enough to use the right one? Would they use the appropriate machining methods?

Fortunately, in such a situation you are not limited to these two choices. A third choice is a firm that specializes in machined plastic parts. A plastic machinist will not only be conversant with materials and methods, but will also have equipment that is used solely on plastic.

A Big Concern

Unlike the metal machining house, the plastic machining vendor can consistently offer uncontaminated product that meets the stiffest standards. Contamination may sound like a small problem, but it can mean big trouble in machining plastic.

Equipment used to machine metal - even if only used for metal occasionally - can contaminate parts with oil-based cutting fluids. Many plastics are hydroscopic, so they pick up liquids they come in contact with. If the parts are being manufactured for FDA-approved uses, this is no small problem.

It is often difficult to adequately clean a machine that has been working on metals, especially if it has been working on stainless steel. This can lead to another contamination problem. If the plastic material is soft, residual metal fragments can become embedded in the parts.

Even if parts are not going to be used in an FDA-approved application, contamination is still a concern. Oil-based cutting fluids chemically attack many plastics. This, in turn, can lead to fatigue, crazing, and ultimately, parts failure. One manufacturer of food processing equipment found this out the hard way. A pressure plate, machined out of polycarbonate, exploded in its very first use. It was later determined that an oil-based cutting fluid, used by a metal shop when machining the pressure plates, had reacted with the polycarbonate material and caused the failure.

Fortunately, problems like this are easily avoided. A good plastic machining firm will have the material knowledge and the right machining processes to consistently give you quality parts.

Choosing: A Checklist

Not all plastic machining vendors are equipped to offer all parts; others may not be able to give you the best prices. The following guidelines can help you locate a fully-qualified, cost effective specialist:

• Material Knowledge

Quiz potential vendors on their knowledge of various materials and applications. Ask them to share the information they have from the manufacturers. Do they have any property charts or handbooks to give you? Specialists in plastic machining should have a wealth of up-to-date information.

Potential machining firms that are members of a national trade association, such as the National Association of Plastic Distributors, may have better access to reference materials and other resources.
Material knowledge is a critical area. Good plastic machining firms must be willing to help educate their customers and help them choose the best material for their application.

• Purchasing Practices

Just as a metal machine shop is unlikely to have the material knowledge you need, neither are they going to be able to purchase plastics in large enough quantities to provide you with the best price.
Find out if the vendor candidates can purchase materials directly from the manufacturer. If they rely on distributors for materials, make sure the vendor is up on the technical side of the business.

Your goal should be to make sure that your plastic machining firm's buying practices are as good as yours.

• Equipment

Ask about the type of equipment the potential vendor used. The well-equipped plastic machining vendor will look pretty much like a metal machining shop, but the bona fide specialist will have equipment that has been adjusted or re-built expressly for machining plastic material.
The right equipment will machine plastic using the correct speeds, feeds and tooling, and won't pose the threat of contamination faced when metal-machining equipment is utilized. The right equipment will also insure higher quality arts, with better finishes and less chance of chips, burrs and other imperfection.

• Quality and Price

Quality, of course, is directly related to price. Make sure the vendors you interview can provide the highest quality part at the lowest price. Can they machine and screw machine all plastic materials using conventional, CNC and tool and die procedure?

Make sure the supplier is familiar with each process you need, as well as with the specific plastic material you will be using. Experience, more than anything else, will help make sure a supplier offers you the most cost-effective part with the best quality.

• Looking For The Best

Selection of a truly qualified vendor is extremely important in today's business environment. The time it takes to ask the right questions will pay big dividends - helping you obtain high quality machined plastic parts. And even though the rules for service and quality seem to be continually evolving, getting the best part at the lowest possible price is still the golden rule of purchasing.

By Alex Curtiss, President of EPP Corp., orig. published in Purchasing Management Magazine. Alex has been in the plastics industry for more than 25 years. He has served on the board of directors of the National Association of Plastic Distributors.

What We Can Do

Ok, I know I'm not posting enough to this blog. It's not that I don't want to post more, it simply doesn't seem to make it onto the priority list as I take care of what's needed and pursue the holy grail of effective web presence. Which is what this blog supposedly exists for.

The website needs a few things... one of which is our capabilities page, missing in action since at least January or so. It's supposed to be something a little out of the ordinary, with a creative edge, with a spirit of fun or at least a close facsimile...

I don't just want to say that we have some Daewoo (or is that Doosan?) high-precision CNC machining centers (a 5025, a 4020 and two moving column DVC 320/40's), high-precision 5 foot by 12 foot Anderson Stratos Pro CNC Router, Daewoo Puma 240 M CNC lathe with active tooling, all of their spec's - travel, accuracy, etc., although I guess that stuff's important. What we really want to get across is the true value we provide for our clients, and most of that is pretty intangible.

John and Scott don't just look at your drawings to pedantically duplicate the features and dimensions indicated. They find out what the part is meant for, look for things that may be changed to make it easier to produce while maintaining or even improving the functionality, make suggestions about materials, and carefully consider how we can produce it most economically. They know the histories of our clients orders and may find we have parts in inventory that can be upgraded to a new rev level. Frequently they consult with engineers in product development to help streamline the design and development process.

In order to do this effectively, they have to understand all of the technology involved, the behaviors of the polymers needed, how the part may be installed into the assemblies, alternate ways of machining and fabricating the part. And they have to take the time and make the connections with the clients to find out what they really need.

The Heroic Struggle of the Little Guys

"Mural, auditorium, right rear, the heroic struggle of the little guys to finish the mural..." Mudhead, Don't Crush That Dwarf, Hand Me the Pliers, The Firesign Theatre

Right now I'm in the middle of: 1) the multi-line, adjustable strip former project, 2) Shop and Home Supply, the eBay Store (finding products - , refining the interface, getting store traffic), 3) Upgrading our website and getting it to show up in th' dang search engines, 4) and trying to get some kind of respectable handle on marketing in general and internet marketing in particular.

Marketing can be a very frustrating thing. For one thing, we definitely want people to know that we have a fierce dedication to creating quality products for them and that we are a "reality based company" - i.e. we employ state of the art technology and procedures and work to our clients schedules and needs. Still, in many ways we're not a typical company. Though we have advanced capabilities and in-depth understanding of our industry, we're still a small enterprise with a family feel. And our attention to and support for each other extends to our customers. We know how to listen to them, to understand the context for what we're creating for them so we can focus on their most important parameters and maybe help them revise their designs for efficiency and savings. We have a lot to get across, and we don't have the resources of a megacorporation.

So, it's likely to take a while to get this all to jell. We need to get all this information technology that I, at least, don't understand yet, to support the mission of our production technology and expertise, and to help introduce us beyond the circle of our loyal customers and the referrals they give us spontaneously.

Our Silicon-based Partners and Buddies

Once upon a time, everything in machining was done by hand, or with precision manual tools operated by hand. Drawings for parts were drafted by hand in two or three dimensions as a basis for the ways machines were set up in the shop. Machines had to be repositioned for each hole or feature in a part. Things took time.

Businesses were also run "by hand" - all transactions were logged and filed, books and ledgers with columns of figures were laboriously filled out and kept in balance with repetitious arithmetical calculations. Letters were typed (before that, hand-scribed), carbon copies kept in filing cabinets, real-time communications became possible only with the miraculous invention of something called "the telephone." Stuff took time to happen.

If you wanted information on something, you had to research it yourself - either at the library (if you can find one anymore...) or by finding someone with the knowledge or resources to ask. It might take weeks to find a source if you had to go through a list of referrals or queries by mail. Now, you just open a browser (say, Mozilla) and click on your favorite search engine (say, the 800 lb. Gorilla), and, Presto!, one point two seven million hits for web pages created by people all over the globe sharing what they know with you RIGHT NOW. We were talking here just yesterday about how we can't really imagine doing things the way we did even a few years ago.

Here at Phoenix Precision Plastics, we use state-of-the-art cyber-tools to create the programs that run our CNC machinery (4 mills, a lathe with "live tooling," and a 5 by 12 foot high-precision router). We can accept drawings from our clients for quoting or for production in pretty much any electronic format (.IGS, .DWG, STEP, .DXF, .DSN, .CDL, .CSF, .FST, .NCA, .CDR, etc.). In many cases, we can save our customers significant expense by being able to translate their electronic files easily into the programs that run our machines. A single program and machine setup can run a practically unlimited number of features on a part, cutting the production time for a complex part from perhaps hours to minutes. These capabilities, along with our commitment to quality and attention to detail, translate into more, better, faster. And as the technology advances, we'll follow its development to provide our clients the highest, most cost effective service possible.

Blogging for fun and profit!

I decided to write this blog because as part of my bailiwick at Phoenix Precision Plastics it's my responsibility to begin to get our web page stats outta the bottom of the basement on the search engines. It was my bright idea to do a lot of the site in Flash because I'm a (wannabe) designer, and with Flash I can get a wicked cool look with a minimum of pain.

If we can't get found on the search engines, then the web site is only useful to people we send the URL to, generally people that already know about us, our dedication to customer service, engineering expertise, on-time delivery, and precision quality parts every time. Hopefully by presenting information of value to you on this blog, and linking back to our website we can start to make those search engine robot spiders happy!

Other than learning about what really works in marketing a small offline manufacturing company on the internet, my current project at Phoenix is helping John Donnelly, our President and Scott Dion, Production Manager, to build a large PGP (pretty good precision), multi-heat line strip former for parts we want to make two bends (this time around) on at the same time. To do this, John found some modular aluminum extrusions on the Web (FAZTEK) for building a strong, clean looking and adjustable frame, and we've been scratching our heads to figure out how to make this machine as simple and versatile as possible, and learning some counter-intuitive stuff about how to achieve precise and repeatable results along the way. Getting our clients what they need as efficiently as possible calls for many kinds of creativity.