The term engineer dates back to 1325 when engineer meant one who operates engines. However, the practice of engineering can be traced back to examples such as the pyramids in Egypt and the Parthenon in Greece. Engineering is the profession of acquiring and applying scientific, mathematical, and technical knowledge to design and implement structures, machines, devices and processes that realize a desired objective. Engineering is a broad discipline that is made up several different branches such as:

• Chemical Engineering
• Aerospace Engineering
• Civil Engineering
• Mechanical Engineering
• Electrical Engineering
• Agricultural Engineering
• Software Engineering

A good career in engineering starts with a good education. A keen interest in math and science is important. Do you like to take things apart to see how they work? If so, then you could make a great engineer some day. Here is a list of the different kinds of engineering careers that may be of interest to you.

Please click on the link and it will bring you to the Connecticut Plastics Learning Center where you can learn more about each field of engineering. There are links to more information about each field, as well as links to organizations, associations and government websites. There are also links to some of the best engineering and technical colleges in the world.

www.tryengineering.org

Additional info can also found at:

The IEEE and IBM have created a new Web site that combines information on engineering careers with interactive activities.

Intended for pre-university students, parents, teachers, school counselors, and the general public, TryEngineering.org lets visitors explore how to prepare for an engineering career, ask experts engineering-related questions, play interactive games, and more.

Visit www.tryengineering.org today!

Our learning center was designed with parents and students in mind. It is full of information on the plastics industry, chemistry and engineering. We hope you find this information helpful.

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Machined Polycarbonate Cube

There is intense pressure to remain competitive, flexible and cost-effective in today’s markets. OEM manufacturers constantly strive to increase market share while streamlining production and cutting costs.

The medical device market is a perfect example. According to Moody’s website, alliances between hospitals and doctors have reduced the influence medical device makers have in selling products directly to physicians. In the future it is hospitals that will be making the purchases. Hospitals operate under budgets and therefore have many reasons to demand price cuts.

The machine shop that can reduce lead times and produce quality parts will have an advantage in this competitive market. Scheduling is the critical link between ordering and execution. It represents a balance between demand, capacity and the supply chain. It is key to remaining economical.

Normal lead time for machine shops is four weeks or more. Customers always ask for better lead times. Here at Connecticut Plastics we listen to our customers. We are a state of the art CNC plastic machine shop that is always adding the latest in equipment in order to increase our capabilities. We can often supply components in 1-2 weeks to meet critical scheduling demands.

Plastic Bonded Manifold

Visit our website to fill out our inquiry form, and upload your drawing. You’ll receive a response within 24 hours. Then call to discuss your delivery requirements. We’ll do our best to meet them.

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Various Medical Plastic Manifolds

Acrylic offers a cost effective plastic with high clarity after machining and polishing. This makes it desirable for manifold applications. However other plastics offer significantly higher tensile strength properties, good clarity after machining and polishing and are far less brittle than Acrylic. See chart below. These materials should be considered along with full design parameters when selecting a material.

Connecticut Plastics has 30+ years of experience with the selection and precision machining of plastics, and we are always available to assist you with your application.

Please visit our website to learn more about our company, for contact info, or to fill out an inquiry form to request a quote. There you can also upload a drawing.

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Typically an engineer will require 3 or less characteristics that are critical to the functionality of the component. A basic search will prioritize and look for a material that can supply all three. The below list presents only the most common machined plastics. Many plastics are available with fillers to enhance particular characteristics. For example, glass fill improves tensile strength while reducing machinability. Molybdenum disulphide improves wear while reducing dimensional stability.

For a thorough search of plastics, please contact the Connecticut Plastics’ engineering department at 203-265-3299 or on the web at www.ConnecticutPlastics.com

Clear Plastics: Stock shapes are typically clear but once machined they become translucent to opaque. Polishing is required to return the component to clear. Polishing methods are direct machine polish, vapor polish, flame polish, and buffing

Good Choices: Acrylic (clearest), Polycarbonate, Clear PVC, Polysulfone, Ultem

Loading Strength (psi): Tensile strength (plastic in tension) and compression strength (plastic under compression) are important values for structural applications.

Good Choices: Ultem, Peek, PPS, Nylon, Delrin

Poor Choices: Teflon, UHMW, LDPE, HDPE, Polypropylene

Temperature Resistance: Consider either continuous service temperature in air or heat deflection temperature if under load.

Good Choices: PTFE, PEEK, Ultem, Torlon, PPS

Poor Choices: Acrylic, UHMW, ABS, PVC

Limiting PV: A combination of pressure and velocity that determines whether a plastic material has enough thermal and structural ability to withstand a bearing application in rotational wear

Good Choices: Peek, Nylatron, Delrin AF, Torlon 4301

Poor Choices: UHMW, PBT, PET Nylon

Dimensional Stability: Machined plastics do not have the structural stability of metals. This is primarily caused by their tendency to absorb water and a high coefficient of thermal expansion. Stable materials have low water absorption with a low CTFE

Good Choices: Ultem, Peek, PPS, PET

Poor Choices: Nylon, UHMW, HDPE, LDPE

Chemical Resistance: Chemical resistance of plastics is variable. Some materials show an almost universal resistance to chemicals while others are very sensitive and stress crack when exposed. Best practice is to consult a reference guide for a specific chemical/plastic interaction.

Good Choices: Teflon, UHMW, CTFE, PEEK

Poor Choices: Acrylic, ABS, Noryl, Polysulfone

Toughness/Impact resistance: A measurement of a plastics ability to withstand a sudden shock or a blow. Do not confuse this with resistance to steady state stress where failure can occur from chemical attack or configuration stress risers. Polycarbonate can tolerate high impact but stress cracks from steady loading.

Good Choices: Nylon, Polycarbonate, UHMW, Peek

Poor Choices: PET, Acrylic, Noryl, Polysulfone

Cost: General measure of cost of the material. Higher performance engineered plastics are more expensive.

Inexpensive Choices: Delrin, UHMW, Polypropylene, HDPE

Expensive Choices: Peek, Vespel, PPS, Radel, HDPEH

Biocompatible: Suitability for use in medical device applications. Plastics carry the USP class VI designation.

Good Choices: Polycarbonate, Peek, UHMW, Radel

FDA Approved:  The Food and Drug administrations’ classification for plastics which contact food.

Good Choices: Delrin, PET, Polycarbonate, Peek

Steam Sterilization – Same as autoclaving, a process where steam is used to sterilize plastics for medical device use.

Good Choices: Radel, Ultem, Peek, Teflon

UV Resistance: Resistance to UV typically seen in outdoor use. Plastics without resistance will age and embrittle. Because of the coloring, most black plastics have at least a small amount of resistance.

Good Choices: Ultem, Polycarbonate (UV stabilized grade only, non FDA), PBT

Poor Choices: Polycarbonate (FDA), Nylon, Acetal

Various Precision Machined Plastic Components

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Each part configuration and application is unique. For specific design support, contact Connecticut Plastics’ engineering at 203-265-3299 or on the web at Connecticut Plastics.

• Flatness: From the extrusion and cooling, plastics have stress gradients through their cross section which are not relieved by post processing at the manufacturer. Plastic’s flatness stability is substantially lower than metals. Consider the following to improve.
  • Balanced design. Dish shaped plastic machined components are notoriously difficult to avoid warpage.
  • .003” per a 4” square, unrestrained, is typical. Tighter tolerances require better fixturing and more machining.
  • Consider specifying parallelism instead of flatness. If the plastic part is attached to another (especially a metal part), unrestrained flatness is unimportant. The plastic part will follow the contour.
  • Consider restrained flatness. Again if attached to another component, the plastic part will conform to the contour.
  • Pick a stable material: Low performance materials will easily warp. For tight flatness requirements, harder plastics are better. Try Ultem, PPS, Peek and Acrylic
  • Hire a plastic machining company. Flatness can change over time while sitting on a shelf in the stock room. Advanced processing really works for flat critical components.

• Threaded Inserts: For single time assembly, threaded inserts are not necessary given proper torque levels are utilized. Inserts do not add appreciable additional holding power. Applications requiring repeated disassembly (usually for cleaning) do benefit to avoid thread stretch. Heat staked inserts are a better solution than Helicoils by giving higher pullout power. Helicoils impart high stress levels into a threaded hole resulting in crazing at the thread root in sensitive materials. Helicoils are acceptable in materials that do not heat stake well and have good toughness like UHMW.

• Polishing: Typically applies to clear plastics like Acrylic, Polycarbonate, Polysulfone and Ultem but is important for finish improvement in opaque materials as well. Polishing methods are direct machine polish, vapor polishing, flame polishing, and buffing. The most professional looking finishes are accomplished by machining and polishing with one vendor. Polishing only services are available but the finish usually is not as good. Heavy polishing can never make up for and overcome poor machining. Melted surfaces in the machining process will invariably result in stress cracking after polishing.

• Finishes: There is continual demand for better finishes to improve product performance. Given the capabilities of modern CNC equipment, do not accept surface finishes above 63 micro inches from a machining vendor.
  • A 32 to 40 micro inch is consider a standard machined plastic finish for a +/- .005 toleranced component and should not incur any additional cost to produce.
  • Finishes below 32 are reasonable and to be expected on close tolerance parts (+/- .0005).
  • Finishes between 10-20 micro inches are typical for a polished plastic component especially as a turned component.
  • Inside milled pocket finishes always have higher/worse finishes. The action of the nose of the endmill does not facilitate clean cutting and chip removal.
  • Exterior flat milled areas can have a very good surface finish
  • In 3D profile milling a good finish requires a large number of passes from a ball endmill. Carefully specify the maximum allowable finish to avoid excessive machine time.
  • Finishes below 10 are difficult to achieve and may require lapping or similar with limited application to part geometry.
  • Some plastics like Teflon cannot have a surface finish below 20 via any method because of the porosity of the material.

• Tolerances: Dimensional tolerance holding is very much configuration and material dependant. However some general rules do apply. +/- .005” is an easy to reach tolerance for all but very large dimensions in unstable material. For parts with a volume of 1” cubed and below, +/- .003 is readily held. For small components, even in soft materials like Teflon, +/- .001 is reasonable. +/- .0005” and +/- .0002” are manufacturable with small dimensions in stable materials. The corresponding surface finish must be improved as tolerances are tightened to avoid measurement repeatability errors.

• Material Selection: There are many good references for plastic material selection by the major manufacturers of both resin and stock shapes. Select the material carefully, as plastics are capable of long term change. Field failures do occur when a plastic component reacts with a chemical in service long after the part has been approved for use by inspection. Be aware that plastic choices are not limited to unfilled materials only. Fillers such as glass fiber can enhance particular characteristics.

• Dimensional Stability: Like flatness above, machined plastics do not have near the same stability as an identical metal component. Plastic components are affected over the long term by many factors

• Thermal change: Plastics’ CTFE is higher than most metals. Some plastics have a measurable change simply though contact with body heat.
• Moisture absorption: Nylon can soak up to 9% of its weight at saturation having a dramatic affect on dimensional change. Try Noryl for hot water applications.
• Creep: Materials like Teflon and UHMW when placed under high pressure will change shape and extrude from a joint.
• Off-gassing: Many machined plastics off gas as a reaction to the extrusion and machining process. Notably, Delrin components shrink over time from the effect.
• Stress relaxation: Both the extrusion and machining process impart stress into a machined plastic component. Post processing can help, however part configuration determines which direction the plastic will relax and change size.
• UV/aging: Plastics age and embrittle especially from exposure to UV or chemicals.

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Our on-line learning center is separated into five sections. The first section provides an introduction to plastics. It discusses the uses of plastics in our everyday life, the history of plastic and plastic chemistry. There are links to other sites with more information.

The second section is the ultimate polymer science guide. It gives the chemical names of some of the plastics that you use every day. How polymers are made, and what is the difference between polymers. There are also links to sites that give more in depth info.

Section three is by far the most popular. It is our ultimate chemistry homework helper, with over 30 links to sites with chemistry tutorials, resources, and practice tests. These links provide information on chemistry for all age groups. This is a great resource for home schooling.

The fourth section is a page with links to chemistry resources on the web. There are links to commercial and government sites providing excellent information, including the periodic table and chemical lab safety regulations.

The fifth and final section provides information on engineering along with engineering resources. If you are considering a career in engineering, you will find links here to websites about civil engineering, mechanical engineering, aerospace, chemical, electrical and materials engineering. There are links to engineering colleges, engineering organizations and publications.

We hope that you find the Connecticut Plastics learning center helpful.   Feel free to leave a comment and let us know what you think.

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Connecticut Plastics stays ahead of the competition by keeping up with the latest technology and materials for every industry they serve. They work with material manufacturers like DuPont, Quadrant, Ensinger, and others to ensure that they receive and provide the latest in plastic polymer materials. With over 30 years of experience providing plastic fabrication services to customers around the world, they have the knowledge and skills to meet industry standards and specifications for almost any project. Close tolerances can be met and difficult parts are never a problem.

Connecticut Plastics uses the latest equipment and machines to provide the parts you need, machined to your exact specifications and delivered on time. Their commitment to quality and efficiency means a smoother production process that produces better results for a successful project. Here is an example of what customer’s have to say about Connecticut Plastics:

“Hi Tom,

Just a note to let you know we received the balance of our order for the 20 machined PETG specimen compression devices, and they were beautiful. Expertly machined, clean as a whistle and flawlessly packaged. They worked well, too.

Please pass along our thanks to your employees for a job well done. I won’t hesitate to use or recommend your company in the future!

-Tom J., Product Development Engineer – Medical Device Industry”

Since its incorporation in 1980, Connecticut Plastics has been manufacturing precision machined plastic components for Original Equipment Manufacturers around the world. Connecticut Plastics takes pride in providing professional customer service and quality products to all of their customers on every single job. In addition to precision machining of plastics, Connecticut Plastics also provides annealing services, small assembly, and plastic polishing including vapor polishing. We also specialize in producing bonded manifolds for our customers who are looking to reduce space, weight and installation time and error by including a fluidic manifold in their design.

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Connecticut Plastics has protocols for testing components for stress after machining. These range from total destructive testing to optical stress measurement. While not all components require annealing, there may be advantages for some materials and part configurations. Materials most sensitive to field failures are Acrylic, Polycarbonate, Ultem, Polysulfone and Noryl.

Failures arising from hasty material selection are not uncommon in the plastic industry. Careful consideration of your application and target performance is crucial to choosing the right plastic material.

Polycarbonate Machined Components - One showing Stress Cracks

Residual stress in machined or molded plastic parts is often a concern for engineers determining life span of a device. In conjunction with annealing, Connecticut Plastics offers stress testing and measurement. We can provide either optical or chemical testing to detect stress concentration after plastic machining. This approach takes into account both material and configuration effects.

Connecticut Plastics has multiple programmable ovens for precise control of the stress relieving process. We can anneal components that are manufactured by us or by our customers. Injection molded blanks also may benefit from a stress relieving process.

Stress relieving and annealing, stress testing and measurement are topics that can be best covered by speaking with our engineering department. Through special processing, Connecticut Plastics can produce a very low stress plastic component. Customers can request a lab stress test along with a production run to ensure suitability for their application. For help with material selection and testing of your prototype please contact Connecticut Plastics. Call Pete Poodiack at 203-265-3299 X 20, or email at pete@connplastics.com.

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Requirements for machined finishes below 32 are increasingly more difficult. In this range, material type and part configuration play a more dominant role. However, using proprietary tooling, a superior finish can be achieved with some materials. Values have reached 10-15 micro inches in certain instances.

Showing Optically Clear Burr Free Surface Finish

Specialized tooling is also capable of optical-quality finishing. Materials such as polycarbonate and acrylic can be machined clear. This process can be configuration limited, however, and is best suited for exterior work. Interior work — such as bores or cavities — have some success, while this technique is not applicable to features such as tapped holes.

Please visit our website for more information on finishes, or to request a quote. Or you can view more photos of plastic components by clicking here.

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Difficult parts are the showcase of production at Connecticut Plastics. This group of components requires our engineers to go beyond traditional plastic machining techniques and learn new, innovative approaches. Please browse our photos here and in other galleries that are examples of our manufacturing capabilities.   These complex components are machined to be springs and have the thinnest wall ever in Peek Optima – .0008″.  Abrasive/unstable material and tolerances to .0002 are typical challenges Connecticut Plastics faces every day.

Sample of Difficult to Machine Plastic Component

Need help with an unusual application? Please call the engineering department at Connecticut Plastics. Visit our website for contact information or to fill out the inquiry form. They are available to discuss material selection, machining concerns and polishing to name a few.  Our strengths insure efficient production, stringent control and quick turnaround to satisfy the highest demands.

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