Damaged Trough from a Shaftless Screw Conveyor

Damaged Trough is repaired using UHMW-PE Sheet

These pictures were taken at a Fertilizer Plant. One picture shows what happens to a Stainless Steel Trough that didn’t use a UHMW Liner to reduce the wear and friction and the other picture illustrates a novel way to Repair and Seal a damaged trough due to a Shaftless Screw wearing through the unprotected Stainless Steel surface. Many Wastewater Treatment Plants would experience similar problems if a Trough Liner isn’t used.

*Vapor Polishing…of all the topics, I get a lot enquiries daily on the subject of Vapor Polishing. Many have wanted information on how to purchase vapor polishing equipment. I have researched this several times and know of no company that actually produces vapor polishing equipment. Most companies in the business already, pretty much have designed and built their own equipment to fit their specific needs. If anyone out there knows of any companies that manufacture vapor polishing equipment, please post their contact information here.

*Can you melt Acetal? ….Yes. It’s crystalline melting temperature is 329F for Copolymer Acetal and 344F  for Homopolymer Acetal.

*What to expect when machining Acetal?…it is easy and very free machining. Use plenty of clearance and rake on your Turning, Boring and Cutoff tools. Good grade of carbide is all you need. See my post on “Machining Characteristics of Acetal” for more detailed information regarding machined, molded and extruded in stresses and how to deal with them. I have a lot of hands-on plastic machining experience so, feel free to ask me questions not covered on our posts.
*Difference between Injection Molding and Extruding Plastics?…as far as physical properties go, when extruding plastics a material with a higher molecular weight is preferred and when molding the opposite is true in order to get material to flow through the small gates and runners under high pressure.  Injection molded plastics are typicallly packed in the mold under considerable pressure which will typically give injection molded plastics a little higher physical properties. When extruding a  material, it is conveyed through the barrel via a screw which goes through a Feed Zone followed by a Compression and then a Metering zone prior to exiting the die. And, when processed correctly good properties are achieved but typically a little less than a part that has been molded. Most applications will never know the difference in it’s actual application.Also, Good mixing is accomplished through both processes, which is important when processing filled materials. This is a topic that could be easily expanded on..if there are any remaining questions regarding this topic, please ask.
*Plastic”Manufacturers Representative”…several enquiries have come to The Plastics Network regarding Manufacturers Representative in the Plastic Industry. Reps in the plastics industry are typlically segemented as to their expertise so, it is important to ask some questions. One segment calls on only OEM’s and even within that group there are subgroups depending on market focus ie: Automotive, Medical, General Industial, Aerospace etc. Another segment only calls on Plastics Distributors with commodity oriented products ie: Stock Shapes, Sheet and related products and most of these Reps come from a variety of Industrial Backgrounds and not just the Plastics Industry. Another segment calls on the Plastics Processors such as Injection Molders, Extruders, Blown Film, Thermoformers etc. …selling Raw material, mold bases, tooling and other support equipment for the plastic process industry.

*Listing IAPD Manufacturers Reprsentative…IAPD has a listing of Manufacturers Representatives in their Magazine. If you let me know what region you are looking for Reps, I wil give you a listing for that area or you can contact IAPD for a listing. IAPD(International Association Plastics Distributors)
*Is Plastic Copolymer or Homopolymer?  depending on the material it could be either so you need to be specific on this question as to what material you are referring to . For example, Acetal has both Copolymer and Homopolymer grades depending on the specific manufacturer.
*Vapor Polishing source in Canada?…I have posted in the comment section of the Topic “Vapor Polishing” various companies that perform vapor polishing in various parts of the country as they become known. If anyone knows of any good companies that vapor polish in Canada please leave information in the comment section. I have had several enquiries.
*PEEK Machining characteristics?…Unfilled PEEK machines very nicely using just a good grade carbide. Small quantities can be machined dry or with  coolant, and is farily stable as far as holding good tolerances. For filled materials such as Carbon or Glass fiber filled…different story. You will have to flush with a good water soluable coolant and Diamond or Similar tooling. Be careful to keep the heat generation down caused by the tooling and use plenty of coolant and make sure your tooling is sharp. Fairly tight tolerances can be held with the filled materials due to the very low thermal expansion achieved by using a filled material.
*Definition “Continuous Use Temperature“…usually a material’s temperature at which it can operate continuously under a load for a  given application. Most material data sheets give a Heat Destortion Temperature (HDT) at both 64psi & 264psi which can be a good indication of how a given material will function under load under various temperatures. This is only a guide and reference as nothing will replace a test to duplicate your actual operating conditions and is always recommended prior to final selection of a material.
*Flame retardant Antimicrobial ABS…compounders such as RTP or LNP can put Flame Retardant and Antimicrobial additives in a building block approach to achieve the desired material for your application. I recommend contacting either company for a suitable compound to meet your requirements. www.rtpcompany.com 

Plastic Machining Coolant?…any good “Water Soluable Coolant” is what you want to use when machining plastics.

From “Wood Composites”, “Biodegradable Plastics”, “Flame Retardant”, “Green Plastics”, “Nanotechnology”, “Antimicrobial Plastics” to “Thermotropic”,  ”Glow-In-The-Dark Plastic Materials”, “Soft Touch TPE’s” plus many others! 

I will be discuss some of these exciting material options below;

“Wood Composites” -  the use of wood in thermoplastic extrusion is a relatively new technology with extensive market growth over the last decade or so. Wood Composite Profiles are extruded using Wood Plastics Composite (WPC) resins. WPC’s are compounded using 30-60% wood filler in the form of Wood Flour or Wood Fiber both of which are available from recycled sources. These Wood Fillers are combined with plastic resins such as HDPE, Polypropylene, PVC or ABS and are processed by extrusion into a variety of shaped profiles (both hollow and solid) that retain many of the favorable qualities and aesthetics of wood but offer enhanced properties provided by the thermoplastic. “Wood Composite” profiles offer good strength to weight ratio, are durable with good dimensional stability, and are relatively inexpensive. Major Markets for “Wood Composites” include the Building Industry (Decking, Roofing Shingles, and Molding) as well as a growing market for Door/Window Profiles, Mini-Blinds, Furniture and Fencing Applications plus many others….

“Biodegradable Plastics” - Alternative material for applications requiring the properties of traditional plastics but will decompose safely in the natural environment ina relatively short period of time. “BioPlastics” that are derived from renewable raw materials such as Plant Starch, cellulose, soy protein, and lactic acid are biodegradable because micro-organisms consume them as a food source. Other BioPlastics are derived from fermentation products like, Polylactic Acid (PLA), and Biodegradable polyesters, Polyhydroxyalkanoates (PHA), Polyhydroxybutyrate (PHB), and Polyhydroxyvalerate (PHV) which are synthesized by microbes with the polymer being stored in the Microbes’ cells during growth. just as we humans store fat for future energy consumption, these microbes store polyester which is a polymer that can be used to produce plastic. “Pretty Exciting Stuff” huh!

“Flame Retardant” - Plastic Profiles combine Non-Halogenated Flame Retardants to the Thermoplastic  Materials for fire safety applications.

The use of Non-Halogenated flame retardants are used in synergy with smoke suppressant technology to provide an increase to the materials resistance to ignition, reduce the burn rate, reduce the spread of smoke emissions and flames while minimizing the plastic dripping during combustion.

“Green Chemistry for Plastic Profiles”  Many material options are now available utilizing Bio-based (Natural) Plastics derived from Soy, Corn and other annually renewable resources. These materials use as a guide the “12 Principles of Green Chemistry” which include: 1) Prevent Waste 2) Design safer chemicals and products 3) Design less hazardous chemical syntheses 4) Use renewable feedstocks 5) Use catalysts, not stoichiometric reagents 6) Avoid chemical derivatives 7) Maximize atom economy  8) Use safer solvents and reaction conditions 9) Increase energy efficiency 10) Design chemicals and products to degrade after use 11) Analyze in real time to prevent pollution 12) Minimize the potential for accidents. This was only a condesed list, the full text is published on the US Environmental Protection Agency Website.

“Antimicrobial Plastic Profiles”  with the growing concerns of our daily exposure to pathogens like bacteria, molds, mildew and fungi a growing trend is utilizing Antimicrobial plastics for such major markets as Aerospace, Medical, Food Services, Military, Consumer Goods, Building and Construction, and Office Supplies just to mention a few. These Antimicrobial properties are embodied within the plastic itself so the Antimicrobial benefits can not be washed away with use.

But How Does this work? Antimicrobials are either natural or synthetic materials that kill molds, bacterial and/or fungi. Since Antimicrobial plastic compounds are directly incorporated into the thermoplastic materials, it makes it impossible for allergens, bacteria, molds, and mildew to survive on the surface, yet these compounds have no known effect on humans and some are FDA approved for contact with food. There are a number of Antimicrobial materials available for use in just about any type of extruded plastic profile.

"Kelbright (TM)- Glow In the Dark Plastic Profiles" : these "Glow In the Dark" plastic profiles begin with a "Bright" glow which deminishes over a period of time, generally within 8 to 10 hours or so. These materials wil last at least 8 hours under typical darkness and can be activated by either artificial or natural light in as little as an hour. Plus, the "Bright Glow" performance of these "Glow in the Dark" plastic profiles are UV Stable. These "Glow in the Dark" materials are currently available in two glow colors - Green or Blue.

These Composite Bearing Materials are Laminated Plastic Materials made by impregnating fabric with thermosetting resins. The physical and mechanical properties of these select bearing grades make them excellent bearing materials.

Composites offer design engineers an attractive, low cost alternative to the traditional materials used throughout industry for bearings, wear pads and other components.

Applications for “Composite Bearings” include:

Composite Bearings in Hydro Electric Plants

Hydro Electric Plants: Butterfly Vlave Seats, Bridge Pivot Wear Pads, Control Gate Bearings, Counter Weight Guide Blocks, Fish Screen Bearings, Lock Gate Bearings, Operating Ring Wear Pads, Running Blade Adjuster Bearings, Trash Rake Bearing & Wear Pads, Trunnion Bearings, Vertical Pump Shaft Bearings, Wicket Gate Linkage Bearings, Wicket Gate Bearings, Wicket Gate Thrust washers, Floating Mooring Bitt Roller Bearings, Chain Guide/Slides, Servo Wear Rings.

Composite Chain and Wear Guides

Composite bearing Materials make excellent Chain and Wear Guides especially for harsh and demanding environments.

Composite Bearings in Forestry Equipment

Composite Bearing materials are ideal in forestry equipment applications as well as other mobile equipment.

Composite Bearings used In Ship Rudder bearings

Composite Bearing materials used in Oil & Gas Applications

On my “Industry Links” page you will find a large listing of Companies, Industry Agencies, Magazines, Industry Specific Links, Industry Organizations and other useful information.

To Highlight some of what you will find on our large “Industry Links” page are as follows:

The Global Plastics Newsletter – by Mel Ettenson, a very informative Newsletter written by people that have been in the industry for many years with lots of good articles, industry interviews , Market Trends and much more…

IAPD-International Association of Plastics Distributors, a good Association to be a part of especially if you are a manufacturer that wishes to sell through distribution channels. Also, a great resource for information in all catagories

SPE-Society of Plastics Engineers, has many regional branches where Industry professionals get together for Networking, Guest Speakers, Sharing of information and ideas. SPE also has a periodical Magazine which has lots of good articles.

SAMPE - Society for the Advancement of Materials Process Engineering – One of my favorite associations. Lots of advanced materials, processes, applications, technical articles. Lots of information on Composites, Polyimides, Advanced Thermoplastics and Elastomers. Great association check-it-out.

IMMNET – Injection Molding Magazine, lots of great articles on materials, application, design, tooling, trouble shooting. If not familiar with the injection molding process, this is a great magazine to learn from.

Matt Web – Huge database for researching thermoplastic materials.

RTP Company - a major material compounder. Their website is rich in technical information,  articles and examples of applications for virtually all industries/materials and much more..

Looking for various agency information NSF, ASTM, UL , etc. you will also find it on our links page.

Doing some marketing? If a Plastics Distributor you may want to visit Machine Shop Web to find machine shops in your region to sell stock shapes to or, Food Processing Equipment Manufacturers website to locate potential customers for your products or, Medical Design Magazine for Medical Industry customers and applications.

Plus, we are constantly adding new links that we feel may be a good resource for information.

Again, knowing where to find information on the Plastics Industry can be very helpful.

“Engineering Plastic Roller Bearing” - A Case Study

Application: Conveyor Roller Bearing for a Food Processing Company

Design Criteria: Needed a self lubricating conveyor roll bearing to withstand repeated wash downs and have a load carrying capability of 300#/bearing under low speed conditions.

Construction: Acetal Copolymer Inner & Outer Rings, 16 ea. Rollers 3/8″ dia. x 3/8″ lg. (alternating 8ea. 302SS &  8ea.  Acetal Copolymer)

Size: 2  1/2″ O.D.  x   3/4″ Hex Bore  x 1  1/2″ Length  x   2  3/4″ Flange Dia.

My approach to the Design and construction of this Roller Bearing was as follows; I used rollers instead of balls for the added load carrying ability plus, with balls there is a “Point Contact” which under large loads will in time indent into the race ways and created a lumpy bearing and load carrying capability would be reduced to only about a third of what a roller can carry. The rollers have “Line Contact” and can withstand much heavier loads. I Alternated the material in the rollers with Acetal and 302SS so there would be no Metal to Metal contact and still not compromise the load carrying capabilty of the Bearing. The end result was a Bearing that was self lubricating, had good load carrying ability and was unaffected by the repeated wash downs. Which I might add, is why I chose the Acetal Copolymer over the Acetal Homopolymer. Acetal Copolymers have better chemical resistance than the Homopolymer Acetals.

If you are  interested in this subject and would like more information please email me or use comment section below.

"Acetal" Rod or Tube Machining Stock

A common problem I’ve seen in the field when machining Acetal Plate or Large Dia. Acetal Rod & Tube is trying to hold close tolerances while machining the entire component in one operation then,  on the next day the parts are undersized or no longer perfectly round .

Some material notes;

When large dia. Acetal rod or tube is extruded an extruded skin/jacket develops as it exits the die and for all intents and purposes holds in some of the extruded stresses. Annealing after extrusion is a big help but, doesn’t solve all the problems. (smaller rod or tube, usually under 2 1/2″,  is centerless ground removing the extruded skin/jacket)

When machining large Dia. Acetal rod or tube the outer skin/jacket is removed which releases  some of the “extruded-in” stresses adding on to the now “machined-in” stresses. Something I learned through experience to combat this condition,  is to do my rough machining leaving only .020″/.030″ per side for clean-up to my final dimensions. I would then let the material sit between 48-72  hours prior to completing my final machining. An annealing operation could also be performed after roughing if desired,  for Acetal,  annealing temps are 305F,(please keep in mind that Acetal Copolymers melt @ 329F & Homopolymer Acetals melt @ 350F),  for 15 minutes per every 1/8″wall thickness, turn off oven and allow to cool down slowly instead of abruptly exposing the material to ambient room temps.

Additional notes; Use a good water soluable coolant,  make sure you are using the correct cutting tools and they are “Sharp” (a good grade of Carbide “C6″ works well with unfilled materials). If drilling a large dia. hole (over 2″ dia.) make sure your drills are sharp and use a smaller pilot drill first. A dull drill or trying to hog-out to much at a time can “Pop” your material due to all the internal stresses involved (extruded and machined).

If post machining an Injection Molded Acetal component,  it is also wise to allow the material to condition at room temp for 72 hours prior to a post machining operation. Case in point… I used to manufacture ball/roller bearings utilizing Acetal inner and outer rings which required close tolerance post machined race ways. After encountering much frustration from the rings moving out of tolerance after sitting in stock for any period of time, allowing the material to condition at room temperature after molding for at least 72 hours prior to finished machining  pretty much eliminated the problem.

Tight tolerances; I’ve had customers put on drawings requesting .0005″ machined tolerance. Well I can hold it! My machine can hold it! But, with a C.L.T.E. of ( 55 x 10-6)  I can hold the finished component wrapped in my hand for a brief period and it will quickly go out of tolerance or, if shipped in the belly of an airplane  at very cold temps will it recover dimensionally or, if the dimension is based on checking at 73F and it’s summer and 98F out and the machine shop isn’t climate controlled or the customers receiving inspection isn’t climate controlled…You can see the problem. So make sure you work with your customer to get a tolerance you can consistently hold and your customer can  live with.

A common mistake I find in the field is for an engineer to look at a data sheet with physical properties tested at Room Temp. (73F) but intend to use the material at a higher temperature say 200F, 350F or 500F and are surprised by how much a thermoplastics physical properties are reduced in the higher temperatures. 

Let’s take three fairly common materials designers/engineers may typically work with; 

The 1st Graph illustrates an Acetal Copolymer with a continuous use temperature of up to 180F,  has a Tensile Yield Strength of 8,800psi @ 73F but a Tensile Yield Strength reduced to around 4,000psi @ 180F (which still isn’t too bad). 

  Click On Chart to View

The 2nd Graph illustrates an Ultem 1000 PEI with a continuous use temperature of 338F and has a Tensile Strength of 15,200psi @ 73F but it’s Tensile Strength reduced to around 6,000psi @ 350F. 

  Click On Chart to View

The 3rd Graph illustrates Victrex PEEK (unfilled) with a continuous use temperature of up to 500F and a Tensile Strength of 14,500psi @ 73F but it’s Tensile Strength reduced to around 1,900psi @ 500F. But, add 30% Carbon Fiber (another topic later) and it retains it’s Tensile Strength to around 8,800psi @ 482F. 

  Click On Chart to View

The point I’m try to make is… when designing with Thermoplastics, study and scrutinize the data sheets carefully against how you intend to use them ie; if you were for instance looking at an Acetal for an application with light/moderate loading at 225F you may want to either look at either adding a Glass/Carbon reinforcement or upgrade your material choice to a material with better properties at your given temperature ie: Ultem PEI, PPS,PPA, PET, PBT, Polyamide etc.

- Lonny Miller

First, I would like to state that due to the risks involved and harmful vapors/chemicals used and special equipment required. You should only work with companies with the experience and proper equipment to perform this process. This is not a process you should attempt on your own!

Ex.- A process used to Vapor Polish Polycarbonate utilizes a strong chemical vapor.  The PC components are then exposed to the Vapor only (not the solution it’s self) for a brief period. After the Vapor Polishing process the PC components must be allowed to dry to evaporate the strong chemical from it’s surface, the components are then heated in an oven to release surface stresses and to rid component of any residual chemicals that may be entrapped.

Again, only work with companies that have expertise in this process. If interested I can give you some referrals to companies that have experience and equipment to perform Vapor Polishing. Vapor Polishing is just 1 of 3 methods commonly used to Polish a Plastic component, Flame Polishing and Buffing are the other 2.