Food-Safe Plastic Bushings

Bushings are used in all types of manufacturing industries and food processing is no exception. Metal bearings such as roller bearings and bronze bearings are widely used but, as in other industries, plastic bushings tend to perform significantly better than metal, permitting less maintenance, increased production, and reduced downtime. Yes, the upfront cost of a plastic bushing is usually more than a metal one. But ask yourself how quickly you would expect a bushing that is a few dollars more to pay itself off with more production and less maintenance work? Plastic bushings are suitable especially when you need:

• Increased bearing life
• Less or no greasing
• Self-lubrication properties
• Better wear and lower coefficient of friction than metals

There are several food-safe (FDA) compliant plastics for this application. One of the very best is Rulon 641: a white, food-grade bearing material with phenomenal load and wear characteristics. Rulon 641 can handle a pressure velocity (PV) value up to 10,000 and is suitable for pairing with mild, 303 or 316 steel. Another bushing material that performs very well in food processing applications is Redco acetal. Acetal is a very hard plastic, but also very machinable to tight tolerances and the homopolymer (white) version of the product is FDA compliant. As is the new blue acetal now showing up more in applications, as the blue has a color different than most foods and that visibility is desirable to many customers in the food processing industry.

Several other plastics can be used as bearings in certain applications: white-natural UHMW polyethylene and certain food-safe grades of nylon or polyurethane as well. However, acetal and the Rulons will often be choices where you cannot go wrong. The first step in us assisting you with your food-safe bushing is to fill out our bushing design form. You can then upload it to our RFQ form and email us here.

Redco Kiln Wheel Bushings

Redco Kiln Wheel bushings are an essential component to sawmills that have large dry kilns. These plastic bushings enable the carts to run freely through the mills and we supply the bushings in three grades:

Redco Blue kiln wheel bushings:

Standard Redco blue nylon kiln wheel bushings are a cost-effective and proven solution as a kiln wheel bushing. The nylon used in these bushings is head stabilized to handle long drying periods in the kiln. These bushings should not be used in sawmills where they will be exposed to very cold temperatures for a sustained period as nylon becomes brittle below -12 Celsius.

Redco Hi-Temp Yellow kiln wheel bushings:

A premium kiln wheel bushing we’ve been developing on at one of our western American branches the last couple of years. The yellow bushings in testing outlast and outwore the blue nylon bushings significantly and use a proprietary material we’ve developed to replace Redco blue kiln wheel bushings at a modest cost premium. The yellow bushings have more than paid for themselves in increased lifespan and, yes, they make the carts run smoother as well. These bushings are a direct substitution for Redco blue nylon kiln wheel bushings but are still not the correct choice in very cold weather environments and do not have increased load capacity over the regular blue.

Redco Phenolic kiln wheel bushings:

Phenolic kiln wheel bushings are used in high load (36,000lbs+) applications or where extreme cold is involved. Due to the properties of phenolic material (a fairly high coefficient of friction), it is recommended to put a grease groove in the bushing.

To work with a Redwood representative on your next kiln wheel bushing order please contact us.

Plastic Bushing Solutions

Industrial plastics serve as an excellent bushing/bearing material in everything from needle bearings to large marine bushing applications. Since many industrial plastics are suitable for different bushing applications its best to know the advantages, and potential drawbacks, of each material. The following is not meant to be an extensive guide to selecting a bushing material, just a primer to the different options:

UHMW polyethylene:

UHMW-PE can serve as an excellent low-load bushing, 500-800 PSI is at the top of its limitations. UHMW has the benefit of being economical, self-lubricating and readily available. Customers tend to be very familiar with this particular plastic and trust it. Areas for concern with UHMW are its relative low-load, and high thermal expansion.

Nylon 6:

Cast nylon (nylon 6) is a widely used bushing material and can handle up to 4,000 PSI. Cast nylon is available in several grades including heat stabilized, Moly-filled and oil-filled. The primary area of concern with nylon is its moisture saturation: 4% in a water saturated environment. Impact and cold environments are also a concern for nylon. Nylon bushings can either be made with much more generous allowances in aqueous environments, or acetal may be a substitute.

Acetal:

Acetal is one of, if not, the best plastic to machine due to its hardness and ability to machine to tight tolerances. Acetal is often a good substitute for nylon in marine environments.

Industrial laminates:

Often just called “Micarta” or “phenolic” by customers, industrial laminates excel in high-load, low RPM applications. Certain industrial laminate bearings can handle in excess of 24,000 PSI. You do need to be aware that these bushings should be lubricated and that certain rotational speeds will not work. If you need to know the specifics, just ask.

Redco 750 and 750 XL

Polyurethane bushings are often an excellent choice. They handle abrasion, impact, and can be molded (perhaps with some machining to finish them). Polyurethane can handle up to 2,500 psi. Cold temperatures may be a concern, and tooling costs are often involved with urethane parts, but the end result are effective bushings that can be produced with low-lead times and in quantity.

For answers to your questions on our bushing or bearing material, contact us today.

When To Choose Tuffkast

Redco Tuffkast has been designed for use in “extreme” applications. But what exactly does this mean? In order to answer that question you need to first consider the properties of regular nylon 6. Nylon 6 can take a lot of load (4,000PSI in operation) and is suitable for a variety of load bearing applications such as outrigger pads, bushings and sheaves. But nylon has three key limitations. Firstly, nylon starts to get increasingly brittle in cold around -10 Celsius (14 Fahrenheit) and many parts of North America exceed that during the winter. Secondly, nylon 6 does not handle impact and shock well and is not well-suited to applications such as impact or bumper pads. On precision parts, especially those with flanges or thin edges, care needs to be taken when handling the part even at room temperature. Finally, nylon absorbs water causing it to swell and making it not the optimal material in marine or “wet” applications.

Tuffkast counters many of these deficiencies in nylon 6. Tuffkast performs well in cold applications and absorbs about half as much water.  However, the area Tuffkast really shines is in abrasion and impact-resistance, notably, Tuffkast marine fenders in British Columbia, Canada helped prevent massive damage to a ferry dock in 2006, a story you can find here. It is this combination of resistance to the elements with the impact and abrasion resistance that makes Tuffkast an excellent choice for many very demanding applications.

If you want to inquire about Tuffkast’s suitability for your application then please contact us today.

Tuffkast vs. Nylon

Redco™ Tuffkast and Nylon have similar applications in the world of plastics such as bushings, bearings, sheaves, pulleys and even outrigger pads. Some customers get confused between the differences in the material and still others are wary of Tuffkast because, as a Redwood Plastics proprietary plastic, it is not nearly as well known as nylon. Nylon is a plastic developed around the time of the Second World War, whereas Tuffkast is a co-polymer (made of different plastic types). Tuffkast is much newer and is slowly penetrating the plastic industry. Many of Tuffkast’s properties counter potential weaknesses of nylon material.

There are three major advantages of Tuffkast over nylon:

1.) Nylon has some of the highest moisture absorption among industrial plastics at 4% on average (after 24 hours saturation). Tuffkast on the other hand will only absorb up to 0.5% moisture in the same time frame.

2.) Nylon does not handle shock or impact well, but this is a strength of Tuffkast.

3.) Nylon gets brittle in cold temperatures while Tuffkast has much better low temperature properties.

As with any comparison there are tradeoffs in selecting Tuffkast. Tuffkast is too “soft” for some applications meaning nylon would still be the optimal material choice. Tuffkast is also more expensive: about 30-50% more than nylon by weight. Regardless, as a company we see applications every week that are better served by Tuffkast. Be sure to consider it for your next project.

For questions on our Tuffkast, nylon or other plastic materials contact us today.

Solution Spotlight – Kiln Cart Bushings

Earlier this year a customer of ours contacted us, frusterated with the performance of their existing kiln cart bushings. The carts were very difficult to move – so much so that motorized equipment was being used to pull and push them through the kiln. Our solution was a new bushing made of a variety of advanced PVM “Pressure Velocity Maximum” cast nylon with an added safety yellow color (to avoid confusion with the existing blue nylon bushings). These bushings performed beyond expectations – the kiln carts now move so freely through the kiln that the only problem is stopping them!

Our improved kiln cart bushing is now in use at multiple mills on the Pacific coast and the feedback has been extremely positive. These bushings are yet another example of the type of innovative industrial plastic solution Redwood Plastics can supply.

Contact us:

E-MAIL: sales@redwoodplastics.com
CDN: 1 800 667 0999
USA: 1 866 733 2684

BUSHINGS & BEARINGS – Why Plastics are Better…

Plastics are among the most obtainable and cost-effective materials used in a variety of applications. They are easy to fabricate, durable and efficient, resulting in an ideal material for bearings and bushings.

Because of plastics sheer usefulness and malleability, some plastic bushing grades can be designed for extreme environments and can withstand extremely high or low temperatures. Others are even suitable for hazardous environments with high levels of shock and vibration.

• Self lubricating

• Outstanding load bearing properties

• Excellent for impact and shock application

• Exceptional wear life and resistance to corrosion

• Low temperature resistance to -80°F

Different plastic grades can also be bonded together. For example, feed rollers would have a softer outer diameter with a harder inside diameter. Bringing these two materials together creates the perfect balance of shock absorption and grip with high load bearing capabilities. Metals (steel, bronze, etc) can also be bonded to plastics.

For more information please visit our website; www.redwoodplastics.com or call us at:

CDN: 1 800 667 0999
USA: 1 866 733 2684

Please Consider:

Plastic Clearance/Tolerance is subject to many variables (i.e. Moisture, Cold Heat) when being machined for specific applications. If lubrication is supplied to a plastic bearing, the load and life are greatly increased dependent on the type and volume of lubricant. Consult our Machining Chart available on our website.