Polyurethane vs. UHMW

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Regarding sprocket applications in particular it seems the default request in 2020 is for “UHMW” sprockets. Indeed, UHMW is used in some sawmill sprocket applications and is widely used elsewhere in sawmills as wear parts. However, the material is not ideal for use in either a drive or idler sprocket – why is this so? Firstly, UHMW is softer than polyurethane or nylon sprocket options. While this reduces wear on the chain, the UHMW deforms easier and also has very poor dimensional stability. In fact, UHMW is notorious for thermal expansion issues which depending on the temperature swing can easily expand as much as 1/4″. UHMW sawmill sprockets also need to be machined which is much more expensive than a molded Redco 750 polyurethane sprocket.

Polyurethane on the other hand is an “elastomer”. This type of material resists deformation by returning to its original shape (at least 90% within 10 minutes of release of compression) and is more dimensionally stable than UHMW while retaining the beneficial low-wear properties it incurs on sawmill chain. They will last longer in the application reducing maintenance downtime. The drawback is that a mold must be created for the sprocket resulting in a one time tooling/setup fee for the customer (unless of course that model of sprocket already exists).

For questions on sawmill sprockets for your application please contact Redwood Plastics and Rubber.

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Why Not Glue It?

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One question that keeps coming up regarding sawmill maintenance solutions is “Why can’t I glue it?” When discussing affixing the plastic solution, for example a wear strip, to a steel backing. The appeal of a glue or adhesive is that it’s easy to apply and would result in an unbroken part that does not require holes or hardware. However, there are many drawbacks to adhesives that mean mechanical fixation is always the best choice whenever available.

What are the problems with adhesives?

  • Different plastics bond with different strength even with the same adhesive
  • Some plastics cannot be bonded at all
  • An adhesive bond is weaker than mechanical fixation
  • Adhesives can be attacked by chemicals or moisture saturation

The benefits of mechanical fixation (weld washers, bolts, or screws) is that the bond will be long-lasting. Even if the fasteners, which are whole or in part metal, start to corrode that will occur slowly and be noticed. It’s very likely the part will need replacement before the fasteners do. Plastic fabricators such as Redwood Plastics and Rubber are familiar with mechanical fasteners, especially weld washers, and carry thousands of weld washers in stock. Redwood Plastics and Rubber  can provide advice on on hole patterns for weld washers or just let us supply the parts complete with holes and fasteners.

Weld Washer Detail

 

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Hi Temp Yellow Kiln Wheel Bushings

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Customers often request our nylon kiln wheel bushings - a decades old solution for sawmills these bushings are long-lasting, reliable, and cost-effective. However, in the past 5 years we’ve started to offer a new variety we call the “High Temp Yellow” version. This version of nylon plastic involves a proprietary mix of fillers and plasticizers specifically for the kiln wheel bushing application. While approximately 30% more expensive, they are much longer lasting and do not seize on the shafts nearly as much as the blue or green plastic kiln bushings can.

Trialed on the West Coast of the USA in the early 2010s, the High Temp Yellows were designed primarily to ensure smooth, dry-running kiln carts. While a white lithium grease is beneficial, it is not required. Despite this, Redwood Plastics and Rubber still offers several designs of kiln wheel bushings with and without grease grooves to suit your preference. These are also available in whatever size you require – just provide the length, outer diameter, and inner diameter of the bushing you require and whether or not you require a grease groove. Due to a variety of kiln bushing sizes available, lead time is typically about 4 weeks as they are all made to order.

For assistance with your kiln wheel bushings please contact Redwood Plastics and Rubber.

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How To Get Your Deadplate Quoted

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Redco Deadplate is an elastomer designed to work as a shock absorber – it takes the energy of impact and transfers it into heat. In the sawmill applications it was designed for, Deadplate takes the impact of the logs or lumber, stopping their momentum and allowing them to continue through the mill. This usually results in a 90 degree change in direction the wood was heading. Of course, the larger benefit of deadening the wood’s impact is to reduce stress on expensive sawmill equipment as repeated impacts can weaken or break welds.

However, Deadplate is not a “one size fits all” application where one size and thickness of Deadplate works for everything. On the contrary, Deadplates come in all different sizes, shapes, and thicknesses. Redwood Plastics and Rubber can help in quickly designing your Deadplate; however, we do need to get some basic information from you to do so.

In preparation for your Deadplate request for quote get together the following information:

  • Largest sized logs or lumber that will impact the Deadplate
  • Estimated weight of the largest log or lumber
  • Estimate FPM (feet per minute) the logs or lumber will impact the plate – if not known, provide the distance the logs or lumber will fall into the plate and at what angle
  • Estimate the current size of the impact zone (the length x width of the area the logs or lumber currently hit)

You also need to advise whether or not it’s logs or sawn lumber that will be hitting the Deadplate as that affects the type of cap that would be put on it. Once you gather that information together then you’re ready to contact Redwood Plastics and Rubber and ask for your quote!

 

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Tuffkast 020 Sawmill Carriage Wheels

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Sawmill carriage wheels are a very popular plastics application that has proven itself over decades and Redwood Plastics and Rubber’s “Tuffkast” proprietary plastic has performed so well in this application that a special grade, Tuffkast 020, was formulated specifically for this one application! The product is slightly softer, which helps it fit carriage rails better and is orange in color.

These are typically supplied as “blanks” where customers give an outer diameter and a thickness of their wheels and Redwood provides discs that are 1/4″ oversized on the dimensions (to permit machining down to size). Machined wheels can be provided complete as well but a fully dimensioned drawing will be needed.

For more information or a quote on sawmill carriage wheel blanks or complete wheels please contact Redwood Plastics and Rubber.

Carriage Wheel

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Why Is Polyurethane Used So Often In Sawmill Applications?

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We occasionally hear from our sawmill customers “You guys want to stick urethane in everything!” The comment isn’t to be mean but it reflects the fact that many applications and problems we are tasked with solving end up with a polyurethane solution. For many people they are surprised that polyurethane can serve any “industrial” applications in the first place, with most people thinking it’s just a type of foam used in furniture and mattresses.

In fact, polyurethane is a versatile material with special properties called an “elastomer” meaning it rebounds when compressed to most of its old dimensions. In addition, it’s not just available in a foam – it can be manufactured in all sorts of solid grades from gel-like shock reducers to bearing grade products capable of taking 2500 PSI.

So, why do we use it in sawmills?

Polyurethane is a problem solver and where it solves issues are with impact, wear, abrasion, and even noise. There no question those are issues at sawmills so lets start with impact, which can prematurely wear or damage equipment and welds. The softer shock absorbing polyurethane, Redco Deadplate, can be strategically deployed to take this impact and save the equipment. A good example of a wear and abrasion solution are our Redco 750 polyurethane L-channels/guides used in OSB plants.

UHMW is widely used in this application but it is a high-load, high friction application that can make UHMW bubble due to heat and deform. Polyurethane will not under the same conditions. Redco 750 itself deserves special mention – a bearing grade product still able to handle high impact with excellent wear properties, it has been used for decades as bearings and SN inserts in mills (as well as C-bars and J-Hooks).

So, why polyurethane?

It simply works and because its properties offer many simultaneous advantages (wear resistant and impact resistant at the same time) it offers unique problem solving solutions many other plastics can’t.

For assistance with your sawmill application, please contact us today.

 

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Rubber Roller RE & RE For Sawmill Applications

Rubber covered rollers are everywhere and the lumber processing industry is no exception. Eventually the OEM rollers you have will have their surfaces wear or get damaged causing them to not convey materials properly, which can cause major production issues! To avoid costly downtime – what do you do? Firstly, hopefully you have spares so that your production doesn’t completely go down. Secondly, you need to get in touch with Redwood Plastics and Rubber, who is a plastics and rubber fabrication and distribution company in North America with a large roller division.

Redwood can offer anything from a “RE & RE” which involves stripping off the old rubber and building a cover with new rubber from the steel core up and can even offer brand new rollers – including getting the steel cores machined for you. They offer several finishes from machine ground to polished and can include options like various treads. You can learn more and download a brochure here.

So, you need a roller RE & RE…What do you have to do? First, contact Redwood Plastics and Rubber with your request. A representative will send you a one-page spec sheet to print, take some measurements, and email back. If you don’t know the type of rubber used on your roller, we would need a sample of the material mailed to us. Alternatively, you can simply ship us an old roller and we can take all the required measurements from it ourselves.

What’s important is crating: roller finishes are sensitive to damage and a crate is the only secure way to transport a rebuilt or new roller. If you do not send the roller crated, we will offer to build you one at a quoted price. Our quality and price is very competitive within the industry. We hope to hear from you soon regarding your roller requirements.

Roller

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If You’re Experiencing These Problems, Plastics Can Help

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This article is non-specific in that it doesn’t discuss a single plastic or application. It is geared towards those involved in maintenance at sawmills, planar mills, and OSB plants when something is wrong and a solution isn’t self-evident. In what type of situations should you consult with a knowledgeable plastics distributor, such as Redwood Plastics and Rubber? While there are countless maintenance issues you can run into, plastics tend to do their best work when the following problems are encountered:

1.) Wear & Abrasion

Premature wear is an issue with many metallic sawmill components over too many machines to describe. This could be anything from various bushings, to chain wear, sprocket wear, sheaves, etc. Plastics that would be used in wood manufacturing applications tend to be very slick and by mating them with the metal components you have, or in cases outright replacing those metal components, your reduce wear and extend part life.

2.) Noise

As we just mentioned, mating a plastic to a metal component reduces wear but it also reduces noise. Many jurisdictions require noise to not exceed a certain level and with all the banging, scraping, and machinery running at a mill it is not uncommon for the noise level to be found to be in violation of code. By swapping out metal mating parts for performance plastic parts you will greatly reduce noise – an excellent example is replacing metal sprockets with Redco 750 polyurethane sprockets.

3.) Shock/Impact (finding broken welds?)

Impact is a major maintenance concern at mills – with logs and lumber constantly being conveyed and hitting things, machinery can be damaged and welds broken. Elastomeric products, particularly rubber and polyurethane, perform very well as bumpers and shock absorbers…Redco Deadplate is an absolute standout for this application. If you have broken welds or other impact damage in your mill definitely get in touch.

Plastics can assist in other ways such as reducing power requirements for equipment, if you have questions please contact Redwood Plastics and Rubber today.

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Trimmer Lug Spec Sheet

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White or black UHMW polyethylene trimmer lugs are ubiquitous at most sawmills. Unlike metal lugs, the softer UHMW takes impact while being gentle and non-marking with the lumber. These are also an easy to manufacture part that Redwood Plastics and Rubber has decades of experience machining.

Need a quote on some lugs and not sure where to start? We’ll make it easy for you with another one of our “oldie but goodie” spec sheets from the 1980s…Merged with the sharing ability of modern technology! Download the picture file below, print it, fill in your required dimensions, scan it, and email it to sales@redwoodplastics.com

Please also tell us the quantity required and if you’d prefer white or black?

 

Roller Trimmer Lug Blank

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Redco Titanium Liner – VIDEO

Seeing is believing! We’ve posted a new video on YouTube of a “before and after” involving our Redco Titanium liner. At issue was a conveyor at a sawmill with a metal on metal flights -> conveyor connection. This was causing slip stick and wear issues which would result in premature wear and increased power costs to pull the sticking chain along.

We supply this liner typically at 1/2″-3/4″ thick with plug holes and weld washers to affix to the conveyor. The result is a dramatic improvement in how the conveyor works. You can view the video here:

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