Apparently we are all doomed, so no doubt we will all be doing a lot of standing around staring into the distance, wistfully thinking of those halcyon days when life was easier, summer meant sunshine for more than four days at a time; you could drive and park in London without having to have pay a congestion charge or make way for Olympic pseudo dignitaries (donít know if I am allowed to use the word Olympic, is it copyright protected?); and keeping fit meant walking to the pub for a few pints.
Not to worry though, because standing around although not ideal, is getting a whole lot more comfortable with the ever increasing range of Rubber Matting and PVC Matting products we are bringing to the market.
MacLellan Rubber has always offered Electrical Insulation Rubber Matting from BS921and IEC61111 to the more exotic ASTM D178 and MIL-R- , all of which you would want to be standing on if you are hoping to survive an electrical discharge up to 50,000 volts. We have also always maintained stocks of the standard Fine Flute Rubber Matting and Broad Ribbed Rubber Matting despite the desperately low prices it now trades for.
What is getting us excited is not the fact that we continue to increase our sales for these core products, but with the onset of increased demands for Health & Safety compliance and the market pressures placed on service and equipment suppliers to innovate and differentiate, MacLellan Rubber are able to meet these needs and are working hard to be at the forefront of changes too.
We have steadily increased the core range of Rubber Matting products to include Checker Plate and Penny Matting, and whilst it would appear that Black is in fact the new, old and probably future Black, we are increasingly asked for Red, Blue, Green and Grey all of which are now stocked to varying degrees.
The Modular Matting introduced earlier this year has already found its way into a venue in east London which I darenít mention again for fear of being locked up in the Tower of London (is that another copyright phrase?) by angry pseudo dignitaries, and is finding interest in offshore applications (again darenít mention the company but you find them laying on the seashore, not pebbles!), and increasingly in Anti-Fatigue and Health & Safety applications.
So whatís next you are no doubt all pleading to be told? How can Rubber Matting possibly be even more exciting you ask? Well thereís no need to stand around looking wistful, worrying about the strain itís causing your back and legs; double checking if there is a trip hazard and potential claim initiated by a dubious no win no fee service provider, the next phase in MacLellan Rubber Matting products is just around the corner and it ticks all of the boxes.
We are working to deliver a comprehensive range of Rubber Matting products for use in Industrial, Pharmaceutical, Technology and Commercial environments. Anti-Fatigue; Cushion Backed; Oil Resistant; ESD; Anti-bacterial; Chemical Resistant; Fire Resistant; Ergonomic; does anyone feel a song coming on? No?
Keep a look out for the e-shot announcements; updates on the website and more importantly next blog.
This is the second in the series and here I thought we should deal with another common and perhaps slightly more technical issue when evaluating Rubber Sheet materials, and answer the question:
Why do I always get variations in the Hardness of my material?
Letís start with the basics - you need the right equipment for the job. Pushing your nail into a material or trying to compare one piece of rubber with another by pulling and twisting just isnít going to work.
There are a variety of manual and electronic Durometer devices available on the market. Manual, hand held devices tend to be most common as they are easy to use and are relatively low cost.
Hand held digital hardness meters were increasingly popular a number of years ago but most of the main manufacturers have since ceased supply due to the increased level of inaccuracies which became apparent in their use.
Electronic devices can sometimes accommodate testing for a range of products including plastics and metals.
MacLellan Rubber doesnít recommend any particular manufacturer but Iíve included images of typical products below.
Equipment should be recalibrated frequently. Most manual units are spring loaded so performance will deteriorate over time. Most equipment is now supplied with reference blocks to enable regular recalibration.
So what about the mechanics of measuring Ė itís simple. Isnít it?
The first thing to bear in mind when measuring hardness is that there is a general tolerance for many standards which typically allows -4 and +5 Degrees on the stated figure. Therefore it is perfectly acceptable for a 60 Shore A material to measure 56 or 65 Shore A and still be within tolerance.
There are different Shore Hardness scales used with rubber, specifically Shore A and IRHD, which many people assume are interchangeable but are not. MacLellan works to Shore A as detailed on our data sheets. If you require any information on the various hardness scales used in polymers you can Ask George on our web site.
Any measurements need to be taken in the right conditions. If it is too cold the material may measure harder, to hot and it may measure softer. Our experience is that this variation can be as much as 4 degrees, which is enough for someone to think the material is out of specification.
We recommend an ambient temperature of between 15 and 20oC. Additionally the material should be flat, any curvature will affect the reading either but reducing the surface area upon which the Durometer is working or by increasing / decreasing the pressure on the indentation needle.
It is important to realise that most hardness meters will only work accurately with a minimum material thickness of 6mm. If your material is thinner then you should ply this up to gain a true reading.
Also a true hardness reading for a material is determined at a point no less than 13mm in from the edge of the material- you would not believe the number of hardness queries we get against rolls that have never been unwrapped.
You should refer to the manufacturerís data sheet for their hardness figure, which should always show the mean figure. Different manufacturers offer different hardnessís for standard products and as such canít always be compared. Typically you may have one manufacture quoting 70 Shore A as their mean hardness +5 / -4, and another manufacture offering a product with a mean hardness of 65 +5 / -4. In theory both could be considered as a 70 Shore A material but in fact you have a potential range of 61 Ė 75 Shore A which may not be acceptable to your customer.
Lastly the method of testing, typically ASTM D2240 or BS903 A26, requires a short pause between the initial indentation reading and achieving the actual reading. This pause period allows up to thirty seconds for the material to relax against the indentation needle. You may see that your Hardness Meter drops as much as 5 degrees in this period to give a true and accurate reading.
We also need to remember that vulcanised polymers are mixed and cured in large quantities and only batch tested. There will unquestionably be variations in physical characteristics within a single production batch simply down to this fact. It is therefore entirely consistent for the hardness of a roll of rubber to vary within the top and bottom limits across its surface and even from one side to another and consequently is not faulty. Some standards allow three reading to be taken within a defined area and the average considered as the hardness figure.
Below I included a summary of the various hardness scales and what materials they can be applied to and below that a number of the more widely recognised hardness test standards which you may come across.
Everyone has an opinion about the Rubber Sheeting they buy and not simply that itís too expensive or not as good as Ďin the old daysí. Common questions we are asked in relation to Rubber Sheeting materials involve hardness queries, thickness tolerances and surface finish. The problem in trying to respond too many of these issues relate to variances in methodology, equipment available, individual interpretations of standards and quite simply custom and practice.
I thought it would be a good idea to ruminate through a blog on these issues and more importantly publish how MacLellan Rubber assess, measure and approve its own materials, with a view to these ruminations being a guideline for Storage; Hardness Measuring, Thickness Measuring and Handling, many of which relate to British and European Standards and where appropriate common sense.
I may not be right about everything but in publishing this and follow up articles we hope to clarify some of our customers concerns and remove some of the areas of conflict that can so easily arise.
The Customer is of course always right, itís just that they are not always correct!
I thought we should start with one of the most common issues which impacts on quality concerns which is the Storage of Rubber Sheeting and Rubber Matting
The principal thing to remember is that we are dealing with a vulcanised rubber which is an elastic product and susceptible to changes in the physical properties if storage conditions vary. Areas which are readily affected by incorrect storage and handling are hardness, flexibility, surface cracking and deterioration. Long term implications of incorrect storage and handling may be a reduction in performance characteristics such as elongation, tensile strength and compression set
These are covered by standards such as BS3734, ISO 2230 amongst others but the main points to follow are:
Store in a Cool environment Ė Optimum temperature will be 10į C, but shouldnít be below 0į C or exceed +30į C as the polymerisation within the material may start to break down. Where temperatures do drop below 0o C you should allow the material to warm slowly before commencing work on it.
Store away from Direct Sunlight Ė Exposure to UV will cause materials to harden and crack.
Material should be wrapped in an opaque, non-reactive packing material for best practice.
Store away from Heat Sources Ė Extreme Heat will cause material to soften and degrade.
Maintain Humidity - A relative humidity between 45 and 75% is optimum. Low humidity may cause material to harden and crack.
Store in a Relaxed Condition Ė Rubber Sheet may take on a compression set or deformation if stored incorrectly or under load. Ideally store standing on its end rather than lying on its side. Re-roll the material so that it is tightly coiled and retains some rigidity. If the material has to be laid on its side then avoid putting too much load on top which will crush the material and may effect some compression set.
Despite following these recommendations we need to remember that vulcanised Rubber Sheet still has a defined Shelf Life after which there can be no expectation that it will perform to anything like the stated characteristics such as elongation or tensile strength.
ISO 2230:2002 amongst other standards categorise materials into one of three groups to determine their initial shelf life when stored correctly and an extension period that can be agreed if the material is show to be in good condition. These are summarised accordingly:
For a full list of Polymers by Classification please refer to our website.
Note shelf life is dependent upon correct storage conditions and cannot be taken for granted. Incorrect storage conditions may reduce the shelf life by as much as 50%.
As a final point in this blog, I should say that all of the team at MacLellan Rubber are regularly updated on changes to standards that affect our business and are willing to provide advice and recommendations where appropriate.
I hope that this first instalment gives all of those with the time and inclination to read it something to consider, whether or not you agree with the statements made. If you do, we look forward to working with you. If you donít I guess we will potentially have more discussions in the future.
Interesting article in Aprilís issue of Works Management regarding stock holding of raw materials and where in the supply chain it should be held.
With so many theories such as Just in Time and Lean Manufacturing exported from the Automotive Industry now so prevalent in many manufacturing business the answer should be obvious.
However many businesses have found that moving the stock holding responsibility down the supply chain is a train crash waiting to happen particularly in such a volatile environment where customers upstream are unwilling or simply unable to give accurate forecasts for future demand. Add to this the supplierís challenges of dealing with long manufacturing or restocking times, accommodating quality issues that may arise and the cost of committing significant levels of cash to a higher inventory and the whole process becomes less attractive for all parties involved.
There is evidence that manufacturers who have imposed a system because they donít want the immediate cost of stockholding have experience increased costs in others areas such as quality control and line stoppage as supplierís loose interest in their business due to the increased costs of doing business and the resultant lower margins.
The message has to be that collaboration throughout the supply chain is essential if any of this is to work efficiently and everyone is going to be happy and making money.
MacLellan Rubber has considerable experience in working supply chain solutions with its customers. With over 1000 tonnes of Rubber Sheeting and Rubber Matting either in stock, manufacture or in transit from our production plants, we service customers by projecting demand 12 Ė 16 weeks forward and provide both onsite and consigned stock holding to customers where appropriate. Stocks are also available to meet the immediate day to day changes that always seem to occur.
If you would like to discuss how MacLellan Rubber can work with you in delivering real cost benefits against your Rubber Sheeting and Rubber Matting products supply, contact your Account Manager or our office.
For the full article click here