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| Frequently Asked Questions |
| Does O&P Enterprises offer a volume discount for their plastics? |
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| Yes, we do offer discounts based on higher volume purchasing. The discount is determined by evaluating each customers unique purchasing habits. |
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| What would O&P Enterprises charge to cut plastic to my required sizes? |
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| We do not charge to cut your plastic to your required sizes. |
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| Is the quality of plastic used to fabricate O&P products really that important? |
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| Yes it is. For many years when plastic was first introduced to the O&P marketplace they were using plastic that had not been stress-relieved. That material also had a lot of regrind in it instead of being virgin material. That grade of plastic is primarily used for industrial uses where quality is not an issue. For medical purposes you want the material to be as stable as possible in order to have successful pulls – the first time. O&P Enterprises only sells stress relieved virgin material. |
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| Is there really a difference in stress relieved and non-stress relieved plastic? |
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| Yes. Chemically these materials are the same and are manufactured the same. But stress relieving of plastic is an additional process that is done after the material has been manufactured. The sheet is subjected to a great deal of heat, pressure and controlled cooling. This helps reduce the “memory” so that the material is more dimensionally stable yielding more consistent pulls with fewer problems. |
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| What is the correct vacuum capacity for effective O&P vacuum forming? |
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| The ideal minimum vacuum pressure capacity would be 27”Hg (inches of mercury) – which is equivalent to 13.5 PSI. However, most vacuums will vary between 20 and 27”Hg. One of the variables that can affect the amount of vacuum you can effectively get is the elevation from sea level where you are located. (Subtract 1”Hg for each 1000’ above sea level. An example would be if a pump normally reaches 27”Hg at sea level, then in Denver at 5000’ above sea level, it will only get 22-23”Hg.) The key to reducing other variables is to keep your vacuum and all connections, hoses, etc. well maintained so that it always functions at the highest capacity possible. The maximum capacity should be maintained during the entire forming process for best results. |
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| Do I really need a surge tank? |
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| A surge tank is an excellent addition to your lab. It will permit longer constant vacuum and will even out pulsations of the vacuum pump. It will also increase the effectiveness of multi-station systems and smaller vacuum pumps. The volume capacity of your surge thank should be at least 6 times the total displacement of all areas to be evacuated at one time. |
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| How do I know what is the recommended oven temperature for heating the different plastics? |
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| The first thing you should do is check with the supplier that provides your plastic. Different manufacturers may recommend different temperatures for their plastics. You will find our recommended oven temperatures in our catalog. |
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| Is it better to pull the heated plastic over a warm/hot mold or a cool/cold mold? |
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| There would be far fewer problems and failures if hot plastic was always pulled over a warm or hot mold. When you place hot plastic on a cool or cold mold one side of the plastic is shocked so that the pull is going to be slightly less stable than when it is pulled over a warm or hot mold. |
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| How do I determine the length of time to leave my plastic on vacuum? |
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| The material needs to be held in place until it is properly cooled. You should be able to put your hand on the material and leave it there with no discomfort before removing vacuum. Remember that cooling takes longer than heating. A very loose rule of thumb is if you pull the plastic over a cool/cold mold leave on vacuum no less than twice as long as it took to heat it. If you pull it over a warm/hot mold then leave it on vacuum no less than tree times as long as it took to heat it. |
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| What causes my plastic to blister or get bubbles when heated? |
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| Trying to heat the material too rapidly is one cause – first make sure you’re using the recommended oven temperature for the specific plastic. If you’re using the correct oven temperature, then reduce the heating time.
Some materials (i.e., TPE, Polycarbonate) will absorb moisture and that will cause this problem. It’s best to keep these materials in their original packaging to reduce exposure to moisture and they may function best if pre-dried. Contact your supplier for directions. |
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| If my material does have bubbles or blisters after it is heated, is it okay to use it? |
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| That would not be a good idea. Any place there is a bubble formed in the plastic will be a potentially weak spot where it could fracture. This is especially true of PETG (aka: Vivak®, DurrPlex, Clear Co-Polyester, DiaClear, Thermocheck), and patients should not be put in a weight bearing device made of this material. |
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| What causes the product I’m forming to have poor detail? |
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One reason is that the material was not heated to the proper forming temperature. Make sure you’re using the correct oven temperature then heat for the appropriate length of time.
Also make sure your oven is heating evenly. Hot/cold spots will result in uneven heating and likely result in poor detail.
Another reason is insufficient vacuum. Make certain your vacuum lines are the appropriate size, aren’t clogged or leaking and that it is functioning properly. See previous question above that deals with the subject of proper vacuum capacity. |
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| When heating my plastic in a frame, what causes it to have too much sag? |
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| This is generally a result of improper heating. Make sure you are using the recommended oven temperature for that specific plastic and that you aren’t leaving it in the oven too long. (If you have problems with your plastic tearing & falling out of your metal frames, try using strips of plastic as spacers between the frame and your plastic.) |
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| What causes my plastic to have uneven thicknesses – too thick in some places, too thin in others? |
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You could have uneven heating of your material. Check your oven for any cold spots.
Too much sag can make it difficult to get an even pull with consistent thickness. Make sure you are heating at the correct temperature and for the proper length of time.
A cold mold can cause this. Try heating your mold before pulling the plastic to eliminate shocking the hot plastic when pulled over the cold mold. |
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| I pulled a Super Flex socket over an old mold and it stuck to the mold. What caused that? |
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| Your mold had probably gotten too dry. When pulling Super Flex over an old mold you can insure that this doesn’t happen by placing a wet towel over the mold for a while so that it can absorb the moisture, or dip the mold into a bucket of water until the plaster is re-hydrated. (You should never pull any flexible material over a dry mold.) |
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| What causes my device to sometimes fracture when removed from the mold? |
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There are a couple of possible reasons for this. The first is that the material was heated beyond its upper forming limit (overheated.) Again, make certain you are using your suppliers recommended oven temperature and that you are not leaving it in the oven too long.
Another reason is basically the opposite – the material was pulled when the material was below the recommended forming temperature. Once again make certain you are using the correct temperature and heating time. |
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| What causes my device to spread when removed from the mold? |
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| The primary reason this happens is because the device was removed from the mold too soon or was not left on vacuum long enough. Even if it is left on the mold overnight, or longer, if it was not left on vacuum long enough initially, it might still spread. Refer to questions above dealing with the issues of how long to leave on vacuum and proper vacuum capacity. |
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| I notice that O&P Enterprises carries a wide range of colored plastics. Isn’t colored plastic more unstable and difficult to work with than the natural plastics? |
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| That was an issue in years past but is not the case today. The colored plastics are manufactured in such a way that they will perform equally as well as the natural plastics. The key is learning the proper time for heating, which can vary from color to color. Once you determine this, you can enjoy providing pleasing choices to your patients. |
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| I was pulling a socket using Linear Low Density Polyethylene (aka: Modified Polyethylene) and it tore. What caused that? |
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| Your material was likely not heated to the recommended forming temperature or was not heated long enough. |
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| Should I use some kind of wicking material (i.e., nylons) on my mold when pulling Super Flex or Super Flex with Silicone? |
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| You can, but you need to be aware that the nylon will melt into the hot plastic. It would be better to use a PVA bag as a separator, or spray the mold with silicone. |
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| How do I determine which material will function best for a particular purpose? |
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This decision is usually made by the practitioner based on the specific requirements of an individual patient. However, a few questions that should be considered are:
How long will the patient be wearing the device?
How important is the appearance of the device?
Is this a weight bearing or non-weight bearing use?
What are the environment/elements that the device will be exposed to in use?
Will it be easy to form and finish for the specified use?
What is going to be the most comfortable for the patient?
And below are some general suggestions of use for specific materials: |
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| POLYPROPYLENE |
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Body jackets, splints, AFO’s, definitive sockets |
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| CO-POLYMER |
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Body jackets, splints, AFO’s, definitive sockets, helmets |
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| LOW DENSITY POLYETHYLENE |
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Body jackets, splints, pediatric AFO’s, flexible interfaces (sockets)
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| MODIFIED POLYETHYLENE |
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Body jackets, splints, pediatric AFO’s, flexible interfaces (sockets), foot orthotics |
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| HIGH DENSITY POLYETHYLENE |
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Definitive sockets, UCB’s |
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| PETG |
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Evaluation interfaces/check sockets, sports masks, burn masks, upper limb (HO & WHO) orthoses where cosmesis is important |
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| KYDEX |
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Body jackets, neck braces, upper extremity orthoses and custom seating |
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| TPE |
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AFO’s & UCB’s |
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| SURLYN |
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Evaluation interfaces/check sockets, flexible interfaces (sockets), spinal & upper limb orthoses, helmets & burn masks |
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| SUPER FLEX |
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Flexible interfaces (sockets) for both upper & lower orthoses, flexible liners for AFO’s, check shoes, foot orthotics |
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| SUPER FLEX W/SILICONE |
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Flexible interfaces (sockets) for both upper & lower orthoses, flexible liners for AFO’s, foot orthotics |
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| OPCHECK |
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Evaluation interfaces/check sockets |
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