FAQ - Venting
- In what size of mould will these vents work?
-
The Short Answer:
We suggest that you start by testing our vents in moulds of not more than 150 litres in volume. As your understanding of the product grows, you can then try them in larger moulds.The Longer Answer:
This is a very simple question which has a reasonably complex answer. One of the issues is that our vents will provide a mild over-pressure. Naturally, as we do not have an intimate understanding of the moulds in your factory, we are unable to guarantee which ones will be able to withstand this pressure. What we can tell you is that this pressure is going to be no worse than the pressure created when a mould is run with a blocked vent.We have observed a mould of approximately 2,000 litres being run successfully with a single 13mm (1/2”) Supavent. Some much smaller moulds, however, have not been successfully moulded with Supavent. This can be the case in large, flat moulds with kiss-off points that are barely close enough together. To help you understand the pressures that are developed inside the mould during the moulding process, please refer to the calculators that we have developed in the technical resources section of the site.
The pressures created are not usually a problem for smaller moulds (less than 150 litres). As we are not familiar with your unique moulds and factory conditions, we are not able to provide you with a definite figure.
Smartvent has been developed in an effort to reduce the amount of pressure developed inside the mould. This will be useful in moulds, such as those with kiss-off points, which require a gentler pressure profile. This design feature in Smartvent will also make it suitable for larger moulds as the size range develops.
Even Longer Answers
You can gain even more information by contacting your local distributor, or by contacting La Plastecnica Ltd directly at venting@laplastecnica.co.nz. We speak English and Italian. - How much do they cost?
-
If you are interested in the cost of the product to your existing system, please refer to the cost-benefit analysis file in the technical resources section.
If you are interested in prices, however, please refer to one of our distributors. If there are no distributors in your area, please contact us directly.
- For how many cycles will our vents last?
-
The life cycles of our venting products are dependent on the conditions to which the vents are exposed. Although our products have been designed to work within the rigours of the rotational moulding environment, they are technical products and need to be treated with respect.
Factors which will affect the life cycles of the vents include:
- Cycle times, PIAT and oven temperatures
- Insulation and the vent mounting method (e.g. PTFE collar use)
- The vent’s position within the mould and the weight of the powder pool
- Operator handling
- The size of the mould
As a rule, you can expect our venting products to last for between 20 and 60 cycles, with some vents lasting for up to 250 cycles.
- How can we make the vents last longer?
-
Cycle Times or Temperatures
The polymer from which our vents are made oxidises at high temperatures. Therefore, the more you can reduce your oven temperature or cycle time, the better. It may surprise you to find out that by using our vents you may be able to reduce your cycle times or temperatures, but it is true!Depending on your current venting method, our vents are likely to increase the pressure in the mould during the final stages of the cooking process. This speeds up the sintering of the polymer, and therefore reduces the Peak Internal Air Temperature (PIAT) required in order to produce a “good part”™. As a first step, we recommend that you aim for a PIAT of 160oC when you mould with our vents, as we have discovered that this produces a product cosmetically similar to a part moulded with a PIAT of 180oC and an open vent.
In order to achieve a PIAT of 160oC, you will often have to reduce either the oven temperature or the cycle time of the part. If you are trialling our venting products with a single mould on a multi-cavity spider, it is wise to place our vent in the product which produces the least well-cured part – on the arm, if possible.
Insulation
Mounting the vents in a PTFE (Teflon®) collar can increase the life of our venting range. Some designs are included here. PTFE collars are especially important in the use of Smartvent products.Although our vents can be used against the line of draw, they will last longer if they are used with the line of draw or are removed prior to part extraction. Similarly, vent life will be reduced if they are mounted in a threaded cap that is unscrewed during each extraction.
Positioning in the Mould
Operators can improve the effectiveness of our venting products by ensuring that they are not located in the middle of large, flat surfaces. As the moulds are rotating in the oven, the powder pool may move at high speed. If it is moving at a sufficiently high speed when it collides with one of our vents, then it may distort the vent. This may cause powder to be released from the mould. Place our vents near a wall or some other feature to protect them from the full force of the powder pool.Operators
Finally, we have had some customers report very short life cycles (less than 10 cycles) for our venting products. All their temperatures were correct. After observing an entire cycle, however, we discovered that the operators were cleaning the inside of the vents (which is usually unnecessary), and tearing the vent in the process. These vents have been designed to be tough, but they are also technical products and need to be treated with respect if they are to last. - Where can I get these vents?
-
We have a number of experienced international distributors who will minimise shipping costs to consumers. Distributors can be located here. If you have any questions or if you do not have a local distributor, please feel free to contact us directly.
- What do they look like when they fail?
-
The most common problem with our vents is an extension or tear in one of the openings in the vent. In Supavent, the tear normally extends from the slit towards the “mushroom” end of the vent. A tear starting at the other end of the slit is normally due to operators checking the vent between cycles (not normally required – see "How can we make the vents last longer?"), which should be discouraged. You will usually see Smartvent fail due to the loss of a “petal” from the top dome.
- Are they up to our regulations?
-
Our venting products are certified to EU RoHS standards. If you require confirmation of other standards please contact us or your distributor directly.