General
Question: Since when does PRIAMUS SYSTEM TECHNOLOGIES exist?
Answer: PRIAMUS SYSTEM TECHNOLOGIES was established at the beginning of 2001. Most of the
employees however have been working in this branch since more than 10 years and have experienced the
technical developments during this time in the hardware as well as in the software area.
Question: Who should I contact in case of a problem?
Answer: One of the merits of PRIAMUS is its experienced employees in the field of plastics processing, in
measuring technology and first of all in the combination of both areas. Please check the section „About us“ on
this homepage to find the current list of our partners as well as information on PRIAMUS. Or contact us through
our e-mail address info@priamus.com.
Question: Can I determine the sensor position in the mold respectively in the cavity by myself or do I always
need to ask a specialist?
Answer: The positioning of sensors in an injection mold is subject to some very few rules of thumb depending
on the type of sensor used (pressure or temperature).
A cavity pressure sensor should be placed near the gate, because here most information will be obtained due
to the pressure loss between the gate and the end of fill (higher pressures and longer active time near the
gate). If problems require this, cavity pressure sensors can be placed at any position inside the cavity
(exception: opposite the gate!).
Temperature sensors however should be placed near the end of fill, because at this position they can be used
in several respects: e.g. for automatic switchover to holding pressure, for the monitoring of complete cavity fill,
for the balancing of multi cavity hotrunner molds and for process control.
Question: What is the advantage of using sensors inside an injection mold?
Answer: Instead of using machine signals with the help of „in mold sensors“ the quality of a molded part itself
can be determined – and therefore be monitored, controlled and documented. I.e. that a machine independent
quality assurance can be achieved using „in mold sensors“.
Question: What do I need to do in order to document the molded parts?
Answer: It is not the point to collect as many data as possible, but to collect the right ones. PRIAMUS software
systems include all important documentation data for each respective application independent from the injection
molding machine used.
Question: Can I only purchase the components at PRIAMUS or do you offer services as well?
Answer: We do not only offer single components, but complete systems and solutions. This includes the
possibility to arrange, supervise and realize special projects.
Question: Can I order PRIAMUS products directly at the machine manufacturer?
Answer: Electronics devices such as amplifiers for instance can be purchased directly at most of the machine manufacturers.
Mold related products such as sensors must be purchased at PRIAMUS.
Question: Does the signal quality get worse when several extension cables are used behind each other? Does this influence the measuring accuracy?
Answer: Basically the frequency range of a measuring signal is being reduced with an increasing cable
length. This however is of no importance for all applications in injection molding (cable length < 20 m). In order
to avoid disturbances, we recommend installing extension cables in a way they will not be moved during the
process (not attached to moveable parts).
Question: Our parts are too simple, the technology is too expensive, this does not pay form y parts, we don’t
need a sensor fort his.
Answer: It is not only the high-tech parts which are subject to economical cost pressure. It is very common
that also cheap articles are only accepted y the customer when faultless quality of all shipped parts (100 %)
can be guaranteed. This however can only be realized with automated quality monitoring systems and part
containment options. Very often parts are not monitored and documented because of cost reasons but
because of product liability reasons (airbag connector, safety closures etc.).
Question: So far we have used competitive products which have been satisfactory. Why should we use a new
system supplier?
Answer:
- We focus on the latest technologies, e.g. charge amplifier electronics, linearized output signals for
temperature amplifiers
- New ideas have been realized, e.g. sensor and sensitivity detection, automatic hotrunner balancing
- Comprehensive consulting from simulation and process analysis to monitoring and control systems
Question: We only manufacture for our own use, we don’t need to document anything.
Answer: It is an economic principle to manufacture as inexpensive as possible but with the best quality
achievable. Especially in case of own needs the costs must be considered in particular. An optimized process
however can never be achieved without using the appropriate measuring means.
Question: We do not have molds for continuous operation and our quantities are relatively low. The
equipment does therefore not pay.
Answer: PRIAMUS has attached great importance to modularity during the development of its products. It is
definitely possible to equip a machine in a way that many different molds can be monitored and controlled with
the same system. For this purpose there are both mobile and stationary systems available up to plant wide
networked systems.
| back to index |
Cavity Temperature
Question: What is the advantage of temperature measurement inside the cavity?
Answer: Cavity pressure and mold surface temperature can basically not be replaced by each other. The
most important question which comes up is: Which problems can be solved with the lowest cost? It could be
one or the other parameter, or both parameters at the same time which will succeed. Example:
- A useful or even automated process optimizing in injection molding will not be possible without using
cavity pressure.
- However there are numerous applications for which the far less expensive measurement of the mold
surface temperature will be sufficient (automatic switchover to holding pressure, automated fill
balance, process monitoring etc.).
- Due to the p,v,T-behaviour, quality control can only be realized with both parameters together.
Question: The cable of my temperature sensor is broken. Can I repair it by myself?
Answer: If the cable is not broken directly at the receptacle sleeve, yes. We recommend to crimp both cable
ends together using a sleeve (crimped connection).
Question: Why should we measure temperature directly on the cavity surface?
Answer: Because at this position there is a direct and defined relation to the shrinkage of the molded part.
Question: Can I use this temperature information to control the mold surface temperature?
Answer: This signal can directly be connected to the temperature controller in order to control the mold
surface temperature.
Question: Can we do without pressure sensors?
Answer: For the balancing of multi channel hotrunner molds, yes. For many other applications, such as the optimizing of injection molds for instance, cavity pressure sensors have the same legitimacy as ever. For process control both signals will be necessary.
Question: Can we machine the front of PRIAMUS temperature sensors?
Answer: Basically no (only in exceptional cases and upon further inquiry).
Question: Are PRIAMUS temperature sensors available in larger dimensions?
Answer: PRIAMUS temperature sensors can be supplied with a sleeve. For details please contact PRIAMUS.
| back to index |
Cavity Pressure
Question: Many advantages of cavity pressure measurement are well known today. Are there further signals
which should be taken into account for quality assurance, or is this sufficient?
Answer: The quality of a molded part results out of the so called p,v,T-behaviour of the plastic melt. In other
words: how changes the pressure, the volume and the temperature of the plastic melt during the molding
process. In order to describe this process precise enough, basically two of the three parameters must be
known. Out of a practical view it is recommended to measure pressure and temperature although, depending
on the application and the problems, one of the two parameters may be sufficient.
The complete fill of a cavity can also be monitored with a less expensive temperature sensor, and this signal
could also be used for automatic switchover from fill to holding pressure. A comprehensive process control
can only be realized by using both measuring signals.
Question: Which cavity pressure sensor should I buy?
Answer: During the recent years some standard sensor dimensions have been accepted in the market and
proved their value in many applications. In many cases a sensor is being selected due to its size. In case there
is enough space available it does not make sense to use a miniature sensor, which usually is more expensive
and less sensitive.
A significant piece of news on the market is the PRIASEDTM system, which automatically detects the sensitivity
of the sensors. The equivalent charge amplifier takes automatically all necessary adjustments which simplifies
the industrial use essentially.
Question: The cable of my pressure sensor is broken. Can I repair this by myself?
Answer: Basically no. In the piezoelectric measuring technique highly insulating cables and plugs must always
be used in order to guarantee the required insulating resistance. Especially in case of cable repair there are
special measures to take. We therefore always recommend shipping the broken cable back to us for repair. We
also recommend to stock one cable at all times. This way you are able to exchange the cable once necessary.
Question: Do PRIAMUS cavity pressure sensors work together with amplifiers of other manufacturer?
Answer: All PRIAMUS cavity pressure sensors can be operated with charge amplifiers of other
manufacturers. Even PRIAMUS sensors with automatic sensitivity detection (PRIASEDTM system) can be
connected via adapter cable to amplifiers of other manufacturers. This however is not recommended because
these products can not detect sensor sensitivity automatically.
Question: Can conventional cavity pressure sensors be connected to PRIAMUS charge amplifiers?
Answer: Standard sensors of other manufacturers can be connected to PRIAMUS charge amplifiers. In this
case the charge amplifiers operate according to the conventional principle. I.e., automatic sensitivity detection
and range selection are being deactivated.
Question: What is the benefit of the adjustable charge ranges?
Answer: PRIAMUS charge amplifiers have a far higher charge range and a far higher number of switchable
charge ranges than comparable products on the market. In this way, a much wider range of applications can
be served (e.g. in the piezoelectric force measurement) and first of all a much better signal resolution can be
achieved.
It is for instance possible to use the same charge amplifier to measure a signal with very low charges and just
afterwards or alternating another signal with very high charges.
Question: Do all machine manufacturer use PRIAMUS charge amplifiers?
Answer: PRIAMUS charge amplifiers can directly be ordered at most manufacturer of injection molding
machines. Should this not be the case the amplifiers can be connected to existing interfaces using an adapter
cable. Please notice that some of these machine interfaces do not meet the latest state of technology. Some
manufacturer can therefore not provide full functionality.
Question: Is it possible to machine the front of cavity pressure sensors?
Answer: Cavity pressure sensors usually can be machined down to a depth of 0.5 mm at the sensor front
(grinding or spark erosion machining). In case of asymmetric machining however the sensor body should be
provided with an anti-twist-device. If you feel uncomfortable to take the decision please contact PRIAMUS.
Question: Can a cavity pressure sensor be positioned in the runner?
Answer: Basically yes, but in practice we recommend avoiding this situation, because the measuring signal
might not give any conclusion about the actual molded part (example: tunnel gate, film gate). In any case the
signal in the runner cannot be used for comparison after the sealing of the gate, which can be very important
regarding the shrinkage of the molded part.
Question: So far it did work without sensors. Why should we use a sensor now?
Answer:
- Scrap rate can be reduced
- Cycle time can be optimized
- Protection from mold damage due to inadmissible pressure exceeding
- Shorter mold setup times (e.g. by adjusting optimum holding pressure profiles)
- Saving energy cost
Question: Cavity pressure technology is nowadays not used anymore. This was used in earlier days when
the machine technology was not as sophisticated as today.
Answer: Unfortunately it is very often not taken advantage of the possibilities of this technology. A cavity
pressure signal provides much more information than just a maximum value for instance. In addition even the
best and latest machine technology provides no option which allows conclusions on the part quality. Machine
signals are set parameters while cavity pressure shows the result out of these settings.
Question: We have used this technology, however without success.
Answer: Cavity pressure technology provides many possibilities on one side, however it requires a certain
degree of experience in order to use these options. PRIAMUS SYSTEM TECHNOLOGIES offers seminars and
training which can be held on-site on request.
Control Systems
Question: Why should I control the injection molding process after I have done already a fill simulation?
Answer: A fill simulation serves first of all for the optimizing of a mold during its design phase, which is at this
moment an extremely effective help. Of course machine settings can be „calculated“ and predicted which helps
to optimize the process up to a certain point. During the actual production however nothing can replace the
measured process data in the mold.
We assume that the process permanently changes due to the ambient conditions. A simulation of the process
can therefore at best show a snapshot. In order to achieve a quality as constant as possible it is necessary to
modify the molding parameters permanently so as to compensate the respective quality variations in the molded
part.
Question: Can I reduce staff by using a process control system?
Answer: Process control systems for injection molding first of all serve to manufacture the required quality of
molded parts fully automatic within as narrow tolerences as possible. Process monitoring systems as well as
process control systems are always connected with a certain degree of automation which finally results in the
saving staff.
Question: Can I optimize any multi cavity mold with PRIAMUS Fill? What about family molds for instance?
Answer: PRIAMUS Fill balances the fill process of multi cavity hotrunner molds. The control principle used
cannot be applied for cold runners.
Family molds however can then be controlled respectively balanced, when the different gates have been
designed according to the optimum requirements. I.e. when due to the gate optimization a simultaneous fill of the
different cavities can be guaranteed.
| back to index |
Applications
Question: Why does a reference cavity pressure curve lead faster to a required part quality than using machine set data only?
Answer: The machine set data do not represent part quality at all. Even in case of two molding machines of
the same type and identical settings this will not necessarily result in the same part quality. Already a different
calibration of the machine controls leads inevitably to a different result. The only possibility for a quality related
mold setup is through cavity pressure and cavity temperature. If these signals are identical the same part
quality can be expected – independent from the set parameters of the machine.
Question: My machine control shows all values such as screw position and pressures and monitors them as
well. Why all of a sudden do I need a Tool Box in order to determine capabilities of the machine?
Answer: Every capability analysis is based on the quality of the molded part. Neither short term capability
(former machine capability) nor process capability can be calculated without quality information of the molded
part itself. In any case either cavity pressure or cavity temperature or weight or dimension of the molded part
must be used. Besides many other software modules the PRIAMUS Tool Box provides the option to analyze
capabilities on the basis of these signals in a simple way. Machine signals alone do not provide this option.
| back to index |
Process Monitoring
Question: Why is it not sufficient to monitor the existing machine signals such as hydraulic pressure?
Wouldn’t this be far less expensive?
Answer: Machine signals such as hydraulic pressure are far away from the actual molding process in the
mold cavity, and physically „cut off“ from the part quality. A molded part which gets only partially filled or which
shows sink marks cannot be detected by a machine signal such as hydraulic or nozzle pressure. Process
monitoring based on machine signals only is therefore not very useful.
Question: Do we need process monitoring at all? How does it calculate?
Answer: Time and again there are statements which question the justification of mold based monitoring
completely or partially:
- „Melt pressure in the nozzle is sufficient“
- „Sensors in the mold are too expensive“
- „Sensors in the mold are only necessary for high tech parts etc.“
Unfortunately these statements are not always based on fundamental process understanding. Example:
- The essential difference between melt pressure and cavity pressure is the fact that plastic melt in the
nozzle never cools down and solidifies, while exactly this happens inside the cavity. It is therefore no
relation between the melt pressure in the nozzle and the shrinkage of a molded part. There is no local
quality information (e.g. about sink marks) or information about molded parts which are molded by a
hotrunner system, based on nozzle pressure.
- The cost for effective quality assurance is „relative“. Looking at the effective savings including all
boundary conditions for almost all applications there are usually convincing arguments for the use of
monitoring and control systems. A simple program for the determination of such systems („cost benefit analysis“) can be downloaded under the menu option ‚Downloads’.
- It is not only the high tech parts which are subject to the economic pressure. It is quite common that
low cost products will only be accepted by the customer if flawless quality for all products (100 %)
can be guaranteed. This however can only be realized with automated quality monitoring and reject
separation.
Question: We control and monitor machine parameters which is more than sufficient. We also have
controlled machines and therefore we don’t need additional sensors in the machine.
Answer:
- Machine signals such as hydraulic pressure are far away from the actual molding process in the mold
cavity, and physically “decoupled” from the part quality. A molded part which is only partially filled or
which shows sink marks cannot be detected by the hydraulic or nozzle pressure. Process monitoring
of the machine signals only is therefore not very useful, especially not in case of multi cavity molds.
- The difference between melt pressure and cavity pressure is the fact that plastic melt in the nozzle
never cools down and solidifies which happens in the cavity. It is therefore no relation between the
melt pressure in the nozzle and the shrinkage of the molded part. Nozzle pressure cannot give any
information about local quality conditions such as sink marks or about molded parts which are
manufactured using a hotrunner system.
Question: My customer does not pay fort his technology, and if I need to pay myself I am not competitive
anymore.
Answer: The costs for effective quality assurance are relative. Considering the effective savings including all
boundary conditions there are convincing arguments for almost all applications to use monitoring and control
systems.
Question: We have never needed a monitoring system so far.
Answer: It is absolutely possible to run a production without quality monitoring. This however is not
recommendable because the final customer may ask for compensation at any time. And the burden of proof
must be done by the supplier. A part related quality assurance does not only improve the part quality, it also
documents it.
|
|
