Frequently Asked Questions

Over - moulding     Macromelt     Moulding Process    Moulding Machines    Mould sets

Frequently asked questions on over - moulding

1.       Can you over-mould a PCB with surface mounted components?
Yes, we have over-moulded hundreds of different PCB’s without damaging boards/components or reflowing solder. Tests show that material injected at 218°C (425°F) typically will cool down to less than 150°C (300°F) by the time it reaches the board. 

2.       Is the final component distorted in any way with this process?
No, not if proper design guidelines are followed. (Uneven encapsulation such as a very thick material section on one side of a PCB with a thin layer on the other could result in warping). 

3.       Will the part maintain dimensional stability after moulding?
Shrinkage ranges from 1 to 1.5% for the different Macromelt materials. 

4.       How can air bubbles be avoided in the final moulded part?
Ensuring that the mould-set is vented correctly and optimising the injection profile is the key to avoiding air bubbles. Densely populated circuit boards may require several steps in the injection profile to avoid any “shadow effects” behind components. We would typically start by optimising flow with translucent materials to detect where voids occur and then change to black materials for production. 

5.       Can batteries be over-moulded without reducing their effectiveness?
Many types of batteries have been successfully over-moulded with Macromelt. However, simple prototype over-moulding for a particular battery is recommended before starting full-scale production. 

6.       Which wires, cables, circuit boards and solder masks do these materials adhere to?
Macromelt® adheres well to most substrates including PVC wires and PCB’s. Henkel Corporation offers adhesion testing of their Macromelt® materials on any specific substrates; this type of testing will identify the most suitable material for a given application. 

7.       When should this technology be considered for grommets and strain relief moulding?
The adhesive properties of the Macromelt® material will offer great seal and strain relief to most wire and cable materials. When true strain relief is needed especially for sensitive cables/applications such as Cat 6 patch cords and connectors, the Macromelt® materials are superior. 

8.       Are over-moulded parts water proof?
Over-moulded components will typically meet or exceed IP 67 rating for the type of environment it is capable of operating in. This means they are dust tight and protected against the effects of immersion. The selection of Macromelt® material grade is critical as there are different degrees of water resistance. 

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Frequently asked questions on Macromelt® Materials

1.       What is Macromelt®?
Macromelt® is group of high performance polyamide adhesives. They are essentially reformulated hot melts with strong adhesive properties designed specifically for insert moulding of electronics. Macromelt® is a thermoplastic material that cures simply by cooling. It does not cross-link nor does it release any toxic fumes. 

2.       What is the minimum tolerance that the Macromelt‚ materials can hold?
Tolerances of 0.1mm (+/- 0.004”) can be met on smaller components. 

3.       Can material regrind be used?
For applications where adhesive properties are critical, regrind should not be used. The regrind material will contain a small amount of mould release agent, which could compromise adhesive properties. Furthermore, the mechanical properties of the material will degrade some from repeated re-melting. For non-critical applications the runners can simply be thrown back into the melt reservoir without any regrinding. It is strongly recommended to confirm that components moulded from “regrind” material meet specifications. 

4.       How do Macromelt® materials compare to engineered resins economically?
Macromelt® rarely replaces traditional plastic materials directly. If a component can be moulded successfully with PVC, there is no reason to consider Macromelt®. If PVC moulding results in high scrap levels as a result of high injection pressure, Low-Pressure Moulding may be more economical as a result of reduced scrap. Typically, the Low- Pressure Moulding operation is an alternative to potting as it replaces several manufacturing operations. Over-moulding with Macromelt® is typically a single step process. When a component is over-moulded with Macromelt® there is normally no need for a separate plastic housing. The over-moulding material becomes the housing. 

5.       Who will provide technical support for the materials?
Henkel will supply material support. Application engineering and support such as prototypes and the development of moulding parameters will be supplied by Engineering Solutions Ltd. 

6.       What is the delivery time for materials?
The Macromelt® OM product line is manufactured in Europe and warehoused in the UK.  Henkel generally keeps about 2 tons of each material above forecasted volumes. Drop shipments from Henkel or Engineering Solutions customers usually take 5 business days form the point the order is made with Henkel customer service. Other Macromelt® materials (used for moulding) are also readily available. 

7.       How are the materials packaged?
Should they be dried prior to use? Materials are shipped in double walled 20 kg (44 lbs.) bags. The materials are nylon-like and will absorb some moisture from the air. The materials are shipped at the recommended level of 0.2% moisture and should be kept in an air-tight container after the bag has been opened. 

8.       What is the typical shrinkage of the materials?
Shrinkage varies during injection and can usually be controlled by packing the mould with pressure. The shrinkage rate 24 hours after injection is 1 to 1.5%, depending on the grade of material. 

9.       Do dyes and pigments added for color change the material properties?
Generally, there isn’t a dramatic change in properties (i.e. black versions of the products are similar to amber). The pigment is extruded into the amber Macromelt material. However, any colored material, which requires opacity (i.e. white), would need a significant quantity of inorganic filler, which will affect most of the properties. 

10.    What is the typical viscosity of the material?
Macromelt moulding materials typically have a viscosity range of 2500-5000 cP at 210°C (410°F). 

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Frequently asked questions on the Moulding Process

1.       How long is a typical injection cycle?
The moulding cycle is dependent on the size and material section thickness of the component. Typical cycle times range from 15 to 45 seconds. Multiple cavity mould-sets can be used to reduce the actual moulding drop rate. 

2.       What is a typical injection temperature for these materials?
Melt reservoir temperature ranges from 190 to 230°C (370 to 450ºF). Depending on mould-set design, this would typically correspond to cavity temperatures of 135 to 180∞C (275 to 355ºF). 

3.       Do the moulds need to be heated?
No, mould-sets are typically cooled to approximately 20ºC (68ºF). The Mould-man® series of machines require no direct mould-set cooling since the mould platens have chilled water circulating through them. 

4.       What is the lowest pressure that parts can be moulded?
2 Bar (30 psig) is typically the lowest practical pressure. For anything lower the runner and gate design become very critical. Injection pressures from 4 bar to 20 bar (60 psig to 300 psig) are typical. 

5.       How do you control the filling of the cavity?
The Cavist Mould-man® series of machines offer programmable injection profiles. A typical profile would consist of filling 90% of the volume into the cavity at relatively high flow rate and then packing at low pressure. Packing pressures are typically from 50 to 150 psig and such pressures will not over-pack a cavity. Packing is critical to prevent sink and voids as the Macromelt® material will shrink when they transition from liquid phase to a solid. 

6.       Are any special de-gating tools required?
No. 

7.       How are the moulds cooled?
The Cavist Mould-man® series have permanent water connections on the side of the machines. This feature allows you to run chilled water through the mould platens. Mould-sets are then cooled via the water-cooled mould platens. Typical mould temperature is around 20°C (68°F). 

8.       How do you ensure sealing of the component?
Selecting the appropriate Macromelt® material best suited to the application is the key to sufficient sealing of the component. Typically the best surface wetting of the component occurs with lower viscosity material at relatively high temperatures. Higher packing pressure may also help ensure surface wetting and sealing. The component design is also crucial. Low-Pressure moulding works best when encapsulating around a component versus filling into the housing. 

9.       Can a conventional heated screw and barrel type machine be used for moulding?
This has been accomplished a few times and unsuccessfully a lot of times. Macromelt has very low viscosity at the correct processing temperatures compared to engineering plastics. This low viscosity can cause the material to bleed backwards through the screw and essentially glue it together. Mould-man® machines use positive displacement gear pumps designed for lower viscosity fluids to inject the molten material into the cavities. 

10.    How much waste do you get with this process?
Typically the material in the runner and gate is waste. This can represent anything from a few percent to 35% for very small components. When runners can be recycled for less critical applications, the waste is zero. With hot runner equipment, most applications will have zero waste. 

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 Frequently asked questions on the Moulding Machine

1.       Does Engineering Solution Ltd provide start-up training for the Mould-man® machines?
Yes. Start-up and training typically takes 2 to 4 hours depending on the number of operators. 

2.       Who will provide maintenance and user support for the machines?
Detailed maintenance guidelines are supplied with the machines and it is strongly recommended to set up scheduled maintenance. Keeping the melt reservoir clean is the single most important step towards success with this technology. Engineering Solution Ltd and Cavist Corporation will also be available for support. 

3.       Is the gear pump on the Mould-man® machines designed for the shot or does it work with a PLC profile?
The gear pump motor is run through a variable frequency drive with a PLC control. The Mould-man® series offers programmable/multi-step injection profiles. 

4.       What is the delivery time for machines?
Typically 12 weeks. 

5.       Are there demo units that can be leased for prototyping?
Prototyping is typically performed at Engineering Solution Ltd facilities. Leasing equipment is possible – please contact Engineering Solution Ltd for details. 

6.       How many parameters will need to be set prior to moulding?
6.1. Installation of the mould-set/setting of zero (closed mould-set parameter)
6.2. The ejector system is activated if applicable
6.3. The injection parameters including temperature, pressure, injection time and cooling time are set.
Including the installation of the mould-set, the complete set-up typically takes less than 15 minutes. When a mould-set is run-in for the first time, extra time must be allowed for optimization of parameters. 

7.       Will a special technician need to be trained in setting up the machine?
All moulding parameter entry is via the touch screen. The training for this will take no more than 1 hour and is also fully detailed in the operations manual. 

8.       What features are on the PLC controller?
The PLC controls temperature of reservoir, manifold and hose, clamp operation, injection cycle including profiles and pump speed (VFD), ejector operation and some safety functions. All parameters are entered through the simple touch screen menu. 

9.       What are the more frequent maintenance items on the equipment?
Most problems are caused by insufficient upkeep of the melt reservoir. If the melt reservoir is not cleaned on a regular basis, charred material will build up on the fins, reducing the heat transfer to the material. This can lead to “short shots” (incomplete over-moulds) and various blockages. If the material is left in the reservoir for days at high temperatures, it will get more viscous and eventually not flow. The melt filter must be replaced as per the maintenance guidelines. The injection nozzle and the pump seal will require replacement periodically. 

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 Frequently asked questions on the Mould sets

1.       What are the best materials for the construction of the moulds?
7075 Aluminum is well suited for mould-set manufacturing. Aluminum offers excellent heat transfer (i.e. short cycle times). Aluminum mould-sets are relatively soft and care must be taken not to damage the cavity surface. If the component to be over-moulded has steel or hard glass filled components, it is recommended to have steel inserts in this area of the cavity. This is generally required when moulding connectors. Mould-set can also be manufactured from tool steel such as P-20. It may be required to cross drill steel mould-sets to ensure sufficient cavity cooling. 

2.       Can the mould be plated to eliminate mould release?
The Macromelt® materials have strong adhesive properties and tend to stick to most surfaces. It may be possible to use some coating for permanent mould release, but we cannot recommend any specific coating systems at this time. 

3.       What kind of mould release is recommended?
After extensive testing of a wide range of mould release agents, one product has shown superior performance. Mono-Coat E-255 from Chem-Trend Incorporated.  We do not recommend the use of Silicone based release agents when over-moulding electronic components. Silicone can migrate over time resulting in partial electrical insulation and non-functional components. 

4.       What type of flow analysis is done prior to mould design?
None typically. However, existing software packages for mould flow analysis can be used for this technology as long as material viscosity is taken into account. 

5.       What are the maximum dimensions for a mould-set for use on the Mould-man® ?
Mould-man® 8000: Maximum 200mm (8”) wide by 150mm (6”) deep. Mould-man® 8100 / 8200 / 8300: Maximum 250mm (10”) wide by 200 (8”) deep. 

6.       What is the delivery time for mould-sets?
Typically 6 to 8 weeks when purchased from Engineering Solution Ltd. 

7.       Are multi-cavity moulds practical considering the single station machine only has 1 ton clamping force and the shuttle and rotary machines only has a maximum of 5 ton clamping force?
Multi cavity moulds are normally used for all production moulding. 1 ton of clamping force may sound limiting, but with packing pressures rarely exceeding 10 bar (145 psig) this will normally allow for cavity cross sectional area of at least 80 square centimeters (12 square inches). 

8.       Will a moulding profile be pre-determined for mould-sets provided by Engineering Solution Ltd?
Yes, any mould-set from Engineering Solution Ltd will be documented so that all moulding parameters can be entered directly. Some minor fine-tuning may be required as a result of different ambient conditions. 

9.       Are the gates on the mould much different than those used in traditional engineered plastics?
Typical gates are 2mm (0.080”) diameter and 0.5 mm (0.020”) long. A tapered design is normally recommended to ensure the gate brakes consistently from the component without any cutting. 

10.    What would be the price range for a typical production mould-set? Prototype mould-set?
The price range for production mould-sets will vary widely depending on number and type of cavities. Four-cavity mould-sets for single station machines will typically range from £5,000 to £10,000. We can offer prototyping services (where the mould-set fixture remains the property of Eng. Sol) for £1,750 to £2,500 which would include 10 to 50 completed parts for testing. For a more exact details and pricing please call us.

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Over - moulding     Macromelt®     Moulding Process    Moulding Machines    Mould sets