PolyGlobal – Toolmaking

Posted on: 6th Aug 2020

PolyGlobal has over 30 years of experience in toolmaking. Their bespoke moulds facilitate the production of new and innovative solutions.

CAD Modelling & 3D Printing

Using Solidworks 3D modelling software PolyGlobal finalise production design from drawings, sketches, or samples. They have the software capability to work with file formats including:

  • STEP
  • IGES,
  • DXF,
  • Photoshop (.psd)
  • Illustrator (.ai)
  • Solidworks part (.sldprt)
  • Solidworks assembly (.sldasm)
  • Solidworks drawing (,slddrw).

The upfront cost of a new mould can be a big commitment, and it is crucial that the design is right. Utilising innovative 3D printing technology, they offer a high- quality prototyping service before final mould designs are sent to production.

3D printing enables them to produce complex yet functional shapes using less material than traditional manufacturing methods. Once prototypes are approved, final mould production begins.

Mould Design Considerations

There are a number of critical considerations to be taken into account when designing or modifying a mould and PolyGlobal’s technically experienced team can help you make the right decisions for your individual requirements.

It is important to consider your future production requirements as there is a direct link between cost effective tooling and the value of subsequent parts.

 Technical design considerations may include:

Side Actors : For parts where there are negative angles (details that are perpendicular to the axis of mould opening) side actors that move outwards as the mould opens may be necessary to allow the part to be de-moulded. These add to the moulds complexity and cost but are not always required. They are dependant on the design of the part and the rigidity of the moulded material and can sometimes be formed by negative steps in the fixed or moving halves.

Ejector Pins : Moulded parts, particularly those produced in hard materials such as nylon, will often need assistance in releasing themselves from the mould. Often, we will use ejector pins to push the part from the mould as it opens. This can sometimes leave small circular impressions in the moulded part.

Surface Finish Options

Once the profile of a particular mould tool has been completed, post polishing can be completed to achieve a more consistent or higher specification of surface finish. For certain parts polishing is also used as a way of improving the moulding process by reducing surface friction while demoulding. In general, most moving sides of a tool require a line of draw finish to aid the ejection of the plastic part off the mould.

The level of polishing on moulds is defined by the SPI scale. There are 12 grades of mould finish ranging from mirror perfect to dull with SPI-A1 being the highest specification.

PolyGlobal’s core options:

A1 – requires tooling to be produced in high grade stainless steel but produces a flawless finish

A3 – accepted as a more general good quality and gloss finish

B1 – low polish finish where all polishing grains will be removed but surface finish will generally appear duller than higher grades

B3 – removal of machining lines to produce consistent finish but polishing grain will be visible

D1-3 – shot blast for a textured/rough finish. Will vary depending on the suitability of shot material/size which is part and mould material dependent

Unpolished – machine marks from mould cutting visible on the moulded parts

In general, the higher the surface finish required, the greater the polishing time involved and therefore cost in tool production. Some polishing standards require the moulds to be manufactured from certain grades due to their reaction to polishing materials. Unless requested, PolyGlobal tooling quotes are unpolished by default.

As well as varying levels of gloss finish, there are a number of graining preparation options for parts that require a textured finish. This is usually a very specific request linked to the application of the parts or to replicate a more traditional material such as leather.

Due to the variance between materials, some moulded parts will appear slightly different to others even though the surface finish of the mould is polished to the same specification. For example, polypropylene components will appear glossier than TPE parts from the same highly polished mould. Where matching an existing finish or reaching a certain specification is critical, samples can be provided in advance of finalising tooling options.

Identification Marks & Engraving

As part of their bespoke service PolyGlobal can incorporate company branding, identification marks and product/part references into your mould.

These can be advantageous in stock management, rotation control, traceability, and the protection of intellectual property rights/ research & development investments.

Material or application specific marks are also available including Food Safe, Recyclable (with or without material identification), CE Marking as well as Registered and Trademark markings.

Mould Material Options

Injection moulding involves extremely high levels of pressure and as the production process lends itself to high volume production, the choice of mould material is an important consideration.

For high volume, high frequency production, particularly of harder materials, steel is an ideal material option. There are different grades of steel, so any after process finishing such as spark eroding or polishing need to be taken into consideration at the design stage.

Aluminium is a more economical alternative suitable for lower volume production runs  or full production runs using softer materials such as TPE’s and softer TPU’s.

Summary

Mould design and manufacture can be a complex process with many aspects to consider. Due to the manufacturing process involved it is important to clarify as many key characteristics of the moulded parts as early as possible such as critical dimensions and critical surfaces.  Equally, small changes in the design process can provide added value in later production that ensure moulded parts are as effective and successful as possible.

PolyGlobal has worked had to deliver a broad spectrum of options for its customers and encourages an open and detailed conversation with their sales team to ensure the right option is chosen, and in turn meet the requirements of the part’s application, usage and quality requirements.

Please contact their sales team if you would like any further information.

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