In this feature for Plastics News Europe, David Vink reviews some of the applications and technical developments on show at SPE's 2016 thermoforming conference and parts competition.
The European Thermoforming Division of the Society of Plastics Engineers held its 10th biannual thermoforming conference in March, at Sitges, along the coast from Barcelona in Spain. The event attracted 240 participants from 28 countries.
Reiner Albrecht, sales director at thermoforming machinery producer Illig Maschinenbau, reviewed the coffee capsule market. He said the capsule format accounted for 2.4% (or 10,000 tonnes) of coffee sold in Germany in 2012, and its market share increased 4% in 2015. Filter coffee had a 70.9% share in 2012, and instant coffee 3.1%.
Coffee capsule markets continue to grow and become more varied, but Albrecht also sees further future potential in tea, soft drinks and food capsules.
He said annual aluminium consumption for classic Nespresso capsules occupies the volume of 50 Statues of Liberty or 33 jumbo jets – “a negative eco balance due to high energy input and a low recycling rate”.
At NPE 2015, Illig said over 95% of worldwide coffee capsule production is on Illig's RDM K series machines, such as RDM 54K, 70K and 75K models, accounting for 1.5bn capsules/month being stacked on Illig PH stackers or STPL hole punching and stacker units. Albrecht said he favours multilayer barrier layer capsules over monolayer ones protected by additional barrier sleeves and said injected moulded capsules are heavier.
The thermoformed Nescafé Dolce Gusto PP/EVOH/PP capsule has an injection moulded dispenser fitted into a punched-out base hole. This 54mm diameter capsule and the 40mm Delizio capsule are produced on RDM 75K / STPL75b lines; Dolce Gusto in a 70 cavity (10 x 7) mould, Delizio in a 91-cavity (13 x 7) mould.
Examples of PP coffee capsules without base holes include 37mm Nespresso capsules thermoformed in a 108-cavity (12 x 9) mould, 47mm Lavazza Blue in 80 cavities (10 x 8), 68mm Tassimo with a pull flap in 54 cavities (9 x 6), 51mm Keurig in 91 cavities (13 x 7) and 40mm Delica's Delizio (in Switzerland, as Cremesso elsewhere) in 91 cavities (13 x 7).
RPC Bebo Plastik's development manager Jürgen Merbach said the late start at Interpack 2014 of thermoformed in‑mould labelling (IML-T) was due to earlier lack of standardisation and low flexibility. Bebo uses an “industry standard” modular design Illig RDM 70k machine for IML-T, favouring high flexibility for frequent changeover. This machine runs in Bremervörde, Germany, using moulds with up to 18 cavities, 20 cycles/min cycle time, enabling maximum 360 tubs/min (21,600 tubs/h) output.
Bebo's first IML-T customer from October 2014 was Bavarian soft and mozzarella cheese producer Goldsteig. It exploits IML-T for premium markets due to multi‑coloured photo-realistic designs in up to eight colours, achieving better finish and greater area coverage than with printing.
Bebo supplied more than 15 million IML-T tubs to Goldsteig within 2.5 years. A Norwegian dairy producer started using Bebo high-barrier IML-T tubs in May 2016, replacing metal.
Also within RPC group, RPC Superfos in Rushden, UK, started supplying IML-T versions of its monolayer PP SuperLight tub and lid in April 2014 for Cucina brand mozzarella cheese made by Francia Latticini (Gruppo Francia), as supplied to Aldi Süd stores. The labels meanwhile also cover the stacking rims as well. Wall thickness below 0.38mm means SuperLight tubs weigh around 50% less than standard 0.6-0.7mm Superfos tubs.
IML-T labels can be applied over embossed tub areas and high gloss and transparent labels are in development. The latter enable see-through window labelled tubs.
Erwin Wabrig of Kiefel said: “No more than 5-10 customers worldwide use IML-T in production conditions.” This is despite advantages such as downgauging and tub height changes without tool changes and generally lower investment than injected IML tubs.
He showed a comparison between injection moulding and thermoforming for a 500ml margarine tub. Injection moulding a 14g tub in a 6+6-cavity tool at 13 cycles/min, for 9,000 tubs/h output, compared with thermoforming a 12g tub in 18-cavity tooling at 18 cycles/min, for 18,000 tubs/h. Machine and tooling cost is lower for thermoforming the tub, at €2m, against €2.5m for injection.
Michel Py, commercial manager at French thermoforming tooling materials producer CGP Europe, said recycled material as a multilayer sheet core layer in thermoformed packaging can ensure cleanliness, or preferably thermoformers can take their own measures to meet cleanliness requirements with monolayer sheet.
Virgin outer layers with a recycled core layer is “a clever idea, but only a theory, as the truth is a little different”, Py said. There are potential risks with inter-layer migration: from the melt during sheet extrusion, uneven layer thickness, material hold-back while sheets pass through calendar rolls, and migration via sheet edges.
Migration can also occur with partial layer thinning during both sheet extrusion and thermoforming, for example in package corners, and between layers via stacked thermoformed cup or tray edges, Py explained. EU regulations allow recycled core thermoformed multilayer PET packaging, but “effectiveness depends on converters adopting a virtuous approach, in the absence of a rigorous test regime”, Py stated.
Thermoformers can achieve good cleanliness when producing monolayer packaging with vacuum application and running at high temperature. But unknown presence of certain chemical additives in recycled PET (rPET) may offset benefits. Although cleaning at the processor involves additional capital expenditure, “multilayer migration risks such as through thinning, layer rupture or during storage do not exist, by definition”, Py stated.
Py said there are challenges with PET trays laminated with PE, resulting in punched skeleton waste being “a cloudy material mixture”. This could be overcome with a patented process in which PE is applied only on the package sealing side.
Other challenges are: coloured PET in recycled waste; keeping non-food-contact and food-contact quality PET waste separate; and financial feasibility for recyclers, depending on virgin (vPET) and rPET price relationships. Although 30% of rPET presently goes into thermoformed packaging, there is a risk this could reduce as bottle-to-bottle recycling increases “and it is anyway dependent on pricing of PET textile fibre sources”.
Horst Roeder, area sales manager at Austrian recycling technology producer Erema, said present low crude oil prices means rPET became more expensive than vPET, reducing rPET in thermoformed packaging incentives. He said Erema's Vacurema inline vacuum reactor sheet process decontaminates rPET flakes before extrusion. Erema had sold 167 Vacurema systems worldwide, which process 1.1m tonnes/year, for extruded thermoforming sheet, bottle-to-bottle, fibre, filament and strapping line recycling.
David Bue Pedersen of Danish Technical University (DTU) said 3D printed tools are more cost‑effective than milled ones. He cited copying machine producer Xerox's evaluation with Stratasys, in which numerically controlled CNC milled thermoforming tooling needed seven days and cost €1,100, while 3D printing plastic with Stratasys fused deposition modelling (FDM) took half a day and cost just €95.
Djamila Oliver of Voxeled Materials referred to the same Stratasys/Xerox evaluation, adding that 3D printing can produce “inherent and controlled porosity” in breathing thermoforming moulds. This avoids conventional laborious wooden mould contour machining and vent drilling of a limited number of holes at, for example, Xerox. A larger number of economically 3D printed vent holes benefits thermoformed part quality due to more uniform vacuum, Oliver said.
Xerox has separately referred to higher design freedom with 3D printed thermoforming moulds, with undercuts enabling snap-fitting thermoformed covers, despite other thermoformers suggesting the parts wouldn't release from the mould.
Maarten Valckenaers, sales manager at Materialise, a company printing more than 2,000 parts/day on more than 100 3D printers, gave “reasons for the thermoforming world to turn to 3D printing”. These include tools for improved thermoforming processing, quality control tools and small series insert production. Valckenaers also referred to large prototypes for pre‑production design verification.
Thomas Tang, Faerch Plast strategy and commercial affairs director, said Faerch has been “proactively driving snap packs, especially with snake-shaped perforation for stronger packs”. He showed inclined trays for chicken legs that present legs horizontally positioned and skin trays occupying 66% less space than others and allowing vertical display.
Tang said bioplastics are “still in their early development stage”, and Faerch focusses mainly on mono-material PET.
Increased rPET use has halved PET CO2 emissions from 35 to 15 kg/CO2/1,000 trays. The MAPET II modified atmosphere adhesive top-sealed rPET-cored PET fresh meat pack, launched in November 2012, won Scanstar and Worldstar innovation awards in 2014/2015.
In a conference sponsor presentation, OMV Polytype described its RM77 fully automatic, revolving in‑mould trimming, cup and tub thermoforming machine with integrated stacking and part handling. The system uses one male and two female moulds, the male one running at full cycle speed, the female ones completing one circuit for each two cycles of the male half. Quality improves by the formed material remaining in the cavity for an additional cycle, yet use of two cavity sets provides for high speed.
OMV claims that with more than 57 strokes/min cycle time, and using a 51-cavity system, the machine achieves a worldwide record output of 174,000 cups/h for 71mm PP beverage cups. A complete mould change takes six hours.
OMV says it first presented an IML-T system at K 2010 on an OMV F25/5 machine. There were meanwhile five OMV IML-T systems running by 2015, two each in Germany and Egypt and one in Australia.
Kai Landsecker of the IKT plastics technology institute at Stuttgart University described how material efficiency, as the most important thermoforming quality criteria, improves with a prototype inline ultrasonic sheet thickness measurement system developed at IKT. Thickness data collected by an “impulse echo” acts as a process “fingerprint” to adjust machine settings, with less rejects produced the more frequently thickness data is provided.
IKT says the system enables 100% control without affecting cycle time or tool handling. Landsecker's colleague at IKT, Benjamin Neubig, later talked about determination of temperature sheet thickness during the thermoforming heating phase.