Top tips for injection moulding machinery buyers

Making the decision to purchase injection moulding machinery is an investment, and one which it is important to get right. Here, Nigel Flowers, Managing Director at Sumitomo (SHI) Demag, answers six of the most popular questions asked before buying.

Q1: How much do IM machines cost?

A: It varies significantly, although with such a diverse range there are economically viable options. For example, last year we launched a special Blue Edition machine giving small and medium-sized trade and technical trade moulders the opportunity to upgrade to a top-level variant of our hydraulic machine with prices starting at £27,500 (ex-works) for a 50-tonne machine and £51,000 for a 160-tonne machine.

Overall, IM machine prices have fallen in real terms. Including a robot in an IM machine can enhance competitiveness. This might amount to an additional £25,000, but what you get is available 24-hours a day. Those who make that investment will often see payback in less than a year.

With packaging formats constantly changing, it makes economic sense to build a complete moulding system that anticipates future applications, with robotic capabilities integrated. Speed, yield, repeatability, reliability, multi-tasking and long-term cost saving are all reasons why end users might opt for a robotic solution. Our customers, particularly in the packaging market, increasingly ask for complete IM packages, which once set up require little modifications or engineering intervention.

Q2: How fast is the ROI?

A: Half a decade ago, all-electric ROI was eight years. It’s now three years, which is more in line with UK ROI expectations.

Unsurprisingly, the entire moulding sector is tremendously focused on reliability, performance efficiency - cycle-time speeds - and quality; the three key components for measuring overall equipment effectiveness (OEE). Total cost of ownership, particularly energy costs and after sales support in terms of process optimisation will play an important role in the future for customers.

Q3: Why is speed so important?

A: Many moulders, especially in the packaging sector, mass-produce components in their millions. To be cost effective, plant equipment needs to be of the highest performance. To address this, cycle times have got shorter, performance has increased, and higher cavity numbers are demanded. There is increasing demand for applications with cycle times between 2 and 3 seconds. Machines with a higher clamping force (typically 580 t up to 750 t) are also in demand.

Ultimately, customers need to examine all of the statistics alongside the machine attributes and process stability. It is our duty to show customers all of the different commercial benefits and how a machine can optimize productivity and manufacturing capabilities.

Q4: Are there any machine limitations I need to be aware of?

A: No. That’s because innovation in IM isn’t machine led, but application driven. So, you just need to select the best machine for your application.

With material still being the largest cost element of a packaging, Sumitomo (SHI) Demag has been very focused on thin walling, increased strength and weight reduction and helping manufacturers to reduce the cost per part. To succeed in the thin walling arena it’s vital for packaging manufacturers to examine every potential application to ensure that the selection of materials, machine and tooling give the optimum blend of speed, quality and consistency.

Q5: Should I opt for hydraulic, hybrid or an all-electric machine?

A: Unlike 25 years ago when you pretty much had two choices - a toggle or fully hydraulic clamp - today’s choice of machinery is a lot broader and each type offers different advantages. For packaging applications, hybrids, such as our El-Exis SP and Systec SP, are popular due to fast cycling speeds and low running costs.

The El-Exis SP is a robust packaging machine ideal for products requiring high speed and high volume, such as bottle closures or cups for medication, and is also ideally suited to thin wall injection moulding with in mould labelling (IML). As El-Exis SP is powered by a combination of hydraulics and electrics, it combines the advantages of both systems, such as the precise positioning of the clamping unit over the entire cycle and consequently smoother and continuous injection cycles, even at maximum load.

Likewise, the Systec SP is good for thin walled packaging applications and was developed for applications that needed less production volume, but higher flexibility. The injection dynamics and speeds are up to 600mm/s, compared to 1000mm/s for the El-Exis. The cycle range is around five to six seconds, and apart from offering increased flexibility, it constitutes a smaller initial investment.

The rationale for choosing a hybrid versus an all-electric IMM is down to the application and filling time process. As an example, filling times for yoghurt cups are calculated at between 100 and 200 ms. With such a short time frame, acceleration is of key importance. El-Exis SP is able to accelerate to its maximum speed within 23 ms. This acceleration can currently not be achieved with purely electrical machines in the clamping force range of 150 to 750 tonnes, and that is why we opt for hybrid machines for certain applications despite our expertise in the area of electrical machines.

Of course, there are, and may be for some time, production areas better suited to hydraulic systems, notably those higher tonnages typically demanded by the automotive and other heavier engineering sectors. Hydraulic machines still remain a popular choice for general purpose moulding.

Q6: What are the maintenance costs like?

A: Very low for both hybrid and electric machines. To illustrate, a 160T machine can be fully maintained according to the manufacturer’s recommendations for as little as £600 per annum. Other than regular safety checks and planned maintenance activities, such as lubricating etc. properly serviced modern moulding machines will, give many years of trouble free production.