Polyurethane moulding manufacturer Midas Pattern Company provides a range of prototype and production volumes of flame-retardant polyurethane moulding solutions from its Bedford-based advanced manufacturing facilities.
Primarily suited to the development of scientific equipment, its other applications include items such as solar panels and housings for electric vehicle charging stations. All items are moulded from the company's composite resin mould tools, which are designed in-house from customer-input CAD data. The mould tools are produced from master patterns machined out via the company's extensive CNC facility, which includes six large Haas vertical CNC milling machines and one ‘very large’ Correa horizontal CNC milling machine.
Compressed air plays a vital role within the machining, moulding and product finishing processes:
- Continuous supply of low-pressure air (approx. 20 psi) is needed for clearing 'swarf' (waste material) that is produced from the soft tooling board surfaces. In this process, seven CNC units machine them out 24 hours a day, seven days a week, and the low-pressure air helps to prevent the build-up of the waste material.
- Low-pressure air is also involved in the batch mixing of the polyurethane reaction materials before pouring into composite moulds. After curing, the moulded items are removed to undergo finishing operations, such as fettling (trimming and cleaning) and shot blasting (removing impurities), in preparation for epoxy or acrylic spray painting. These processes, especially the spray booths and shot blast plants, require a constant and reliable supply of compressed air.
AUDIT & RECOMMENDATIONS
As part of Midas’s Green Initiative (MGI), the company called upon the services of Atlas Copco premier distributor Anglian Compressors to conduct a performance survey of the compressed air system, which had been installed for 10 years and comprised of two Atlas Copco 22 kW, fixed-speed rotary screw compressors, as well as a small VSD unit. The MGI began in April 2019 and was introduced by Midas MD Alan Rance, who decided to bring his personal and professional carbon footprint down to zero. (Details can be found at www.is.gd/hiyaho).
Anglian measured the usage patterns of the air supply, learning that the demand fluctuated throughout the week and had also changed considerably over the 10 year period. This was down to a combination of the production equipment used, the number of staff and the operating hours. Depending on what process is running, different volumes of air were required, causing a fluctuation in usage.
The minimum requirement needed by the factory was 12 l/s, and the maximum was 105 l/s. The VSD machine also had reliability issues and lower output than the fixed speed units, meaning that at times, it did not have enough capacity to provide the full air requirement needed. The fixed-speed compressors were, therefore, doing most of the work, running on and offload and wasting energy. A spokesperson explains: “With fixed speed compressors, you are not able to start and stop them continually because the motor will burn out due to the starting currents.What happens is when the compressor has reached its upper pressure set point, it stops producing air by going offload. However, as the screw is still turning, power is still being consumed. VSD machines work differently; they adjust the speed of the rotary screw to match the air requirement – the faster it turns, the more air is produced.When the air demand is less, the unit turns slower, producing less air, consuming less power and eliminating offload running.”
Anglian recommended that Midas replaced the small VSD machine with the larger 37 kW GA37VSD+ compressor and retained the two fixed-speed compressors, each with an output of 53 l/s, as back-ups. The GA37VSD+ compressor is said to have a free air delivery of 133 l/s, enough to supply all the air that the site requires, and thereby reducing energy consumption and service costs.
It was also noted during the survey that the compressed air system was running between 9-9.9 bar − considered to be too high in relation to the application needs. It was therefore recommended that system pressure on the new VSD machine should be reduced by 0.2 bar increments on a weekly basis. At 8.4 bar, this procedure is said to have reduced energy requirement by 10.5%, while further reductions of the pressure down to 7.5 bar were not thought to have had any adverse effects on the performance of the production equipment.
Furthermore, Anglian Compressors advised Midas Pattern Company of the benefits to be derived from sectioning off the factory so that work areas could be shutdown when they were not in use. This is said to guarantee that no air is wasted when equipment is not in use. The firm also recommended that the CNC machines were pre-programmed to shut off the swarf removal air blast once the process was completed. Midas designed the system of controllers, solenoids and pipework, and then retrofitted it to each of their seven CNC machines to ensure that when the programme finished running, no further air was consumed.
The combined effect of these measures, following the introduction of the VSD+ compressor, has reportedly seen the night-time usage reduce from 10-35 l/s down to just 5-20 l/s. Daytime usage is also said to have been lowered as people are now aware to switch off equipment when not in use. In addition, the amount of energy used on site for generating compressed air has also reportedly been reduced by around two-thirds to just 78,104 kWh, representing a total saving of £14,554 per year together with an estimated ROI (return on investment) payback of 1.5 years.
The compressed air system upgrade alone has also reduced the company's carbon footprint by some 50 tonnes of CO2. When combined with the effect of the other measures that the company has taken in using less energy and improving its green credentials across its business, that figure is said to be closer to 60 tonnes.
Alan Rance, managing director at Midas Pattern Company, says: “Midas has achieved its success by inventing, developing and implementing techniques analogous to metal casting. We are, in effect, a plastic foundry that has invested in cutting edge technology while maintaining and cherishing traditional expertise. We have always applied this approach with our equipment suppliers too – it wasn't just a question of price, their product offering had to be the best in terms of quality, performance, and longevity. But now, with the Midas Green Initiative, we see environmental responsibility as the foremost criterion.
"I am a passionate environmental advocate, and this is reflected in every aspect of the company's climate-conscious ethos. It is self-evident from the 100% LED lighting throughout the plant, and our zero-landfill waste output. Up until recently the plant heating has been achieved with 10% biogas and 90% carbon neutral gas. Now, I am delighted to report that we have signed up a three-year supply contract for 100% biogas. That means every unit of gas we burn is replaced by a 100% truly green one.
“What’s more, our staff and customers are encouraged to go electric with their vehicles and use our two, free EV charging points on-site and, as a responsible plastics manufacturer, we have expressly excluded all forms of single-use plastics from our premises."
Rance concludes: “Midas Pattern Company, Anglian Compressors and Atlas Copco share the same green principles and a common purpose. They were 100% with me all the way."