{"id":288,"date":"2016-10-05T10:58:20","date_gmt":"2016-10-05T10:58:20","guid":{"rendered":"http:\/\/www.plastikcity.co.uk\/blog\/?p=288"},"modified":"2021-06-21T11:10:27","modified_gmt":"2021-06-21T11:10:27","slug":"are-gravimetric-dosing-units-worth-the-extra-cost","status":"publish","type":"post","link":"https:\/\/www.plastikcity.co.uk\/blog\/are-gravimetric-dosing-units-worth-the-extra-cost\/","title":{"rendered":"Are Gravimetric Dosing Units Worth the Extra Cost?"},"content":{"rendered":"

Gravimetric colour dosing units (also known as continuous or loss-in weight units) have been around for a while, so we asked the PlastikCity<\/a>\u00a0Ancillary Partners for some feedback that would help our readers to make a more informed decision when considering their options.\u00a0<\/strong><\/p>\n

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We appreciate that despite design improvements (such as inclined feed screws), volumetric units are not as controllable as a unit that utilises load cells to continuously monitor and adjust material flow. Our mission was to see if you can\u00a0justify the additional investment. Our results were surprising.<\/p>\n

Q&A –\u00a0some questions we raised with the suppliers…<\/strong><\/p>\n

Current sales levels \u2013 What is the current split between the two designs?\u00a0 The average came at to around 65%<\/strong> in favour of Gravimetric.<\/p>\n

Initial investment \u2013 for a single station unit to suit a 250 tonne IMM, what is the approximate price premium<\/u> involved?\u00a0 The average answer we received was \u00a31100<\/strong>.<\/p>\n

Accuracy \u2013 Are we correct in assuming that to ensure you achieve the minimum percentage of dosing required, e.g. 2%, a user should be setting the dosing unit above this threshold if using a volumetric model? If yes, what would be the recommended setting in order to ensure a minimum of 2% is added? The general consensus was that in order to avoid having to continually check weigh sample doses, 3%<\/strong> would be a typical setting.<\/p>\n

Is this still the case with Continuous dosing technology, and how close to exactly 2% can be reliably achieved?\u00a0 The average figure was 0.1%, so dosing would be set at 2.1%.<\/strong><\/p>\n

\"jenco-graph\"<\/a><\/p>\n

Our analysis on pay-back<\/strong><\/p>\n

A typical 250T IMM with 50 or 52 mm screw size producing a component weighing 225g (50% of typical shot capacity) with a 40 second cycle will consume 20.25 kilos of raw material per hour.\u00a0 To achieve a minimum 2% addition of masterbatch, the Volumetric unit will dose a total of approx.\u00a0 0.61 Kilos per hour, compared to 0.43 kilos in the case of the continuous dosing unit.<\/p>\n

If we ignore cheaper black and white masterbatch for the purposes of this exercise, a typical coloured universal masterbatch should cost in the region of \u00a35 per kilo when bought in bulk.<\/p>\n

This equates to an hourly saving of \u00a30.90 when using the more accurate technology, meaning payback (based on the average additional equipment cost provided) would be achieved in around 1200 working hours – WOW!<\/strong><\/p>\n

Other considerations<\/strong><\/p>\n

Based on the most common responses we received, other benefits associated with the higher cost continuous dosing units include:<\/p>\n