Gammadot Rheology

28/05/2026

I was looking for an archived document earlier today and came across a PDF copy of the instructions I produced for the very last piece of software I wrote from scratch, and it took me right back to the Noughties!

Early on in my career, I really enjoyed writing software, ranging from data logging / analysis programs for new pieces of kit being developed at Rapra Technology, (as it was), to viscosity data processing & modelling software - I especially enjoyed coding the graphical plotting of data.

Nodecon was a piece of software I wrote to enable the conversion of Second Order Viscosity model 'node points' - these six viscosity values were derived from modelling experimental data to produce the coefficients required for input into one of the two major flow simulation software packages of the time, Moldflow & Fillcalc.

From the 80s up to the 00s, both packages used the same viscosity (second order) model to fit experimental data and produce six 'Node point viscosity values' (six viscosity values at set shear rates across the three measured temperature curves), but selected different shear rate points to produce these coefficients, therefore the node points were not interchangeable between the two software packages.

Nodecon took a set of node points and then recalculated them to be able to successfully use them within the opposite package (i.e. Fillcalc node points be recalculated into Moldflow format & vice versa). It also allowed you to plot the curves across different shear rate ranges to study the predicted magnitude of viscosity at extremes of process range.

The second order viscosity model was replaced many years ago with the Cross-WLF model in main stream flow simulation, and the old second order viscosity has faded into obscurity, but the PDF was a pleasant reminder of a big part of my life working for Rapra and the wonderful friends I made there. 😊

13/03/2026

Twenty years self-employed…. That flew by! And I can hands down say they have been the best two decades of my life & career. Prior to this, I spent 18 years at Rapra Technology Ltd, (16 of which I was responsible for the rheology dept).

And now, with the support of my testing partners, I’m proud to have grown Gammadot Rheology into a global leader for the provision of Thermosetting plastic & rubber material characterisation services, specifically for Autodesk Moldflow flow simulation. In addition, Gammadot also provides thermoplastic testing services for all the major simulation software houses, routine rheological quality control & failure analysis support.

Thank you to all of the companies, colleagues & clients (many who have become firm friends over the years), that have helped, sustained & championed me over the past two decades – here’s to our continued relationships and further growth & prosperity!

PHOTO GUIDE
Top Row (L-R): First day in the new laboratory (2006), delivery of my first Capillary Rheometer by Roy Carter, RIP – still sorely missed (2007), Plastics Design & Manufacturing (PDM) – Gammadot’s first exhibition (2008), Securing ‘Characterisation Partner’ status from Moldex 3D (Taiwan) – Kenny Lu, Director of World Sales & I (2009), Receiving Gammadot Rheology’s ‘Preferred Service Provider’ award from Steve Shaw, Rapra Ltd (2014) & informal visit from Russell Speight, Autodesk Moldflow Director of engineering, to discuss the transfer of Thermoset testing & Moldflow data fitting services to Gammadot Rheology (2024).
Bottom Row (L-R): Porpoise P9 Twin Bore Capillary Rheometer, Reologica StressTech High Resolution rotational rheometer (One of four in service), Ray-Ran 6MBA Melt Flow Rate Instrument, Monsanto R100 Oscillating Die Rheometer with bespoke data-logging & analysis software, PvT (Pressure, Volume, Temperature) apparatus developed by Rapra Technology Ltd, Malvern Instruments RH2000 bench top Twin Bore Capillary Rheometer.

18/09/2024

Introducing the RH2000 twin bore capillary rheometer, a recent addition to the Gammadot Rheology testing suite.

This excellent bench top twin bore rheometer can perform similar testing to our flagship Porpoise P9 twin bore capillary rheometer, but will be dedicated to characterising low viscosity materials to high shear rates (200 1/s to 100,000 1/s), utilising brand new 0.5mm diameter capillary dies.

For further information on capillary rheometry visit: https://gammadot.com/capillary-rheometry/

18/06/2024

This month saw Gammadot Rheology complete it's 1000th client project which, in the 18 years since forming the company, means I've personally worked with almost 3000 grades of different types of (mostly) polymers, and when you add that total to the amount of materials I tested / characterised in my previous life as Rapra Technology's Rheology Dept., it's a pretty good amount! 🙂

Onwards to the next 1000...

13/07/2023

I was transported back to 1988 again this morning running the trusty old ex-RAPRA Monsanto R100 Oscillating Die Rheometer!

One of the first instruments I was trained to use when I joined my ex-employer as a technician in the rubber dept., every rubber compound we produced back then had it's cure characteristics measured on the R100, allowing compound moulding cycles to be determined.

Eventually in the '90s it was superceded by the MDR2000 and decommissioned - it wasn't used again until I took it off their hands in 2006, on the birth of Gammadot Rheology. The R100 was then fully refurbished with upgraded digital temperature control and a bespoke data logger software system written for it.

With the rubber industry adopting the Moving Die Rheometer (MDR) as the standard method for determining the cure characteristics of rubber stock in latter decades, the R100 gets less and less use but, there are still many companies that have vast quantities of historical rubber cure data derived from ODR testing, and so still have use for ODR measurements.

I only wish I was as thin now as I was in 1988! 🙂

14/03/2023

Always a good show at the NEC.

Register now

27/02/2023

It's been a long time since the last post on here! Frustratingly, the majority of the interesting, non-routine testing performed at Gammadot, is confidential and I can't talk about it. So, here's the Porpoise P9 twin bore capillary rheometer being set up recently to run some high shear viscometry on a range of materials that I was also going to video, to document any change in extrudate (the extruded material strands) as the shear rate (flow speed) increased.

A capillary rheometer is basically a highly instrumented, accurately controlled, ram extruder. The most common configuration is that of vertically mounted heated barrels containing capillary dies of known, accurately measured, L/D ratios. Above each die entrance situated in the barrel wall is a pressure transducer. Closely fitting pistons are driven into the barrels at exactly controlled constant speeds and pressure drops generated at the capillary dies.

These pressure drops are allowed to stabilize at which point readings are taken. The speed is then increased to the next pre-determined point and the stabilization sequence repeated. This is how we obtain shear viscosity versus shear rate curves.

Measurements are normally made using two capillary dies - a long die (usually 16:1 L/D ratio) and a short (zero length) die . This enables the use of the Bagley end correction formula. The overall pressure drop through a die consists of an entrance pressure, pressure drop along the capillary length (land), and a small exit pressure. The Bagley code removes the entrance & exit pressure effects, the corrected pressure therefore relating to steady state pressure flow within the capillary only.

In addition to providing the required viscosity data for applications such as injection moulding / extrusion flow simulation (software), capillary rheometry is ideal for discriminating processing problems such as melt fracture / shark skinning, die swell, and slippage flow.

For more information: www.gammadot.com