Aug 3, 2017 | By Benedict
UK additive manufacturing powder company LPW Technology Ltd has published a laboratory service datasheet on Carney Flow testing, a process used to confirm consistency between metal powder batches and to assist investigation of failed 3D prints. The company sells a flow testing kit called PowderFlow.
Lots of powder production companies claim to offer the best solutions for metal 3D printing, with the word “flowability” bandied around a lot.
And with good reason too: flowability, the rate at which a powder flows (into the 3D printer), can indeed speed up and improve the 3D printing process. However, it’s often quite hard to measure—especially without expert training and high-end equipment.
LPW Technology, a UK-based leader in metal powders for additive manufacturing, has just published a datasheet on “Carney Flow Testing,” a method for accurately determining the flowability of a metal powder.
The company says the process can be used to check consistency between different batches, and to investigate powders that have produced faulty 3D printed parts.
“The Carney Flow test is one of the most recognized tests for measuring powder flow,” commented Lisa Holman, LPW’s Quality Engineer. “The ASTM B964 standard recommends it for powders that do not readily flow through the Hall Flow funnel, and it’s one of the comprehensive portfolio of analyses we undertake in our in-house laboratory.”
Flow can be influenced by a number of factors, including moisture content, morphology, and particle size distribution. Powders with good flow are generally better than those without, but even the most free-flowing can become contaminated or have other problems.
For this reason, it is essential to have a process for evaluating a given batch of metal powder. This enables businesses to identify the cause of a problem when dealing with a failed print, letting them determine whether the 3D printer or the material is at fault.
“If powder flow problems are indicated, the cause can be further examined and costly down time investigating the machine avoided,” LPW explains in its datasheet. “However, if the expected flow is achieved, analysis of the machine and the process can reasonably be undertaken.”
The Carney Flow test involves taking a sample of 150 g of powder and pouring it through a funnel. An empty dish is placed under the funnel. If the powder fails to start flowing, one light tap on the funnel rim is permitted to kick things off. A timer begins when the powder starts flowing, and is stopped the instant the last of the powder exits the orifice of the funnel.
The total flow time is recorded to the nearest 0.1s. Three repeat measurements are taken, and the times averaged to give the result.
Companies can use the test to measure the flowability of a powder, or to see if a batch is consistent with others.
Although LPW carries out the test in its own laboratories, it is also offering a kit which allows other parties to conduct the test on their own premises.
“To enable end-users to assess powder flow on their own premises, we have developed the LPW PowderFlow kit which contains all the equipment necessary to check not only Hall and Carney flow, but also apparent density and angle of repose,” Holman explained.
The kit was first launched back in January 2016.
“I’m sure all users of metal powders will find the PowderFlow Kit a useful addition to their testing regime,” said LPW Commercial Director Phil Kilburn at the time of the product’s release.
Posted in 3D Printing Materials
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