Tag: drnick
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Why is there (what looks like) orange contamination in my powder?
Bizarre as it may seem, in the past few weeks, I’ve had two different consultancy customers report powders with this same problem. They sent me samples and parts but, even before they arrived, I suspected that the problem was gas fading. Some of you may have experienced this phenomenon before, and wondered why it happens:…
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Ask Dr. Nick: Why does the same mold need different cook times in a different rotomolding machine?
Rotomolders who have multiple machines often find that, if they move a mold from one machine to another, an adjustment in cooking conditions is invariably required. The differences between machine performance can be considerable. Whilst this may be expected when moving from one style of machine to another, an adjustment may even be required when…
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Ask Dr. Nick: How does cold weather affect the rotomolding process?
You may have heard that in England, when we’re not obsessing about Brexit, we often discuss the weather. This is odd, when you consider that, other than a lot of rain, we don’t see extremes of weather that often. Recently, we’ve experienced what we Brits would regard as some cold weather, although it’s been nothing…
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Ask Dr. Nick: Can I fix gaps in a parting line?
A badly fitting parting line is a regular pain in the neck, for a number of reasons. The most notable annoyance is that, as the mold rotates in the initial stages of heating, powder spills out from any gaps that exist. This wastage of powder can cause an under-weight part and, even if the spillage…
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Ask Dr. Nick: Avoiding “Angel Hairs”
On ARM’s most recent What’s Your Problem? teleconference, there was a question asked about powder piping systems, especially about avoiding and dealing with “angel hairs”. I provided some follow up to the molder after the call, which we’re happy to share here for everyone’s use. My first recommendation was to contact ARM’s mainstream pulverizer supplier members, who should be able to offer good advice. They are…
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Ask Dr. Nick: What’s an Acceptable Scrap Rate in Rotomolding?
Recently an ARM member from Latin America phoned in with a technical question and we got into a conversation about the vexed subject of scrap. I appreciate that it’s a bit of a prickly issue and probably not something individual rotomolders would be keen to discuss openly. Not being a molder, I was probably more…
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Effects of pigments in dry mixing: What REALLY happens to physical properties?
Many parts of the North American roto industry still rely on using dry color materials. The main reasons for this are reduced cost and operational convenience. However, it is generally recognized that using dry color, rather than fully compounded pre-color, can result in a significant loss of material properties. If you’ve sat through as…
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Thickness Control – What’s Possible in Rotomolding?
As we all know, a significant benefit offered by rotomolding is that we can achieve even wall thickness, compared to other processes. One question that rotomolders often ask me is: how much thickness control can I actually achieve, in normal practice? I pondered this question recently, while I was preparing resource materials for the ARM…
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Removing Stuck-on Debris from a Mold
Our legal counsel notes: Dr. Henwood speaks for himself and not for ARM as a whole. We encourage feedback but comments should be on technical matters raised. Dr. Henwood’s responses are solely his responsibility and not ARM’s. As part of a recent consultancy assignment, I needed to make a long run of parts in one…
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Rotomolding Styrenic Polymers – is it feasible?
ARM Technical Director, Nick Henwood, is sharing a series of articles on rotomoldable polymers other than PE, PP, and PVC. Our legal counsel notes: Dr. Henwood speaks for himself and not for ARM as a whole. We encourage feedback on this project but comments should be on technical matters raised. Dr. Henwood’s responses are solely…