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Operating three Newbury injection machines used for overmoulding, Mitcham Canada runs black colour for long periods,
making purging very time-consuming. By switching to Dyna-Purge, the company decreased purging time from 1-1/4 hours to 30 minutes, a 60% reduction in downtime.
Cable splice produced by Mitcham before (left) and after (right)the overmoulding process. By using Dyna-Purge instead of
virgin polyethylene to purge, the company has lowered its cost to purge by 52%.
Samples of consecutive shots after introducing Dyna-Purge K into the machine. Dyna-Purge has solved the problem of
black specks appearing after purging while providing Mitcham with faster, cleaner transitions between colours.
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Situation:
Mitcham Canada, Ltd., of Calgary, Alberta, operates
three Newbury 30-ton injection moulding machines,
processing polyurethane rubber at barrel temperatures
ranging from 193°C to 204°C (380°F to 400°F). With the
growing popularity of consumer products combining
hard and soft polymers, Mitcham specializes in
overmoulding to fill that need.
Purging to change colours — often once a day —
Mitcham would run virgin polyethylene through their
machines. Continuous extrusion purging was not possible
due to attached shut-off nozzles. In addition, the
design of the equipment led to a significant amount of
material hang-up, while long periods of running black
colour made purging very time-consuming.
Consequently, Mitcham would spend, on average,
1-1/4 hours to purge at a labor and material cost of
C$85.22 per purge.
Solution:
Use Dyna-Purge K, a grade specifically designed to
purge 'soft-touch' polymers from the barrel and screw
at 143°C to 260°C (290°F to 500°F).
Results:
- Downtime for purging was reduced by 60% - from 1-1/4 hours to only 30 minutes on average.
- The overall cost per purge is now only C$40.88 - a 52% improvement!
- Since Dyna-Purge cleans thoroughly and effectively on the first pass, Mitcham is experiencing faster, cleaner transitions between coloured products.
- Dyna-Purge solved the problem of black specks occurring after purging.
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