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Replacing a Composition Caster Temp. Controller

Started by Dave Hughes, June 10, 2023, 08:18:18 AM

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Dave Hughes

Here's a video from Forum regular Kevin Martin showing how he replaced the old pot temperature controller on his Composition Caster:

QuoteIn this video I build and install a modern temperature for the pot on my Monotype Composition Caster.

This machine is used to cast type for letterpress printing, and has the ability to cast composed text, that is, type already set into words and lines. This avoids the laborious job of hand-setting type and ensures the type is newly made giving crisp impression of the fine details of the letters. Like letterpress itself, this machine is commercially obsolete, and only used for niche markets.

The type is cast from a molten metal alloy which must be kept at a consistent temperature to produce good type. On my caster the old Partlow mechanical controller had failed, and I chose to replace it with a modern electronic controller that uses a thermocouple to measure the temperature of the molten metal. Just as with the original controller, this switches power to an electrical contactor which in turn switches the power to the electrical heating elements.

I made a custom enclosure for this in a separate video.

More information on this project, and the caster itself, can be found on my blog:

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Ready for installation:

Thermo controller of the Monotype casters, replacing traditional with mercury switch.


Nice retrofit! Do you have pictures with the cover in place and installed.

Here you see the advantage of the smaller form-factor controllers: They are more likely to be mountable within the existing temperature controller housing.

What did you do for a thermocouple/thermistor?

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