Solving metal accumlation on pump rod

[KPMartin]

I'm hoping someone out there has a suggestion for this problem:



As the linotype runs, a bit of metal hardens around the pump rod on each pump stroke. Eventually this lump of type metal gets large enough to cause problems.

It seems that the part of the rod that goes into the metal during a pump stroke is not itself above the melting point of the metal, so a little metal hardens there. As the lump grows I expect it acts as a bit of a heat sink, making that part of the rod even cooler, and so accelerating the accumulation of metal.

I should mention that pot on the caster is not left on all the time, and the machine is often run with the pot having been on only for an hour or so, and that might explain why the rod isn't hot enough. I expect that after having the pot on for several hours, this part of the rod would no longer accumulate metal.

A higher pot temperature might cure this but I don't think that is a proper solution because this would cause problems elsewhere.

Perhaps once the pot is molten I should run the caster through a casting cycle but stop it when the pump is operating. This would put the piston deep in the metal, allowing the rod to heat up. After a few minutes I can then run the cycle to completion. My only concern is whether this would leave metal hardened in places it shouldn't (e.g. the mouthpiece?), or perhaps it would overheat the mould.

Leaving the pump rod unhooked from its lever would not be sufficient because the pump piston is buoyant in the type metal.

Anyone have any suggestions?

[Mechanic]

A build up of metal on the rod is a common problem It is hard to tell from your photo, but you appear to have an aluminium sleeve on the the rod. These sleeves were introduced to prevent the problem.

Mostly it is something you live with. There are a few things you can try. When you clean the plunger remove the buildup of metal. Take a fine file and remove any burs on the rod then mix up graphite and oil or grease and rub the mixture on the shaft where the metal is building up. Better still buy a can of Carnauba Wax. You should be able to buy it at a good hardware store. Use that on the rod and the piston.

Also make sure you keep your metal level up in the pot. The temperature of the metal should be between 535 and 550 deg f

[Mechanic]

Have a read of this. Check that the hole in the bottom is clear of dross.

[KPMartin]

Hmmm, I thought the image I put in would also be a link to the full-size image, but apparently it is not. The original image url was in imgbb (and there was a choice of full image or thumbnail) but this forum software appears to have copied the image rather than linking to its imgbb location so all that is left is the thumbnail.

Yes, there is an aluminum sleeve there. As described ("tightly fitted at both ends") I would expect the sleeve to have exactly the same temperature as the rod it is covering, at least when the machine is idle. Though during constant operation it might be heated up enough by its frequent dips in the pot to remain above the melting point. It would probably be more effective if it were tightly fitted only at the bottom.

In any case I'll try out some of your lubricating/release agent suggestions.

I don't know how much of that lump is pure metal and how much is trapped dross.

Out of curiosity I might also use my infrared thermometer to measure how much the temperature varies along the length of the rod.

[interrobang]

The sleeve is F-6193 on page 104 of Catalog 52 Casting & Driving.

If you toss slugs in the crucible, rather than feed ingots you'll find this is an acute and recurring problem. Feeding clean metal is the way to avoid it.

Lacking the sleeve, and ingots to feed, at the end of a work session, and while the plunger rod is still up to temp, you can use a 1/4 chisel and a small hand sledge to carefully knock the drossy "mushroom cap" back into the pot.