After much thought about my problem with second shot, and with little help from any manuals, I’ve got my caster to behave properly.

The second shot problem was caused by an incorrect adjustment in the pump crosshead and linkage area. The pair of levers that operate the pump have a slotted hole and spring plunger in the link that joins them. When the pump is not in use, this plunger is supposed to be compressed a tiny bit, and it ensures that the pump piston is firmly held at the top of its stroke. The plunger also compresses if the pump piston jams in the down position; very old casters did not have the slot, so a jammed pump would either stall the caster or break something.

The adjustment is described in Casting Machine Adjustments, on page 161 in the copy I consulted:Note that the reference to the pin 32H1 being in the center of the hole in the lever refers to the older casters; in newer casters like mine this hole is a slot in the lever and all that is necessary is the 1/64″ clearance produced by a half turn of the adjusting screw.

Here is the adjustment on my caster, as seen from the rear:

Upper arrow is the adjustment screw 31H8, lower arrow is the locknut 31H9. The yellow thing is a sensor for my pump stroke counter.

On my caster, there was no overthrow in the adjustment, and the pivot pin in the linkage had a bit of drag but was not fully loose, and that was enough to allow a bit of a squirt as the pump descended after casting.

The frustrating part of this episode was that the two manuals that described the “second shot” problem never mentioned to check this adjustment. They just contained vague explanations about spring pressures being wrong with no hints as to how to check or adjust them:

From the ‘Monotype’ Composition Caster Manual. A very similar explanation exists in The Monotype Casting Machine Manual.

With this problem tackled, and a new type clamp installed in the type carrier, I got a good font cast:The run was still not problem-free, but the remaining issues did not disturb the lines of type. The remaining problems were:

• The first type in the line would occasionally fall over in the type channel if it was very narrow (e.g. ‘i’ or ‘l’). This letter would then fall out of the channel altogether, but for font casting missing one lowercase letter is not important, and it also did not leave a significantly shorter line. I thought the type channel had a ridge which engaged the nick of the type, which should prevent this; this is something else to look into.
• On one occasion, the galley cycle was missed; I had to stop the run, remove the extra types that should have been on the next line, and rewind the computer interface to the start of the line. The galley trip is a touchy adjustment; if set too sensitive it will trip during a single justification cycle (which it should not), and the sensitivity depends somewhat on the caster speed.
• During the galley cycle, the rule would sometimes snag on the type in the channel and lift it up as it rose; the type would drop down again each time before the column pusher moved in onto the galley, but there is definitely a chance this might derange the type. This might be due to a slight curve in the rule causing it to press the type against the column pusher a bit.
• I still have a bit of a temperature control problem: Keeping the casting running cool enough for larger type meant that the nozzle could freeze when casting a long run of narrow characters. I got around this by shutting off the mould cooling water while a long run of narrow characters was casting. This is only an issue for font casting; in true composition casting one does not encounter long runs of i’s and l’s! A very distant possibility in the future would be to have the computer interface automatically control the motor speed control of the VFD to vary the motor speed based on a running average of the widths of the type being cast.

Yesterday, I tried to cast another font of 12-point Caslon Old Style (Lanston 12-337E). The computer and pneumatics worked flawlessly, but the type kept misbehaving in the type channel.

The caster seemed to be doing something known as a “second shot”, where a bit of molten metal squirts up and adheres to the foot of the type after the jet is cut off.

This metal causes the type to ride high in the type channel, not pack tightly to the adjacent type, or force the (spring-loaded) type channel to open up a bit and so allow the other properly-cast type to fall over or turn sideways. The type also jams as it transfers from the type channel to the galley. Sometimes the metal breaks off and is dragged into the type channel area where it prevents the type of lining up neatly.

There are actually two causes of extra metal at the foot of the type. The other cause is known as “bleeding feet” which occurs when the jet is cut off before the metal has solidified completely, and a bit of metal oozes out through the still-molten part of the foot of the type.I have several reasons to think this is second shot and not bleeding feet:

• The caster is running borderline too cold as evidenced by the fact that in the same line as the bad feet I was also getting nozzle freezes. Bleeding feet occur when things are too hot.
• The extra metal almost peels off completely with only a tiny patch left adhering (though still enough to affect height-to-paper). I think bleeding feet would produce a solid well-adhered blob of metal.
• The metal looks like a squirt; it has the appearance you would expect from the “splat” of molten metal and looks like all the other metal decorating the floor and walls around the caster. Bleeding feet would tend to produce a compact, nearly round, blob of metal.
• The amount of metal exceeds what I would ever expect could ooze out of the foot of the type.

That being said, I’m at a loss to explain how this is happening. It has to be occurring after the type carrier and mould crossblock have moved completely to the right, exposing the foot of the type. By that time the pump has completely returned to its idle position. I only found one troubleshooting hint in the manuals relating to second shot, and it was a rather hand-wavy explanation of the source of the problem which did not really fit with how the mechanism moves. I’ll have to re-read that in detail to see if I can make sense of it. I’ll also review the timing diagrams I found in a (very old) manual to see the exact timing between the pump motion and the type carrier motion.

One strange thought I just had, related to the caster running borderline too cold, is that before the nozzle drops away from the mould, it (the nozzle) freezes just enough to seal it. After the nozzle drops away, heat conducted up from the nozzle base re-melts the metal, so any residual pressure in the area would cause a little squirt of metal. Again, I’d have to take a close look at timings to see if this is plausible (and still would need a theory on the source of the residual pressure).

Perhaps I could also take a slow-motion video of the pump operating to see if anything odd happens when a second shot occurs. The problem here would be identifying which pump cycles in the video had a second shot and which did not. Murphy’s law will of course dictate that if I try doing this the problem will go away!

The problem perhaps seemed to be worse when casting narrower type.

One problem analysis technique I sometimes use is to consider what has changed since last time (when the problem did not occur). Before this casting run I removed the pump body, cleaned the piston, chased oxides out from around the heating elements, drossed and cleaned the metal, and reinstalled the pump. I also topped up the metal, giving a very full pot. Serves me right for trying to run things sparkly clean!