Status report:

My coin press has been "down" for several days. This is the first time since 2008 that it has been non-functional for more than an hour or so. I was just starting a production run when it reported the error "clutch valve failure". In that state, the press will not operate. That is a major issue and it is extremely difficult to repair (the clutch valve is behind the flywheel, which weighs thousands of pounds, and it has to come off to get at the clutch valve).

But, this is not the first time it has reported that problem. A few weeks ago there was a similar incident. At that time, I checked and re-tightened all the electrical connections involved. I adjusted the air pressure regulators (not by much). Then when I restarted the press, the problem was no longer indicated.

So last week when it happened again, I didn't think the valve actually failed. So I did the same thing - checked electrical connections (to a greater extent this time), and adjusted air pressure and oil pressure (somewhat more this time around).

I started up the press and, at first, it reported the same "clutch valve failure" again. But after a minute or so of resetting the status, the error mysteriously disappeared. At this point I attempted to resume production. But now there were two new problems. First, the "low oil pressure" indication light came on. I had adjusted one of the sensors to a threshold that was too high. Fixed that. But the main new problem was that the ejection mechanism was malfunctioning. Over the next 20 hours (most of it in one session), I kept trying all sorts of things to correct it, including adjusting the air pressure back to where it was at the start of all this. There are also mechanical adjustments on the ejection apparatus, so I manipulated those as well. But no matter what I did, it refused to function properly. At the end of a minting cycle, the press pushes up on the lower die to force the struck coin out of the collar. And then the last step in a stamping cycle is for the lower die to drop back down into striking position again. No matter what I tried, the lower die would either not eject at all, or it would stay in the upper position and not drop back down into striking position.

After studying how the ejection process works (by examining the press - there are no manuals), I decided that the problem must lie in this gizmo that is mounted on a bulkhead inside the press near the flywheel. It has an electrically-operated solenoid that manipulates a plunger inside the valve body. Air pressure comes in the two ports on one side of the body, and the plunger position dictates which ports on the other side of the body receive air pressure. Air pressure sent to various cylinders at various times is what determines the operation of the ejection mechanism.

Here is the "gizmo":

The electrical solenoid slides easily off the tube:

So my first thought was maybe the solenoid was bad. I looked in my cabinet of old spare parts that came with the press and found that I actually had eight more of them. Here are two, side-by-side:

So I grabbed one of these replacements and installed it. I started up the coin press and as soon as I pushed the striking buttons, an ENORMOUS shower of sparks and smoke erupted from the area of that newly-installed part. I was on the opposite side of the press and it looked like a 4th of July fountain going off. I shut off the press immediately. The carnage stopped at that point. I ventilated the room and went to inspect the damage. Here is the original solenoid (on the left) and the replacement (on the right):

The original solenoid has a sticker label, but nothing else on it:

There is no sticker on the replacement. But it did have some specifications molded into the side:

You wouldn't believe how many sparks and how much smoke came out that little hole and the vertical rupture in the casing. But there is the problem right in front of my eyes. The original solenoid was rated at 220/110 volts. This one, 24 volts.

I figured that the valve body was also toast at this point. So I found a similar replacement in my cabinet. I installed that new valve body and the original (correct) solenoid. I started up the press and performed some test striking. The ejection mechanism attempted to function, and did function properly on some strikes, but on other strikes it failed. Still, that was an improvement. But I was perplexed as to what to do to make it function reliably.

Then, as luck would have it, I found a little note that had been taped to the valve body or bulkhead. It apparently fell off when I removed the original valve body from the bulkhead, and I later noticed it sitting there. The note reads: "August 3, 1993 / cleaned & lubed":

If the US Mint felt it important to clean and lubricate the valve body, then I should do the same. It came apart easily after removing the five screws on the top:

Inside it is rather simple. There was little in the way of dirt and gunk inside since this was a newly-installed part (by me). But the little bit of old grease inside was somewhat sticky. So I lubricated it well and put it back in. The ejection system functioning was different, but still problematic. So a remaining question I had in my mind was, what is the little lever on the valve body for ? I determined that it was an adjustable air bleed. When set fully counter-clockwise (as shown below), the lower die would stay in the lower position and not eject at all. When the lever was set full clockwise (as shown below), the lower die would eject, but refuse to drop back down into striking position. I found that this was a critical adjustment, and the lever had to be carefully set in the middle of the range:

So I've done a few test strikes since then and it seems to be working correctly now. I will know for sure later today when I do a lot more stamping. I am hopeful that this valve body malfunctioning is what was responsible for the phantom "clutch valve failure", since both are related to air pressure.

So after much consternation and a couple VERY long work days, it seems to all come down to needing just a little lubrication in the right spot. I am going to put the (revised) note back where it was:

Such is the life of a mint operator. At least, I know a lot more about the ejection system. Now back to work.

.

Thank you for posting the status update, on the work you had to do to the mint press.

I find it interesting as I work with machinery and sequence of operation. All the machines I work around are Allen Bradley control logic except for a few machines we repurposed from another location that were Siemens - but essentially those are black boxes and only the manufacturer can access the program which is terrible.

The old mint note is cool too, and I have a few coins that came with small detailed notes (date acquired, price, etc.) that I've continued with in a similar manner.

Thanks to @COCollector posting the link to the mint press on Daniels website, I re-read it and its very neat.

I'll say it again, when I first heard about Daniel Carr it was due to the pioneer gold he was making around 2012ish , I though it super interesting and a great story that a guy bought a decommissioned mint press from the Denver mint, set it up and started striking privately minted gold coins in different weights - how cool.

Congratulations on your venture and thanks for the awesome coins medals and tokens!