Coining Process

Are the steel keys heavier?

Maybe try increasing the air pressure.

Not much experience in coining, maybe lubrication may help, if it doesn't interfere in the coining details

You could introduce a sensor to detect the occurrence of a "weld" and prevent the stroke and sound an alarm.

Have the ejected key pass through a photocell beam. If the beam is not broken use the signal to stop the press. Use change of state on the leading edge of the break to protect against misalignment of the beam or a key stuck in the ejector chute causing a malfunction.

At the work rate quoted you will have less than 0.5 seconds for the absence of a signal to stop the process. The mechanism that feeds a new key into the press will have much less inertia so will be quicker to respond, but if tooling damage is likely to be costly, I would try to stop both. If the feeder and press are mechanically linked consider using another jet of air to blast the key out of the feeder before it is put into position. CAUTION I have only used this on large industrial presses at up to 30 shots/minute, you may need to slow down your rate from 50 shots/minute to get any technique to work reliably.

Sorry....pressed the submit rather than the edit. If you operate the machine in single shot mode and only allow a second shot if you see the signal, it will be easier to modify than controls than trying to interrupt the continuous mode.

Some good fixes here already so I won't comment on that. Though a light or laser beam could be reflected off the key blank and decide almost instantly if a key has remained or not and stop the process. It would not even be expensive of difficult to make, using a small PIC as the logic....easy peasy.

The reason for this "micro-welding" as I think you called it, is due to the fact that the dies are steel and the key is steel. Similar materials. Possibly an oil based lubricant on the steel keys/dies may cut the frequency of the problem?

Whereas the other keys are dissimilar metals to the dies and therefore would not normally weld with each other.....the word weld implies a similar type of metal by the way....though it is true that certain dissimilar metals can be welded using special equipment, but not as in the case of the hardware here....

I built punch press machines, dies and additional tooling many years ago. I also had the great idea of using air as an ejector, but it really is not the best way and prone to difficulties, as you have found, when changing materials. But there is a way to make that key come out ever time. An air poppet ejector. I use them in injection molds when ejector pins are not possible due to design restrictions. They are completely flush when installed but in this instance I would install them .001/.002" below the surface. Die striking might over compress them. But when the air is applied they rise up and exert a mechanical force, based on the air pressure used and once they break the surface adhesion of the part to the die, the air flow continues the ejection process. In your case I would also keep an air flow at right angles to the ejection to remove it from the working area, which I assume you are already doing. This poppet will remove the key from any "micro-welded" conditions, or "stiction" regardless of which material the key is composed of. You may find that the repeated die strikes wears these poppets out since they are primarily designed for molding. Keep them offset as much as possible from the logo area but still captured enough to do the job. Here is a link for some good quality air poppets. But there are many other manufacturers so a little home work might be appropriate.

https://na.dmecompany.com/Catalog/CatalogListing.aspx?CatalogId=DSO&CatalogDetailId=192

It would be great if you could positively identify the cause of the sticking before you engineer a solution, but in many cases this is not practical. Micro-welding would not be my first guess. I would guess that the keys expand slightly during the embossing process and contract when the embossing die is retracted. The silver and brass keys have a much lower elastic modulus than the steel keys, so they shrink more after the die retracts. The steel keys shrink less and become a press fit in the locating die. If you can accommodate slightly looser locating tolerances on the brass and silver keys, I would simply try increasing the clearance in the locating die.

Brass alloys are usually more resilient than steel alloys. Coining any piece of metal makes it slightly wider, but steel does not spring back as much as brass, so a steel key is more likely to get stuck in the die. Similarly, high pressure during firing causes any cartridge case to expand, but steel cases sometimes get stuck in the firing chamber because they do not contract as much as brass cases. I am not sure what "new sylver" is. Google says it's a Belgian popular music group. I'm guessing it is also the name of a proprietary nickel alloy that is more resilient than steel.

Good point. Let's not forget that the key blanks could themselves be magnetized.

Well thought out, great idea.

Constant hammering can cause the earth's magnetic field to be sort of "printed" into some machine parts, aligning all the little natural magnets.....it may not be a strong field, but it could be important to the way the machine works when using steel blanks....

Very likely. Steel parts that have run around a vibratory (or other bulk) feeder often become mildly magnetized. Running them through a ring de-magnetizer just before the feeder exit should eliminate that as an issue.

However, incorporating a Mechanical means of freeing the blank form the die after embossing will be the most reliable means of fixing your problem. A small ejector mechanism, in addition to the air blast would be best.

I'm curious, was the steel part always part of the plan for this tooling?

No for this tool is for used all three material and also for aluminium keys.

We solve this problem with better design of a tool, Thank you all for the answers