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Really Bad Type ...

Started by Jason, July 12, 2022, 06:54:35 PM

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Jason

Hi folks,

I'm midway into casting a font and suddenly my type has turned truly awful.



The face is badly deformed, as if the metal is draining out before it freezes. This suggests temperature, but I've increased/decreased temp, more/less water, more/less air, and still terrible.

Or, there's not enough metal getting in the mould to fill the face. I thought maybe my pump was bunged up, but dropping the piston showed a good, full stream of metal from the nozzle. Still, I pulled the pump and cleaned it. No improvement.

I increased and decreased speed, no luck.

Any suggestions?

Jason


Andrew Dolinski

Hi Jason

Sorry to see you experiencing such faults with your type.

It's difficult to identify the root cause as I don't ever recall having faced such a bad problem.

My initial thought was that your pump was blocked. However you say you cleaned out the pump. I take it that your hat valve is ok and that the small hole in the valve is clear?

Next thought is whether the piston is blocked, especially the grooved washer.

Andrew

Ed Denovan



George Miller

Well it's not on my fault finding list either and I'd certainly like to know the answer in case it happens to me. Could you try changing pump, piston, nozzle and mold one by one to see if any of them make a difference?

Good luck

George

Jason

Hi guys,

As I mentioned in my email to some of you, I've tried a lot of things, mainly what everyone has suggested:
  • pulled the pump, cleaned it, hat-valve clean and hole is clear, bottom cap is tight
  • pulled the piston, took it apart, cleaned it, grooves in washer are clear, reassembled according to spec (tighten, back off half turn, tighten lock nut)
  • pulled, stripped, cleaned and reinstalled mould
  • drilled out nozzle and pump passage

Other suggestions have been pump operating adjustments, which I'm about to start. This seems a possible cause because, unlike every other time I've installed a pump, it does NOT want to fit into the operating levers. I have to push down on the top lever to get the pump into position, and it really wants to slide out. This is a new scenario, so something's not right there.

I did do some pump adjustments when I switched to 72pt set-up a few months ago, and recently switched back to small (casting 18pt now). All components on top of the machine are set up correctly for this size, I've triple-checked.

Also, recently I had a flat-mat pop out of the holder, which caused a serious splash and the machine stuck and broke my Type Pusher Lever.  That break-down may have something to do with all of this: perhaps it threw my pump adjustments out of whack?

However, that doesn't explain that I cast 18pt for 4 or 5 days after that issue without this problem showing up. Hmmm.

In any case, it seems Dan Jones' thought that I might have zinc in the pot is doubtful. As the manual says:

When only a few thousandths of one per cent of zinc is present, the effect is immediately noticeable on the surface of the molten metal. The freshly-skimmed surface of properly melted metal should be bright and mirror-like. Metal contaminated with zinc, however, will not skim cleanly; there will be a strong thick film which immediately re-forms as the skimmer is drawn through the surface.

After pulling the pump out this morning I did a good skim, and here's the result 15mins after skimming:



Good, clean mirror, so that's good.

After cleaning the pump and piston again this morning, I'm now heading out to go through the pump adjustments.

Fingers crossed...

Jason



KPMartin

Although your test indicated your pump has good volume, it might not be able to pressurize properly. Watch your pump as the caster is running. If the piston goes a long stroke (this is subjective, it depends on the size of type being cast) it means the metal is leaking out somewhere.

It could be a worn piston, of if it started suddenly, it could be a piece of dross has become lodged in the piston valve (English piston only). It could also be a leak by the nozzle but those are pretty easy to see.

Jason

Hi folks,

I compounded my problem earlier in the week by a human blunder. When cleaning my piston I noticed that some of the threads on my piston bolt were worn, so I took my spare piston and swapped the bolts. What I didn't notice was that the two bolts had different amounts of threading (one for the short piston-end (14-36pt) and one for the long piston-end (6-14pt comp). I then tightened up the end, installed it on the handle, backed it off half a turn, snugged up the lock nut, and put it in the caster. Immediately, I had the problem of swiss-cheese type and very little metal coming out of the nozzle. I thought perhaps I'd put the lock nut on the wrong way around, so I took the piston apart again and discovered, to my horror, that the nut was ruined (pieces broken off). This is because I used the wrong bolt with the wrong piston end, putting too much pressure on the nut. Luckily, this didn't damage my piston head, and I had a spare nut, so once I realize the error and replaced the (worn) piston bolt, put it together and back into the pump, I then had a good, full, steady volume of metal out of the nozzle.

I then completed my pump action adjustments. As a recap, I also cleaned the pump thoroughly, and the mould, and did multiple thorough skims of the pot (to keep it really clean while soaking and cleaning piston/pump parts).

After all of this mucking around, I cast up some 18pt quads to cut in half, and they came out good and solid. I then tried casting some type and, to my great surprise, it had good face.

I only had an hour to cast yesterday (after all the mucking around), but I'm heading out now for a 4-hour session. Fingers crossed the type remains good.

I'm still planning to empty and clean my pot, but I want to get through casting this font first.

Thanks, everyone, for all of your help and suggestions.

Jason


Jason

Hi again everyone,

Well, I'm not exactly sure what did it, but I'm back to casting good type. As my last post indicated, things looked good at the end of the day yesterday, and I got a good 5hrs of casting in today. Aside from some flash (due to the mats) the type is coming out solid, and with a good face.






As I say, I'm not sure if it was cleaning the pump (twice) or the piston (three times), cleaning the mould, thoroughly skimming the pot (multiple times) or working through the pump adjustments, but one or all of these seem to have done the trick.

Thanks so much to all of you who made suggestions.

I'm still planning to empty the pot to clean it and adjust one of the elements (which, like Kevin's, sticks up out of the metal), but I'll finish up this font first.

Jason

KPMartin

Jason,
I'm assuming that the bolt you used was only threaded partway so what bottomed out was the cone nut against the end of the threaded portion of the nut. This generates a force that will try to split the nut, either if overtightened of perhaps from differential metal expansion in the heat.

Indeed, if the cone nut is broken, the pump will develop no pressure. If you operate it manually it can still squirt plenty of metal, but if you plug the nozzle (hold a piece of hardwood against it) you will find that you can still bottom out the pump piston because the metal can just backflow through the piston bore.

For the pump head, I've had to make my own cone nut (what you call the "locknut" I think) because the only one I had was damaged (this was 14 years ago, yikes!). I think I'm also using a modern hex socket head cap screw to hold everything together. I had to run a tap into the end of the piston rod to allow that to fit (because of the difference in thread angle, modern bolts don't fit in Monotype tapped holes of the same nominal thread size). This is not ideal practice for stressed threads because if you switch back to a Monotype bolt in a modern-tapped hole, all the force will be taken by the tips of the thread of the bolt against the root of the thread in the hole. But then few of the fasteners in Monotype equipment are stressed much in that manner.

Jason

Thanks for this Kevin. I'm unfortunately back to the really bad type, and I'm a bit worried by your comments. I've been using a modern tap/die to clear the threads on my piston, piston bolt, and the cone nut. Everything still seems to fit and tighten nice and snug, but based on what you've written I've now altered the thread angles in these parts. My cone nut is in good condition, and I've cleaned and adjusted the piston a dozen times, but still getting this crappy type. I've turned off the pot for the day, but I'll try what you say about plugging the nozzle to see if I can still push the pump down manually. If so, based on your comments, I'm still getting back-flow.

There's also still the possibility of contaminated metal, so I may have to bite the bullet and empty/clean the pot. I really wanted to get this font finished before doing that, but I'm wasting day after day fighting this probem, so it may be time to just get it done.

Nick (Effra Press)

Sorry, I don't have a lot of time to look at forums, so I've missed a bit of this. Jason, if you think it'd be helpful, we could do a Zoom call sometime and see if we can talk through the problem.

As a side note, I've been talking to my dad (a now-retired metallurgist) about zinc contamination of typemetal, and he had some interesting thoughts. It gets fairly complicated, but I'll try to write it up, as this is probably the select group of people who'd find it interesting. The basic takeaway, though, is that it's very unlikely in the situations we're talking about- far more likely to be a different problem.

n


KPMartin

Jason,
I think you're worrying too much about the difference in thread forms. Unless you're assembling an engine cylinder head or high-pressure piping, the difference in thread forms will be very unlikely to be a problem.

Let's face it, no one uses a ratchet and socket wrench to tighten fasteners on a caster. Yes, you might use one, or an impact driver, to loosen something, but when tightening things you just are not applying enough torque to the fasteners for the thread shape mismatch to matter.

But I still do not feel it is a problem with the alloy. That would not come and go like a light turning on and off.

Also, I certainly hope your "tighten nice and snug" does not include the piston head! It has to be loose to allow metal to flow. The cone nut should, however, be tight against the piston stem (handle) thus holding the bolt from turning.

I forget now whether you've checked your metal temperature. A flaky thermostat could explain why the problem comes and goes.

Jason

Thanks Kevin & Nick,

Kevin, I thought the same thing about the alloy: if it's contamination, why did I get a couple of days of good type, and then back to bad stuff? Nick, good to hear your dad's thoughts as well.

Kevin, I'm adjusting the piston head as instructed: tighten the bolt to the cone nut, tighten into the handle, turn the bolt back half a turn then snug the cone-nut to the handle, so the piston head should have a half-turn of play (and make some noise when shaken).

I'm printing today, but next time I spark up the pot I'll do your test for back-flow Kevin: plug the nozzle then push down on the piston to see if it will still go down.

As for temperature, I'm largely flying blind. I have three thermometers. When I set the pot gauge to around 670, one of my thermometers says around 670, but the other two show 40 less (around 630). So, do I trust the pot thermostat and the one thermometer, or the other two thermometers that closely concur? Hmmmm.

I'm still thinking it's a pump/piston issue, as after cleaning the pump and piston yesterday I got good type for about 40 sorts, then shit again. Something in there still isn't quite right.

Jason

Jason

Kevin, tried your piston test yesterday: pushed the wood handle of a wire brush to plug the nozzle and pressed down on the piston: it won't move, so I don't think it's a back-flow problem. Still, something's up, as I still can't get reliably good type. I keep thinking pump. I have three of them, so am going to slowly work through and try each one, cleaning each thoroughly before testing. If the problem persists with all three of them, then I've ruled out the pump.

I have to be honest: many of the other adjustments on the machine confuse the hell out of me. I try to stick to recommendations in the manual, but there are still parts I don't quite understand, and I wonder if I have one of those out of whack. What's weird, though, is that I've cast on this machine on and off for over 8 years and have never had this problem before. I love casting, and love the machine, but it's seriously pissing me off lately. Especially now that I'm cutting mats and want to test cast them!

Jason

So, today was all about serious diagnostics. My gut has been telling me that my horrible type was linked to one of or both of these things:

problems with the pump
problems with pump adjustments

Therefore, I spent the first half of the day thoroughly tearing down and cleaning all four of my small type pumps. Three of the pumps are complete (pump body, end cap and hat valve), but the fourth is missing the hat valve. Here's an image of soaking one of the pumps and the cap/valve for cleaning.



During this process, for each of the pumps, I pulled the nozzles out, thoroughly drilled them out, drilled out the pump arm with the correct Monotype drill rod, cleaned the nozzle-seating cavity, and cleared all threads. These things were very clean when I was done.



I then, very carefully, went through the pump adjustments in the manual once again. Something I'd noticed was that the pump didn't want to stay seated when put into the pot: there was lateral pressure pushing the pump to the right, so that the latch that drops down into the pump mount kept popping out. I had to push down on the piston levers to get enough clearance for the pump to seat properly, but that tension came back as soon as I let off the pressure on the levers. This didn't seem right, hence going through the adjustments again.

Another thing I noticed is that MUCH more metal was coming out when I allowed the piston to drop in the pump, which was a good sign. And I did Kevin's back-flow test (plug the nozzle with a piece of wood and gently try to force the piston down: it wouldn't budge, so no back-flow).

After carefully making the recommended adjustments, the pump seemed to seat more casually, and it was time to pull the trigger.

As I'm about to report in the "Venturing into matrix engraving..." thread, I think I'm back on track. The first handful of sorts had nice clean walls, a detailed shoulder, and good face and edges on the character. So, I swapped in my new home-made matrix and tried that...



Not too bad. The face of the mat needs a light rub on some emery cloth to reduce edge flash, and the face of the type isn't terrific (I'm still working on fine-tuning my cutter tips), but this is solid, type-high type.

I ran a few 6" foundry lines off the machine and they were consistently good, so I'm optimistic that the thorough pump cleaning and pump adjustments have me back on track.

I also managed to accomplish another fix I've been meaning to get to: my elements on both sides were peeking up out of the surface of the metal, so I placed a wrench on the element and tucking a long screwdriver under the pump mount, I gently pressed the element down. To my surprise, both of them slowly sank, and stayed down when I released pressure.

So, a good day of progress!

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