Tuning Huma reg sealing disks too soft

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Seeker

Seeker

Member
Jan 23, 2022
584
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Europe, Poland
Hi,

I discovered that the tiny nozzles of all my Huma regs are not straight. They are slightly off center - crooked. I had to use a magnifying glass to find it out. The white sealing disks offered by Huma are very soft - they are not made from delrin. Soft sealing material is more forgiving and it can compensate the fact that the nozzles are not straight and square.

I fixed that by making the nozzles square - resurfacing. I replaced the white disks with delrin ones. It all gave me much better consistency and no reg creep which I had experienced before.

Thanks.
 
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Yes Huma discs are very soft. I prefer FX regulators over Huma.

In Huma, soft disks work very well when these are new but with the passage of time the system shows issues of creep etc.

Once I used delrin to replace Huma soft disk but it didn't work as Seeker said that the other contact area is not square. 

Thus for use of delrin disks, the mating part must be made square. 

Bhaur
 
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The huma regulators I have rebuilt had a delrin disc in them from the factory. The rebuild kit from huma also is a delrin disc. 

Screenshot_20220527-225418_Chrome.1653740602.jpg


Wonder why they used a different material in your Huma regulators?
 
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I have been making replacements from Delrin stock obtained at McMaster.

https://www.mcmaster.com/8738K16

I can vouch for what Seeker and Mubhaur are saying...the OEM part is noticeably softer. I don't know what their material actually is, or if it is a blended material that's mostly-Delrin-so-lets-call-it-Delrin, or if it has something to do with how it's made. It looks to me that it is a soft core material, possibly foamed, with a solid skin.
 
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Sometimes I wonder why I buy tuning regulators which I have to tune.



As I said, I replaced that soft disk with a true delrin one which is considerably harder. I polished it with a 7000 grit wet paper and I glued it together with a shaft using some very thin glue. I also made the nozzle square. There is a very simple test to verify if the nozzle is nice and true. Just try to place the piston vertically on a flat surface so that it can stay straight on the nozzle. I guarantee you won't be able to do it with a factory piston unless they changed something which I tend to doubt. The last thing which I did was the belleville washers polishing. I used a thin layer of NanoOil on them. Everything together gave me what I expect from a tuning regulator.

Lastly, next time I disassemble the reg I will use NBR90 orings because the biggest one has some signs of extrusion.

Every single detail counts when it comes to precision pneumatics.


 
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The first time I rebuilt a Huma reg, I went through this thought exercise but didn't want to influence your thinking before asking. 

No doubt you have a point if the disc is a loose fit down in the reg body, such that it has the potential to shift laterally and get pinched at a different spot against the valve seat each time the regulator cycles. Bonding it to the piston will help ensure the dimple remains aligned to the raised orifice.

I decided against bonding it for a few reasons:

1. Concern that a trace bit of adhesive could break free and cause a problem.
2. Uncertain of what adhesive (e.g. epoxy, cyanoacrylate) will actually bond well to Delrin, further increasing the potential for #1.
3. Increased effort the next time the seat needs servicing (getting old adhesive off the end of the piston).
4. Inability to simply flip over the disc to expose a fresh surface.
5. An abundance of caution since many of the ones I rebuild are for other people so I try to avoid introducing things that could make it hard for them to get it serviced in my absence.

With those considerations in mind, I instead size the disc for a slip fit to the regulator body and just let it float. In high end regulated guns (Thomas, Daystate, etc.), the ES is frequently around 10 - 15fps and no evidence of creep when checking first-shot velocity after a 24 hour idle period.
 
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HuMa seat disks IMO only get damaged for two reasons ....

NOT using the 2mm grub screw in adjustment bonnet to DAMP fill rate / speed, which allows spool to impact seat faster causing denting.

NOT Manually screwing down adjustment bonnet until it bottoms out to get a turn count when wanting to get an idea on current position.



As a tuner and having been using Huma regs for many many years ( 2 previous designs worth of time ) have serviced / rebuilt 100's and the seat is not an issue so long as the 2 above reasons are adhered too.
 
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If speaking of the Raised " Volcano Rim" portion of the adjustment bonnet against sealing disk ?

We will have too agree to disagree. There done on a rotating CNC lathe, where concentricity is guaranteed. Hole is in the middle and rim is created facing off end stopping short of the hole, O.D. is machined and threads cut very likely without re-fixturing. Now the exact sequence of programmed steps I have no idea.



Just understand that parts in the round spun on Lathes really have no way to get such features out of center unless done so deliberately.



Scott S



PS,

let me add ... Threaded parts with always have radial clearance or they would bind up. This makes for a place where if there is dirt, a hair or any garbage at all in the threads of the adjustment bonnet it could side shift it a few .000 and make the seat not centered within housing or upon the disk.
 
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It is clearly visible that the hole is off center.



I am not sure what program they use but if such small details like the 'volcano rim' (or, as I called it - a nozzle) are machined in soft material like brass then bad things can happen easily. I am not a CNC expert though. I know for a fact that resurfacing the 'volcano rim' and using real delrin made the consistency considerably better. Anyway, no more Huma reg for me.
 
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