[SMMAssociates]

If the part is MIM'd properly it will produce a part equal to or better than investment casting (which most parts are made by nowadays). The issue is MIM allows molding a far more detailed part which has designers sometimes making parts too intricate and far too delicate. The PXT was an honourable attempt but just too delicate a design.

LDA:

Mine broke in the square cross section area of the hook part. Had to have been a void or metallurgical issue of some kind - it's quite a bit bigger than the Browning extractor gets anywhere along it's length....

I would have expected the little projection that holds the two halves together to be the failure point, or perhaps the "hole" in the main body. The hook would also be suspect.

Guess we should take a poll as to where these breaks occur?

My view is that the MIM parts are basically tossed into the parts bin straight out of the oven, and from there go right into a gun. Parts which are subject to stresses when machined, fitted, etc., are more likely to break before shipment, and thus don't need the same level of inspection, and the QC folks may have missed that. I'm not sure that any inspection will catch a poorly cooked (I forget the name for the final process), but it should spot voids and other "guaranteed" failure points as well as molding issues.

Regards,

 

[LDA]

LDA:

Mine broke in the square cross section area of the hook part. Had to have been a void or metallurgical issue of some kind - it's quite a bit bigger than the Browning extractor gets anywhere along it's length....

I would have expected the little projection that holds the two halves together to be the failure point, or perhaps the "hole" in the main body. The hook would also be suspect.

Guess we should take a poll as to where these breaks occur?

My view is that the MIM parts are basically tossed into the parts bin straight out of the oven, and from there go right into a gun. Parts which are subject to stresses when machined, fitted, etc., are more likely to break before shipment, and thus don't need the same level of inspection, and the QC folks may have missed that. I'm not sure that any inspection will catch a poorly cooked (I forget the name for the final process), but it should spot voids and other "guaranteed" failure points as well as molding issues.

Regards,

You are absolutely correct, MIM parts are not subject to the same handling rigour as even invesment casting (breaking off the mould & machining), after coming out of the sintering oven they would go to heat treating then black oxide and be dumped in a bin for assembly. MIM is primarily a replacement for investment casting and produces its cost savings in the reduced handling, machining and finishing of the parts.

I commissioned a MIM facility and am intimately knowledgable on the process. Such voiding is due primarily to two reasons: the sintering powder was not mixed properly with the polymer carrier, backbone and surfactants in the raw material, or convoluted flow patterns in the injection mould cause shear stresses in the flow which causes the powder to flow uneven in the carrier. I would be curious to see where people are having their failures.

The Para slides and frames are invesment cast and have also been know to have voiding within then, this ussually comes out during the sanding and sandblasting and the voids are welded up to avoid scrapping the parts. These types of voids are primarily cosmetic in larger parts but can prove fatal in smaller ones.

 

[robertbank]

Lda

Have you spoken to Para and others to see if they weld up their frames & slides when they find a void or are you surmising this. Seems to me to be a rather odd practice considering the stress the frames in particular go through.

Stay Safe

 

[SMMAssociates]

LDA:

The former day job was a plastic extrusion facility. We owned a molding plant, too. I did QC work for a while before getting into computers, and while not exactly an expert, I know which end of the molding machine holds the goodies .

I concur 100% with your comments. Plastics generally flow better, of course, but I've seen some hilarious results with mixed materials - colorants & fillers actually, as well as some oddities during color changes as the "system" is flushed out from one color to another.

All kinds of interesting things can happen....

100% inspection is the only way to go with MIM parts because they're just not stressed at all.

If you're lucky (like my shooting buddy's new Kimber), the part (a thumb safety's "long" lever) will break before you get more than a few miles on it. The hazard is something like my extractor, which lasted about a thousand rounds. (In my case it may have been over-the-top reloads - we're not really sure.) They should break a lot sooner ....

Bob:

I'm not sure about the "welding up" story, but there are low-stress and zero-stress points on the frame that might be candidates. However, I wonder how the cosmetics would be. Unpainted steel (or SS or Aluminum) ought to show the scars unless the polishing job is perfect (which ought to cost more than sending the frame back as scrap). Painted frames might let you get away with this, but I wonder. I guess we need to ask if anybody's had a hunk of frame fall out....

Regards,

 

[robertbank]

Cast parts will fail and do. Forged parts can and do as well. One has to remember their were gunsmiths before casting of parts turned up in the firearms industry.

I seriously doubt Para or any gun manufacturer would accept welded up frames for production. Why bother? Their cost on a per item basis is insignificant to their production costs and less so on a competed gun. I respecfully submit that it would not be in their interests to do so and am confident that if spotted such frames/slides would simply be discarded.

Stay Safe

 

[SMMAssociates]

Bob:

IMHO the MIM parts are more likely to surprise the owner unless they're 100% inspected. Investment casting is next on my list of things to worry about because there are also flow issues that can provide voids or bad materials (contaminants) that can screw things up. However, I think they tend to still need some machining and handling that should find the really nasty problems.

I don't know what Para would do about the frames - there probably are some non-essential areas that could be handled, but you're right about the cost issues. Not to mention the PR issues.... Much of a gun frame is kind of flimsy, too - welding thin materials takes a lot of skill to avoid warping things. That's not cheap....

Regards,

 

[robertbank]

Much of a gun frame is kind of flimsy, too - welding thin materials takes a lot of skill to avoid warping things. That's not cheap....

Exactly! The labout costs to play around with such issues would be more than the frame in the white would cost. I am sure they just toss any frames/slides that have problems. Watched a TV documentary on the production of Glocks. At the end of the line if the gun failed to fire they just got tossed in a garbage pile.

Stay Safe

 

[SMMAssociates]

Bob:

Dunno....

If I had a "ready to ship" Glock (or 1911) and it wouldn't fire, I think I'd have some trainees around to check it out first before tossing it....

But the concept is accurate. All but the most minimal reworking is just too expensive.

OTOH, one could suppose that some of that stuff ends up in lunch boxes....

Regards,

 

[robertbank]

Show was 60 minutes and they did a piece on it a number of years ago. Just wasn't worth fooling around with. Quite a production line though.

Stay Safe

 

[SMMAssociates]

Bob:

Don't know about Glocks, but if Colt, S&W, Springfield, Kimber, or Caspian (and probably a few others) want to send those rejects this way....

Regards,

 

[LDA]

Cast parts will fail and do. Forged parts can and do as well. One has to remember their were gunsmiths before casting of parts turned up in the firearms industry.

I seriously doubt Para or any gun manufacturer would accept welded up frames for production. Why bother? Their cost on a per item basis is insignificant to their production costs and less so on a competed gun. I respecfully submit that it would not be in their interests to do so and am confident that if spotted such frames/slides would simply be discarded.

Stay Safe

I am aware that the welding did occur because I worked for Para and have witnessed/done it myself. Castings can be tricky because they may be porous, but I was successful after only a couple of tries with a TIG welder (and I'm no welder by trade), just blob a bit on and grind it down.
As for cost savings, a frame that was discovered when the casting first arrived would definitely be discarded, but the time when these particular issues would arise were when the frames were being hand finished prior to sand or bead blasting. At this point all the CNC and hand finishing labour has gone in to it and the 5 min it takes to do it can be worth it. One has to realize these are strictly cosmetic defects on a few out of a thousand frames or slides, and if a void is discovered under the trigger gaurd or on the mag well these are areas that provide no structural support. All the important bearing surfaces have been machined.
I cannot say if they currently do it - if production is substantial enough that they have given up on any reworking of parts, I can say at the time it just felt wrong to toss a perfectly good part away.

 

[shane45-1911]

This has moved WAY off topic.
Closed.