Author Topic: Need Machinist to make a Pellet Swager (Read 19491 times - 2 votes)
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darkcharisma · « **Reply #60 on:** July 26, 2018, 11:19:25 PM »

i dont think Ken has a “step” in the skirt taper like the ones here from China.

subscriber · « **Reply #61 on:** July 26, 2018, 11:23:50 PM »

Duy,

It looks as if that narrow band at the punch OD is intended to have excess lead bleed past the punch. Some of the videos of (similar?) Chinese dies being used show the flash being trimmed off by sliding a blade over the top of the two die-halves while they are still together.

Is this the plan; or how will excess lead be bled off?

darkcharisma · « **Reply #62 on:** July 27, 2018, 12:16:00 AM »

Like i said in a previous post before while we were discussing about psi. the lead will be bleeding off around the punching die, and gets cut off with a razor knife or something like that. simple and stupid is the motto here. well, more like...i dont wanna do anything else fancy to drive cost of production up haha.

subscriber · « **Reply #63 on:** July 27, 2018, 12:41:41 AM »

Bleeding around the punch works. Ease of use, and cost are the main factors, after pellet design quality and "production" consistency.

Wayne52 · « **Reply #64 on:** July 27, 2018, 01:05:02 AM »

Those are looking really nice for sure !!!

ken47 · « **Reply #65 on:** July 27, 2018, 01:17:06 AM »

Actually I use CAD to drive manufacturing decisions, My punch has a steps which are with reference to the balance of the pellet. The CG is adjusted through depth of the rear cavity. My design has CG at centroid of the pellet while being 18 grains and 7mm long.

subscriber · « **Reply #66 on:** July 27, 2018, 01:48:41 AM »

Quote from: ken47 on July 27, 2018, 01:17:06 AM

My design has CG at centroid of the pellet while being 18 grains and 7mm long.

Ken, I could not imagine anyone putting this much effort into making dies, unless they were designed in CAD.

The relationship between the CG and the centroid is important:

1. Diabolo pellets that work out of smooth bore barrels have their CG well forward of the centroid because they rely completely on drag stabilization.

2. Bullets usually have their CG behind their centroid and must be spun "fast enough" about their long axis to remain stable in flight.

There are an infinite range of possibilities between these two principles. I would suggests that FX smooth twist barrels operate closer to #1 than #2. Thus, your pellets may work better out of barrels that achieve faster spin rates, than FX smooth twist barrels. If that is the case, a different base punch design could be made that works with smooth twist; even if that requires reducing the pellet weight to 16 grains...

Ultimately, results on target are all that count; not theorists who sit at home, commenting on the real work performed by others. Keep up the good work.

darkcharisma · « **Reply #67 on:** July 27, 2018, 02:09:34 AM »

Sub, all theories will be tested to rule out negative possibilities as much as possible. for me, pellet or bullet. i still prefer the CG to be right at midline as a starting point. with swaging, you can vary this CG as you make different punches. i am sure casting makes adjusting the CG easier with different hollow pins provided. That way, we have control over how the pellet acts in flight, thus accuracy. if these are not accurate and we can't tweak it, then it's failure!

Ken, i see some differences in your punch design compared to HEN punches from China. I'll show it below, little machine can take care of it and doesn't effect CG and centroid much (also see posted pictures above). you can also find pellets from JSB also has this 90 degree inside step and still keep their skirt thickness to .026inch that is 0.66mm

subscriber · « **Reply #68 on:** July 27, 2018, 02:16:45 AM »

I might be confused, but isn't the lead bleed path at the OD step I added, shown in blue?

darkcharisma · « **Reply #69 on:** July 27, 2018, 02:24:22 AM »

no Sub,

That is the punch stop for it to touch the punching plate when hammering! I can even see the HEN punches sometimes stops too short and creating less of a 90 degree inside angle at the skirts. I am telling you KEN, i got eyes for little details man.

See the third picture Sub, the crossed white section is the punching plate on top of the cavities. the punching plate has hollow cavities underneath to allow for lead bleed, then sliced off with knife. either machine down little at the tip or the hole length of punching rod like shown

subscriber · « **Reply #70 on:** July 27, 2018, 03:24:23 AM »

Thanks, Duy. Makes perfect sense now.

ken47 · « **Reply #71 on:** July 28, 2018, 12:50:17 AM »

I Got the 90 degree step on the punch DarkCharisma, its 0.02 mm in length. just a little bit of machining will do it. I will make one today. Guys I am moving to tool steel and I am using EDM to make the new prototype, The S.S. is way too complex to machine (what I mean is that my reamer simply glides on surface and chips off small grains creating a bearing surface which is not uniform, with tool steel I will have a good amount of material to cut using reamer) . I measured the pellets the head size was 5.48 not 5.52 what I had designed, SO.... We are going EDM.. The combinations for EDM were tested yesterday and the first spark combination gives a predictable allowance of .XYZ mm. hence a tool can be designed accordingly. CNC is time consuming and tools don't last longer.

Sub I am using CAD to design and FEA to simulate results.

subscriber · « **Reply #72 on:** July 28, 2018, 01:38:38 AM »

Ken, you have some serious skills. That includes recognizing when to change paths, and move to something that should yield better results.

EDM will result in cavities that are slightly "frosty". The roughness that this texture imparts to the pellet may be of no consequence, although purist may prefer a smooth look. Roughness all over the pellet may reduce its overall drag, by creating small eddies in the manner that shark skin does. The roughness may also increase the Magnus effect; where the pellet is driven up or down by cross-winds.

Anyway, If you do have roughness that is of a large enough magnitude to make the pellets hard to remove from the die-halves, then a post EDM polishing process would be indicated. I don't know if anyone does electrochemical polishing of die cavities, but abrasive polishing should work fine - as long as it is applied evenly.

The bottom line is that you may have to EDM to a diameter that is perhaps 0.025 to 0.05 mm undersized to allow for polishing to final diameter.

I recognize that you are developing a process to create these dies. This involves room for what some may call, error. I don't see a learning step as error.

Once you have figured out your working recipe, making other dies, in other calibers and configurations should be easier and more profitable.

subscriber · « **Reply #73 on:** July 28, 2018, 02:20:33 AM »

As pellet roundness is important, you may need to rotate your EDM electrode slowly, as you burn the cavities.

Continuous electrode rotation should not be required, as the amount of steel eroded per spark event is small, and the electrode erosion even smaller. A play-less chuck that runs true, and has a ratchet mechanism to increment it springs to mind.

An incremental electrode rotation of perhaps 35 degrees, every so often should work. Just ensure that the increment does not divide evenly into 360 degrees, else you could end up with a "lobed" pellet. Ditto, the angular "timing" of continuous rotation with respect to the sequence of erosion events. Let the burn events and electrode rotation "phase slip" relative to each other, to evenly distribute any erosion unevenness.

Or you could make two sets of identical non-rotating electrodes; where the second set evens out the deviation in roundness, induced by erosion of the first...

darkcharisma · « **Reply #74 on:** July 28, 2018, 03:52:48 AM »

Sub, i have no idea how edm works, and their terminology. so are the processes you explained. do you have or work with EDM and may be able to produce some of these molds to possibly include a video of whats all involve in its operation?

Ken, good choice to go with Edm and tool steel. i have seen some very good products cut with EDM to tight tolerance at a local shop.

ken47 · « **Reply #75 on:** July 28, 2018, 04:26:30 AM »

Sub, Thats some serious info. I think that making 2 set of tools will prove to be effective with existing machine setup. I will post some pictures of the tool once its made (next few hours). Thanks for the info Subscriber.

subscriber · « **Reply #76 on:** July 28, 2018, 05:30:21 AM »

I wish I had my own EDM machine. Lots of youtube videos on making them at home. Of course, to erode metal accurately, the electrode stage has to move on precision rails, under backlash-less control; just like a decent CNC machine.

My EDM experience is indirect. The latest is related mostly to plastic injection mold manufacture; where I am the product architect, rather than the tooling or end product manufacturer.

That said; understanding what happens to EDM electrodes makes it easy to predict that the electrode will erode unevenly when you burn one die-half at a time; unless the electrode is rotated (or mitigating the effect by replacing it with one or more identical electrodes for a "finishing cuts" that are repeated at full depth).

If you finish eroding one pellet's "pocket" in the die-half, then move to the next, the last "pocket" will be measurably smaller than the first; due to electrode erosion. As you want all the pellets to measure the same, you want to burn each pocket partially, before moving to the next; and so on. That way, all pockets see about the same degree of electrode erosion and their diameters should be much closer together.

You can probably monitor electrode erosion by measuring the faces nearest the steel being cut, from time to time. That knowledge should enable you to implement an effective mitigation strategy.

Wayne52 · « **Reply #77 on:** July 28, 2018, 06:17:06 AM »

Quote from: ken47 on July 28, 2018, 12:50:17 AM

I Got the 90 degree step on the punch DarkCharisma, its 0.02 mm in length. just a little bit of machining will do it. I will make one today. Guys I am moving to tool steel and I am using EDM to make the new prototype, The S.S. is way too complex to machine (what I mean is that my reamer simply glides on surface and chips off small grains creating a bearing surface which is not uniform, with tool steel I will have a good amount of material to cut using reamer) . I measured the pellets the head size was 5.48 not 5.52 what I had designed, SO.... We are going EDM.. The combinations for EDM were tested yesterday and the first spark combination gives a predictable allowance of .XYZ mm. hence a tool can be designed accordingly. CNC is time consuming and tools don't last longer.

Sub I am using CAD to design and FEA to simulate results.

EDM is the cat's meow when it comes to precision on tool steel, that mold shop my brother helped put together bought a nice EDM a few years back, my brother even mentioned if I had everything ready as far as the Cad Cam(CNC for the mold block) part goes that I could get them to make something at a very reasonable price. He even said that most everything that he's been doing in that shop recently has been prototype stuff.

subscriber · « **Reply #78 on:** July 28, 2018, 06:18:12 AM »

Info on rotating EDM electrodes:

https://www.researchgate.net/profile/Janak_Valaki_phd/publication/284443119_DEVELOPMENT_OF_A_MICROCONTROLLER_BASED_ROTATING_ELECTRODE_ATTACHMENT_FOR_RAM_TYPE_ELECTRO_DISCHARGE_MACHINE/links/56533fba08ae1ef92975eba6/DEVELOPMENT-OF-A-MICROCONTROLLER-BASED-ROTATING-ELECTRODE-ATTACHMENT-FOR-RAM-TYPE-ELECTRO-DISCHARGE-MACHINE.pdf

Basic operation of sinker EDM. For the pellet dies, the sinking would be "sideways", rather than down:

darkcharisma · « **Reply #79 on:** July 28, 2018, 10:25:58 AM »

Quote

my brother even mentioned if I had everything ready as far as the Cad Cam(CNC for the mold block) part goes that I could get them to make something at a very reasonable price. He even said that most everything that he's been doing in that shop recently has been prototype stuff.

Wayne, i like the sound of that...reasonable price. can ya tell your brother to actually make one?
Really neat stuff Sub

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Need Machinist to make a Pellet Swager

Author Topic: Need Machinist to make a Pellet Swager (Read 19491 times - 2 votes) )

Author Topic: Need Machinist to make a Pellet Swager (Read 19491 times - 2 votes)
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