A new method? Hybrid DT

[ryokox3]

Well I've been working like many others for the perfect solution to powder coating. I don't think we will ever get perfect, but we came a long way in a short time. Recently I decided to do some experiments to make the process better. The Airsoft BB Dry tumble method is quite new and really works well. If you use a powder like Super durable wet black, you get almost ES results in one try.

Still Some have it work really well, and others have trouble, not to mention some powders do not behave. Some people can't pick out the boolits with nitrile gloves without removing the powder, so we use hemostats, pliers, or other rigged up tools. Personally I think it has to due to humidity and the amount of static created. So I went about experimenting and after many failures I have something that works really well.


I started with my #5 plastic bowl, but I think this would work as well with a stainless bowl, or any other kind as we will be taking away the need for the #5 plastic. I lined the bowl with some tin foil then added powder and boolits. I did a BBDT to make a 'control' group. Then with some other boolits in the bowl I connected the ground clip from my ES gun to the tin foil. Next I removed the powder hopper from the es gun and ran a wire from the positive element to above the powder. I have the Craftsman ES gun, but I'm sure you can do similar with the HF one. I'd love for someone to show a few pics of that Es gun set up the same for comparison.

OK, now to make myself more clear here are a few pics.


Here is my wire attached to the positive element of my ES gun.



Here you see my lined bowl. The ground clip is on the outside of the tin foil. Inside the bowl is the other end of the positive wire from the ES gun. You do not want it too close to the bottom of the bowl as it will spark. I plan to use a lid and thread the wire through a hole in it to control depth. For this test I just held the wire+ bowl in one hand to swirl and ran the es gun with the other. The es gun has no powder in it, it just is making a charge.

The results were great. I got average coating with my control group, but once I ran the pc gun the powder jumped onto the boolits. It was even charged longer so I could add boolits and they coated well without continuing to run my es gun. With great results I decided to try a finicky powder. Picked up some HF yellow and tried them. Without the es gun they did not want to DT. With the ES gun method they were very well coated.


Here are some of my results. The bottom pink boolit is from the control group and it has some bare spots. The others used this hybrid method. Also you can see 'whiskers' especially on the HF yellow ones. That is not a PC defect, it has to do with pressure casting in this mold causing whiskers in the vent lines. These boolits are actually from my reject pile.


Smash test. The HF one looks like it needs some more time baking, but none of the flakes came off.

I hope this helps others. Let me know your thoughts. I do plan to do some more playing to refine the process.


Hmm, after previewing this post... Am I the only one who thinks HF yellow is really orange?

-Ry

[a.squibload]

So you're putting a charge on the powder?
The hot wire doesn't touch the powder or the boolits?
Interesting, could get or make a high voltage charge circuit
pretty cheap without buying the whole gun.

[Blanco]

A new acronym ETP (Electro Tumble Plated).....isn't that the same one for the pregnancy test??

[ryokox3]

So you're putting a charge on the powder?
The hot wire doesn't touch the powder or the boolits?
Interesting, could get or make a high voltage charge circuit
pretty cheap without buying the whole gun.

Pretty much. The hot wire does get powder on it as some gets airborne. You also no longer need the BBs. That will make picking the boolits easier. You do need to get it petty close to the powder and I admit I had it spark a bit when I got too close. Still I did not feel any shock. The modified lid will make the positive wire much easier to control.

Not sure if PC can ignite when airborne like grain dust in a silo. That is the main reason I'm avoiding the sparks so much. Maybe someone smarter than me knows the answer to that. Your high voltage setup sounds like a nice option to those without an es gun.

Yes I'm charging the powder. Granted the boolits should be getting a charge also but I think the ground prevents that somehow.

[ryokox3]

A new acronym ETP (Electro Tumble Plated).....isn't that the same one for the pregnancy test??

I like it. Or maybe etc - Electro tumble coated, though that already is a common acronym.

[ryokox3]

Ok when doing this method, do not forget to put the ground clip on or else you will get a little shock. Other than that one oops I'm liking the results of this method.

[Smoke4320]

Not sure if PC can ignite when airborne like grain dust in a silo. That is the main reason I'm avoiding the sparks so much. Maybe someone smarter than me knows the answer to that. Your high voltage setup sounds like a nice option to those without an es gun.
[/QUOTE]

yes you can ignite the powder with a charge .. I have done it twice while spraying bullets.. big flash and fire .. fairly easy to put out .... would highly recommend you NOT put a lid on the bowl.. could have an explosion..
just like a grain bin ...

[ryokox3]

I'm glad you said that Smoke. Thank you for the warning.

[a.squibload]

Good weather for casting last night, storms rolled through.
Not so good for dry tumble, had trouble getting the powder to stick.
High humidity the culprit?
Did my first double coat. Boolits were hot for the second DT,
seemed to help. Might see about getting some volts on them.

[ryokox3]

I wonder if I can charge just the powder first before swirling or adding boolits. Just dip the wire in the powder in the bowl. Will need to have a high spot to prevent the sparks. Maybe a project for tonight.

[blueeyephil]

So, I wonder if my electric fence charger would work? 5000 volts with a good ground. Touched it a few times with the weed eater last might. I was wearing rubber boots and still got a good tingle.

[ryokox3]

So, I wonder if my electric fence charger would work? 5000 volts with a good ground. Touched it a few times with the weed eater last might. I was wearing rubber boots and still got a good tingle.

That might work, Hopefully it is not so much a charge that it is too thick

[ryokox3]

Last night I had good results with 'charging' the powder without shaking it. Basically I added boolits to the foil in the bowl, attached ground clip. Added powder and then ran the charge over the powder. No shaking yet so powder was not airborne to risk igniting. Then I shook it, and in as little as 3 -4 shakes I had very good coverage. It was thick enough to have to tap my hemostats on the bowl side to get excess off the boolit. I could not simply pick the boolits with my nitrile glove as it came off then, but with the hemostats it worked better than asbbdt. Also my house is very humid this time of year, and it raining outside probably did not help.

[castcat]

Good experiments that you've undertaken. A thought occurred to me about your setup and my quest to perfect these PC methods AND reduce the labor content. What if one were to use your grounded bowl setup and the hemostats to pick up an uncoated bullet and just dip the driving band section of the CB"s into the powder WHILE the hemostat is attached to the positive wire, thus charging the CB's and attracting the negatively charged power to the positive charged CB/hemostat probe? Of course you would have to insulate the hemostat to protect from shock, but if this worked you'd only be handling each bullet once to attach to hemo, dip into powder, and deposit onto baking sheet/non-stick Al foil/parchment paper. Then bake , remove, cool, dump into bucket. No swirling, shaking, BB's, carefully picking up CB's etc. What do you think?

[popper]

High humidity the culprit? Yep, try leaving the powder in the AC space, with a paper towel over it to dry any 'left-over' powder. It only takes 26 mVolts across the heart to 'defib' you so be careful. Most wire insulation is only good to 600 volts. I tried to spray with the ES gun into a bowel of boolits that was on a grounded plate - didn't work. Your grounded bowel seems to work better. Might try a ES screen suspended under an insulated cover, grounded bowel. Hit the pedal, off the pedal then swirl? Trying to charge the boolits doesn't seem to work. Sure made pretty boolits.

[ryokox3]

no the boolits need to be on the ground side rather than charged, so I think the charged hemostats will not work. Now if they are part of the ground that may but you still need to charge the powder. Not sure I'd want to be touching the ground though so insulated hemostats would be required. I make sure to have an only plastic section of the bowl so one hand is not touching anything conductive. Anyone recall the correct way to say the phrase 'finger to finger, hand to heart'. Something like that, basically if your 1 hand completes a circuit it stays there while if both hands it then goes from hand to heart to other hand.

[a.squibload]

Yep, you don't want a path through your body.
Also watch for leg touching metal table, etc.

Powder application is getting interesting, lots of good ideas.
Thinking if the boolits get too much charge they might look like shag carpet,
but that could be useful, maybe if several thousandths extra diameter is needed?

I was in Wallyworld today, got some black plastic BBs, will give that a try.

[castcat]

no the boolits need to be on the ground side rather than charged, so I think the charged hemostats will not work. Now if they are part of the ground that may but you still need to charge the powder. Not sure I'd want to be touching the ground though so insulated hemostats would be required. I make sure to have an only plastic section of the bowl so one hand is not touching anything conductive. Anyone recall the correct way to say the phrase 'finger to finger, hand to heart'. Something like that, basically if your 1 hand completes a circuit it stays there while if both hands it then goes from hand to heart to other hand.

I agree, the hemostat should be the ground side, the bowl the positive side. I did an experiment with full wave rectified 120 Volt AC, current limited to 1.6 milliamp. Could only get approx 120 to 150 volts this way and dipping the ground attached needle nose holding a bullet got very little more powder than dipping without any DC applied. I couldn't find any specs on the hi voltage supply on the ES guns at HF. Not in their owners manual. Anyone know what the voltage is on these devices? I'm getting ready to toss an old non-flat screen tv (tube type) and I could strip out the HV flyback power supply. They generate 20k volts approx.

[popper]

HF is about 11Kv, better ones run ~ 20Kv. If it's a color TV, ~ 35Kv. You get pretty sparkles if you use carbon bleeder resistors. BW used 19 Kv. there was a guy about 1 1/2 yrs ago that was making & selling the HV brick - DIY powder coating gun. IIRC was about the same $ as the HF on sale.
When I was dealing with radar, TWT & laser, HV is was 'one hand in the pocket, one on the probe'. After you wake up you get a trip to the ER for an EKG. Don't bother to ask.

[castcat]

popper, thanks for the HV info. Looks like I will be cannibalizing an old color TV soon.