stainless steel and temperature control

[lewisss]

Hi, just wanted to share some screens from device monitor,
and wonder if anyone can tell me what is going on here.

with NI200 the selected temperature is hit and it remains there nice and steady,
with titanium it gets to the temp and then fluctuates a little
with 317L Stainless it gets to the temp then fluctuates quite wildly

Now the vape on all three is very good so i have no complaints, in fact i prefer the taste of the SS out of all three, and it is a dream to work with.

I am presuming the difference in the charts is because the temp coeficient chart gradients are a lot shallower on the SS therefore the resistance difference between two temperatures is a lot smaller than ni200 or titanium, which would also explain the slight variation on the TI coils.

am i correct in thinking this ?

Thanks in advance

  

[VapingBad]

I would think you are right and the mass of the coil also affects how smoothly it can be regulated.

[bingwhip]

Did you try and do a dry cotton test?  Even if I turn mine way down below 420 (normal cotton browning) it still burns the cotton.

I've been having similar issues with mine.  Though, unlike yours, it's not a good vape.  What I've found is I have to lock my resistance about 0.03 or so below what it's reading, or it gets way too hot.  So hot my cotton bursts into flames.
I'm hoping this can be worked out in a firmware update, as SS is really the reason I bought this mod.  I understand the limitations and difficulty of TC at such a low variance, but it seems WAY off as it is.
I don't know if this is a good place to post this, but I'm hoping we could get a discussion going.  There's almost no info I can find on SS TC usage and I'd really like to get it running reliably, without force offsetting ohms.

Hcigar VT200
Subtank Mini RBA Section
26ga 316L 9wrap  2.3mm ID 0.80 ohms

[mknight]

Could it be that you need to use tcr for 316l? I noticed most ss out there is 316 or 316l. Getting killer performance with dual coil, 24g at 0.2 ohm.
Setting tcr to 0.001

[lewisss]

quote "mknight

8 hours ago Could it be that you need to use tcr for 316l? I noticed most ss out there is 316 or 316l. Getting killer performance with dual coil, 24g at 0.2 ohm.
Setting tcr to 0.001"

317 and 316 should perform pretty much the same as each other, 317 is just a bit more corrosion resistant than 316 (which should mean safer possibly)

I have downloaded the 317l csv from steam engine which should match the difference in resistivity between 316 and 317

The 'L' just means there is less carbon in the alloy which just means they are more resistant to intergranular corosion when used for welding......I trust we are not vaping at those temperatures!!

for anyone thats interested here is the difference in resistivity:-

[lewisss]

bingwhip said:

Did you try and do a dry cotton test?  Even if I turn mine way down below 420 (normal cotton browning) it still burns the cotton.

I've been having similar issues with mine.  Though, unlike yours, it's not a good vape.  What I've found is I have to lock my resistance about 0.03 or so below what it's reading, or it gets way too hot.  So hot my cotton bursts into flames.
I'm hoping this can be worked out in a firmware update, as SS is really the reason I bought this mod.  I understand the limitations and difficulty of TC at such a low variance, but it seems WAY off as it is.
I don't know if this is a good place to post this, but I'm hoping we could get a discussion going.  There's almost no info I can find on SS TC usage and I'd really like to get it running reliably, without force offsetting ohms.

Hcigar VT200
Subtank Mini RBA Section
26ga 316L 9wrap  2.3mm ID 0.80 ohms

Dry Burn experiment

Ok a controlled experiment all settings  as follows
power setting 100 watts
preheat power 200 watts
preheat punch 5
preheat time limit 1s
puff for 10 second (auto through device monitor)

test at 350, 400 450 degrees farenheit all test done on velocity rda with muji cotton
coil 1: ni200 0.4mm 8 spaced wraps 3mm diameter 0.91 ohms stable on escribe

i wont put pics up for this one !!! graph eratic as expected, but there was no charring or colouring at alll until i took it up to 500 (just a slight colour to the cotton)550 (light brown charring)and 600 degrees, dark brown charring)

Coil 2:- titanium .4mm 8 spaced wraps 3mm diameter 0.452 ohms stable on escribe

Well that surprised me! almost identical results to the NI200 no colour change at 350,400 450, very very slight colour at 500, light brown at 550 anddarker at 600, but not as dark as the ni200 at 600.

now for the 317L...

Coil 2:- 317L  0.45mm 8 spaced wraps 3mm diameter 0.529 ohms stable on escribe

350 degrees very light brown similar colour to the NI200 and TI at 500 degrees,
400 light brown again, similar colour to the ti and NI at 150 degrees higher,
450 burnt through the cotton,
600 ignited instantly


so there you have it...
it seems that SS is getting about 150 degrees hotter than NI200 or Ti throughout the range, so either the csv file is wrong or the csv file is wrong, ..... i cannot think of a second reason!

but it fits with my experience with all three wires, i like NI and TI at 420-480 degrees and 317L at 300-340..


I hope this has helps. and i agree we need more disussion on SS I am sure someone could ccome up with a revised resistivity csv for stainless

[VapingBad]

SS covers a large number of alloys, resistivity is no the same at the Temperature Coefficient of Resistance that the DNA used to gauge temperature.  The simple answer is if temp limiting is not working you almost certainly have non matched alloy and TCR.  Hopefully wire vendors will start to provide TCR  curves in the near future.

IIRC the video Brandon did on the DNA40 launch with PBusardo he explained that a difficulty with ss was the variance in the alloys.

(ss will not be nearly as accurate as Ti wish will not be as accurate as NI)

[lewisss]

VapingBad said:

SS covers a large number of alloys, resistivity is no the same at the Temperature Coefficient of Resistance that the DNA used to gauge temperature.  The simple answer is if temp limiting is not working you almost certainly have non matched alloy and TCR.  Hopefully wire vendors will start to provide TCR  curves in the near future.

IIRC the video Brandon did on the DNA40 launch with PBusardo he explained that a difficulty with ss was the variance in the alloys.

(ss will not be nearly as accurate as Ti wish will not be as accurate as NI)

thanks for the reply, after reading more on steam engines TCR calculatorit states
"

Sensitivity

Under "Sensitivity", you'll se a number like for instance 81 %. This means that in the temperature range typical to vaping, the resistance change will be 81 % of that of the resistance change would have been for a pure Ni200 coil. (A Ni200 coil will always score 100%.) A higher number means that your temperature control will be more accurate.

It is theoretically possible to score higher than 100 %, but first you'll have to find a coil material with a higher TCR than Ni200.

How low you can go while maintaining reasonably accurate temperature control, depends on your 510 connection, your atomizer, your building skills, and more."

and as sensitivity= temp control accuracy here are the figures for different coil materials:-
kanthal A1 0%
Kanthal D 1%
nichrom N60 9%
SS316L 17%
SS317L 20%
titanium 1 59%
NI200 100%

[bingwhip]

VapingBad said:

SS covers a large number of alloys, resistivity is no the same at the Temperature Coefficient of Resistance that the DNA used to gauge temperature.  The simple answer is if temp limiting is not working you almost certainly have non matched alloy and TCR.  Hopefully wire vendors will start to provide TCR  curves in the near future.

IIRC the video Brandon did on the DNA40 launch with PBusardo he explained that a difficulty with ss was the variance in the alloys.

(ss will not be nearly as accurate as Ti wish will not be as accurate as NI)

Shouldn't there be minimal variance though?  We're not just talking SS "wire" here.  We're talking 316L SS wire, which is a pretty specific makeup.

Whelp, before just making claims, I did google it.  "316L" Fe, <0.03% C, 16-18.5% Cr, 10-14% Ni, 2-3% Mo, <2% Mn, <1% Si, <0.045% P, <0.03% S
That's a 2.5% variance on carbon, a whopping 4% variance on Nickel.  So yeah, we're dealing with potentially very different TCR curves on any steel it seems like.

I think the solution is we need better TCR curves.  My SS build seems to read quite consistently.  It has a very regular climb in resistance as it's heat goes up.  So I just need to correct the values.  I wonder if I could contact the vendor I got the SS from for a more specific data sheet on what it's composition is.

[VapingBad]

I think that the specs for ss are more about corrosion resistance and hardness so allow those variances in make up which could change the TCR considerably, I am no expert.   This is why I feel that wire vendors should be providing the TCR in an ideal world.

[blueridgedog]

I have a roll of 316L and will be giving it a try.  I am curious if anyone has a curve they are happy with - going with the default (steam) from the start.

[Robbybob]

I think there's more factors than just composition that affect a materials TCR. NiFe30 is available with quite a wide range of TCR's from 0.0030 to 0.0050. We requested some NiFe30 in tempered from a wire manufacturer and were told that while they could produce it they couldn't guarantee the TCR unless it was annealed. So either the way it is annealed can affect the TCR or they can only measure the TCR accurately by annealing the material.

Also with a material with a low TCR such as SS the temperature increments are much larger.

As far I understand 304 and 340 are a better choice for temperature control if you want to use a stainless steel

[acorpcop]

I've been using 316L in TC with good to mixed results.  I've found that a heavier gauge helps with the bouncing around of the temp, likely due to the mass of the coil.  Best results I've had   are with 20g.  Available all over at crafts stores as 316L beading wire.  Torch the living snot out of the wire to anneal it as it is "half hard" as is.  Difficult enough to wrap when softened.  

That 20g is beast mode vapeing with a DNA 200.  24g was "meh."  Did not even try 28g by itself.  

SS claptons were an epic fail.  Hotspot issues and issues from the oxidized layer that forms on SS. . . really odd combo.  Could not get it to behave itself.

[Jaquith]

I've run across this topic and had the same thoughts about SS TC issues. The SS316L wire I received using the TCR files would glow my coils orange and light my cotton on fire. So I don't know if it's my wire or not, but I manually edited the Steam Engine's DNA 200 SS316L profile. After 7 attempts it seems to be regulating better and my cotton isn't lighting on fire. 

Values I'm using now:

Temperature (degF)	Electrical Resistivity
-58	0.923064
68	1
212	1.05
302	1.105
392	1.147
482	1.2
572	1.225
800	1.29

[Digiplay]

I've tried two 316L wires, and I've tried three stainless curves and none of it is accurate.  I'm guessing we need to make our own.  I have a vested interest in creating my own temp curve - but I don't know how to do it or if it is reasonable for an average user to do so .

Does anyone have a link to a how to on creating the profiles? I bought a pound of 316L on ebay, and the wire is very good, I just can't work with it in temp control - a pound is roughly equivalent to 1500 ft, for about $18 shipped... as you can see with that quantity It would be great to accurately profile it.

Some users have stated that the change is too miniscule in resistance to get accurate readings from stainless - at least to the level of nickel.  I haven't found Titanium particularly good either, but better than stainless

[lewisss]

Hi I have been struggling too with stainless steel for a while as it is a dream to work with and I do have a work around where I have got the vape exactly how I want it! It does involve using escribe and it is just a way of changing the settings slightly on my ss profile so that the device makes the chip and temp control work a different way. When I get home tonight I will get some screen shots and run through some examples of what I do. Currently running a 2.5mm 9wrap dual spaced coil of 317L .5mm 0.18 ohms at 440f and 55watts. On a velocity and Hcigar vt200 And it is great! I am using the steam engine ss317 csv With this system you should be able to do any ss coil and get the same results. Sorry to make you wait , but I am working at the moment. Will post back in about 8 hours

[lewisss]

Sorry I am late but this is what i have found works best for me!

now I know there will be those of you that will say i am not using this in temperature control, but when my dripper runs out of juice i can feel it backing off so the temp control is working.

Ni200 I can quite happily set my temp and put the power at 200 watts and know that when the temperature reaches my setting the curve will flatten out and stay level at that temp till the juice runs out.

MY THEORY
Stainless :- we have seen that as the csv for stainless is such a shallow curve a very small increase in resistance = a large increase in temp . so the dna 200 has to keep cutting out and adding power leading to ss being an inconsistent vape.

not so much inconsistent but more ''thin'' , NI200 has practically a constant power going through it once it reaches the set temp whereas with SS the DNA 200 chip is just not fast enough to keep up with the minute changes of resistance.

So we need to work around this. and this is what i have done.

below there are three screenshots from device monitor.

the first one {ss100JPG} is how i would normally set up NI200. temperature where i want it 400f, and power at 100 watts. and as you can see we have the usual unstable pattern when we reach temperature which leads to the thin, weak vape.

the second one[ss20} is dropping the power to 20 watts and increasing the temp to 440F

here the temp and power jump up with the preheat punch and then the temp dips before climbing again.  This also leads to a thin weak vape.


the last one {SS40} is the point i have found with this coil and this juice a get excellent result temp 440f power 40 watts. although the temp never reaches my target temperature it hits immediately with the preheat punch and then just climbs steadily till i stop drawing on it. 

So yes I know it is a bit of a PITA but it is worth working with the tools we have to get this result.

why? because not only am i getting a nice consistent thick vape. I am also getting back the subtleties of flavour in the juice as the heat ramps up. something I didn't realise I was missing until i tried this.

**the graph was set at 15 seconds and the average puff was 3.5 seconds**

Have a go if you have time. I think it is worth it.
 ss 100.bmp      ss20.bmp      ss40.bmp      

[techbearus]

Thanks for sharing @lewisss .. makes a lot of sense now.. was testing DNA200 @ 40W power and same for preheat to simulate a Dicodes and it is a lot smoother compared to 100W preheat with 54w power settings..

I can now better understand how the SS profile can be better tamed with optimal (lower) power ..  it doesn't hit the temperature or give warm/hot vape but definitely gives a smoother vape, so I keep these two in different profiles and use them as my mood dictates ... (smooth and silky) or (rowdy and warm) ..

[Jaquith]

Has anyone tried the values that I posted? Also if you dry burn, cotton burn test, what happens? While I edited my CSV file in Excel, here's a link to the actual file http://www.filedropper.com/dna200-ss316ldjaquithv7 Good luck and any feedback would be appreciated.

[m4k3r]

Jaquith said:

Has anyone tried the values that I posted? Also if you dry burn, cotton burn test, what happens? While I edited my CSV file in Excel, here's a link to the actual file http://www.filedropper.com/dna200-ss316ldjaquithv7 Good luck and any feedback would be appreciated.

I'll try it out this weekend and report back. Picked up some 316L from a local craft store and wasn't too satisfied with the flavor or warmth of the vape. Thank you for this.

[snake1210]

Jaquith said:

Has anyone tried the values that I posted? Also if you dry burn, cotton burn test, what happens? While I edited my CSV file in Excel, here's a link to the actual file http://www.filedropper.com/dna200-ss316ldjaquithv7 Good luck and any feedback would be appreciated.

been running my 317L with this profile for the last hour and it is regulating the temp a lot better im getting a more satisfying and constant vape experience now thanks for that Jaquith works a treat 

[Jaquith]

I appreciate the feedback! I know it runs a tad warm, but when I change the values it gets more unstable, but I'll tweak it probably this weekend and if I can get it better I'll post it here. Thanks again.

[m4k3r]

Jaquith said:

I appreciate the feedback! I know it runs a tad warm, but when I change the values it gets more unstable, but I'll tweak it probably this weekend and if I can get it better I'll post it here. Thanks again.

Reporting back after slapping together a dual coil build in my Twisted Messes rda. I must say, damn. Thank you for this. I wrapped 20g 316L around 2.4mm 8 times. Reading .08 ohms. Temp control is working nicely so far. Nice smooth climb to 450F (never going much past 350F surprisingly) and completely satisfied with the vape. Haven't done a dry burn test yet but hopefully will get around to it this weekend.

Edit: Ohms locked at .08. 450F@50W, preheat=200W, punch=5,time=1s

[Jaquith]

Thanks for the feedback. I've been using a 0.40 Ohm dual coil 26 gauge SS316L at 60W with 75W, punch=2, 1 sec. If I use 100W, punch=5 or higher and > 1 sec it can give a dry hit if the wicking isn't fully saturated. 24 gauge is easier and regulations better, so I've been testing on the most 'fragile/sensitive' conditions.

[DDolan]

Does anybody have any experience using G plat? I've been playing with Gplat with the temp control and it just doesn't seem to work as well as nickel I keep tweaking my curves but I still can't seem to get it 100. Im just trying to not use nickel It doesn't last long and im not trying to rebuild every two days and not be able to dry fire my coils.