Steel Mk8 nozzles?

[Joe Larson (aka Cymon)]

Does anyone make Steel 0.4mm MK8 compatible nozzles? So I can be one step closer to calling my prints "food safe"

[Jetguy]

Not that I am aware of and I've been in the loop on most things.

The only one bragging about being food safe is the Prusa hotened?

http://prusanozzle.org/

 

I just did some searching myself and you see a bunch of silver looking pics of nozzles, but all the dscriptions are saying that they are a base material of brass.

[Jetguy]

The only other stainless nozzles I ever knew of for a MakerBot were the MK5 and MK6 nozzles. They were stainless as well.

Good luck finding those. If you do find some, tell me where!!!

[TobyGadd]

Can 3D-printing really be considered food-safe? Under a microscope, there are so many nooks and crannies that could harbor bacteria. I don't see how a part could get really clean, especially since heat can't be used. I'm not sure that bleach could reach all of the recesses.

[Jetguy]

While I agree with that statement fully, it's been discussed every couple of months and I was hoping to avoid bringing it up.

 

Rather than harp on why it's safe or not, if they ask for a stainless nozzle, I was just trying to point out what I know about where to find them. In the end, on this foodsafe thing, it's not what I think anyway. The user is the one who has to sleep at night and face the people they feed. I say let them deal with the fallout one way or the other.

[TobyGadd]

All true. As another guy who works in the food industry, I just wanted to make sure that the OP had considered the issue. It would really suck if he got a bunch of people sick at a restaurant or something--or had his business shut down by a food inspector--all because he simply wasn't aware of previous discussions.

[Jetguy]

See, I knew Joe had seen all  this before- see here https://groups.google.com/d/msg/makerbot/345Lzzxnbjo/qKuNNAZi07MJ

[Joe Larson (aka Cymon)]

And Joe wrote this:

http://www.3dhacker.com/3dprinting/entry.php/66-Food-safe-filament-unless-you-re-3D-printing-with-it

Yes, I know that lye is caustic, acetone is flammable, and 3d prints are not food safe. I also know that there are 4 reasons why they're not food safe, brass nozzles are one of them. The other three are the material, the layers, and the fact that "food safe"is an official designation that you have to apply for. The are food safe plastics, you can vapor smooth the layers away, but I am not going to apply to the FDA to get a food safe certificate. Happy?

[Brow pinch]

I can't find any mk6 or 7 nozzles anywhere, but I'll admit I want looking that hard since I wasn't 100% sure they'd fit. If they do I'll broaden my search.

[Jetguy]

Sorry, MK6 won't fit your machine. I was trying to give an indication in history of bots that had stainless nozzles and that list if very small and impossible to find these days.

Again, the MK6 is a rather large thread, so big I bet a MK7/8 nozzle fits inside it.

[Joseph Adams]

Joe, I might be willing to try making a couple for you. I know it's probably pretty tricky, but it could also be fun (at least just for a couple) I've been wanting to try making some nozzles; got a 4 axis CNC mill and lathe at my disposal. If there was any real demand for them I could have a bunch made on a screw machine. What grade stainless do you think you need, 316?

[Dan Newman]

On 20/03/2014, 6:03 PM, Joe Larson (aka Cymon) wrote:
> And Joe wrote this:
>
> http://www.3dhacker.com/3dprinting/entry.php/66-Food-safe-filament-unless-you-re-3D-printing-with-it
>
> Yes, I know that lye is caustic, acetone is flammable, and 3d prints are not food safe. I also know that there
> are 4 reasons why they're not food safe, brass nozzles are one of them.

But you can leech out the surface lead: 1 part hydrogen peroxide (common 3%) and
two parts white vinegar. Soak the nozzle for 5 minutes at room temp. The brass
turns a buttery color. If the solution starts turning green and the brass dark,
then you've soaked it too long. (No harm done, just way too long.) This technique
of removing surface lead from brass is done in home brewing.

Dan

[Joe Larson (aka Cymon)]

Adams, steel grades is something I don't know anything about. Is a cnc machine for four this job? If this we wood I could see it being made of of a dowel that you sharpen, tap, and drill out. Still, I'd be willing to try out anything you make.

Dan, I've never heard of that technique. Interesting.... I may give that a try just for the silliness of having it.

[Ryan Carlyle]

316 or 316L would be ideal as far as standard stainless grades. 304 or 430 might also work but I'm not sure about long-term corrosion potential at elevated temp and contact with various plastics / build plate treatments.

What type of stainless are the thermal barriers made from?

[Joseph Adams]

No, CNC equipment is not a requirement for this job. I was only qualifying my resources so you knew that I had the capabilities to actually get his done and produce accurate parts.

-Joe

> On Mar 21, 2014, at 8:18 AM, "Joe Larson (aka Cymon)" <joeal...@gmail.com> wrote:
>
> Adams, steel grades is something I don't know anything about. Is a cnc machine for four this job? If this we wood I could see it being made of of a dowel that you sharpen, tap, and drill out. Still, I'd be willing to try out anything you make.
>
> Dan, I've never heard of that technique. Interesting.... I may give that a try just for the silliness of having it.
>

> --
> You received this message because you are subscribed to a topic in the Google Groups "MakerBot Operators" group.
> To unsubscribe from this topic, visit https://groups.google.com/d/topic/makerbot/VJaAHQj5DNE/unsubscribe.
> To unsubscribe from this group and all its topics, send an email to makerbot+u...@googlegroups.com.
> For more options, visit https://groups.google.com/d/optout.

[Joseph Adams]

Blanked one out tonight.  Just need to drill the 0.4mm hole (have to order a micro drill) and thread it.

[Joe Larson (aka Cymon)]

Are you going to test it out or do you need me to?

[Au Groups]

why do you need steel nozzle?

--
You received this message because you are subscribed to the Google Groups "MakerBot Operators" group.
To unsubscribe from this group and stop receiving emails from it, send an email to makerbot+u...@googlegroups.com.

For more options, visit https://groups.google.com/d/optout.

--
Mike D., Au Group Electronics, www.AuElectronics.com

[Ryan Carlyle]

Food safe printing. Brass is not FDA approvable, so to speak. It has lead in it.

You can use a food-safe material but the printer itself can't be certified food-safe unless the extrusion path is stainless steel.

[Joe Larson (aka Cymon)]

Please, please, PLEASE read the rest of this thread. It's been covered before and it's painful to retread.

https://groups.google.com/d/msg/makerbot/VJaAHQj5DNE/7-SPdMK9AX0J

A steel nozzle will not make your prints food safe, but it will be one less barrier to being food safe.

[Joseph Adams]

Not sure what you're saying Joe, but if you're referring to Ryan's comment, I think he was just answering AU's question.

[Joe Larson (aka Cymon)]

On Saturday, March 29, 2014 5:26:06 PM UTC-6, Joseph Adams wrote:

Not sure what you're saying Joe, but if you're referring to Ryan's comment, I think he was just answering AU's question.

I was referring to AU's question, the answer to which has already been covered. Ryan had a good answer, too.

[Fastrack]

Lol.  Not this again.  Almost every tap I've installed in recent years has some brass in the flow - granted the water you drink is not heated to 240C, but still.........!  The "lead" in brass is surface lead from manufacturing, as Dan pointed out - do a search.  I would be more concerned with the voids left in a print.

Lego is ABS and kids chew on it..  if you acetone vapor a piece there are no voids, now I wouldn't boil water and drink from it, but a funnel or cold liquids (egg separator) I made I don't see an issue.

But Joe was merely asking about a Steel nozzle, I wouldn't think it would conduct the heat as well as the brass.

Ben

http://www.thingiverse.com/fastrack

[Ryan Carlyle]

I'm much less concerned about what's in the 3d printer than the FDA will be if you try to get it certified.

Is there even a real process for certifying 3d printers for making food containers?

[Jetguy]

While I agree stainless has a lower rate of conduction, contrary to common belief the plastic is NOT primarily melting in the nozzle. Heater blocks themselves are at least a good solid 10mm thick . The stainless thermal barrier tube and the nozzle BOTH have 5mm of threads that interface into the heater block. If the heater is the source of heat, heat radiates in both  directions from a center plane. Proof is in pictures of an disassembled extruder that actively had PLA printing, then was rapidly cooled to give a look at what really happens inside.

You can clearly see the EXACT change in diameter where the filament melted inside the thermal barrier above the heater block nearly 7mm before it ever touches the nozzle. This is why I keep telling folks, nozzle clogs are nearly never the nozzle.

They are a blockage in the thermal barrier transition zone. The proof is in that picture right there.

[Ryan Carlyle]

Getting a little OT here, but I'm pretty sure you could build a "de-clog" circuit by attaching a heater to the cooling block. When the filament jams up the thermal barrier from excess retraction, you would heat up the cooling block a bit above the glass point of PLA, and push the now-softened clog back down into the hot end.

Hear conduction through the nozzle is only critical at very high extrusion rates or if you're using a PTFE tube style extruder that doesn't have any significant melting in the thermal barrier. Any MK8 design stainless steel nozzle ought to be fine at normal extrusion temps.

[Joseph Adams]

Ok, finished...I think. Not bad for the first shot, but not perfect. I didn't have a good enough center drill and the .4mm drill walked on me a little. So, the extrusion hole is probably about .002-.003" (.05-.07mm)off center (you can see this in the attached picture). Also, I think I might need to take a little more material off the taper so that the land at the end is a little smaller. Not sure how much this matters; opinions?

[AL M]

I looks pretty darn good Joe .They are tough to get centered I went through the back side and it followed the large hole down to the tip .This is done with a .5 bit. and you can see its brass and i know ss would be a little tougher. I would say if done for duel , just do a head alignment it go.Again looks good

Al

[Ryan Carlyle]

Looks good. I would say a bigger land is better. It means more heat transfer cross-section to the tip. And it means you can extrude a wider bead of plastic if you want and still get good results.

[Joe Larson (aka Cymon)]

I've had nozzles from makerbot that were more of center than that.

[AL M]

I ordered white brass ,i wanted to try .5 ,they went right in the garbage .What Joe just made in SS will work perfect 

[Joseph Adams]

Joe, let me know where I can ship this thing.  Is there a way that we can exchange information privately?  I'm torn on whether or not I should test it first.  I'd like to give you the honors, but I also would like to know how it performs while it's still in my hands so that I can learn something if there is something to be learned.  Guess I don't have strong opinion either way, just a quick disclaimer though (sorry, I have to protect myself):  I don't make any warranties or guarantees regarding the performance or safety of this nozzle.  I won't be help responsible for any damage that occurs as a result of using this nozzle; use at your own risk.

Again, sorry for that, you can't be too careful.

Oh, one last thing.  I don't know the exact grade of SS, (just grabbed what we had laying around) but it is magnetic so I can tell you it's at least a 400 series.  If this works out and you want me to make more, you can purchase the exact grade and have it drop shipped at my address.  

[AL M]

Joseph ,

 Would mind if i ask how long did it take to make start to finish

[Joseph Adams]

Eh, probably about 2.5 hrs. Would only take half that if I had to do it again though. A lot of that time is figuring out machining strategy and inspecting an existing nozzle. Wrote a quick program to do a pecking cycle on the mill for the 0.4mm hole that only took .001 cuts. Didn't have a chuck for the lathe that would hold a drill that small, plus not enough spindle speed anyway. Plus had to machine the hex because I couldn't find hex stock the right size (although I didn't look that hard).

Thought about drilling from the back side like you suggested btw, but was worried about hanging that little drill out there far enough to reach.

[AL M]

Well if you get into making more here is what i used If this helps.The bits are delicate but the brass is soft , SS not so much anyway Nice job.

  AL

[Joseph Adams]

Thank you. That's a sweet little drill collet, where can I get one?

-Joe

[AL M]

I had to go to Flee bay Jetstools . I didnt shop to hard on this think it was about $6 they also have bits

On Thursday, March 20, 2014 10:50:00 AM UTC-4, Joe Larson (aka Cymon) wrote:

Does anyone make Steel 0.4mm MK8 compatible nozzles? So I can be one step closer to calling my prints "food safe"

[Joe Larson (aka Cymon)]

I've buzzed you out of the groups, Joseph.

[Joseph Chiu]

The flip side to that is that for really thin layers, it feels like I got better results with a smaller land tip.  This is anecdotal, as I've not done a more formal A/B testing, and I'm currently all pointy-tipped.  Add one more experiment to add to the to-do list!

On Tue, Apr 1, 2014 at 2:13 PM, Ryan Carlyle <temp...@gmail.com> wrote:

Looks good. I would say a bigger land is better. It means more heat transfer cross-section to the tip. And it means you can extrude a wider bead of plastic if you want and still get good results.

[Hammerhead]

Not looking to 'stir the pot' (pun intended) but thought I'd share a few thoughts on the 'food safe' issue.

About six months ago I printed an oversized burger press for myself out of ABS (egads!) consisting of a base, lid for pressing and internal 'plunger' to help release the formed patty.  When it was done, I sanded it smooth on the interior and wiped all surfaces with acetone to help polish it, even it out, and seal whatever openings there might have been.  After every use I use detergent to get the grease off and then scrub with some powdered cleanser with bleach.

I can report that after dozens of burgers made and eaten, I'm still here to tell the tale.  The way I figure it, I'm more likely to get hit by a meteor than suffer from any ill effects of brass-nozzle-printed-food-unsafe-abs product.  Would I use it for long term storage?  Probably not, but for this purpose, it seems more than adequate.

Hope this helps.

[Joseph Adams]

Quick update.  At Joe's request, I did install the nozzle on my 2X and test it out today.  It went well in general but there are definitely some differences regarding performance characteristics.  It should be noted that I duplicated the tip angle based on a set of 0.25mm nozzles that I had laying around, which were 80 degrees, while the standard 0.4mm nozzle has a 90 degree taper.  I mention it because I think it has an effect on how the nozzle dissipates heat and therefore affects nozzle operating temperatures.   When running PLA, it was necessary to run about 20 degrees hotter than usual to avoid overloading the stepper (this was not true for ABS).  I'm not sure yet if perhaps this is only because the nozzle takes longer to reach steady state due to the lower thermal coefficient of SS.  Or to put it another way, the nozzle may not actually be at the temperature that the TC is reporting at the beginning of a build because it hasn't had enough time to reach the same temp as the rest of the hot end. 

I still want to compare extrusion diameters with the new nozzle and a standard nozzle; I can report that the new nozzle extrudes a filament that is 0.52mm diameter for PLA and 0.47mm for ABS.  I haven't repeated for the standard nozzle yet.  I have confirmed that the physical diameter of the new nozzle gauges at 0.40mm, maybe slightly under.  Otherwise, the nozzle seems to work ok.  That's all for now.

-Joe

[Ryan Carlyle]

ABS itself is more thermally conductive and has a lower heat capacity than PLA. That makes it relatively easier to melt with the same heat flux capacity through the nozzle.

[Joe Larson (aka Cymon)]

On Wednesday, April 2, 2014 5:42:56 PM UTC-6, Ryan Carlyle wrote:

ABS itself is more thermally conductive and has a lower heat capacity than PLA. That makes it relatively easier to melt with the same heat flux capacity through the nozzle.

I did not know this. Maybe that's why I have less problems with ABS than PLA. 

[Gian Pablo]

Yes - that is exactly right. Anything that causes the flow of filament to stall (nozzle too close to bed, filament feed issues) can lead to a blob of softened plastic forming at the point where the filament enters the block.

[Gian Pablo]

What is the internal geometry of the nozzle like? In particular, how at what angle does it taper from 1.75mm to 0.4mm internally?

I spoke to someone who'd worked at Makerbot R&D testing this specific issue, and he said he got surprisingly different results from trying different internal taper angles. Let me check back with him and confirm what worked best - it was different for ABS & PLA.

[Joseph Adams]

I think this is a good point and makes perfect sense (from a purely mechanical perspective considering a free body diagram) that the internal taper would affect counter pressure at the nozzle.  I didn’t give it much attention because I assumed it was just a standard drill point taper (118 degrees, could be 135).  It’s tough to inspect without cross sectioning and destroying a nozzle…although I could use some metrological casting material, but didn’t want to get that involved.  I don’t have a clean standard nozzle that doesn’t have some leftover plastic, but I could inspect a 0.25mm nozzle.

 

-Joe 

[Ryan Carlyle]

A few reasons why the internal angle could matter:

• Obviously the cross-section of metal affects the temperature gradients and heat fluxes (although maybe not by much)
• Smooth transitions create somewhat less pressure drop at a pipe constriction than abrupt diameter changes (although at these low flow rates, I'm skeptical about how much this matters)
• Creation of stagnant dead zones in corners may allow plastic to thermally decompose and gunk things up
• The rate of necking down in diameter may affect the alignment and crystallinity of the polymer chains being extruded -- this can marginally affect the strength, heat capacity, pressure drop, and a variety of other parameters

[Ryan Carlyle]

FYI -- MBI nozzle dimensions:

[Joseph Adams]

Ryan, thank you for providing the dimensions.  Unfortunately, it doesn’t detail the internal taper angle, and I don’t think there is enough information to trig it out.  Could take a graphic measurement if we knew that it was to scale (probably is would be my guess).  Assuming it’s to scale, the angle is certainly smaller than drill point (looks like about 60 degrees) which means I would need a custom ground tool to duplicate.  I did find 60 degree drills on mcmaster but smallest size available is 3.0mm, maybe someone else supplies smaller.

 

[Ryan Carlyle]

It does look like 60 degrees to me too. I'm pretty sure you can be a few degrees off and it won't matter.