The J-Head Lite will blow your face out

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ohioplastics
I know 316 steel is available, but I don't know how much of a difference it makes. The benefit of stainless steel is it's low thermal conductivity compared to brass.

No was speaking of different stainless steels - there are virieties oftypes exist.Types
Was speaking yesterday - there is a Injection molding process and they have similair issues so using chrome coating of the stainless steel.
Have asked about samples made with different stainless steel types but it is the slow process for me and would require few months to get anything.

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ohioplastics
Thanks to all who communicated these issues to me BTW. It's really helped improve the quality of my product moving forward.

Yes think it is for everybody's benefit. It is a nice variant!

Got mine today. It's the prebuilt version if that matters. My first impression is that it's very well built. It heats up like a champ and the temperature seems fairly accurate. I do suffer from being unable to reliably extrude PLA though. From 180 - 210 I was still getting jams. When the jammed filament is pulled out it looks to have melted/deformed in multiple locations and not just at the junction with the heated end. It's almost like the entire chamber is getting too hot. I think the reason it can work at such high temperatures is because the plastic is so hot that it can be forced out even if misshaped.

Edited 2 time(s). Last edit at 01/24/2014 11:57PM by jaeg.

I've heard people using a cotton ball soaked in olive oil to help PLA extrude. Has anyone tried this?

http://www.makerbot.com/blog/2010/02/06/oil-helps-pla-yes/

It's really just a MK7 hot end, nothing too special about it that it shouldn't extrude PLA.

Edited 1 time(s). Last edit at 01/25/2014 05:49PM by ohioplastics.

I use canola oil to keep my Bowden extruder from binding up. Some of it does end up making to the hot end, and I'm pretty sure that's why my flow problems have disappeared on my eMaker Huxley with its stock hotend. The way I do it is to take a paper towel and lightly apply it to the first 12" of filament, before I put it into the extruder. Oh, and canola oil has a higher smoke point than olive oil (not by much apparently... about 10-15 degrees higher if you're comparing refined canola to extra virgin olive oil).

I would certainly like to hear if "oiling it up" helps anyone's PLA flow problems. I've received my J-Head lite but haven't assembled it yet. It will be one of the first things I try, after building and polishing the inner stainless piece, but would like to know if it helps anyone else.

Hi, tried further with the setup.

few pictures here: (.3mm nozzle) PLA 210deg
Test Print

when it was going stuck - was releasing the plastic with heavy pull and what you can see the strange shape at the end is the place where metal piece connects the PTFE cap.
tighten that a lot while it was hot - make things better but still if I cool the head and then try next print the plastic is not going through - have to push it with knitting needle(1.8mm) - borrowed from my wife. After that could continue print. Again think the bridge setting was too fast - so the lego brick was not finished as it stuck again.

Few other things - with this thermistor I could not make the system temperetature stable (auto PID).

Some of the further improvement I've tried on the hot side of the metal barrel - to use washer made from teflon baking sheet. Cut it with scissors 1.5mm internal and 6 external. this makes the perfect connection without any gap, reduce heat conduction.
Think will add it also to the other side of metal.

How is your J-Head lite doing after improvements?

Am using Sprinter and configure it the following way
in Configuration.h:
// 7 is 100k Honeywell thermistor 135-104LAG-J01
#define THERMISTORHEATER 7

what is the voltage and resistor in the heater of yours?
It is 12V supply in Sprinter and the resistor in this heater is 6.8 Ohm. Was thinking should I replace it with 4.7Ohm one?

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ob1canob
Finevlad, your plastic is melting in the barrel.

Is it correct it should not melt in the barrel? So should I add bigger radiator to keep it cool?

Did the Teflon baking sheet washer help at all?

The barrell has about 8mm of unobstructed space between the heater block and the teflon holder. There's room for 1 nut and a metal surface to absorb the heat. The current heat sink on the Lite is pretty decent for those constraints. Adding more insulation won't help and is in fact counterproductive.

The melting point of PLA is fairly low, so the teflon holder is well within it's temperature limits during this aplication. With less friction in the new barrell, it shouldn't be neccessary to run PLA at a higher temperature. It's been running PLA at much lower temperature in recent months.

Keeping up with the technical data is a challange. We definetly need more user feedback to define the speeds and temperatures of PLA and ABS, as well as construction methods.

So, are you using PLA without any oil lubricant? Or with?

I'm using vegetable oil with the PLA still. I'm afraid expanding the steel barrel to accommodate a 4mm ptfe tube will lead to more heat traveling up the barrel and ulltimately degarding the long term servicability of the ptfe holder.

I think solving this issue would mean switching to grade 5 titaniium barrels to account for the less mass that comes with a 4mm ID x 6mm OD tube. But, this material is only available to me in 1/4-20, which means I'd need 1/4-20 heater blocks and nozzles.

For now, the metric system is necessary for international sales.

If you think about the setup - the barrel ID is 2mm while the plastic is 1.75.
Heat conducting is not only through metal but plastic as well.
So If hot end is left hot for some time - then plastic start melting higher and start touching walls of the barrel that are relatively cold and stick.
The teflon washer is working in so it is limiting the plastic connection in this case, beside the good contact between barell and nozzle.
So I believe it is working in my case.
Maybe it is because the PLA I have have a high melting temperature. With the new one I've got recently it is even higher.

About the contact point of the nozzle and barrel.
What I've found is that in the current assembly it is quite hard to keep them coaxial and tight.
Had to sand them first to make good surface and then was srewing while keeping 2mm rod inside of both.
The washer is good in this as it is like rubber filled all uneven surface.

With this washer was actually able to do first print.

Maybe I'm wrong in something. but would be nice to see what heat model do we have with this setup.
As this is just experiment setup for me at the moment I've got few more different barrels of different shape and metal type and with teflon lining. Metal type is different as magnetic force is different I can feel it. All stainless steel.
Time is limited to conduct all combinations and my setup is not optimal for doing changes so don't expect me to try it over night. The next iteration would likely be next weekends only.
What I've already noticed - the other barrels I've got all have chamfered end where it is connecting to the nozzle.
You can imagine as steel is harder it would push into nozzle for better contact with less heat conduction in this point.

The one with teflon tube inside was some bad as they cut tube slightly more and now it has the same issue where plastic fill space between tube and upper of the barrel. was thinking I need to cool barrel extra - this is in the plans.

Edited 1 time(s). Last edit at 04/11/2014 05:31AM by finevlad.

That's a really interesting point about PLA. I might have been too focused on the thermal properties of the metal components, that I ignored the the fact that PLA has a very long transition zone.

I think I'll have to use a fan to shorten the transition zone, which brings up a whole notther set of issues. Unfortunately I can't just go on thingiverse and use a shroud made for the J-Head because it wouldn't fit, and I need a shroud, because even with the ceramic insulation, the fan wouild over-cool the 3W heater. I'm a lot better at putting holes in metal than I am at designing 3D fan apparatuses, but I'll give it my best shot.

Generaly, I've been applying high temperatures to PLA to negate the jamming caused by the plastic sticking to the walls of the tube (~230C). I have had some sucess at lower temperatures with the addition of the vegie oil, but the optimal setup to go about extruding PLA is as of yet undetermined. I just put a .3mm nozzle on today and I'll do some testing.

The chamfering the SS tube would be great to do, but it'd add about $1 to the unit cost, and I'm not sure it'd make that big of a difference.

How much would it cost me to get a SS tube with a 3mm bore?

Disclaimer: I'm clueless, So don't think there is anything smart to follow.

I'm currently using a Huxley style hotend on my Smartrap. It's worked pretty good so far. It uses a 3mm bore in which you insert a 3mm OD 2mm ID PTFE Tube into. I'd like to try that here.

I just bought one, hasn't arrived yet.
It said i bought the last one!
I will mainly just be using ABS. Should i consider oiling it too?
Looks like a interesting design, I like that you can buy most of the things at a hardware store!

Good luck!

Also, I will be using a full time fan on the hot end. So it shouldn't be a problem for me, But would there be any way to increase the structural rigidity. I would think it would be better if you didn't leave it to the PTFE to hold the whole thing together.

Best of luck!
Sage

Oil on ABS isn't necessary. The only problem is with PLA. Some times the fan can over cool, so make sure you can control it's speed. You can place a thin steel mount between the heater block and the copper heat sink to support it from there if you want. Congrats on getting the last one. I've got the first. Printed for a good half a year. I'm gonna donate it to the Smithsonian, but I don't think they'll be interested.

Ok.....so even with the full time fan the ptfe melted. i was only running my hot end at 220c and don't know how it happened but when i looked over at the print the ptfe was distorted and the rest of the hot end had fallen out of the ptfe.. when i poked the ptfe with some pliers it was soft and bendable...i know my hot end temp is right because if i lower it a few degrees the abs wont extrude.
would you consider a redesign?

Sage

Did you contact me on Ebay? I don't have any record of you buying one.

Edited 1 time(s). Last edit at 07/02/2014 02:25PM by Cameraman.

Or are you sure you bought it from me? I remember there was a rash of people buying the kits and assembling them (not very well) to resell them for less than I was charging. That's why I decided to stop selling kits and cut the price of the assembled hot ends. I took a pretty big hit financially as the kits were very popular, and I'm not getting as much for assembling them, but it was the right thing to do for the brand.

Do not buy from 123monika310 on ebay! Or any other scamster trying to sell knock off gear pretending it's the real thing. I do not believe in retail and there are no authorized retailers for this product. This product requires a meticulous assembly process to function properly. You can not just slap the parts together and expect it to work. They need to be assembled while hot for the components to seat together properly. If there are any others out there who have been sold a knock off, please contact me. Thanks Sage.

Finally got my repstrap running and printing. I just printed the 20mm box with the J-Head lite MK-II using PLA. No jams so far. The heater does seem a bit anemic though, with the PLA cooling fan blowing on the bed at 25% power the hot end drops in temperature from 190C to 170-175C (still ok for PLA). Maybe I need to re-calibrate the PID with the fan blowing? With the fan off, no problems (I might not really need the fan).

Oh and PLA sticks like glue to hot glass at 65C that has been cleaned with acetone.

In any case, I now have an Aluhotend on order from Oz and we will compare the two.