hotend type ?

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hotend type ?

Postby lennym » Sat Dec 15, 2012 6:40 am

Hi guys,
I've been thinking about upgrading my 7x12 ZTW to add some 3d printing capabilities and besides the seemingly necessary extruder motor and the hot bed pcb,

I am wondering what hot-end should i get.
It seems that most people go for the j-head or the MB nozzles.
Would love to hear some opinions which way should i swing among these two.
My criteria are reliability and feature size. I am willing to spend a little extra for having less down-time and debugging non-flowing filament.

BTW - what is the downsize to go to as low nozzle opening size as possible (i saw they go to 0.35mm, what am i risking if I go that low ? )

I also found this guy here:
http://reprap.org/wiki/LulzBot/Budaschnozzle

It costs around $100 on amazon, but seems to be somewhat of a better quality - had anyone had any experience with it and ztw ?

Thanks in advance,
Lenny
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Re: hotend type ?

Postby roller » Sat Dec 15, 2012 11:34 pm

Firstly, on nozzle size, the most height you can lay down in a layer is in direct proportion to your nozzle size. So a bigger nozzle can do a slightly larger layer height than a smaller nozzle. This means faster prints as the nozzle can lay down taller layers. Generally though most people will go for smaller layers to give a higher print quality. So in such cases a smaller nozzle is better because it also puts out a narrower extrusion which means thinner, more accurate walls.

0.35mm are really the standard in nozzle size. Pretty much everyone has moved to this size with 0.5 being the old standard. Smaller than 0.35 tends to produce more issues like jams. In fact if you are going to try some of the more experimental filaments like wood, a 0.5 nozzle is better because it will get less jams from oversized particulates.

JHead and Makergear are good hotends. Makerbot are not ... in fact everything Makerbot produces is ok but not great. If you want the greatest flexibility you should look at the Arcol or soon to be released Prusa hotends. These hotends do not use a PEEK insulator so they can go over 250 degrees Celsius. This opens up materials like PP3DP/UP filament, polycarbonate, nylon, PTFE and PEEK as you can easily go to 300C with both. These are also great hotends but discussed less regularly because they are more expensive and a little less readily available (Prusa's hotend isn't even out yet http://prusanozzle.org/). The Makerbot hotends now use PEEK/PTFE free design too but the barrel is too short and I find it has more overheating (heat getting up into the extruder body and premelting filament causing a jam) issues that Arcol (or Prusa is likely too based on posts/claims Josef has made).

Budaschnozzle is also a solid choice but it is based on an older Arcol design and reintroduces PEEK so it has the same max temp limitations of JHead and Makergear hotens. If you are going to pay that much buy a real Arcol.

If your choice is between Makergear and JHead, choose the Jhead - it's easier to assemble and repair if something goes wrong.
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Re: hotend type ?

Postby dls6398 » Fri Jan 04, 2013 2:11 pm

Just a comment on temps and alternate filaments. The location of the temperature sensor can affect the perceived temperature needed for extrusion. The UP! printer filament when used in an UP needs to be set to 270-ish, but can be used in a Mosaic or M2 at 210-215 with good results. The reasons for this discrepancy is likely due to the different types of hotends, and differing locations of heat sensors.

I have a couple of the makergear power-resistor heat cores where the temp sensor is located inside the aluminum block rather than taped to the side of the nozzle as it is with the standard ceramic-nichrome heat cores, and I have to set my temperatures 20-30 degrees higher on the resistor blocks to get the same extrusion characteristics from the same filament that I do from the ceramic heat core hotends.
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Re: hotend type ?

Postby roller » Fri Jan 04, 2013 10:48 pm

So true - and I always point out to new users you can compare temps. You must go through the whole filament/temp calibration process with each new hotend to learn where the melt/optimum/fizz points are.

Not only does positioning make a difference but success of your thermal coupling (turn the thermistor 45 degress and you will get a very different reading) and even the mapping accuracy of your specific thermistor in the firmware table. Much of the temp to resistance reading table is a guess in Marlin and that to the fact your specific thermistor may have slightly different properties to the intended model makes a significant difference in the end.

Also, you can use the Up filament at lower temps than the official 260C rating and actually the Up printer temps float around a bit to control layer adhesion for raft/support removal.
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Re: hotend type ?

Postby abobotek » Sat Jan 05, 2013 7:46 pm

dls6398 wrote:Just a comment on temps and alternate filaments. The location of the temperature sensor can affect the perceived temperature needed for extrusion. The UP! printer filament when used in an UP needs to be set to 270-ish, but can be used in a Mosaic or M2 at 210-215 with good results. The reasons for this discrepancy is likely due to the different types of hotends, and differing locations of heat sensors.

I have a couple of the makergear power-resistor heat cores where the temp sensor is located inside the aluminum block rather than taped to the side of the nozzle as it is with the standard ceramic-nichrome heat cores, and I have to set my temperatures 20-30 degrees higher on the resistor blocks to get the same extrusion characteristics from the same filament that I do from the ceramic heat core hotends.


It's possible that the temp measurement (i.e., combination of thermistor, A-->D circuit, and thermistor table) is different between these machines. 210 to 270 is a _huge_ difference.
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Re: hotend type ?

Postby abobotek » Sat Jan 05, 2013 7:49 pm

I'm using a Zen extruder with a QU-BD .35mm hotend with a custom heatsink on the barrel between the extruder and heater block. It seems to work well, but it's the only one I've ever used. Personally, I would go for a larger nozzle if I had to do it over again to speed up printing of larger items. The 12x12 3D is not very rigid, so I have had to limit acceleration; this makes for slow printing.
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Re: hotend type ?

Postby roller » Sun Jan 06, 2013 12:51 am

It's possible that the temp measurement (i.e., combination of thermistor, A-->D circuit, and thermistor table) is different between these machines. 210 to 270 is a _huge_ difference.


The Up! actually uses a platinum RTD which produces very accurate known temperatures for the firmware. Most thermistor tables for reprap firmwares where generated by testing a few temp points for resistance and every other value in between is interpolated so there is some significant variation between actual temperature and what the firmware is reading.

That and all the thermal coupling, location and heat chamber/heating element variations mean the two hotends are not comparable.

For comparison my Up! prints/melts one of my PLA filaments at 170C while my makergear hotend with Marlin 1.0 gets the same flow rate/resistance at about 185C. Meanwhile I have an ABS that I do at 210C on the reprap but the same seems to be at a similar viscosity at 230C on the Up!

So you can see a swing both ways there - it's really hard to compare.
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