Didn’t realize that little bit of exposed brass in an Ubis 13 between the ceramic heater and the biege piece above it needed airflow.
I’m working on increasing the cooling and the current setup has too much air flowing right at the heater. So, I took the cloth/silicon ‘sock’ from the older +Printrbot hot end and slipped it over the one on the Ubis 13 - doubling up the blanket if you will.
Then I started having jamming issues - like an hour+ into a print. Took a few wrong turns to figure out that the second sock was too big and heat creep was causing problems.
Trimmed the second sock to fit better, leaving that little bit of brass exposed and we’re back in business!
We now ship our hotends with a silicone sock so it doesn’t cover the heat break. But that hotend has a design flaw with using PEEK to prevent heat creep instead of the fan. The fan is positioned too high up because the fins start off too high as well. The peek part needs to be rid of. There’s a good reason why all metal hotends don’t use PEEK, it doesn’t do anything.
So the flaw you mention is we have too much insulation between the hot and cold end? Our ceramic hotend had all peek and never needed a fan… ever. We sold 10s of thousands. But they were all assembled by us - no kits. Peek is the perfect material for a heat break but it is very very expensive, so we reduced the amount needed, supplementing w anodized aluminum to save cost. If peek is a design flaw… let’s put it up against any other all-aluminum hotend without a fan and see how flawed it is
The 13s doesn’t even need a fan for a lot of applications (shorter prints or larger tip prints that draw more heat off of the hotend). We recommend the fan to allow it to be fool proof for people who don’t want to think about it. I’ve had people write me and ask why I say it needs a fan… they have never run a fan. My reply is always: redundancy and caution.
(Easy, brook, you are sounding snarky!)
We made the 13s to have everything on it be replaceable. We still assemble them but the manual we wrote explains everything and has a nice diagram detailing the proper sock installation.
Looking at that manual, it somewhat confirms, and somewhat corrects my understanding of why I was getting heat creep jamming.
My blower fan is mounted too high and is pretty much hitting the heater directly. This causes the PID algorithm to pretty much run the heater at full throttle. I’m guessing that extra heat was more than what could be stopped by the PEEK insulator. The extra sock, as seen in the picture, I thought would reduce the amount of heat being generated, but because it was too high, it also let the PEEK insulator and thermal link get too hot and the plastic started melting/swelling too soon.
I have trimmed the 2nd sock to match/fit with the first one (still running double insulation), and I’ve lowered the blower fan by about 10mm (not pictured). Currently I’m 1.5 hours into a 5 hour print with not sign of jamming so far.
Also, the print that was causing problems had a layer height of 0.15mm, a hotend temp of 200C and a print speed of 20mm/s.
@Brook_Drumm Sure, we used to sell all PEEK hotends as well and they never had a fan and worked fine. But there’s a temperature ceiling to it and a limit to what you can print. Once you pass that ceiling, you need active, not passive cooling.
In the case of all-metal hotends, you want a very sharp heat break. The PEEK you have on there stretches the heat break over ~10mm distance, creating a gradual thermal change instead of a sharp one. Have you tested this theory using a FLIR thermal camera to compare? We have done this in the past, so that’s why I mention it.
If you get rid of the peek and move the fins all the way down to the heat break like all regular metal hotends, you’ll not only shorten the length of the hotend (therefore increasing build height), but you’ll also save a lot of cost on material and assembly.
In addition, just because a PEEK hotend can extrude plastic up to a certain temperature, that does not mean you’re not over-working the extruder motor. The easier it is to extrude for the motor, the more precise it is.
We always rated our hotends at 275c… still do. For a huge majority , basically almost everyone, that is enough.
What temp did you rate your (past) peek hotend at?
What temp do you rate the all metal ones now (and do they have teflon in them?). Do you use a thermistor? Is it a 1%?
Mr Ubis spent 30 years at Hp… ran a failure lab for printers… ran the most expensive, crazy test equipment I’ve ever heard of… he’s a trip he’s doing great work!
Btw: on the hotend and electronics, i don’t want to just save money… I want quality so we make them both right here in USA - Lincoln, Sacramento, grass valley… local. Quality and control and reliability. I think it is your two most important choices in printer design.
If memory serves me right, our first hotends that were completely peek and teflon (similar to J-head) were rated to about 220 C. They also didn’t come with a fan and didn’t have any sort of heat break. Just a regular modified J-head.
I just think if you have a fan and your thermal break is stainless steel, a peek isn’t necessary. Everyone’s doing it without a peek and E3D has been for a while now as well. Works fine. Not really about saving money, just reducing redundant parts and improving performance as a result.
Our fans for example are smaller than your fans it works just fine for us. That’s because we blow air directly onto the heat break as well. Small things like that can make a huge difference in performance.
I appreciate this! I’m open minded about my design choices. I’d like to do some tests with these two approaches to find out cost/complexity/performance comparisons. One may have clear advantages, or it is a wash. I think we all should know. Of course there are related cascading needs that should be considered based on individual manufacturer’s values and priorities. With so many hot end designs out there, there has to be some best practices established so innovation can be recognized. A different approach isn’t valuable unless advantages can be proven and communicated w the public.
If I discover there are improvements we can make, I will immediately admit it, explain why and change. I try not to assume anything but emotion and legacy decisions sometimes get in the way
Had a great talk w Carl today! The design choices we have made have solid engineering to back up every one. Now He and I just need to build some demo rigs to convey the message.
