The heat transfer within an FDM extruder is critical to good performance. The faster the feed (more filament volume) the more critical the heat flow within the extruder becomes.
The problem is any air gap in the flow path from the heating element to the extruder nozzle. Conductive heat cannot jump gaps such as screw threads. It converts to radiated heat to span the gap then back to conductive. The gap does not have to be large, The effect is like a huge resistor in electrical flow. Perhaps more like a spark gap.
If one has ever assembled a heat sink onto a CPU or any other critical heat transfer requirement, you know a “thermal paste” is required to ensure an absolute intimate connection and flow path for conductive heat.
Yet, this is never factory applied in our critical heat flow extruder connections. Probably because off the high temperatures of 250C and higher
I have been applying high heat anti-seize compound to the threaded barrel, between the heating element, thermal mass block, and the threaded feed barrel. I have not applied any to the nozzle threads for fear of introducing foreign material into the nozzle.
Electronic CPU heat sink compound is only good to 200C., Not suitable for this use. I bought Locktite LB8009 anti-seize. Used on automotive exhaust threaded components. Not really a thermal paste but permits extremely tight no-gap screw-in assembly without seizing. Use sparingly as there is some volatile off-gassing (smoke/odor) of the low-temp base carrier material on first heat. Good to 1350C so the high-temp material is not affected by extruder heat.
The improvement to extruder performance with tight threading has cured 99% of the flow issues with my extruders. Nozzles now never “plug-up”. They actually wear down the tips after many months of continuous fault-free performance. It works for me.
For many operators (people), poor nozzle flow appears to be a plugged nozzle. So the nozzle is changed. In changing the nozzle the threaded connections are disturbed and everything “tightened up” a bit solving the heat transfer problem (for a while). Thus, it appears it was a plugged nozzle issue.
Some folks raise print temperatures trying to improve flow. Sometimes to the point when the filament breaks down, gasses (cooks) off (thought to be proof of water) and actually burns on the nozzle, Result is an actual debris plug.
Improve the thermal conductive path of the extruder. Every assembled component needs to have high temperature compound to eliminate every possible air gap, no matter how small.
I greatly improved the performance of my extruders. Conductive thread compound should be an industry standard with 3D print extruders the same as heat sinks on CPU’s.
Search “High Temperature Heat Transfer Compound” for other brands. There may be something other than the high temp anti-seize I use, Must be suitable for temperatures 300C and above.
The big issue with Cetus is there is no manual leveling of the print surface. A thick raft is used to build a level surface before starting the intended print.
This takes considerable time and some wasted material. The material consumption is no big issue unless one is close to the end of the spool.
PETG is particularly sensitive to everything being “right” with initial layers.
I use G-code produced with Simplify3D. It has much better control of variables than offered with the stock UPStudio slicer/print software. There is a new Beta for UPStudio which shows promise but stopped working on my WIN10 PC.
UPStudio is still required - to load 3rd party G-code to Cetus. Simplify3D cannot communicate directly with Cetus.
PETG extrusion temperature is 150C. with a 90C bed. I am presently using 0.25 layer height with +200% for the first layer (0.50 height) This is required to help compensate for the un-level bed. I am using 100% extrusion flow with a 0.4 diameter nozzle. non-solid infill is set at 150%
These figures don’t seem extreme, and what I have found as necessary to get good non-raft PETG prints on Cetus.
Sone factors when set too high tend to push the Cetus extruder close to its flow limits. Missed steps (clunking) can be heard if pushed harder. This is the feeder gear slipping on the filament and cutting a notch. This will usually stop filament feed.
Travel (print) speed is also quite low with PETG, 2100 mm/m with under-speeds of 60%. Rather slow but PETG is also speed fussy.
Note Well: These are setting that work for me. Your results will certainly vary. Use these settings as an example of where you may have to go to get satisfactory PETG prints on a heated bed Cetus.
After the learning experience of additive manufacturing making plastic Junque designed by other people, I asked myself, “What’s in the process for me?”
I admit it was the technology and the low cost equipment that first drew me in. I am a techno-type person attracted to complex operations.
My spouse declared before I had my first piece of 3D printing hardware. “I don’t believe you haven’t started 3D printing” She knows me well after 57 years of companionship.
I was aware of the process many years earlier but hadn’t realized there was a new breed of lightweight and low cost “hobbyist” hardware available. I was hooked and permitted to engage. She lit the fuse.
Nine printers later, I pause to contemplate. One thing stands out is the amount of plastic I have processed into “stuff”. Making stuff is what it is all about. Learning how to do it was the initial motivation.
It soon became apparent, most of the stuff is what I started calling plastic “Junque”. How many plastic skulls does the average person need?
I quickly tired of printing “other peoples” designs. The real creative juices flow when I can use 3D CAD software and graphic software like ZBrush to create printed objects of my own design.
Time to move away from Junque making.
I see the 3D print process as a tool. It is not my goal to “get the machine running” to watch it perform. I pretty much have that under control. All CNC is fun to watch. Not a good use of personal time.
The hardware I own and use is not junk (normal spelling). The major weakness is rigidity and capacity. Three dimensional printers need to be rigid and stable as every professional grade CNC machine tool. The bigger the size, the more massive they must become.
I have no desire (at this time) to produce massive 1 piece plastic items. My plan is to use the smaller machines I have to their full capacity when necessary.
Larger prints require longer run times. This has become my standard method of operation. My “moving on” thoughts are to design and produce larger and higher resolution prints. Consuming more raw material. 100 and exceeding 200 gram components not unusual. 12,16, 20 hour print times.
My previous recent posts in this blog are indicative of my “larger is better” printing goals.Moving On
Printing small parts to be assembled into larger items is a very good way to make larger items. I always avoid the mind-set that a product design must be created in a single all-inclusive 3D print.
Nice when it can happen but most large items are component assemblies.
“Moving On” goal is to produce less Junque by concentrating on larger and superior quality items. Not interested in how fast I can print, but generating the highest quality for the purpose.
It’s still plastic but it should be high quality plastic…