RE: CORE One and soft TPU
Could you please tell me exactly which brass nozzle you used? I'd like to buy one and give it a try.
RE: CORE One and soft TPU
I haven't tried this yet If you have a filament splicer, you should be able to cut a section of PETG long enough to feed through the PTFE tubing. Then splice it onto the TPU to act as a stiff leader. This should allow for a standard loading process and then just purge out the PETG until it pulls the TPU through to the nozzle.
The bond between the PETG and the softer TPU's will likely be weaker that the more rigid TPU's, but it should be enough to at least load into the extruder.
RE:
The splicing trick sounds interesting. I haven't had much problem printing various hardness TPU as long as I don't use a CHT nozzle, but loading is very problematic.
On my MK4s, I printed a replacement festo fitting to help avoid getting hung up on threads in the extruder when feeding from an MMU tube, but haven't had a chance to see if something similar can be done for my CoreOne. TPU definitely seems more difficult to feed on the CoreOne than it was on the MK4S, even with an MMU.
RE: CORE One and soft TPU
The splicing trick sounds like a good option. I went ahead and purchased a Sunlu splicer and will be fusing a PETG lead to my Prusa Flex 95A tonight. I'll report my experience as soon as I can. I am hoping I won't need to loosen the idler screws nor remove the PTFE tube goin into the extruder.
RE: CORE One and soft TPU
Could you please tell me exactly which brass nozzle you used? I'd like to buy one and give it a try.
Prusa Nozzle brass - 0.4 mm
RE:
I asked DeepSeek AI about this issue and it seems to be not that easy to compine soft and rigid filaments together ...:
### ⚠️ **Problems When Joining TPU with Rigid Filaments**
1. **Elasticity Mismatch**: TPU is flexible (up to 600% stretch), while PLA/PETG is rigid → The splice often **snaps during extrusion** or in the Bowden tube.
2. **Temperature Conflict**: - TPU melts at **210–230°C** (burns above 240°C). - PETG requires **230–250°C** → Weak fusion.
3. **Poor Adhesion**: TPU bonds poorly with PLA/PETG → Mechanically fragile connection.
---
### ✅ **Practical Solution: Use a Rigid Filament "Feeder Guide"** Instead of welding, **print a stiff sleeve** to stabilize TPU:
1. **Design**: - Print a 10–15 cm **PLA/PETG tube** (1.75 mm outer diameter). - Drill a **1.5 mm hole** through it (for TPU).
2. **Usage**: - Thread TPU through the sleeve → Feed the **rigid section** into the extruder. - Once the extruder grips the TPU, it pulls itself through the guide.
---
### 🔧 **Alternative: Spacer Method (No Splicer)**
1. Print a **mini PLA spacer**: - 2 cm tube with **outer diameter = filament size** (e.g., 1.75 mm) and **inner hole = 1.5 mm**.
2. **Steps**: - Slide TPU through the spacer → Attach to the TPU tip. - The **rigid spacer** guides TPU into the extruder. - Remove once feeding starts (slips off automatically).
---
### ❌ **Not Recommended: Direct Splicing** If attempting anyway:
1. **Material**: Use only **TPU + PLA** (avoid PETG).
2. **Settings**: - Splicer temp: **200–210°C** (minimum for TPU). - **Short overlap**: Fuse max. 1 cm.
3. **Post-Processing**: - Smooth the joint with a **heat gun** (avoid "beading").
**Expected Outcome**: - Success rate < 30% (often snaps in Bowden tube). - Risk of **clogs** from detached TPU remnants.
---
### 💡 **Better TPU Feeding Alternatives**
1. **Angled Cut**: - Trim TPU at a **sharp angle** (like a pencil tip) → Reduces resistance.
2. **Manual Guidance**: - Hold TPU with tweezers **behind extruder gears** until gripped.
3. **Direct Drive Upgrade**: - Shorter filament path vs. Bowden → Far easier TPU feeding.
---
### 🧪 **Pro Experiment: Hybrid Filament** For specialized TPU: - **Polyflex TPU (95A Shore)** bonds better with PLA than softer variants (85A). - **Pre-treat TPU** with acetone → Improves PLA adhesion.
RE: CORE One and soft TPU
The splicing trick sounds interesting. I haven't had much problem printing various hardness TPU as long as I don't use a CHT nozzle, but loading is very problematic.
On my MK4s, I printed a replacement festo fitting to help avoid getting hung up on threads in the extruder when feeding from an MMU tube, but haven't had a chance to see if something similar can be done for my CoreOne. TPU definitely seems more difficult to feed on the CoreOne than it was on the MK4S, even with an MMU.
I actually tried it and it still got stuck... that said, I didn't use a 20cm lead, I used a 3cm lead... which probably wasn't long enough.
I do like the splicer, as I can take multiple partial rolls of petg and put them together. I'm waiting for my spool winder to arrive...
RE: CORE One and soft TPU
Why don't you open the top cover, remove the PTFE, disable the first sensor and feed the TPU directly into the extruder (see my picture here: https://forum.prusa3d.com/forum/postid/753295/).
This works perfect.
Also I had problems using the "normal way" with the long PTFE and first sensor. It printed for 10-15 minutes and then stopped, telling me to change the filament ... might be, because the PTFE is way too long and does to much resistance.
RE:
I asked DeepSeek AI about this issue and it seems to be not that easy to compine soft and rigid filaments together ...:
[...]
1. **Design**: - Print a 10–15 cm **PLA/PETG tube** (1.75 mm outer diameter). - Drill a **1.5 mm hole** through it (for TPU).
2. **Usage**: - Thread TPU through the sleeve → Feed the **rigid section** into the extruder. - Once the extruder grips the TPU, it pulls itself through the guide.
Last time I looked, TPU also came in 1.75 mm thickness. And I would really like to see how one drills a 1.5 mm hole into a 1.75 mm diameter rod, over a length of 10 to 15 cm.
May we assume that the rest of DeepSeek's advice is as sound as this bit? 🙄
RE: CORE One and soft TPU
You might be right. But the first part seems true for me. Those two types of filemant won't fit together. Also the different temperatures will be a severe problem.
RE: CORE One and soft TPU
You might be right. But the first part seems true for me. Those two types of filemant won't fit together. Also the different temperatures will be a severe problem.
I am not so sure about that. Many people have combined TPU and PETG in a print, to make solid structures with molded-on seals etc. In that scenario, the first filament that gets deposited has largely cooled down by the time the second material is molded on top, and users still report very good adhesion.
Of course, the contact area is not huge when splicing filament strands. But the joint only has to last for a single "pull in the TPU" cycle. I guess one would also cut the joint at an angle to increase the contact area? I feel reminded of splicing audio tape, back in the day...
RE: CORE One and soft TPU
I prefer the direct feed to the extruder ... much more secure and easy 😉
RE:
Why don't you open the top cover, remove the PTFE, disable the first sensor and feed the TPU directly into the extruder (see my picture here: https://forum.prusa3d.com/forum/postid/753295/).
This works perfect.
That is what I'm doing, but it's a pain to remove the PTFE tube from the fitting, and if you just unscrew the fitting instead, it eventually cuts the end of the tube. It probably depends on how much TPU you print and whether you just leave the tube disconnected and feed everything from the top, or if you only disconnect for TPU, but for me it's a hassle I'd prefer to avoid.
I agree that splicing would also be a pain, but we're all just looking for options and that's an interesting one I hadn't thought of before.
I'm also not sure yet where the TPU is getting stuck - I'm not convinced it's the bend. I've been able to feed PP normally which is also very flexible, but less elastic.
RE: CORE One and soft TPU
Could you please tell me exactly which brass nozzle you used? I'd like to buy one and give it a try.
Prusa Nozzle brass - 0.4 mm
I have also had success with the 0.6 mm nozzle - https://www.prusa3d.com/product/prusa-nozzle-brass-0-6-mm
I have been unsuccessful with the HF or CHT nozzles in any size on both my MK4S and CoreOne - my guess is that it has something to do with the internal geometry.
RE: CORE One and soft TPU
I used the Sunlu splicer to join a PETG lead to my TPU filament, and the splice itself worked perfectly — no compatibility issues between the two materials. The PETG portion loads and purges through the hotend without any problems. However, once the TPU reaches the extruder, things start to go wrong.
As soon as the TPU begins feeding, I can hear the extruder gears slipping. This causes the filament to bunch up, and it never makes it far enough to complete the purge. I’ve tried several combinations of idler tension settings, toggled the filament sensor on and off, and even attempted to manually guide the filament through, but nothing has worked so far.
RE:
Could you please tell me exactly which brass nozzle you used? I'd like to buy one and give it a try.
Prusa Nozzle brass - 0.4 mm
I have also had success with the 0.6 mm nozzle - https://www.prusa3d.com/product/prusa-nozzle-brass-0-6-mm
I have been unsuccessful with the HF or CHT nozzles in any size on both my MK4S and CoreOne - my guess is that it has something to do with the internal geometry.
I suppose is not important the nozzle diameter but the nozzle type. Unfortunately the solution didn't come from Prusa help consultants with whom I spent hours making different tests but fortunately from an online friend who are printing TPU on a Prusa XL using brass standard nozzle. Almost I wanted to return the printer because I wasn't able to pass the nozzle cleaning test then, when just by luck I passed this test I couldn't pass the first layer!
I don't know why in the assembled version Prusa doesn't allow you to choose the textured bed and the nozzle from ordering (it is an assembled type so I suppose I don't have to change something after I receive it and I have just to turn it on and print as their commercial say )!
Otherwise is a great printer!
RE: CORE One and soft TPU
I couldn't load Ninjaflex, but it took a harder type.
My next try will be with the ridiculously soft Chinchilla. Wish me luck. Or if you've already printed with it, give me a heads up on how to: