Are other H2D owners having trouble with multicolor prints? My purge tower collapses every single time…
I’ve spent 200+ hours on the same famous MakerWorld model, trying all sorts of different settings.
It’s not an adhesion issue – the build plate is perfectly clean.
I’ve tried printing this same model for over 200 hours without success. Every single time, the purge/prime tower falls down… and always under the same circumstances: during a dual-color layer on the purge tower.
Here’s what I’ve already tested:
• different infill percentages,
• added +0.6 mm Z-hop,
• changed speeds,
• even slowed everything down to 50 mm/s,
• modified the ramming settings,
• moved the purge tower to multiple different locations…
Nothing works.
Eventually I figured out what’s happening: the right nozzle creates a “blob” (a little ball of filament) whenever it purges into the tower.
When the printer switches back to the left nozzle and continues building the tower, that blob causes the failure.
I even took a picture of a tower right before it collapsed – you can clearly see the blob I’m talking about.
It always happens on a dual-color layer, and always at the exact moment the right nozzle purges on the tower.
I’ve tested both with and without the “Skip into purge tower” option in Bambu Studio – no difference.
Another important detail: the blob always appears in the exact same spot as the extra bit of filament that oozes from the right nozzle during color switching.
The higher the Prime tower gets, the more the nozzle scratches when I scrape it. I created a ticker and only received one reply about how to make the tower more stable, but the problem remains. They need to do something with the software. The nozzle scratches deeper and harder into the tower until it falls over. Bambu only sends standard replies. Interested and solution-oriented are different.
At the end, you can clearly see the nozzle pulling on the prime tower. This had broken off, and an attempt was made to save the tower with magnets to complete the print.
The Ticket anwser:
Dear Customer,
Thank you for contacting us.
For this issue, there are two possible solutions:
Reduce the first layer printing speed, which can significantly improve adhesion.
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Increase the extra rib length to make the prime tower structure more stable, as shown in the image below.[image]
We already know that there’s a firmware bug regarding to the stringing of the tower. But I’m not sure if it’s causing all the tower failures, hopefully it is as it might get fixed in the next update.
I printed a 33-hour print at a height of 9 inches (23 cm). Only towards the end did I need to change to a second color. Until the color change, the prime tower was printing cleanly. From the color change onward, the problem that caused it to topple over becomes clearly visible again.
After changing the nozzles, the print head moves to the prime tower and begins feeding filament along the way. It scrapes this off against the tower, causing stringing on the tower. This creates a raised area on the top surface of the tower as the filament is stripped off. This naturally hardens. Then, at some point, it prints the outer wall of the prime tower to complete the layer, and in doing so, it noticeably scrapes over this raised area, which is caused by the premature filament feeding. Scraping over this raised area eventually causes the tower to fall.
So it can only be a software issue. I currently have an expensive H2D printer with which I can’t produce high-resolution, multi-color prints. Bambu simply has to act quickly
I have an open ticket with Bambu regarding the prime tower. First, they gave me a tip on how to make the tower more stable. Now I’m supposed to experiment with the volumetric speed. I don’t know if Bambu really takes us seriously, given the ticket responses I’m getting. I’m currently testing on high towers, but I haven’t found any solution.
Ticket Answer from Bambu:
Dear Bambu Lab Customer,
Thank you for contacting us and providing such a detailed description.
This is not due to the filament being sent out too early, but rather the heated filament flowing out of the nozzle under the effect of gravity. You can solve this problem through the following operations:
Adjust the retraction parameters
You can find the setting overrides in the filament Settings, where you can adjust the filament retraction parameter to increase the retraction distance and pull the melted filament back to the nozzle, reducing the filament spinning in the middle.
If the extrusion rate is too high, the retraction may not be able to pull the consumable back in time. You can slightly reduce the “maximum volumetric speed”, which will slow down the extrusion speed and make the backdrawing more effective.
[image]
If you have any further questions or require additional assistance, please don’t hesitate to contact our customer support team. We are here to help.
I am about to print a 200mm high 4 color PLA part with additional PETG as support filament.
I don’t want to see my tower failing just before it reaches its maximum height.
So I am wondering if using an older version of Bambu Studio would fix the prime tower issue.
I’ve had this issue since I got my H2D, which admittedly isn’t that long ago in the full scheme of things. I attempted with the beta firmware, with beta Studio, now the full new releases. As well as the old previous full releases that were not in beta. The prime tower is a mine-field mess in every version I’ve ever tried it in. I can see where when it gets past a few hundred mm it is unusable. I had a very simple ABS/ASA print dual color/material print that just destroyed the prime tower at about 45mm. I let it go since I knew it was close to finishing at 50mm, but if I needed to go any further it would fail.
It’s infuriating to spend this much on a machine that simply cannot handle its own features.
Bambu’s response is at least nice that they acknowledge gravity-on-fluid dynamics (something I sorely miss in software filament profile) but this isn’t that.
Tangent: Calculating the capillary forces of retracted filament in a nozzle vs gravity vs surface tension would be really cool, and probably help provide an “auto” setting for retraction-distance, based on the length of the travel.
Everything worked perfectly with my H2D for the first month or two. Recently though, I’ve been running into an issue where the tower keeps getting knocked over or collapsing mid-print. I’m running the exact same files that used to print without any problems, but now they consistently fail about halfway through. Hoping there’s a fix for this soon.
Looks like a missing movement across the nozzle wiper to me.
