Prime tower problem

[alandpoole 0]

Hi,

I have a ultimaker 3 with up to date firmware. I have a problem with the print tower not forming when I am using PLA and PVA. I currently make a PLA raft for plate adhesion.

I have seen many posts about the prime tower falling over after a few cm in height, but my problem is different (at least for now). The first PLA layer is not sticking to the PVA raft and as such, the prime tower never builds. The model its self sticks to the raft without problem, only the quality becomes crap because of the primed material getting mixed up with the model.

(i am currently experimenting with increasing prime tower flow...)

Can someone help?

Thanks,

Alan

[alandpoole 0]

Correction,

I make the raft in PVA. I also fixed the initial adhesion problem by setting the prime tower flow to 150% and making an initial layer overlap of 0.2mm.

However, i still have the problem that because the PVA does not stick to the PLA, the primed PVA material gets dragged across the print and ruins it. Can anyone help?

My suggestion is that a firmware update could be made to have two prime towers, one for each nozzle/material.

Thanks in advance of some support.

[fbrc8-erin 272]

Are you using Cura 2.3.x or the Beta 2.4?

I'm finding the Beta 2.4 prints really nicely without a prime tower (by default). Beta 2.4 does some new things with controlling the temperature to reduce oozing and the need for a priming tower. Here's my latest-- sliced in Beta Cura 2.4, design by XYZWorkshop.

Not quite all the PVA is off in the photo.

Could you include some pictures of what's going on with your printer?

[tomnagel 126]

Is Active Leveling turned on?

The z-distance between the 2 nozzles needs to be calibrated really carefully. Active leveling (especially since firmware 3.5) does that more accurate than most people can do manually.

I agree with Erin, go for Cura 2.4 without the primetowers in most printing profiles.

(keep an eye on the release of Cura 2.4 next week, and update your beta version. There is a bug in the beta2 version which harms the PLA/PVA interface)

And most importantly: stick with the defaults. You should have good results with these. Only after you have good results with the default profiles you should start optimising settings.

You mention for example that you have increased flow to 150%. The side effect may be (a little bit of) grinding in the feeder, leaving bite marks in your filament. A series of such bite marks will drastically increase friction in the bowden tube, causing underextrusion further on.

[gr5 2,172]

My suggestion is that a firmware update could be made to have two prime towers, one for each nozzle/material.

 

Yes! Please! This! I have been asking for this since the beta test back in... august 2016?? Although it's true that the new cura 2.4 is pretty amazing at controlling nozzle temp such that there is often zero leakage and zero need for prime tower.

An alternative is to place your own prime towers:

[alandpoole 0]

Thanks for the suggestions everyone.

I'll try to get away without using the prime tower, and probably have ago with the new software next week. anyone know if I can register for alerts for these kind of updates?

And, should I choose to have a go, can you explain how I can make my own prime towers?

cheers,

[gr5 2,172]

I did a print last night with PLA/PVA and no prime tower and it came out great. Cura beta 2.4.

[shassel 2]

I have the same problem. Doing a dual-extrusion set up in Simplify3D, prime tower always fails. First layer doesn't adhere, even though the rest of the print is fine. The resulting spaghetti creates more problems than it solves.

[shassel 2]

So I got rid of the priming tower and used an ooze shield instead. That failed to adhere and got tangled up with the print.

Why to the priming tower and the ooze shield fail to adhere when the rest of the print does fine?

[gr5 2,172]

Ooze shield doesn't connect well with the bottom because it's so thin so that's not surprising.

The prime tower falling over issue is very common and easily fixed. The main problem as far as I can tell is a bit complicated - basically because of how tempered glass is made the center is thicker and the 4 corners are thinner but we level near the 3 screws so you end up with it mostly flat except the rear 2 corners are low. Having the glass farther from the nozzle makes it so parts don't stick well there - bascially THE MOST IMPORTANT thing to getting plastic to stick to glass is that you squish it a bit. The more you squish it, the better it sticks.

So one solution is to test your glass and confirm that it is not as flat as desired (just drop a ruler across it in different angles) and ask for a new one from your reseller.

Another solution is to move the prime tower to the rear center.

In addition to both of these I recommend you do not use auto level and that you do not use paper when leveling (level such that the nozzle touches the glass).

 

[kmanstudios 1,120]

I gave up on the priming tower because of the time it extended printing by as well as sheer waste of material.

I use the ooze shield a bit every now and then, but for the most part, I am finding (I am on Cura 3.0.4) that it does quite nicely without it. I do have to play a bit with initial temps due to the differences in materials, but it does work quite well.