Jump to content
Ultimaker Community of 3D Printing Experts
upatamby

Prime blob knocked down (Cura/UM3)

Recommended Posts

Hi,

I'm new to 3d-printing so I prefer using the standard settings of Cura.

Every print starts with a prime blob. I guess that's ok. But as soon as the prime blob is ready the print bed starts raising at the same time that the print head starts moving. That causes the print head (to be more precise: the bottom of the front fan) to hit the top of the prime blob. If the prime blob is PLA then it just flattens a bit but it stays on its place. But if it is PVA then the prime blob often falls down and sticks to the print head. The print head then drags the blob onto the center of print bed, ruining the rest of the print. 

 

Request:

Isn't it possible to alter the Cura-software (or is it the firmware?) so that the print bed waits a second before starting to raise after the print head has started to move to avoid this collision?

Share this post


Link to post
Share on other sites

@upatamby it is controlled by a mix of ultimaker cura settings and firmware configurations as far as I know.

See: https://community.ultimaker.com/topic/17772-is-anyone-else-having-issues-with-the-initial-knead-of-material-being-pulled-into-the-print/

 

Personally I would prefer a simple line like everyone (prusa, makerbot) does to prime the nozzle as I had some problems at the start too. It's just once in a while now. 

If you don't want the prime blob you can disable it in cura. Search for: "Enable Prime Blob".  If disabled I recommend to use a few skirt line or a bigger brim to prime the nozzle.

 

Maybe Ultimaker will change or add more options for priming in the future but this can take a while due to varios reasons. 

My idea would be a tap under system called advanced -> priming strategy -> prime blob, prime line, maybe even something else.

Share this post


Link to post
Share on other sites
4 hours ago, upatamby said:

Cura version is 3.1.0.

Printer is Ultimaker 3 Extended with firmware 4.1.4.20171204

Same configuration here...although, not sure of the firmware version, but latest as far as I know. But, I do not have the printer blob problem. It did happen a version or two back of both Cura and firmware.

 

Do you have anything to stick the glob to the plate in that area? For instance, when I brush on my PVA slurry, I make sure to put some in that area and the prime blobs stick just fine.

Edited by kmanstudios

Share this post


Link to post
Share on other sites
8 hours ago, kmanstudios said:

Do you have anything to stick the glob to the plate in that area? For instance, when I brush on my PVA slurry, I make sure to put some in that area and the prime blobs stick just fine.

 

I tried using glue but that didn't work. Perhaps PVA slurry will work (I didn't try that). But just grabbing the blob with a pair of tweezers seems an easier work around.

I think the main cause of the problem is that the print bed is raised before the print head has fully moved aside. The collision between the blob and the print head should not happen. Of course there are several work arounds, including not printing a prime blob at all, but I would prefer a software change so that this collision doesn't happen anymore.

Is this possible?

Share this post


Link to post
Share on other sites
12 hours ago, upatamby said:

 

I tried using glue but that didn't work. Perhaps PVA slurry will work (I didn't try that). But just grabbing the blob with a pair of tweezers seems an easier work around.

I think the main cause of the problem is that the print bed is raised before the print head has fully moved aside. The collision between the blob and the print head should not happen. Of course there are several work arounds, including not printing a prime blob at all, but I would prefer a software change so that this collision doesn't happen anymore.

Is this possible?

I imagine grabbing the blob with tweezers on a dual filament print to get annoying really fast :'(

Hopefully you/we are lucky and the UM dev's are going to help you in this regard. 

I think it would be best, if you do not mind, to upload a short video to make analyzing the problem easier. 

@robinmdh didn't you implement the priming sequence on the UM3? 

 

Share this post


Link to post
Share on other sites

@upatamby Sorry for the late reply.

It looks quite normal. My machine does prime the same way but I'm lucky that the blob stays put on my machine (knock on wood). 

Personally I'm not a big way of this procedure as I think a line like Prusa and all the others use works better but for now thats how the UM3 primes. 

Hopefully someone from Ultimaker can help you out as this should not happen!

Share this post


Link to post
Share on other sites
On 7/1/2018 at 8:37 PM, upatamby said:

See: 

 

 

Put some bed adhesion helper (glue, hairspray, something) on the purge area.

 

Also if you did the load/unload manually of the filament this happens very easily since the firmware is made to work automagically knowing how much to purge is needed or if the head was ourge before or not. 

 

But it can just fail if the corner doesn’t stick to the purge. Easy solution = glue/hairspray

 

Ofc before anything, remove the glass and clean it with hotwater and avoid touching the glass with the hands (human grease is the best way to loose bed adhesion) @gr5 has a nice video explaining how to leave a bed glass nice and sticky

  • Like 1

Share this post


Link to post
Share on other sites
2 hours ago, neotko said:

 

Put some bed adhesion helper (glue, hairspray, something) on the purge area.

 

I'm using hairspray now for a while. This is an excellent solution for the PLA-prints, but it's not enough for the PVA-blob. I think the primary problem is the movement of the printbed that causes a collision between blob and printhead. That should be solved in the firmware and/or slicing software. All other solutions are just work arounds.

  • Like 1

Share this post


Link to post
Share on other sites
17 minutes ago, upatamby said:

 

I'm using hairspray now for a while. This is an excellent solution for the PLA-prints, but it's not enough for the PVA-blob. I think the primary problem is the movement of the printbed that causes a collision between blob and printhead. That should be solved in the firmware and/or slicing software. All other solutions are just work arounds.

 

Oh yes indeed, the prime sequence is quite horrible imo, for the last weeks I did use a um3 I changed it on S3D to make a purge+move, much safe and less problematic if something went wrong. But on UM3 the prime is controlled by the printer firmware, and editing the json through ssh can get messy if something goes wrong you just brick the machine (like changing wrong one comma). And knowing um way of do stuff if this only affects 1% or less of the users they will never touch it, just like um2 firmware, as soon something is 'good enough' they stop pushing forward.

Edited by neotko

Share this post


Link to post
Share on other sites

I hope UM changes this because it happens with both PLA/nozzle1 and PVA/nozzle2.

Never understood why the nozzle dips in the PLA/PVA when we are supposed to keep it clean...

The PLA wants to stick to the bottom of the printhead and gets dragged along as well

  • Like 1

Share this post


Link to post
Share on other sites

Even though I rarely get the blobs pulled into the print, it is always getting knocked over by the printhead. This goes for both cores. When the blob gets dragged into the print or just dragged around, it is usually because I have not used anything to stick the surface to the print.

Share this post


Link to post
Share on other sites
On 21.1.2018 at 4:00 PM, kmanstudios said:

it is always getting knocked over by the printhead

Yes I noticed this as well. Sometimes it's quite annoying as some filament sticks to the head and falls down later on :'(

 

On 21.1.2018 at 3:37 PM, gr5 said:

@nallath - Could you watch the video above and read only upatamby posts and comment?  He only has problems with PVA, not PLA.

Isn't @nallath in charge of cura? *| As it is a firmware "problem" @Daid may be the better person suited? 

Would like to add that I don't have problems with PLA too but with Poly-Support.

Share this post


Link to post
Share on other sites

As far as I know, we disabled the prime poops. Or, at-least, Cura has the capability to do so.

 

Technical background: There is the custom "G280" command that does the priming and sets the current E value to whatever the filament position is compared to the hotend. So "G1 E0" will put filament at the tip of the nozzle after the G280.

As we noticed the priming poop was giving problems, but we did need to account for backwards compatibility. We added "G280 S1", which does set the filament position, but does not do any priming poop. As our filament position tracking is now quite good, as long as you don't bypass the filament loading/unloading on the machine priming isn't really needed.

I don't know what is the default in Cura.

  • Thanks 1

Share this post


Link to post
Share on other sites

I have the same problem, and I've also realized that priming in one form or another is needed because sometimes the filament isn't loaded as it should. So, without priming, parts of the first layer will not be printed as the filament isn't where it should be. So all the printcore extrude at the beginning is hot air, until the filament reaches it.

 

By default, the 'Enable Prime Blob' option is checked in Cura, meaning it will do the prime poop thing.

  • Like 1

Share this post


Link to post
Share on other sites
1 hour ago, Brulti said:

... and I've also realized that priming in one form or another is needed because sometimes the filament isn't loaded as it should.

 

That's exactly why I like to use that prime-blob. 

 

@Daid Is it really that difficult to change the firmware so that after the prime blob is  extruded the print head and print bed do not start moving together, but have the print bed wait a second (until the print head has moved away) before it starts raising? This would solve the whole problem.

  • Like 2

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×

Important Information

Terms of Use Privacy Policy