Hitting support layers / ZHOP settings

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Shane
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Hitting support layers / ZHOP settings

Postby Shane » Mon Dec 11, 2017 8:28 pm

Hi all,

I'm having a problem with the nozzle hitting the tops of support layers in some areas as it skims over the top.
I can hear it go thud-thud-thud as this happens. I can see scoring lines on the supports.

I saw this happen on a smaller test print, loads of support fell off and I cancelled the print.

So I read up a bit and I understand I needed to enable zhop, which I did. Zhop is now 0.02mm (was zero, am applyig the principle of small changes and see what happens). Avoid travelling through holes also on.

Now I'm printing a large object with a lot of support layers, and again I can hear and see the thud-thud-thud.

I can see how Angus's (Makers Muse) print failed when his supports fell over after many hours of being whacked.

What should I do? Is zhop the solution? Does zhop work? What should I set it to?
Cheers
Shane

Using 1.75mm PLA with the Standard-N2Plus-PLA template, adjusted as above.
In image, you can see the line between the two rectangular areas. Yes, my 3rd print and its huge!
Attachments
supports.jpg

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Michael.P@Raise3D
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Re: Hitting support layers / ZHOP settings

Postby Michael.P@Raise3D » Mon Dec 11, 2017 10:26 pm

Hi Shane,

I would like to check if you have adjusted the Left and Right nozzle offset? After the Z-Hop adjustment did you change your preset profile being used? If you were using the "Fine" profile for the small parts and the "Speed" profile for the larger print then the settings did not carry over.
Michael Petitclerc, Technician
Tel: +888 963 9028
Web: http://www.raise3d.com

Shane
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Joined: Mon Dec 04, 2017 1:10 pm

Re: Hitting support layers / ZHOP settings

Postby Shane » Tue Dec 12, 2017 12:25 pm

I've only got a single nozzle.
I've checked the profile again after sending to the printer, and the zhop setting is still in place.

So, either zhop is not working, or 0.02mm is not enough. (I assume a positive value is "upwards"?)

the supports are quite long so the stress of the nozzle running over the top is being accommodated so far, no failures.

but I've done 3 prints now (new printer) and apart from the one which was vase mode (and by definition this scraping does not happen) but with these 2 prints using supports, I've had 100% problem with this scraping (admit its a small sample size!)

Ta
Shane

Shane
Posts: 19
Joined: Mon Dec 04, 2017 1:10 pm

Re: Hitting support layers / ZHOP settings

Postby Shane » Tue Dec 12, 2017 9:02 pm

Hi
(I'm sure I answered previously but my post awaited verification or something).

anyhow, I've only got one nozzle.
I check the template again and its got zhop of 0.02mm enabled.

can I check
a +VE zhop means the nozzle moves up, away from the bed?
is 0.02mm typical, (I guess more is worth a try)
can anyone verify that zhop is working?
thanks
Shane

Shane
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Joined: Mon Dec 04, 2017 1:10 pm

Re: Hitting support layers / ZHOP settings

Postby Shane » Wed Dec 13, 2017 8:06 pm

Hi again,
diffent print, higher zhop, no improvement.
see attached. Now zhop is 0.5mm
it just is not working.

OK so I also have "avoid retraction inside model" checked.

So: if zhop only happens when there is a retraction and the above is also checked, then zhop wont actually do anything?

Can Raise please confirm?

And if thats true, then why is zhop linked to retraction, its a different issue that zhop is dealing with - running over and breaking/bending the layer just printed when print head is moving.....

Rogman
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Re: Hitting support layers / ZHOP settings

Postby Rogman » Wed Dec 13, 2017 8:51 pm

I noticed in your picture that the cap is on the end of your fan. if you are printing PLA you must remove the cap so that the PLA can be cooled quickly. PLA will curl if not cooled properly and could be a cause for the nozzle strikes. * I have N2's and N2+'s no N1's so if the cap if permanent and right fan is the cooling fan then forget what I said. :lol: *

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Vicky@Raise3D
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Re: Hitting support layers / ZHOP settings

Postby Vicky@Raise3D » Thu Dec 14, 2017 4:16 am

Avoid retraction inside model won't affect Z hop for support structure. That option only works for the inner structure of model, such as infill. But support is outer structure, the retraction will still be there to trigger the Z hop.

Shane
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Re: Hitting support layers / ZHOP settings

Postby Shane » Thu Dec 14, 2017 10:28 pm

Hi.

Thanks for the replies, but OK: please see attachment. I have zhop enabled, but there is still scoring. it makes a hell of a noise.

So, the nozzle is scoring the support and the inside of the print (its doing both): then what settings shoudl I use to avoid this please?
It sounds awful.

cheers!
Shane
Attachments
20171213_195522.jpg

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Mecha_Monster
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Re: Hitting support layers / ZHOP settings

Postby Mecha_Monster » Fri Dec 15, 2017 12:05 am

Shane;

As Rogman suggested, remove the small cap that is coveting the bottom part of your left fan. Maybe that is one or part of the problem.

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Vicky@Raise3D
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Re: Hitting support layers / ZHOP settings

Postby Vicky@Raise3D » Fri Dec 15, 2017 7:05 am

For such long-distance movement, there should have retraction triggered.
May I ask the gcode and data file of this model to take a look?

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jetdillo
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Re: Hitting support layers / ZHOP settings

Postby jetdillo » Sat Dec 16, 2017 6:48 pm

Shane wrote:Hi all,

I'm having a problem with the nozzle hitting the tops of support layers in some areas as it skims over the top.
I can hear it go thud-thud-thud as this happens. I can see scoring lines on the supports.

I saw this happen on a smaller test print, loads of support fell off and I cancelled the print.

So I read up a bit and I understand I needed to enable zhop, which I did. Zhop is now 0.02mm (was zero, am applyig the principle of small changes and see what happens). Avoid travelling through holes also on.


I've had good results when I set my Z-Hop to, like 0.11 or 0.12mm.
This was when I was printing structural parts for a robot which involved long traverses across the face of the part a couple times at every layer.

DeX
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Re: Hitting support layers / ZHOP settings

Postby DeX » Sat Dec 16, 2017 11:25 pm

I had that at the beginning. then I reduced supports flowrate (90%-95%). problem solved for me.
z-hop increases printing time a lot... ugh..

EldRick
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Re: Hitting support layers / ZHOP settings

Postby EldRick » Sun Dec 17, 2017 4:43 pm

.02mm = .0008", i.e. less than one thousandth of an inch. Not enough. Try .2mm.
Last edited by EldRick on Mon Dec 18, 2017 6:01 pm, edited 1 time in total.

Shane
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Re: Hitting support layers / ZHOP settings

Postby Shane » Mon Dec 18, 2017 12:12 pm

Even 0.5mm not working.

Vicky thanks I'll send you a file. Do I attach here or do I mail you directly?

Will also try the flowrate issue - cheers.
Shane

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Vicky@Raise3D
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Re: Hitting support layers / ZHOP settings

Postby Vicky@Raise3D » Mon Dec 18, 2017 12:47 pm

Both OK.

Daws
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Re: Hitting support layers / ZHOP settings

Postby Daws » Wed Feb 07, 2018 10:40 am

What was the outcome of this? I also have the issue of the nozzle hitting supports and knocking them off.

I have also noticed that the nozzle hits inner parts of the model, not just support parts. I left a print running last night and it was knocked off the bed by the nozzle hitting. The shape of the part was basically a simple extrusion profile of an oval with a central web, each time the printer did the outer profile and part of the central web, the nozzle travelled to the outside and hit the central web.

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Vicky@Raise3D
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Re: Hitting support layers / ZHOP settings

Postby Vicky@Raise3D » Thu Feb 08, 2018 7:04 am

Daws wrote:What was the outcome of this? I also have the issue of the nozzle hitting supports and knocking them off.

I have also noticed that the nozzle hits inner parts of the model, not just support parts. I left a print running last night and it was knocked off the bed by the nozzle hitting. The shape of the part was basically a simple extrusion profile of an oval with a central web, each time the printer did the outer profile and part of the central web, the nozzle travelled to the outside and hit the central web.


Yours is a dual-extruder machine or single one? Have you tried with Z hop setting enabled?

Daws
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Location: Qld, Australia

Re: Hitting support layers / ZHOP settings

Postby Daws » Fri Feb 09, 2018 1:38 am

Hi Vicky,

Mine is a single extruder machine. Z-hop is not enabled, I realise this could help alleviate the issue but I feel it would be simpler and more effective if there was a setting to tell the extruder to move around the perimeter of the model rather than straight across freshly printed sections, this could be a problem for larger models but using z-hop means it would have to be enabled for every print which would increase print time.


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