Pros and cons um2 hotend vs umo

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Neotko
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Pros and cons um2 hotend vs umo

Post by Neotko » April 17th, 2016, 7:09 pm

Well I been doing a lot of adjustments to the slicer settings to finally set my um2 hotend on a production ready state and I want to share my findings, since I think this wasn't done before.

This it's the same object, printed at the same speed on2 machines. Oiled, cleaned and with very good umo+ gt2 belts and misumi shafts.

Image

At first sight everything looks ok on both.

Lets check the umo+ and look at the 2 of the 27
Image

More about that gap later. I finally found what makes the umo+ suck a bit (and we should design something to fix it)

Ok now um2
Image

So, um2 looks better at doing flat layers (it really does) but... (ok more about this later)

So. First of all umo temp was 210, um2 had to be 220. But not because I can't print at 210, but because on um2 hotend at 210 this happens.

Check from left to right 210-215-220C using faberdashery pink.
Image

To get the glossy 'on' on um2 I must print 10-15C higher than umo. Ok this might be the pt100 but also, I can print at 210C without any feeder problem. And on umo I never got this matte effect not even at 185C. So it's weird but I have this effect on faber pla's (mint, blue, pink, vanilla). So I think must be because the hotzone of um2 hotend it's just smaller (umo hotzone it's almost 2-3 times longer).

Ok. The last VERY weird stuff.

Check this ringing effect. Left umo+ Right um2
Image

Remember that both machines have the same slideblocks, misumi shafts, gt2 and they where cleaned and oiled today. And both machines used the same spool, and both have the same aceleration/yerk settings and even the same IRobertI umo feeder motors with mk7.

I think the wood of the umo hotend absorbs part of the vibration (makes sense?) and also since umo frame acts/vibrates like a guitar, the ringing effect on um2 hotend it's bigger.

Has anyone ever tested a umo+ hotend on a um2 frame to check this?

Ok now back to that top layers.

I been going bananas with this issue since I saw that um2 could do an almost perfect second top layer.

If you have an umo/umo+ you know that the hotend area, that has the peek/ptfe wood pushing down the coupler, has a gap of 0.2-0.5mm that you can't remove because that would crush your coupler and make a lot of problems. Well. This gap tilts the hotend by a very very small angle. Making worse toplayers. You can compensate with heat, etc. but the hotend will always be tilt (to solve this I must print one extra top layer and that's more filament & time). And that's why um2 hotend does better toplayers, because it isn't tilted. Easy way to fix? Make spacers for the 4 points of the wood, and one of that 4 should have his height lowered by the same amount of the gap. This should fix the wood/aluminium peek holder/hotend Tilt. I need to actually design something for that because you can level the bed to be like the 4axes but you can't compensate the hotend tilt unless you crush the coupler, and that's a really bad idea since it would bend and die sooner.

So guys, what do you think? :D

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Re: Pros and cons um2 hotend vs umo

Post by Neotko » April 18th, 2016, 2:39 am

Umo tilt hotend photos:

Image

Image

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Re: Pros and cons um2 hotend vs umo

Post by Amedee » April 18th, 2016, 3:08 am

Neotko wrote:Umo tilt hotend photos:
Booooh! Very bad mounting :lol:

Always use shims to get a flat mount...

Image

And thank you for the comprehensive review!
Phil.

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Re: Pros and cons um2 hotend vs umo

Post by nilrog » April 18th, 2016, 3:09 am

Shouldn't all 4 spacers be of same height? I haven't yet assembled mine so I don't know exactly how it looks. But from your pictures it looks, to me, like the alu-plate is not high enough in the courners so if you tighten it all you squash the coupler? If you had 4 spacers with the correct height the coupler would not be squashed and the tilt would be gone.

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Re: Pros and cons um2 hotend vs umo

Post by nilrog » April 18th, 2016, 3:10 am

Amedee wrote:Booooh! Very bad mounting :lol:

Always use shims to get a flat mount...

Image
Just what I thought :)

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Re: Pros and cons um2 hotend vs umo

Post by Neotko » April 18th, 2016, 3:36 am

Weirdly enough never saw anything about how to fix that. Thanks @amedee !

They should add that to their 2years old manual :D

Time to shim the hell out of my UMO's!

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Re: Pros and cons um2 hotend vs umo

Post by Neotko » April 18th, 2016, 3:39 am

Oh also anyone tested a umo hotend on um2 frame? I wonder about the ringing effect being higher. Ofc the umo hotend weight more but still. It's weird.

I'll shim my UMO's and run some more tests.

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Re: Pros and cons um2 hotend vs umo

Post by LePaul » April 19th, 2016, 9:48 am

Now you have me wondering if my UMO is flush....let me check some photos

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Re: Pros and cons um2 hotend vs umo

Post by Anders Olsson » April 23rd, 2016, 2:02 pm

Sorry for not being so active here lately, I have been very busy with various things.

Just recalled this topic when I printed some inserts for sample boxes today.
I am using the original feeder, a solid (adjustable) spacer and a ruby nozzle.

The parts have straight walls with two line widths thickness and are oriented with the walls in the X-Y-direction according to the photo:
2016-04-23-7121.jpg
Strangely, the surface still gets this ringing-effect:
2016-04-23-7120.jpg
I am a bit suspicious if what we see is vibrations from the filament feeder rather than ringing from the X-Y-movement, since ringing should not be present more than a few millimeters after the head changed direction?

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Re: Pros and cons um2 hotend vs umo

Post by Amedee » April 23rd, 2016, 2:07 pm

Could that come from the infill?
You van check if there is a correlation with the infill pattern...
Phil.

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Re: Pros and cons um2 hotend vs umo

Post by Neotko » April 23rd, 2016, 2:43 pm

I never seen that much ringing since I got the um2 hotend. But also I think the problem it's mostly related to the linear bearings.

It's just a gut felling. I want to test igus linear bearings, but since thee sell it at 22mm long (vs 35mm standard bearing) It's far from a fast mod. Also this gut felling it's from using 2 bad bearings and changing to misumi ones (freaking expensive bearings).

There's so much vibrations on the machine just from linear bearings that could be changed to a ball-less system like igus (but really expensive).

Isn't there any sound vibration absorbing print material? A fast test could be to print the hotend black plastic with a vibration absorbing filament. Maybe carbon works for that? Just thinking out loud.

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Re: Pros and cons um2 hotend vs umo

Post by Neotko » April 23rd, 2016, 2:52 pm

Btw @Amedee the quality of my too layers has improve considerably with the shims.

Image

First and second top layer. The gaps on the second are perfectly normal since it's a very small object with many small infill areas. But quite an improvement! The third layer was just almost perfect and the fourth a bit overkill but great for finish, before that the fourth was a must.

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Re: Pros and cons um2 hotend vs umo

Post by Anders Olsson » April 23rd, 2016, 4:20 pm

Amedee wrote:Could that come from the infill?
You van check if there is a correlation with the infill pattern...
In my case, with the sample box inserts, the walls are 0.8 mm thick so there is no infill.
That, and the fact that the head travels only in the X- or Y-direction when printing the walls, made me start thinking about if the feeder can play any role?

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Re: Pros and cons um2 hotend vs umo

Post by Neotko » April 25th, 2016, 12:51 pm

Anders Olsson wrote:
Amedee wrote:Could that come from the infill?
You van check if there is a correlation with the infill pattern...
In my case, with the sample box inserts, the walls are 0.8 mm thick so there is no infill.
That, and the fact that the head travels only in the X- or Y-direction when printing the walls, made me start thinking about if the feeder can play any role?
In theory it's just vibrations from the x/y when it did change direction. A quick way to see if it's the feeder or the yerk it's change the acceleration to 1000-1500. The problem with that it's that infills on small areas tent to fail because the change of speed on the feeder.

Also, if you print using x & y if the effect banishes it might be just that, because printing rotating 45º makes the yerk be absorb by x & y motor/parts.

Maybe on your lab you have access to a fast fps camera to record the vibration?

On mine I see a clear difference from adding oil to the x/y but it's very small. I suppose that if you remove one of the hotends to make it weight less it should change also.

That's why I think that a linear bearing not made of metal spheres with oil should help. Also igus have some materials that are shock absorb. If they absorb most of the x/y change it should cut the ringing, and that could be really amazing since it's one of the most visible effects of printing at decent speeds.

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