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Miscellaneous questions regarding UMO

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Dear community

I have been using an UMO for the last few weeks know. I got it used for a good price (approximately $300) and I am getting used to the device, but nevertheless there are still many open questions. Thanks in advance for your help.

I got terrible warping with PLA which destroyed all my prints. For me this was an absolute nogo and therefore I decided to buy the quite expensive heated bed upgrade kit (about same price as I paid for the UMO^^). Installation took a while and was finally successfull. The manual is of higher value, however one thing they did not mention and it took me quite a while to figure it out: The Z-step setting has to be changed. Sine the Z-Motor is exchanged with the upgrade, the value of 533.3 is no longer valid. Here is my first question:

1) I changed the value to 200 which I found to be correct for the UMO+. Is it also true for the UMO with the heated bed upgrade kit? What's actually the benefit of a reduced amount of steps/mm? It should be worse in terms of resolution?

During the upgrade according to the manual, I had to replace the top z end switch but not the bottom one.

2) Is it correct that the bottom z switch stays untouched and is no longer in use since the new bed does not have that bar to even reach the bottom switch?

3) There was a quite big bag with some lubicrant delivered with the heated bed upgrade kit, however it is not mentiond what the purpose is. Does anybody have an idea?

4) When I studied the pictures of the manual of the upgrade kit, I realized that my print head looks different. I checked with the UMO assembly manual 1.1 and this really is the case. My print head does not have that teflon coupler which is often mentioned in conjunction with nozzle blocking. I even have no possibility to install one; If I do so, I can no longer fix the bolden tube with this little "coupling" (don't know the right word), since there is no possibility to place it on the top of the print head as seen in the manual. What are the pros/cons of my (I suppose) old print head? What would you recommend to do? Replace it with a 3rd party device like the E3Dv6?

5) Sometimes when I watch my UMO I'm afraid it falls apart just in a second. High vibrations are probably not the best idea and I would like to limit the acceleration of the printer somehow. I read somwhere that there is a possibility to do so, but I just could'nt find out where I can set this value?

6) What first layer line distance is recommended for printing with PLA on glass (with or without heated bed)? There is an explanation in cura however, I never understood what it actually means. It says something like "it sticks better when the lines are more spaced"? Does not make sense for me?

7) Before a print I always have to extrude quite a bit of material by hand, otherwise the print start is unsuccessfull. How can I tell cura to extrude more material after droping the bed but before starting the actual print?

8) I noticed that the stepper motors get quite hot, I would assume somwhere between 40-70°C. Is it normal? What is causing those high temperatures even for the z-stepper which is quite out of work for most of the time?

9) Do you have any recommendations on how to do a calibration ot the printer if really accurate prints are needed (+/- 0.05mm) ? If I design a piece in CAD, I basically want to use the correct dimensions. I can increase wholes a bit because they tend to get smaller, but changing the other dimensions before the print would be inconvenient. Of course I can scale up the whole piece in cura by about 0.5% to compensate shrinkage. But, what do you do for complex geometries? How can you predict shrinkage then?

So, thats enough for the moment. Any help would be highly appreciated.


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1) Correct

2) Correct

3) The copper grease or the green lube? Copper greease it's used on the bolts that tight and level the bed, I think it's on the manual but if you don't see it just tell me. The green lube it's for the z motor threated rod.

4) Maybe your umo it's a old old first hotend. The hotend v2 has ptfe coupler and it's the standard on umo/umo+. Make a photo, that always helps.

5) Aceleration can be changed by Ulticontroller, do you have the little screen where the sd it's plug in or your umo doesn't have it? I mean this http://wiki.ultimaker.com/UltiController_v1

6) That's quite not well explained indeed, I remember my first days. Align the head so it almost touches and don't touches the bed, by eye works, better with a paper. There's some info on the ultimaker stuff tip and tricks about how to level the bed, also on a ultimaker app for mobiles.

7) Well on the cura start gcode there are some lines that make it prime less or more if you edit them. Post your gcode start (advanced mode) and I'll tell you what to edit, this way you learn also :D

8) Stepper motors should be ok at that temperatures, just remember to always 'hear' the mainboard fan working, because the chips needs to be air cooled on umo.

9) There are many posts about that stuff around... I'll check it.

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I just completed this upgrade a month ago so I may be able to help!

1) I made no changes to the Z steps. I followed the directions, upgraded the firmware and made sure to note the Heated Bed Upgrade.

2) Yes, you replace the top switch but not the bottom.

3) That large thing of grease is for the washers to the aluminum bed contact. The small green one is for the Z-screw

4) Could you post a photo of the print head? If you have an Ultimaker Original, as I do (kit form), you shouldn't have to change anything there. (I also do an Atomic Pull every time I change filaments to make sure the nozzle is clean)

5) I would have to search but there is an XY Jerk or something like that in the Ulticontroller. The UMO is a noisy, chattery machine. It's a lot like an R2-D2...loyal but noisy!

6) There's a lot of different ways to explain it. Essentially the best way came from GR5. Use a piece of paper as a guide, so that it can barely slip through between the head and print bed. With the 3-point bed, I start at the back, then the front right, then the front left. I then go the center and check, using the back adjustment as needed. I repeat this once. When you have a print, add 3 to 4 lines of Skirt. When the print starts, you will see the skirt line being laid down. No filament? Bed too close. Filament look too rounded....bed too high. Filament look smooshed into the glass....perfect. You may have to adjust those knobs a bit frantically but this does work very well. (Silver filament very hard to see on bed!)

7) In the Start/End GCode tab. Near the bottom is a line that shows, be default, extruding amount (3mm). I crank mine up to 10.

8) I've never checked my motors for temperature. My printer is in the basement where is stays around 65F

9) I do not know! I know you want to account for shrinkage but unsure how much

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Thank you for your answers.

1) I did the firmware upgrade too, but somhow something must have gone wrong. I had to change the z-stepper value manually.

2) So why is there a bottom switch at all? Did they shift this function to the software?

4) Here is a picture:


What are the disadvantages to the newer print head?

5) Yes, I have the ulticontroller. What is a reasonable limitation for the acceleration?

6) I know how to do bed levelling with the paper. Based on the description I assumed that the value changes the horizontal distance of the lanes. If I got it right, it changes the vertical distance between two layers? Do you have any example? Lets say, layer thickness of the first layer is 0.3mm and the first layer distance is set to 80%. Does it mean that the nozzle is 0.8*0.3=0.24mm above the glass plate for the first layer?

9) Nice would be a tool to somehow simulate the expected shrinkage. I just printed a part where I was completely surprised when I measured dimensions. Several distances where quite the opposite than I would have expected.

Ok, I have further questions and just continue numbering.

10) Yesterday I had a buggy print. The piece was a box with compartments, "vertical walls" with a thickness of 1mm. These walls were not printed solid but somehow interrupted. It was like two walls, one 0.2mm thick and another one with 0.8mm instead of one single wall with 1mm. This issue was not concering all walls but just a few of them. I assume this is not a printer issue but rather a cura / slicer issue? What might do the trick?

11) I read that some people do decrease the bed temperature after the first few layers. Makes sense, since electricity costs about $1 per 24h and for PLA you basically need the heated bed to ensure a nice first layer. Can anybody tell me how to do that?



Edited by Guest

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Your questions...

1)  I recall someone else had troubles with their steps.  @SanderVg might have some more information on that.  I had that worry too, but the firmware upgrade worked for me

2)  I don't think the switch is used at all now.  There upgrade instructions do not say to do anything with it.  I wondered that too.

3)  There's no 3!

4)  I do not have that print head.  Another one for Sander to chime in on!

5)  There's been some discussions in here about the XY Jerk settings.  I am not sure what the final resolution was.  You could do a search (be patient, it has issues) and see what is in those threads.  Hopefully someone else can chime in

6)  Leveling...I am not sure how to answer those.  I know that it is essential for that first layer to get mushed into the build plate for a smooth finish.  I struggle with this when using lighter colored filament like silver, which can be hard to see on the glass plate when glue stick smeared on   :)

No 7 or 8...

9) @gr5 might have some knowledge on this subject

10)  Not sure, I'd have to see what the others suggest.

11)  I control the bed temperature through Cura (make sure Cura has the right Printer Profile for you, you need the heated bed to show up).  I set it to 60C at first, then once the first layer is down, bring it down to 52 (via the Ulticontroller).  There's a lot of hit or miss here and GR5 has posted a lot about it (again, searches).  I also found the gluestick is a very good thing for allowing lower temps (like 40s) with good adhesion.

Edited by Guest

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Assist91: Since you bought your UMO used, there are a few maintenance things I would consider doing.

First is to check if the alignment of your two 6mm printhead axes is ok. With the power off, you should be able to move the printhead in the x and y direction with two fingers; there is a little resistance, but it should be easily doable and it should be sort of even. If there is wobble in resistance you want to check for wobble in the axes.

The UMO came with two template things to help align the axes. They fit over the 8mm x and y axes and have a bunch of circular grooves for the 6mm axes. If you don't have those check this thingy. The directions there explain how to adjust the alignment. This is pretty important.

Before you check if all your pulleys and belts are tight, take a look at the positioning of the belts in the pullies. Ideally the belts run in the center of the pullies. Start with the short belts between motor shaft and axes. Then move the x and y sliding blocks close to the pullies and check that the belt goes to the center of the pulley. If not, loosen allen screw in pulley, slide over, re-tighten allen screw.

I would go through all allen screws on all pulleys to make sure they are nice and tight.

Next check that your belts are tight, especially the short ones.

Taking off the 8 bearing caps at the upper front, left, right and back of the housing is easy, getting some of them back on is a pita because the nuts are hard to put where they need to go. But the caps might be a source of friction; there are several good printed replacements around.    

A drop or two of fine sewing machine oil on the printhead axes every few weeks will do them good. 8mm axes do not need oil, and z screw takes the stuff in the green plastic thing.

I would also check that the sprocket on the feeder motor is nicely aligned with the large feeder wheel. And I would take a real close look at the feeder (i.e. take it apart) to see that all is clean and as it should be.

Heated bed z-stage: I just upgraded my UMO with one and had the same z-steps issue despite sw update. I found that the housing is really close to the back wall; I might need to do some light sanding to prevent friction. If the power is off and I gently tap the bed, it will sink by itself. Happy with that. Also very happy with the 3 levelling screws.

A well levelled bed is kinda essential for a good print. The best accessory by far that I printed for my UMO is the Z level adjuster. I level the bed with the 3 screws, then set the gap using this thingy. Works very well.

So much for maintenance - I am sure others can contribute some valuable thought.

10) vertical walls: when printing with a 0.4 nozzle, make sure your walls are a multiple of 0.4. The 1 mm walls make the slicer do all sorts of things.

The "Initial layer line width" under Cura advanced (I use 15.4.3) is quite usefull: It determines the spacing of the bottom lines in the horizontal direction. 80% means less gap, i.e. lines are closer together for a more solid layer.

Hope you have fun with your printer.

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Oef, so many points and responses.

Maybe it is good if @assist91 gave a status update on where (s)he has still some questionmarks.

@aggertroll, really nice write up on the maintenance part. Some solid tips.

@LePaul, thanks for being so helpful!

4) That is the first printhead. It has been a while since I have seen it.

I would recommend to update it to the hot end v2. You probably need to send an email to the reseller in your area because the default pack only has the hot end. You need to replace the top and bottom of your housing too. (the drawings are also on our github. Do you have access to a laser cutter?)

The advantage is that it is more reliable and less stress on the bowden tube and the heath doesn't travel up as far so less prone to clogging.

1) (I'm just gonna do the number random ok?:p) Yes, the new firmware should update your Z-steps. Make sure to select you have a heated bed as an upgrade. An upgraded Ultimaker Original with an heated bed is different from an Ultimaker Original+. They have different electronics.

9) shrinkage / 'Several distances where quite the opposite than I would have expected.' What does this mean? Did you expect it to fail but it didn't? If the accuracy is off you should inspect the short belts. I think Aggertroll mentioned it in his maintenance post. That directly influences the movement of your printhead. You can tighten them by loosening the motor and push it down. By tightening it (screws are on the outside) it should be more accurate.

10) keep the wall thickness a multitude of your nozzle size. Also sloppy short belts can influence the strength of your walls.

8) They indeed get quite hot. Don't have to worry about that. They can take it. If you do, you can source heatsinks to draw away the heath.

Let us know if you have any further questions!

And pictures of your prints (especially if you have questions) are always helpful!

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1) (I'm just gonna do the number random ok?:p) Yes, the new firmware should update your Z-steps. Make sure to select you have a heated bed as an upgrade. An upgraded Ultimaker Original with an heated bed is different from an Ultimaker Original+. They have different electronics.


We've seen cases where something went wrong:


Not sure why, probably on printers where people tinkered with Zaccel.

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Thanks for your answers. Let me do a summary:

1-3) done

4) Regarding the old UMO print head: Do you really recommend to buy a new(er) original printhead? Would it not be a better option to go for a 3rd party solution like the E3Dv6?

5) done, at the moment I'm printing at really low speeds anyway, therefore its not the most urgent issue.

6) If I understand it correctly, the mentioned variable changes the horizontal distance of the lines just for the first layer. For a given area, if you put a value of 50%, the distance between the lines is halved which implicitly means that there are more lines needer to fill the area?

7-8) done

9) I don't get accurate dimensions yet. This will be caused both by shrinkage and bad calibration of the printer. The quality of my print was fine which means, that some dimensions were oversize, others untersize, but not quite the way than I would have expected. Regarding accuracy, I will give more information below.

10) I don't understand what the key issue is when printing 1mm walls with a 0.4mm nozzle. Ok, I will try using multiples of the nozzle size next time. But as far as I understand, the lines have to be overlapping a bit to get a continuous layer. If you include some overlap you won't get a width of 1.2mm by printing 3 lines?

Ok, I will give you some more information regarding my printer. I bought it used, and therefore I expected some maintenance to be needed. I contacted the Ultimaker support and they gave me a quite detailed answer. Regarding maintenance, they basically told me that there is nothing needed beside of lubricating the rods regularly.

I had terrible warping even with PLA and therefore I was doing quite a bit of research on what options there are. So far, it ended up by buying the heated bed upgrade kit which really is a huge improvement and basically solved multiple issues regarding bed levelling, warping and finally overall print quality. The bed is worth every penny, but nevertheless, I'm not quite done yet.

What I noticed quickly was the fact that my print head can be moved by hand but not without applying some force. The movement is not smooth and linear and by watching the pulleys you clearly see wobbling. I already did align the axis parallel to the rods with the mentioned tool (http://www.thingiverse.com/thing:715901). At the moment I don't see any easy way to improve the smoothness of the printhead.

Yesterday I printed this calibration piece whith is mentioned in this thread: https://ultimaker.com/en/community/19518-umo-wrong-dimensions-in-x-direction?page=1#unread

The result is not that satisfying. Measured dimensions:

x: 99.8mm

y: 99.07mm.

z: 4.99mm

z-axis is fine, x axis is just ok, but y axis is far off.

I will adjust the stepps to see if I can correct this error, but this is basically not fighting against the cause? I don't know where the error is produced, the belts seem ok, the short belts I even tightened.

I'm one of those persons which are not satisfied below 99%, therefore I have in mind:

-upgrading to GT belts and pulleys, I already ordered some from robotdigg.com. This probably has to include an upgrade of the xy blocks as well?

-upgrading to a new pring head with dual fan setup

-upgrading the feeder

It's only one week since I got my heated bed upgrade kit. Beside the accuracy regarding dimensions, my printer prints just fine and therefore I did not perform any other upgrade yet. But I wan't to do that for sure, I don't want to spend to much time printing a piece with many varying dimensions until I get the jackpot.

If anybody can give me further advice regarding GT upgrade, I will take it ;-)

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Thanks for your reply.

4) let me invert the question; why would it better to go for a 3rd party upgrade?

The v2 hot end has been around for quite some time and has a good record. And if you ever need help, there is a bigger chance people will be able to help you here with the Ultimaker hot end (although I know there are several E3D hot ends too.) I guess in the end it is what you feel most comfortable with.

5) what speed are you printing at currently? i.e. what do you consider slow?

You lost me a 6).. sorry.

10) in theory you may have a point, but just give it a try and you'll see it works.

Not sure if there is a margin in Cura. (if it doesn't, it is probably a mechanical issue).

Rods; have you checked if they are still straight?

Making sure the rods are a perfect '+' and oiled with sewing machine oil that should be the start. When you have the rods out, it could also be worth your while to check if the bearings are still OK.

What feeder do you have on your UMO?

I don't think replacing the X and Y slider blocks is necessary with new belts.

How is the overall surface quality of your print?

When holding the printhead, can you 'wobble' it, or is it very rigid?

Some inaccuracy can also be caused by the friction from the rods.

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E3D hotend works well, if you don't print pla. With PLA on E3D hotend and 3mm (and being a new user) you will have quite a ride to make that work. E3D hotends on 1.75 have a inner ptfe tubing that make them work better with pla. Anyhow to wire all, you will need to read read read read read a lot.

V2 Hotend works really well, unless you want to print a lot at 255C+ materials.

As SanverG says, check the rods/shafts, move the head and check that they don't do this:

E3D hotend works well, if you don't print pla. With PLA on E3D hotend and 3mm (and being a new user) you will have quite a ride to make that work. E3D hotends on 1.75 have a inner ptfe tubing that make them work better with pla. Anyhow to wire all, you will need to read read read read read a lot.

V2 Hotend works really well, unless you want to print a lot at 255C+ materials.

As SanverG says, check the rods/shafts, move the head and check that they don't do this:


when you move the head. If they do, they might be 'banana' also it could be the bearings, anyway, check it.

If you get GT2 to upgrade the belts/pulleys, you need a new sideblocks. Read all this info https://ultimaker.com/en/community/15874-mxl-vs-gt2-print-results and use, for example, this really nice sideblocks: https://www.youmagine.com/designs/twisterblocks

To calibrate x/y if you didn't got the calibration sticks that come with the machine, print this: https://www.youmagine.com/designs/adjustable-axis-alignment-tool


I'm one of those persons which are not satisfied below 99%

You got a 1000 machine for 300$, you should be at least a bit satisfied :D

Edited by Guest

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Thanks again for your answers.

Regarding Rods: How can I check if they are straight without disassembling? Quite difficult. What I can assure is that I have aligned them with the tools mentioned before.

How do I check if the bearings are still ok?

Regarding the feeder; I don't really know. It looks like the original one with an improved gear.


Regarding print quality and accuracy:


I had to draw the black line in order to focus the camera. The surface quality of the bottom is fine most of the time. Sometimes the lines are not perfectley touching in some areas, which obviously results in a rougher surface.

The accuracy is quite off, despite the calibration I have done. The piece should be 30x40mmx3mm but in fact it's 29.75x39.8x3.05. Should it not be better?



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