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philip

Printing Small Objects - UM Original

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Hello everyone,

I am trying to print small objects with letters inside.

I looked through the forum and also on the google group for Ultimaker. I found some threads about thin walls and shell thickness but I didn't come up with a solution.

I have an Ultimaker Original without any upgrade and I am using Cura. I am not an engineer, I am trying to learn code and hardware but I hope you understand that is not so easy.

I upload a test to Youmagine. This is the link: https://www.youmagine.com/designs/letters-test

In a thread I found that with Cura printing objects of this dimension it can be really difficult because the software doesn't give the instruction to fulfill the gaps between the shells and the shells and the infill results to be not connected.

Someone suggested to use Slic3r, I arranged the gcode with this but then it is not possible to upload the file in Cura. (I also installed Repetier-Host but I don't want to change firmware or whatever it is needed as far as I have always used Cura with other objects and I have obtained great results).

I printed some samples and the "best" result that I have had until now is the the one on the right in picture. These are the setting that I used:

Test Letters

Quality

Layer Height (mm): 0.10

Shell Thickness(mm): 0.4

Enable Retraction: V ticked

Fill

Bottom / Top Thickness: 0.4

Fill Density: 20%

Speed and Temperature

Print Speed (mm/s): 10

Printing Temperature: 220

Filament

Dimaeter: 2.85

Flow %: 100

Machine

Nozzle Size (mm):0.4

Retraction

Speed (mm/s): 40

Distance (mm): 4.5

Quality

Initial Layer Thickness (mm): 0.2

Cut Off Objects Bottom (mm): 0.0

Speed

Travel Speed (mm/s): 100.0

Bottom layer speed (mm/s): 5

Infill Speed (mm/s): 5.0

Outer Shell Speed (mm/s): 0.0

Inner Shell Speed (mm/s): 5.0

Cool

Minimal Layer Time (sec): 5

Enable Cooling Fan : V Ticked

Retraction

Minimum Travel (mm): 1.0

Enable combing: V Ticked

Minimal Extrusion Before Retracting (mm): 0.02

Skirt

Line Count: 2

Start Distance (mm): 3.0

Minimal Length (mm): 150.0

Infill

Solid infill top: V Ticked

Solid infill bottom: V Ticked

Infill overlap (%): 15

Fix Horrible

Combine Everything (Type-A): Not Ticked

Combine Everything (Type- B): Not Ticked

Keep Open Faces: Not Ticked

Extensive Stitching: Not Ticked

Maybe with better settings is possible to achieve something better. If anyone can help I'll really appreciate it.

Thanks!

gr5 edit: Moved the image link up higher in the post and made it link direct to photo

 

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your youmagine page is marked as private.

I think that your top/bottom layer is responsible for most of the artefacts.

I would go for Xmm bottom/top thickness height where X= the height of your proposed object

I would have 0 fill - this essentially produces a solid object as you have been trying to cover the top with a o.4mm thick layer of molten plastic!

For something this small I print cool and slow - cooler than your 220 - something like 210 if your machine can produce a noodle at that temperature.

And slightly faster than 10 as you don't want that hot nozzle on the layer too long - say 20mm/s

change all the speeds to 20.

then change the minimal layer time - I never remember which way, so I raise and lower it in Cura and see what the build time is - if the time goes UP then it is taking longer so this is the right way - basically on a small object you want to ensure that the nozzle gets clear of the filament to let it cool. (Though I don't fully know if that is the right direction :))

Have a go with some of those settings - but the main one is to go for 100% infill (by changing the top/bottom layer thickness.)

And the temp and see what happens.

I tend to write the settings that I am printing - so 210/20 for 210 degrees 20mm/s and you have a permanent record of what is going on.

James

 

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minimum layer time isn't an issue for this part as it takes more than 5 seconds per layer.

It is difficult to print "holes" or "openings" on a UM printer. I have tried this in the past. One solution is to print vertically - I think it will look much better if you print with the long, thin edge down. You will need brim.

Another solution is to use 2 colors. This will come out much better. Print the word "hello" in one color, then end the print, remove filament, put in new filament of contrasting color, then print a simple rectangle on top - you don't need to have the second part know about the letters. Here is an example:

cell phone case for samsung galaxy S4

 

To get the two prints to line up I made the words inside a box of equal size such that the second layer printed a rectangle, then I manually removed the second layer from the print with a text editor so that the print would halt before printing the second layer. That way when placed in Cura both prints were aligned even though they were sliced separately.

 

For the upper part it is better if you do a thick bottom layer - say .3mm so that there is more room for the plastic to squeeze around the letters and into the cracks. And print it slow although 30mm/sec is probably fine.

 

If you choose the 2 color method, please post results as I will have suggestions to improve it! Also you can print the second color *on top* instead of on the bottom if the top is flat. This would be most easily done using "pause at Z" and changing filament in the middle of the print.

 

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Hey Guys,

thanks a lot for your answers, this was fast and sorry I didn't check till this morning.

Apologies that my youmagine page was private, now it is visible same link https://www.youmagine.com/designs/letters-test

James thanks a lot for all the instructions.

You was right the top/bottom layer and the infill at 20 % was messing up the printing.

The Height of the object is just 1 mm, so yes it was ridiculous printing at 20% infill.

I decrease the temperature to 210 and yes it has helped.

Also I notice on the samples that I printed before under extrusion. I wasn't sure it it was coming from the settings or a problem with a feeder. At the end, I change the diameter of the filament to 2.8 and I sort it out that problem (the filament is the one that came with the printer, an Ultimate Blue PLA 2.85 mm, they told me is not the best but I didn't think the diameter wasn't correct).

Also is better to print at 20 mm/s than 10 mm/s: I didn't expect that, my idea was less faster more precision, instead if it goes slower there is again under extrusion.

I changed the Print speed and the Bottom Layer speed to 20 mm/s. James you said to change all the speed settings to this value, do I need to change also Retraction Speed and Travel Speed?

It seems that the Retraction speed is the one that is causing problems.

The zone around the "H" is still the worst one;the infill does't attach to the left perimeter and in the middle od the letter there is gap and over extrusion inside the perimeter.

I found that is very important having the bed calibration perfect and also checking the machine when is starting(if the filament is coming out smoothly or not).

gr5 thanks for taking the time for sharing your method, I am not sure is going to work for this tiny object (it is a test) I think it's better to try in one material. My fault that I didn't upload right the STL file.

Letters Test 3

Here the settings that I used this time:

Quality

Layer Height (mm): 0.10

Shell Thickness(mm): 0.4

Enable Retraction: V ticked

Fill

Bottom / Top Thickness: 1

Fill Density: 100%

Speed and Temperature

Print Speed (mm/s): 20

Printing Temperature: 210

Filament

Dimaeter: 2.8

Flow %: 100

Machine

Nozzle Size (mm):0.4

Retraction

Speed (mm/s): 40

Distance (mm): 4.5

Quality

Initial Layer Thickness (mm): 0.3

Cut Off Objects Bottom (mm): 0.0

Speed

Travel Speed (mm/s): 150.0

Bottom layer speed (mm/s): 20

Infill Speed (mm/s): 0.0

Outer Shell Speed (mm/s): 0.0

Inner Shell Speed (mm/s): 0.0

Cool

Minimal Layer Time (sec): 5

Enable Cooling Fan : V Ticked

Retraction

Minimum Travel (mm): 1.5

Enable combing: V Ticked

Minimal Extrusion Before Retracting (mm): 0.02

Skirt

Line Count: 2

Start Distance (mm): 3.0

Minimal Length (mm): 150.0

Infill

Solid infill top: V Ticked

Solid infill bottom: V Ticked

Infill overlap (%): 15

Fix Horrible

Combine Everything (Type-A): Not Ticked

Combine Everything (Type- B ): Not Ticked

Keep Open Faces: Not Ticked

Extensive Stitching: Not Ticked

 

Thanks a lot!!!

 

 

 

 

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I think you're having a backlash issue. The "indents" of the H do not line up, and the O is oval instead of round, which are both indications of backlash.

This is usually a case of too little tensions in the short belts. Which requires unscrewing the motors a bit, pushing them down, and screwing them back tight.

 

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Hi everyone and thanks for your help!

I don't know if this problem is connected to the one above, but it is the first time that I have.

I was printing a file for a client and at one point went completely wrong, it seems the extruder start to print on different coordinates moved far from the supposed to be and keep progressing away. I don't know it it's something wrong in the gcode or in the STL sent me by the client.

 

Wrong coordinates

 

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Most likely you have either skipped steps (usually due to fast moves not happening correctly), or simply a loose pulley that is allowing the motor to slip (most likely one or other end of the short belt).

Power the printer off, and move the head around by hand, using fingertip pressure on both sliding blocks at the same time. Check for any tight spots, or differences between the axes. Apply a light oil light sewing machine oil to the horizontal rods.

Tighten all the pulley grub screws - especially the ones on either end of the short belts. It can be a good idea to make a mark on the pulley, and the shaft next to it, using a permanent marker, so that you can see if the pulley slips, relative to the shaft it's on, during printing.

 

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Illuminarti thanks again for your quick answer!

I have done those checks and operations other times and I have done it yesterday after Daid suggested. I did it again but no one pulley is moving and everything is tight. I am almost sure everything is good, but i need to say that before it starting to go wrong it makes a tough sound like a "knock on wood".

Failed at same layer

Check this picture: is it a coincidence that the printing went wrong three times exactly at the same layer?

it can be anything about firmware, gcode or software related?

I was printing very good stuff, now even the ultimaker robot has gone these shifted layers....

 

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It's not a coincidence, but it's something about the path on that layer - maybe it has a longer faster move that causes the skipped steps or slipping. Alternatively, is the print curling up off the bed? If the head catches a curled bit of print, that could account for the thunk, and then throw it off. But the sound could just be the skipped steps.

Try reducing your travel speed and see if that helps.

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Thanks again for your wisdom!

Yes, looking at layer view mode in Cura at that layer seems two blue lines almost cross each other. The file is water tight but I think there are irregular meshes. Btw Repetier Host doesn't recognize the printer or it's me that I am looking at the wrong settings.

The head probably caught a curled bit of print, if I am looking at the three wrong attempts in the picture there are some of them. What makes me wondering what happened in particular is in the part at the bottom of the picture:there are four paths in wrong positions and they seems to go further wrong in progressive way.

Failed at same layer

I am printing again with different settings and, indeed, didn't mess up at that point but it has done after.

 

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Can you confirm if it is only the X axis that is slipping? Or only the Y axis? Or both? In the bottom print it looks like only the X axis.

There is a bug in an older version of Marlin from a year or more ago related to moves when all 3 axis move at the same time. It is rare to move all 3 axes at the same time. Illuminarti understands this bug better than me.

I still think you have a slipping pulley. Did you remove the stepper motor for the slipping axis and mark the rod and pulley and then later check that? And tighten that pulley the most? There are 6 pulleys that can slip - 4 on the long belts but maybe you forgot the 2 on the short belts?

The problem is definitely either slipping pulleys or slipping steps. To avoid slipping steps you can try to lower the jerk and acceleration. Speed is not important. You can lower both using the ulticontroller if you have one. But this is a bad solution because it means you are changing software to avoid a hardware issue (friction).

 

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Hi everyone and thanks again for your answer.

gr5 I can confirm that only the x axis that is slipping. I am not English, so apologies if I am saying a silly thing, but I would use "jumping" rather than slipping because when it happens I hear a sharp sound, like a knock on the wood.

I don't have an Ulticontroller, for the same reason I am still using Cura 13.12 but I bought the printer on October and I update to the last firmware.

To sum up, from what you said, it is definitely an hardware issue and not a software issue or the design that I was trying to print. It was an STL file that was watertight but I didn't design by myself and the person that has done it hasn't done for 3D printing and it is not used to this printer. Maybe, try to printing something different from usual has triggered behaviours of the printer that I didn't experiment because I print "easier" stuff.

You said friction and you gave me a clue and probably you are going to blame me :oops: for have not mentioned before that it usually occurs a failure to the z axis: when I bring long down the bed and then it needs to go up, sometimes It is audible that the motor is working but the rod doesn't move. Further, I have done a stupid thing because I didn't have oil sewing machine, I put the green lube on the x and y axis. There is a lot of friction in moving those two by hand, but the motors doesn't have any problems to do it.

About the pulleys I signed and check all 10 (the 8 on long belts and the 2 on short belts for the motors). I can tell you that at 99% they are strongly tight, i leave the 1% because I am not an engineer.

Instead is it possible that now there is too much tensions on the little belts?

Thanks!

 

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Sorry - I missed this post.

It's easy to clean off the grease, just use rag or paper towel. Then use oil - any oil. Baby oil. WD40. It is best to use oil with no additive. But any oil will work.

However sudden moves like your issue are usually not friction but instead are loose pulley. I think you missed 2 pulleys - the ones on the motors. Take the X motor off and tighten that pulley also. There are 6 pulleys per axis - not 5.

Also consider using a permanent marker to put a small dot on the pulley and shaft of all 6 pulleys so you can see which one is slipping.

If this is a UM Original kit, the kit should have included extra set screws that are silver color (shiny). Those set screws are better than the ones that come inside the pulleys.

Black Screws = good

Silver screws = better

 

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