Are these prints good or bad?

Hi all,

I'm a newbie in 3D printing. I just received my Robo3D 2 weeks ago. Still playing with it to get the setting right.

I printed a couple of parts last night. I would like to get some feedback from the experts in this forum.

One of my observation is that the bottom layer are flatten out which increases the dimensions of this layer comparing to the desired dimensions.

All feedback are appreciated. If thing does look right, please let me know what could be the root cause so I can search for a solution.

Thanks,
P.

 

Hi P,
That is a good first layer. It is necessary to have it squished onto the bed to ensure proper adhesion otherwise many prints will pop off. Remember that you probably set the initial Z height with a piece of paper thickness? This is basically going to be the thickness of that first layer. In the slicer settings you chose a first layer thickness equal or greater than the subsequent layers. This thickness setting is greater than the paper thickness of the nozzle so the extra plastic oozes out the side and makes the extra wide ridge on the first layer. It is standard procedure to either ignore this ridge or to trim it off with an exacto knife.


On the Lego piece it looks like you have very good bridging underneath.

The top layers are not filled completely. Others please help comment on this - but I will suggest playing with the filament setting for extrusion multiplier. Try bumping it up a few percent at a time and testing. Your filament diameter could be a bit undersized and the extruder not producing enough plastic. This can also compensate for an improperly calibrated extruder/hobbed bolt.

In the third photo there is some poor adhesion, possibly missed extrusion or too fast a print speed. Do you get any plastic shavings built up on your hobbed bolt? This can cause filament feed skipping. For poor adhesion you can play with the extruder temperature. Also try printing the outside walls slower.

The Lego knobs are a bit messy but not bad. This might be improved with filament cooling settings and perhaps a lower extrusion temperature. Cooling can be key for small structures like this and it will pay off to study and understand the settings.

BTW - Nice Lego plate! a 2x4 block was the first thing my son designed in Sketchup and printed when we got the printer. Now we have over 20 printed Legos to add to his huge collection. I was supprised at how well they fit together and with real Legos (after some tweaking). You can trade off that bottom layer thickness for adhesion but will always need to trim off the inside and outside. Also you might try putting an extra lower layer at the top of the cylinders to help them stick to the bridging better. Just use a pull tool to make the cylinder top thicker.

 

Ok, I would recommend that you change one setting by itself in small increments to make sure if you fix it you know what you did. I recommend starting with temperature and try decrease it by 5. If it looks worse then increase by five. If it looks better increase by five again.

You may choose to increase it by a smaller amount and that's great but it will take longer. Doing something like a lego brick is very difficult becuase it have huge bridging area and small details that if you temp settings are not quite perfect, then it will not look to great.

Stick with the calibration cubes and play with the settings. You will be looking for straighter edges and possibly better infill at the top.
BUT as you were only printing for two weeks, I think you are going down the right track. Good Luck

 

Steve and Soupaboy,

Thanks for the great feedback. I will start playing with the temperature settings first with that settings and will post the results here.

BTW, I have few additional questions.
If I changed the resolution layers from 0.3mm to 0.2mm or 0.1mm,
1. Do I need to recalibrate the Z axis?
2. Are any other settings affected by changing the resolution layers?

Thanks,
P.

 

Alright. The result is getting worse and I don't know how to fix it .

Here are the settings
Temperature 190/185.
layer height: 0.3034mm
infill: 0.4
speed: perimeter: 20mm/s
the rest is 50mm/s
extrusion multiplier is 1.0 (issue is still the same when I chose .9)
Adjust the belt tension on the y direction.

The result is : bad . Did I do something wrong?

 

Just to give you a couple of area's to look at,

Is the filament having a hard time extruding? Could also be hobbed bolt tension. Make sure the springs are nice and tight, I actually have a nut under the bolt head that I can wind down into the spring to give extra tension. Make sure the filament isn't having a hard time feeding in, could be fiction against the slot in the top of the Robo. Could be a nozzle clog.

Is this PLA? Judging by the low temp I'm guessing so.

Is the bed having any trouble moving? Or is it rocking?

 

The first few layers look fine.
Have you tried printing at 190 through the whole print instead of dropping it down?

 

Kevyn,

It maybe the hobbed bolt tension. I will clean the hobbed bolt tonight and tighten the springs again.

warlocke,

haven't tried that. I will give it a try before cleaning the hobbed bolt tonight.

 

Generally, if you have any filament shavings in your hobbed bolt at all you will have extrusion problems. That may not be the only issue but it will certainly contribute to any other problems. If you have a non-grooved bolt you should replace it. Also like Kevyn suggested you should tighten up the idler bearing that pushes the filament into the hobbed bolt. I just added more washers to each side, five total I think. I never get any shavings in my bolt setup. What does your bolt look like?

 

Ok,

I think I found the issue. The issue is from the hobbed bolt as Printed Solid mentioned.
It makes clicking/grinding noises while I'm printing. I added 4 flat washers to spring loaded screws. I was able to completely print a 15mm cube; however, the issue came back again after that.

Here are more observations:
1. The filament was shaved more than half of its diameter at the hobbed bolt. (maybe the spring loaded screws are too tight?). Hence, the filament was unable to extrude out from nozzle.
2. shaved materials were melt and leaked on the top of the nozzle.

 

I agree, 185 may be too low for that filament and causing too much back pressure. I usually do a manual test with the hobbed bolt idler pulley loose. See how much pressure it takes to push the filament down by hand as you vary the temperature.

That back pressure is probably causing the hot end to leak. See some recent posts where that new (black) hot end can leak and now they fixed it.

I really don't trust that hobbed bolt at all. It looks like it is designed to shave the filament instead of gripping is with more circumference/surface area like a standard grooved bolt will. I would get a new one from ebay. Specify the hobb to be 15mm from the base of the bolt head. I have had no filament shavings since replacing the bolt. I feel like a broken record with the number of times I've said this on the forum.

 

Okay, things are moving forward a little since yesterday.

what I did last night and tonight:
1. changed the spring with higher stiffness. Using the tension from the spring to keep the filament close to the hobb bolt. Shaving the filament was no longer occur. See image below for the uniform mark from the hobb bolt.



2. Slow down the speed of the z axis feed rate and running speed as shown below. Also, turn off the "auto enable cooling fan".



Outcome:
1. Successfully print without shaving for the first 10 layers (printing the Z axis stabilizer). Last night was all shaving and couldn't print the 2nd layers.


2. Filament was binding and folding after that as shown in the image below. This caused the extrusion failed as you can see on the top layer of the above image.



Any suggestions for the next steps? I'm not sure if I want to reduce the speed since it is already really slow.

Thanks,

 

Well, as said before you definitely want more heat... at least that's been my experience with PLA. I've even done first layers near to 195, but that's not really recommended; weird warping and layer messiness may occur with too much heat. Speed doesn't seem to be the strong suit of this printer, every time I've tried to turn it up bumpy edges and a lot of undefined edges occur, so you might just want to keep it at a speed that looks to be making a clean print, because there are consequences for printing too slowly also. I had the filament shredding issue when I first got the printer, and the trick isn't always more pressure, its just giving the machine enough heat so the filament can pass through easily. Try manually selecting "extrude" or push the filament through by hand to see or feel the resistance, that was how I did it, albeit I'm only just getting the hang of this finnicky machine. Oh, and if you get it working to your liking, heat up the bed (if you have that option) to a moderate temperature like 40, it actually helps a lot if you choose to print without the painters tape

 

For the red PLA I like using 220
I use hairspray, start the bed at 70 going to 55.

Is your a Robo filament or other?


When I had filament issues I heated up a bobby pin till red hot and stick it into the extruder. I pushed hard and felt it give, meaning that there was filament in there. I was able to pull it out and free a blockage.

It looks like either you have a blockage or your filament is too thick. Is that 1.75 or 3mm?


Sent from my iPhone using Tapatalk

 

It may just be the picture but that hobbed bolt looks very strange to me, the grooves don't look right.

 

I usually associate that type of deformation with "heat creep" where the hot end is not cool enough at the top and the filament deforms causing a blockage. In your settings, you have no fan use at all and I would at least check the "auto fan" if not "fan always on" option. That should help keep the filament cool enough not to deform until it actually reaches the hot end. As a test for temperature, try keeping the hobbed bolt out of the test by leaving it open and feeding filament through by pushing it manually. When you find a temp that offers minimal resistance and flows nicely, print with that temp for a test print (with the hobbed bolt back in action). Of course, make sure the path to the hot end is clear before anything else. If you cna't get a decent flow going, your PTFE tube may be at fault.
Good luck!

 

As a check, heat up your nozzle to the temp you are using. then with the Wade feeder unscrewed and open push the fillament through. It should push quite easily and extrude.
If it is not coming out easily then either; temp to low. or issues with ptfe tube or nozzle.
I dont see any kapton tape; is the thermistor firmly in place?

 

thanks for all the feedback, guys. I think I solved the problem for now, but tuning is still in process

Peter: I bought 1.75mm PLA from Sainsmart.com (through Amazon). They recommended to use 210C

Michael: the hobb bolt doesn't seem to be an issue in this case. By adding the spring stiffness and not installing the two retainer-spring screw too tight, I don't see the shaving any more.

1d1 and scotta: cooling and thermistor were actually the main root causes of the issue. see my experiment below.

-------------------------------------------------------------------------------
Here were what I did last night:
1. Tighten the nozzle against the black thing (don't know what it is called) tighter since I still see some leaking between the gap.
2. Secured the thermistor in place by adding two piece of metallic wires. I found that the thermistor was not secured. It was freely coming in and out during the fast movements.
3. Then increased the extruding temp to 210 and enable to cooling fan.


Results: Ta-daaaa. Not as smooth as I want but it is a huge step from two night ago. My next piece will be the right hand side of the Z axis stabilizer