Prints Coming out all...Strange

Mostly Printed CNC - MPCNC Troubleshooting
#1

I tried my MPCNC for the first time as a 3d printer. For some background info, I bought everything except the extruder on this site. I read the extruder tune up guide, and everything from the start seemed okay. The thermistor was set in, I even added thermal paste. The resistor was already centered in the block, and the bearing was spinning. When I tried to print, it looks okay at first but afterwards, I realized that the quality was pretty terrible.I am printing with Inland orange PLA at 230C

There seems to be a ton of under extrusion, since I can see through the print at times, especially where theres a flat overfill. In general the part feels weaker than it should. Keep in mind I used the recommended settings for the print. I was printing one of the corner foot posts.

Another issue was, the stepper for the extruder actually got so hot, I believe it shut off entirely. Mid way through the print, the extruding stopped but the rest kept going. The problem I have now is, the stepper got so hot, it warped the PLA printed tool mounter, so now I can shake the extruder with my hands :frowning: Better buy a new mount.

Any suggestions on how to get these prints better? I tried changing the temp and had little success. I thought the recommended settings would go better, but I think my extruder is all off or something.

#2

Do the 100mm extrusion test and see if it is correct. So many thing that could be wrong but how far off it is or isn’t really narrows it down.

#3

I fixed nearly everything, as now I can print decent quality. The problem was the mk8 bearing, it was totally locked up. I also had too high of a current limit on the driver for the extruder stepper.

The last issue I really have is the print accuracy. I can’t tell if it’s the emt I am using, but the edge of prints sometimes come out rough. It’s not my extruder, as I can sort of see and feel the jitter and little vibrations of the printer head. Any way to fix this in software or is it my rails? It’s not that bad but it’s something that could be improved.

I also jb welded the part of the feet where the conduit is held in, and am using an extremely sturdy table.

#4

Make sure the top bearings aren’t riding on the welded seam of the tubes. They’re kinda rough.

#5

It seems to work okay for now, but the edges still seem to be a little unsmooth compared to the parts that I ordered from here. It isn’t too bad, but on prints with small circles, I can see and feel the slight jitter that results in somewhat junk quality. I can remedy this by slowing it down a litte, but it only makes minor improvement and that’s printing at 30mm/s which feels a little too slow in my opinion. It might be my rails but I checked and everything seems fine. Maybe it is tension bolts?

#6

Print pics would help. Machine size, electronics and hardware being used, lots of details gets a better response. In this case you really need pics as well.

I print at 30mm/s on all my printers (not just mpcnc), 35mm/s max. If you want to go faster you will probably need to tune the acceleration and jerk settings in the firmware to match. z-axis length is going to be a huge factor here.

#7

Okay, here are some pictures

[Album] Imgur

http://imgur.com/948fPOx

I bought everything from here, except the extruder which I got on ebay. I tuned it up the way the tutorial said, and it seemed to actually be pretty good from the start, but the bearing wasen’t spinning. All that is fixed. The z axis has 6.5 inches of travel.

I am running the recommended settings, .4mm nozzle. I tried going to .3 and changing the software. I got better prints(obviously), but the uneven texture was still there. But now that I look closer at the print, it seems as though it is software. The sample piece on the picture has rafts, and as you can see, some parts of the cylinder are way cleaner than others. The top and bottom look way cleaner than the middle.

I want to print idealy at around 45mm/s. This printer is going to be making mostly structural parts, so I chose PLA cause it shrinks less. Dimensional accuracy is most important to me, so I am considering printing slower because it’s worth the tradeoff.

#8

Something isn’t right, with that print. I print inland pla at 213. Try that first.

It could be your slicer, or something else but please lets only change one thing at a time.

You should try some test prints first. I use the robox vase, printed as a spiral vase at 60% size as an extremely fast test print, once you get that looking good move on to real parts.

Getting settings right with a part that requires support is a bad idea.

#9

Okay, I printed at all the recommended settings, and here are the results for the vase.

[Album] Imgur

Looks pretty good to me, makes me believe either my machine hates printing anything else but slow, or that I have a slic3r problem. I notice small ripples in the smooth form, but thats from the rails for sure because they’re extremely consistent. The other piece I posted was completely messed up, like the extruder was laying the plastic all sloppy. I was printing at 215C first layer, 210C all other layers with orange PLA from Inland. My problem isn’t temperature because I tried every temp and certain parts always end up like the first one.

#10

So if you didn’t change anything else. You used the same settings and printed the vase, the only thing it doesn’t do is retract. That is a good setting to look into. I retract 1mm on the mk8 and only after more than 3mm of movement. retract speed is at 35mm/s.

If that isn’t it it just probably comes down to how you are slicing it. parimeters, speeds, infil, overlap, ect. maybe travel speed try 60mm/s

The vase looks pretty good so you know it isn’t the machine, extruder, or filament.

#11

Hmm…tried the same settings with the vase on the part, still the same result. i tried messing with the retraction, nothing. I am really confused now, it has to be software. When i watch it print, I can’t really tell what it is doing wrong. I feel the vibration a little more than usual, but it seems to be an issue on especially, the round part. Maybe it is my stl file…not sure. I tried the 3dbenchy boat test and it has that kind of sloppy look to it still. It’s where the outside surface looks rough and bubbley. Overextrusion? Not sure yet

#12

I wish I could help. I have two printers with wades extruders on them and they print like that on some parts (not that bad but similar). I can print the exact same parts with the exact same gcode on the mk8’s and it comes out perfect.

I assumed it was retraction. I’m not sure now.

#13

It might still be, but as far as I tested it isn’t. Such a mystery. I still find it weird the vase printed fine but the RC Car piece I modeled isn’t. I tried testing all of the retraction settings and all gives the same result. The 3d benchy boat turned out okay, but had that same issue with certain areas. It has to be retraction cause the pieces that require it are the ones that turn out the worst. The only thing I changed that made it look a little better was the extrusion multiplier to .95 instead of 1. But that’s not really the proper fix.

#14

It occurs to me one of my bearings is not spinning on the rails. It is one of the bearings on the gantry. I wonder why this is? Maybe this is the issue? It is the bearing closest to where the rails meet on one side. All other bearings make contact and have enough friction to not spin, but this one is just free floating, regardless of the position of the gantry relative to the rest of the machine.

Upon further inspection…it seems as though the rails themselves are flattening out and causing a loose fit…this is probably even worse. When I take the machine apart and isolate the gantry, i can wiggle the pipes around and feel the play between them. Depending on where I put my force, it causes the wipe to ride on 1 bearing vs the other. Is this normal at all? It feels like there’s too much play between the gantry bearings and my rails. I am using the correct rails, 3/4 inch emt. It just seems to be the worst on the flat sections.

#15

Was about to start a new thread until I saw yours, which I still may have to do. I just finished up my build and am seeing what I think is the same issue as you. I get this wavyness on all 4 sides.

The difference though I am using the standard mega/ramps 1.4 stack. My electronics were salvaged from my Prusa I3 that was used to print all the parts. I reflashed with the firmware on this website. I believe the only thing I modified was the extruder E-steps.

I was thinking it had something to do with the machine shaking, my build is 24x36 and 12 inches tall. I have tried adjusting the acceleration down in the firmware and have tried printing very slow but still get the same wavyness.

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#16

Yeah my prints look like that too. No matter what part, there is a generally waviness and clear lines to the outside surface, but sometimes the rectangular infill is perfectly straight 45 degrees, so I got no idea. In general my build seems very unsmooth, even though it is nailed down and the outer rails feel very solid. I can’t wiggle them with my hands.

#17

Yyuont - yours is a bent z axis screw. It gets magnified the longer your axis. So at 12" you are always going to have a hard time. So mke sure it is straight and in the coupler correctly.

Kevin - I thought you were doing pretty good. Have you tried a different part other than the bad one and the vase? The parts that come out like that for me on the wades are the ones that have thin walls, like the pen mount. but they come out fine on the mk8. So if you did a 25% infill 20x20 cube does it print right. It really could be the part.

#18

Yeah I did the cube, and a lot of other prints. Most of the square geometry parts look okay, but the smooth ones like the vase do definitely have these waves you can see. I am guessing this these uneven layer are from just general vibration caused by the unevenness in the zinc coating. When I watch it print at 30mm/s, I can see and feel the bottom of z axis wiggling just a little too much. Yours seems much smoother in this video of yours with the old gantry https://www.youtube.com/watch?v=nVKHlX3NaTA

Especially on the circles or round parts, I can definitely see more ripple effect in my printer for sure. Your conduit seems a little more smooth then mine, maybe it is just the conduit who knows. Especially when I tested 50mm/s, the shake was really obvious, but that’s too fast for default acceleration for sure. When I tried printing a bottom corner piece, the inside had all these small ripples. Not as smooth as the ones that I used to build it. In terms of geometry accuracy though, its nearly spot on with the only complaint being the holes are generally printed to small.

Another thing that concerns me is that one floating bearing, that has to be incorrect.

#19

As far as I can tell the z axis screw seems to be turning straight. I removed the rod and rethredded into the coupler. Also rolled it across a glass plate and didn’t notice any bending.

#20

Yeah me too, hmm. Upon looking at the forums it seems a lot of people are having this jittery problem in general. Makes me think it is software, or slicing. I printed the test piece on the slic3r recommended page, and it turned out pretty nice. No obvious errors, but still the lines across the print just like jyount. Then I printed a funnel shape and it looked all terrible again, except on the shaft of the piece where its just a straight cylinder. Man I am so lost, I will post more pictures if necessary.