XY shifting problem

hey guys,

I've been scratching my head over this issue since I got the printer (a chinese Mingda 5 ) couple of weeks ago. Terrible support from them and my feeling is they are not even aware of all the issues that their printer have (as long as they see some plastic coming out of the nozzle they think they got a decent printer to sell.) Anyway I am posting some pics to better illustrate the issue. These 2 cylinders are printer at 0.3 mm , once sliced with CURA and the other with Simplify3d . Not even bothering here about the blobs for now (yeah other numbers to figure out) but I am just trying to understand what is causing those repetitive XY shift on Z. Excluding the slicer software since the problems is there regardless, and after reading and searching the internet for the problem I though that the cause of the problem might be the Z screw. I then attached 2 markers to the platform and I lifted the platform for about 10-15 cm (those black mark is the pic) and I cannot really relate the print issue with those marks.
What is your thought about it? I just know dont know what else to tweak. The print speed was I think 40 mm/s so not that high. Material is HIPS...but ABS showed the same print temp between 230-240

thanks a lot
MArco
Attachment 4107Attachment 4108Attachment 4109

XY shifts are usually simply due to loose linear motion parts. It is hard to see from the pictures if the machine uses belts or screw rods. If it is using belts, tighten them as much as you can. The next step is to do a movement calibration test. Have your extruder make a spot on a piece of paper taped to the print bed, then move the extruder 100 mm using your interface. Measure how far the extruder actually moved. If you can get into your firmware you can alter the number of steps the motor uses to move a known distance.

Another point is that when buying a printer, be wary of ads written in Engrish.

Old Man Emu

thanks for your answer sir!
The printer uses belts and they seem to be tight enough to me. The only way that I could see the problem go away is to reduce acceleration values (and print speed as well) by A LOT...too much as I would never want to print that slow :)
I tried to do what you said to make 2 marks on a piece of paper but I have to say that the distance traveled (I tried only Y axis) was spot on when I measured it. So yeah I must be something else I guess :/ I will keep on scratching my head :)

Possibly damp filament maybe but not sure, just a suggestion.

You'll have to check the calibration of the X axis as well.

It is hard to tell from the photos where those objects were positioned on your heat bed when they were printed. Please print another cylinder, doesn't matter which slicer. Just for speed's sake, stop the print when the cylinder is half printed. Before you take it off the bed, take a photo from the front, square on (will show X-axis movement) and one from vertically overhead ( will show Y-axis movement). Then put a dot with a marker pen on the +ve Y side and +ve X side of the top surface of the cylinder. This will assist in later identification of position relative to the extruder. Post the photos and we'll see if we can determine anything from them.

Just another thought - check that the extruder assembly is tightly attached to the carrier.

Old Man Emu

That looks like a slightly bent leadscrew. As the screw rotates, it causes the table to wobble. I'll wager the pattern of bumps lines up well with the threads.

Quote:

---

Originally Posted by wackyvorlon

That looks like a slightly bent leadscrew. As the screw rotates, it causes the table to wobble. I'll wager the pattern of bumps lines up well with the threads.

---

It does look like this. This can be exacerbated if both ends of the lead screws are fixed. One end needs to be free or the bend in the lead screw will translate to movement in the axis.

Quote:

---

Originally Posted by evilmaul

thanks for your answer sir!

---

Paleeese!

You don't call an Old Man Emu "Sir", unless you have heard that I have been knighted by Queen Elizabeth in the New Year's Honours.

OME

thanks for your answers guys. This printer has both ends of the lead screw fixed. After I freed the top that waviness issue seems to be gone, yay! Now dealing with other things like finding out good param for either Cura or Simplify3d to get some decent prints. So many things to tweak argh.. Right now with SI3D I can get nice prints but no matter what I tweak in the retraction settings (I tried them all) I still get some blobs/zits at the beginning/end of each new layer sigh