Problems with Bulldog light extruder and Hexagon

Hi,

I've just started with 3D print but I'm allready at the point to give it all up again.

I've got a Ordbot with a Bulldog 1,75 extruder and a Hexagon 0,4 Hotend at 24V and a Rumba board with Marlin. I just started with PLA as it should be the easiest at the beginning. I've just started wiht 195°C maximum Speed of 20 mm/s. I don't know how to call how the extrusion looked like. I will call it "bumpy". Let's see it on the picture from the prim where you can see it best:



And also a typical print:



The "bumps" come in a regular interval. At the picture above ~7mm. These 7 mm continue also at the corners.

I tired out a lot a read lot around for days. Finally I wrote a mail to the german distributor where I bought the Hotend and the Extruder. He said, that I should increase the tempreature up to 220-230°C. E voilá I get my first nice prints.

Realy high motivated I wanted to continue the calibration of the printer in topics of cooling and so on. But suddenly the printer starts again with the same problems at 225°C !!!???. I didn't change something at the extrusion settings. So what is going on here?

I've no further ideas how to continue. I'm only frustrated. I searched around in the web and the forum without finding a solution. I hope realy somebody out there has an idea what it could be and how to fix it.

Thanks a lot in advance.

Regards

Andreas

There are a number of things to look at. The regularity of the blobs says maybe the drive gear on the extruder motor is dirty (full of plastic powder from grinding filament), or slipping on the motor shaft- check the grub screw(s). Another possibility is that the motor current is set either too high or too low. If the motor gets very hot it is probably too high. If the motor doesn't get warm it is probably too low. Check the spec and check your motor driver current. Another possibility is that the temperature is swinging up and down between fully melted and not so melted plastic. Have you run a PID autotune on the hot end? If not I suggest you do so.

Hi,

I've checked all that parameters in advance. It is clean. The motor current is OK and also the Tempreature....!?

Hi,

Within the last days I tried out several prints at different temperatures up to 240°C. Without any success. Then suddenly one day I get perfect prints. This day I tried out to change a stepper driver from extruder E1. This driver seems to be defect because I needed to reduce it steps down to a quarter. Before came out a mass of PLA. But the print was perfect!? I started to calibrate the printer. The next day I was really looking forward to come home to start printing the first real things. But f...k! This prints started again as bad as before. I don't know what is going on! At the moment I left the printer beside without any knowledge how to continue. I realy hope that somebody out there as seen this print problem and gives me a hint how to continue.

Regards

Andreas

Hi,

Is realy nobody out there who can help me? Acutally the printer is only a useless something on my sideboard because I have no idea where to proceed. Maybe I should try out another hotend/extruder? I don't know...

Regards

Andreas

It looks like your layer height might be too big. What layer height are you printing at with that .4mm hot end?
I run max .3mm layers for fast prints and .2mm for slow prints.

All my test prints where with 0.2 mm.

Fixing things involves checking everything, and then checking the things you're sure it couldn't possibly be. Have you checked the grub screw on the extruder drive gear? Have you checked the wiring between the extruder and the controller? Is the hot-end fan running continuously?

If it extrudes smoothly when you command it manually via pronterface (or whatever host software you may be using), and you've looked at all the mechanical and electrical connections and come up empty handed, the problem is likely the slicing software. Which slicer are you using?

Also check if the hobbed bolt isn't slipping. See if tightening it makes a difference. When printing the extruder gears should be constantly moving, if it stops now and then while it should be turning there's a grub screw loose like the digital dentist said.

I use Slic3r in repetier host on a marlin firmware. Everything that could be checked ist checked. What realy confuse me is, that one day it work's great and the next day it's again all scrup. In general it is scrup, but there had been some days with great results. And the next day it was again a useless peace of maschine.

Make sure the coldend is cool-warm to the touch. Also, hold onto the filament as it is going in and see if the stepper motor is skipping steps. Check the tention on the hobbed gear and see if it is slipping. Check that the thermistor is reading temps correctly. Mine read 275 when it was actually 235. Mine had all four of these problems and after fixing them, it worked extremely well.

How does you measure the tempreature? Actually i have only a infrared thermometer. That does not measure on blank aluminium correctly.

I don't think it's been said before, but I would expect the Hexagon hotend to be most suitable for ABS and not PLA.

There is no PTFE liner inside, this basically means it's terrible to print PLA with it. The problem is likely caused by the PLA plugging before the transition zone.

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