K8203 melted barrel, after jamming problems

K8200 3D Printer K8200 - Issues while printing
1

I have melted the metal nozzle assembly off of the plastic k8203 barrel (that surrounds the PTFE tube).

I am working with ABS (1.75mm, of course). The temperature was measured, by the thermistor circuit, as below 200 degrees. I was pre-heating the extruder after cleaning the nozzle. I had the fan running at half speed, aimed above the metal parts, and aimed at the plastic barrel.

I have also been having problems with the filament failing to feed under motor control. The motor pushes the filament, and the filament seems to spring back with a “chunk” sound. Usually, if I apply some manual pressure to the filament, to assist the motor, it will move and extrude. I began trying to use the fan (it was off in early attempts) just prior to the meltdown incident.

I believe some of my initial problems were a partial clog of the nozzle, that was permitting some extrusion, but at an inconsistent flow rate, sometimes unrelated to the filament motion. After trying cold pulls, I tried reaming the nozzle with (a) a brass wire brush bristle, (b) a piece of magnet wire, © a safety pin (that did not fit through the hole). The plastic did seem to flow more freely, but then the barrel melted and the metal parts fell off of the extruder.

I am concerned that the thermistor may not be reading temperature accurately, as the hotend clearly overheated, but this was not detected by the controller. Most of the time, the temperature seems responsive to whether the power is on or off, but not always. I also have trouble heating the hotend above 250 degrees, when the fan is running. I have had it up to 260 degrees, before I tried unclogging.

I am hoping for some help with:

  1. troubleshooting the problems I had with the filament jamming,
  2. replacing the plastic barrel that holds the PTFE guide tube.

I would be happy to convert this to a bowden extruder, except I lack parts to substitute the bowden tube for the plastic barrel. Can’t print parts without a working extruder! (I’m going back to mess around with the 3mm extruder, while I plan a repair of the K8203.)

I’ll appreciate your comments; thank you in advance.

P.S. I’ll also appreciate instructions on how to examine and report the firmware version that is loaded in the controller, as well as any other key software version numbers. I’m still following all of the Velleman instructions about firmware, and I’m using the Marlin release that supports the Z-upgrade plus K8203 plus the VM8201 standalone controller.

P.P.S. Do we have a wiki somewhere?

2

Velleman should make better extruders , The E3D is far better extruder then the stock versions of Vellemans K8200 and the K8203

Far better cause it’s cold section (the plastic part of Velleman) is made of aluminium completely closed and with ribs a small fan is blowing on this cold end , mounted on a holder
that clips on the E3D cold-end.

I had the K8200 stock extruder, replaced soon whit a K8230 but their lousy designs

I sold meanwhile those parts.

I don’t use the thermistors anymore. far too much problems with, if not in the begin, there sure will be a moment of malfunction.
So I switched to thermocouples, a simple technique, and, the thermocouple controller at least says when then it has to be replaced. (red led)

I build my own 3D printers from now on.

If this cold section is melted, sure extruder temp far too high but it’s wise to set the ventilator at 100% to cool this section.

An with cooling , not the way that Velleman does it but with an air tunnel that brings the air directly to this part.
Sample designs can be found on thinginverse.

If the filament retracts and it’s not the motor that causes the movement, and the extruder is on temp, then You have to adjust the pressure of the extruder arm.

The extruder pushes the filament but if the force to doing so get’s too high then the filament slips suddenly and that will cause this effect, so add more pressure on the extruder arm.

The platic cold end should not melt but cool this part always at 100%

Note: hot ends must not be cooled, the printed object ok in some cases but that asks a very fine air tunnel.

3

Thank you for your comments.

I have an e3d hotend, but I need to find the parts to attach it to the printer. I was hoping to print the parts! I should have bought a kit.

I’ll appreciate recommendations for e3d kits for the printer.

Thanks.

4

Do you still have the old 3mm extruder?

Then I would print these parts with the 3mm extruder. Designs can be located on thingiverse look for K8203
For instance : thingiverse.com/thing:1110030

The usual bracket is in fact a clamp that fits secure around the E3D hotend.

or buy the part from reprapworld:

reprapworld.com/?products_detail … m61C8uxKUk
This part is made of plexiglass 6mm thick. ok, 4,39 euro (

Fit’s on the base plate of the stock 3mm extruder.

5

StefaanC, again thanks for generously sharing your experience.

I will take your advice about the thermocouple. I am religious about temperature control now!

Once I get temperature control on my 3mm nozzle (maybe with a thermistor, but I now limit my time on thermistors), I’ll print the parts for replacing the Velleman nozzles. I’ll need to educate myself about configuring the controller. My education is getting a head start with my frustrated thermistor efforts!

I expected adventure, and this is satisfying. No trouble with wondering what to print next (ha ha)!

6

Note that the Velleman controller has no thermocouple input.
I use a Megatronics V3 that has thermistor inputs but also two thermocouple inputs.

The problem with many controller boards is: they are simply to slow for high speed, high accuracy.
The atmega runs at 16Mhz, this processor is too slow for high speed at high accuracy.

Mircrostepping at 1/16 or 1/32?
Sure not further due to slow microcontroller.

So I’m planning to sell my own designs, around may 2016

7

I wonder if my controller is defective. It is a replacement after I (mechanically) damaged the original one. The extruder temp is stuck on 40+ degrees. The bed temp is at 5 degrees or so. I have tried multiple thermistors, no change. I tried switching the connectors at the controller, the temp stayed the same on both sides. I tried substituting a resistor, and the bed thermistor changed, but not according to the thermistor table, as far as I could tell, but it did change. The extruder temperature reading is not affected by different resistances.

The thermistors read at about 100K ohms, plus or minus about 20k ohms.

I have been trying to follow the instructions for updating the EEPROM after flashing the Marlin firmware. I’ve tried all versions of Marlin from Velleman. I’ve tried changing the thermistor code from 5 to 1. I’ve made sure that the EEPROM chat was defined.

I’ve not had any success with this replacement board. Is there a way I can return it to Velleman and let them test it?

8

I bought a dual extruder on a K8200 (ops) … one extruder if fine the other has trouble in pushing filament as described in the previous post.
Since the flow is discontinuous it does not stik to the bed plate and the item does not shape slice after slice … but rather remains unformed here and there on the bed :frowning: :frowning: :frowning: :frowning: :frowning: :frowning: :frowning:

Do not want to change extruders but start using the printer … someone can help me suggesting the rights thing to do to let this extruder work properly?

Thanks a lot to anyone may help!

9

I have had new success by (a) replacing the controller with a known good controller, and (b) increasing the current to the extruder motor, to 1.5A, by setting vref to 0.6v for that motor.

The original, 3mm extruder has been working well mechanically since then, and prints small parts successfully. On larger parts, like the case for the sd card host, I’m having (what I think are) temperature issues. It’s a new adventure, in a series of welcome puzzles that challenge me.

10

I suppose is something mechanical rather than motor related, but for sure i’ll check (I remember 0,7v - 1/32 driver).

Thanks

11

I just finished the install of K8203.

Some things I noticed:

  1. Extruder ran backwards in left hand mount
  2. The PLA default file wouldn’t load into slic3r versions cited. I wound up reverting to the 3mm PLA file and making the changes for 1.75.
  3. I used a second continuous fan on the isolator, connected to the 12vdc output for the LCD plug
  4. The hot end wouldn’t make temp without a ceramic blanket to isolate the thermistor from the fan.
  5. I used a second, software controlled fan for printed parts
  6. Extruder is a pain to load filament into. The holes are inaccessable without removing the filament tensioner to line the filament to the hole in the base of the mount. This hole could really use a countersink.
  7. They changed the PID values in the default EEPROM load, and I don’t know why.
  8. The steps/mm is 150 in EEPROM, if you want to skip reloading Marlin.
  9. The stepper driver wants a 5mm heat sink
  10. The stepper driver was set to .9VDC when installed, I adjusted it to .8 per Wrongway’s guidance

I do, however, like the print quality. It took 5 iterations of cal cubes to get it right, but this last one is my best ever.

12

wow long list.
a small step on #6. same issue. but I noticed that if you give a conic shape to the end (with a cutter you give to the end of the filament the shape of a pencil) the filament loading is not so problematic.