extruder thunk noise

I built an i3 printer recently and have an extruder problem that I have not been able to solve. During a print the extruder makes a random loud "thunk" sound. I can see the filament moving in reverse for a split second like it's binding. If I print faster than 30mm/s it makes the noise nearly all the time. I have retraction disabled to rule it out. Using Slic3r and Marlin firmware. I have an E3D v6 lite hotend with direct drive. It only does it during an actual print, if I run an extrusion with pronterface it doesn't do it. I really notice it during fill but it also happens on perimeters. Randomly not enough material is extruded. Prints are still decent. This is my first printer.

So far I've calibrated the extrusion rate, first thing I checked.
Cleaned the nozzle and replaced the ptfe tube
raised the temp to maximum for the filament
tried different types of filament, pla, abs and petg
reduced print speed -30mm is the max I'm going now.
checked nozzle gap from bed with sheet of paper, it's level.
replaced thermistor to rule out low temp
increased power to extruder to 0.85 amps

Considering replacing the stepper motor but I don't think that's it. Steppers are kysan 1124090.

Any idea what the problem could be?

It would be beneficial to insulate the hot end block. This will drastically improve the function of the cold end block and keep the filament from melting to high up into the tube. There are photos of my insulated Mk7 hot end in the links in my signature.

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-David

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By "thunk" do you mean that your motor is skipping steps?

It could be skipping steps...or just jamming but I thought it would stop extruding entirely. I took apart my hot end and found the ptfe tube wasn't all the way against the nozzle so that could be my problem. I burned out the heatbed mosfet on my ramps so now I am waiting for parts to arrive.

Edited 1 time(s). Last edit at 01/20/2016 10:59AM by ashdavely.

I had the same sounds on my FT 2020 and it was skipping steps because there was too much tension on the filament. (I had added a part in preparation for auto bed leveling and it was pushing the spring loaded idler) Also, soon after I got the printer, on the extruder drive, the drive gear sits back in the stepper motor bell housing and it's shaft was dragging on the motor housing. I had to remove it and put it on my lathe and cut a few thousands off of the diameter.

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Folger Tech 2020 i3 and FT-5 as well as modified JGAurora A5 with direct drive E3D/Titan. All running the BLTOUCH.
Great kits. Having fun and running the heck out of them.
Running Marlin 1.1.0 RC8 on the i3 and FT5. Custom firmware on A5.
Folger Tech Wiki board >[folgertech.wikia.com]

Your motor may not have enough torque to be able to drive the filament, i had to upgrade to a geared extruder, since my cheap Chinese stepper didn't have enough torque to extrude. Once I upgraded i didn't have any problems.

Thanks for your reply. This issue is still ongoing and I do think it's the motor as I have rebuild the hotend several times and there is nothting wrong with it. I've ordered a slightly better stepper motor to try but probably should have ordered a geared one. I don't know if a geared motor will fit my direct drive setup as I am unable to print parts now.

My extruder stepper isn't delivering hardly any torque. I could very easily stall it by gently holding the filament while printing which duplicated my original "thunk"l issue. I increased the power on the driver as much as I could without it sounding strange and got a slight improvement. If i try to stall it now though it stops turning and makes a faint whining sound. There is no way this motor is delivering 76 oz/in torque.

I also manually pushed filament through the hot end and a fair amount of pressure is required. It's not so bad for the first 10-15mm but seems that more pressure is required. Raising the temp helped with this slightly. My nozzle is 0.4mm.

How much torque is need for a extruder stepper motor?

The torque needed depends on several factors, but boils down to overcoming the resistance of pushing the filament through the nozzle. Temperature, nozzle size, cooling, filament material, stepper speed (steps/mm), etc, all have a bearing on the amount of torque needed.

Some extruders exert more mechanical torque than others, allowing for less robust stepper motors... for example, a Wades extruder uses a set of gears to increase the torque.

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-David

Find me online at:
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Check out my FolgerTech Prusa i3 (plexi) at MindRealm.net

It's probably 'thunking' because you're trying to print too fast. 30mm/s is getting close to as fast as you can get with a e3dlite6, although increasing the temp can get you up to 50mm/s, but I've not been able to go over 50mm/s with just the lite6. You might think about purchasing the volcano heater for your lite6 and that will greatly increase speed.

I hadn't considered that 30mm/s was to fast. Advertised speed was 20-50mm. I will try 20mm when I get everything back together. 20mm/s is a very slow print.

I print at around 50mm/s with my i3 and e3dlite6, and I'm pretty sure that about has high as you can get it, reliably. I print for customers and outside perimeter quality is very important, so while I can and have gone over 50mm/s, that speed is perfect for me in terms of quality and quickness.

Also, when printing fast, sometimes the extruder is pushing filament into the hotend too fast and the hotend can't keep high enough temp to keep up, then the filament can bend causing the skip. Raising the temp can definitely help if that turns out to be the case.

What temp do you print at 50mm/s? Are you using volcano?

No, I'm not using the volcano, yet... I just received the parts to make the v6cano(volcano+v6) but I have too many orders from customers to install it yet.

I print at 50mm/s with 60mm/s infill at 200-210C on my i3.