migration to dual bowden extruders

I started to rebuild my Prusa i3 Ramps/Mega combo to work with a dual Bowden E3d-clone setup. The Bowden is a direct drive with the small hobbed gears of Makerbot MK8.

I reduced max_PWM for both extruder-heaters, because the 5A fuse can´t deal with 2x 3.3A.
Q: Would I have to run PID autotuning again?

I find it very difficult to change filament. The e3d clones have a pneumatic fitting, but I can´t push the PTFE tube through the fitting into the upper chamber. The filament doesn´t find it´s way into the heat barrier. After adding a M6 nut to the barrier to counter the heatsink, I have another gap between the barrier and the internal filament guide in the heatsink.
Q: Are there fittings available were I can push the tube through, or do I have to drill it?
Q2: Should I drill the filament guide in the heatsink too?To be able to feed the PTFE tube down to the barrier?

Although I´m pretty experienced with adjusting the z-zero bed level, I can´t make the first layer stick as well as before.
Q: Is it possible, that the lower weight of the extruder keeps the filament from being pushed deeper into the blue tape? It seems the long hotend is far more "giving" as my former Makerbot MK8 direct drive extruder.

-Olaf

Edited 1 time(s). Last edit at 07/21/2015 01:34AM by o_lampe.

By any chance your teflon/ptfe/bowden tube somewhat thin e.g. inner diameter roughly 3-4mm? I guess that explains why the filament didn't get into the heat break, Don't know if you have the original e3d, but the original e3d ptfe tube, inner diameter is around 2mm. I'm using direct drive, I didn't insert the ptfe tube although I have one, I have to adjust my mount for it a bit

Also try not to have a common hot end design; teflon tube inside the heater block. Because with this you are no where using a normal generic type hot end often can't get past 250'c

You can try adjust the z home offset in eeprom setting

Hope this helps

You can't have too many PID autotunes. It wouldn't hurt to check the numbers again.

There are fittings available where the PTFE will pass through. I have also drilled one thru and it seems to work out ok, it still grips the tube.

On the v.6 clone I have now, the PTFE goes right down through the heatbreak to the heater nozzle.
A previous one I used was, as yours, with a step just below the fitting that the filament would catch on. I had to take out the fitting every time.

'In theory' you should be able to drill right through the heatsink and heatbreak of yours to fit the tube. How easy or successful that will be, is down to you.

What's the extra M6 nut for?

How much 'give' does your hot-end have? You'd get best results with it firmly clamped.
Maybe the thermistors of the new ones is reporting a higher temperature than the previous and the first layer is not as hot as you think?

-a

Quote

What's the extra M6 nut for?

How much 'give' does your hot-end have? You'd get best results with it firmly clamped.
Maybe the thermistors of the new ones is reporting a higher temperature than the previous and the first layer is not as hot as you think?

Thanks for your advice!

The M6 nut is located between heatsink and heater block. The barrel is countered in the block by the nozzle, but I needed the M6 nut to counter the barrel to the heatsink. Others counter the heatsink with the heater block, but that's a bad idea. Maybe a spring washer would also work?

I have a loose linear bearing on the bottom x-rod. The nozzle seems to have a horizontal play of approx. 0.1mm.
I wanted to avoid banging the x-end off the smooth rod again. But to replace the bearing, I have no other choice.

-Olaf

Ah, I see. You may transmit some heat through the heatsink.(But if it works - it works)

I think my heatbreak screws into the heatsink barrel tight and then the other end locks against the nozzle in the heater block to leave a gap between the block and heatsink.

Awkward X-axis. No easy solution? I think you have to 'bite the bullet' and fix it - you will regret it later. Can you add something? A clamp?

-a

I took a deep breath and drilled open the pneumatic fitting.

First I drilled open the heatsink.
Then with the fitting installed, drilled through the heatsink acting as a guide.
I reduced the length of the drill to keep the clamping mechanism intact.

Cleaned everything with alcohol to avoid later clogging.

The next step was to mount the heat barrier upside down. Now I have the all-metal part in the heater block and the Bowden PTFE tubing goes all the way into the heat barrier.
Pretty excited to do the first print soon...
-Olaf

Wow,
trying to print with a dual head is hard!
Two days of adjusting the nozzle heights, bed alignment and z-zero but still no useful result.

I´m almost tempted to build a tilting mechanism to rotate the hotend carrier around the y-axis and lift the unused nozzle out of the danger zone.

How many degrees would I be able to turn the hotend but still have good printing results?
-Olaf