Rostock 3D issue resolved that was causing long print jobs to fail

I finally resolved the most annoying issue I have had. Print Jobs Failing because of the head getting caught on excess plastic deposit at some point through the print job.
I am using a J-head Hot end, they are wonderfully made but one feature on it seems to be a problem on the rostock. Where the filament is extruded there is a small lip or ridge. This can get caught on any over extruded plastic which is catastrophic for the rostock floating head. So I filed it back to a smooth curved tip instead. It seems to have worked. I also added springs under the headed bed so that in a crunch it could move down out of the way if it really needs to.

Here is a 1.5 hour print job completed. Previously 3 attempts at this failed at one point or another



Print quality is actually exceeding my Sells Mendel at the moment

Its actually hard to tell here as this red transparent PLA I am using is impossible to photograph, It comes out looking like crap but I am really happy with the results I managed to get tonight.
After many many failures at trying to print Admiral Akbar on the rostock, I finally found the settings that worked best.
The first picture on the left shows the fine support structures that I was able to print even with a bowden extruder which amazed me. Even on my Mendel, some of these finer structures would not print or would collapse. The second picture shows the final model which looks so much better in real life than it does here. These models are a tranparent red plastic. They look really terrible here but the actual model look quite good.

Basically the mods I made to the extruder tonight really seem to have paid off.
* Replacing the standard hobbed bolt with a precision Arcol Hyena
* Mounting the Extruder in a bridge and shortening the PTFE tube
* Much tweaking and playing around with the settings in Slic3r (I think the most important changes in slicer were experementing with the retract settings and adding a 1mm lift.

Rostock Fiinally printed something reasonable

Finally got it working reliably enough to print something. I had to slow it down and loosen the tension on the belts a little. But it ran solidly for 1.5 hours. See just have to say nasty things sometimes :-)   Its a mobile phone holder. 8cm high .3mm layer height.

Rostock 3D with my own unique placement of the Extruder

OK this is my final iteration for this design for now.
These are all of the mods from the original design:

• Mounting the extruder on a bridge suspended under the top of the rostock. This sits just above the home position and being in the middle right above the centre of the plate also gives me the shortest possible bowden tube which I am hoping will improve response on the extruder retracts.
• Addition of 2 x 20mm fans on the hot end
• The threaded rods in the back corners and near the front smoothrods to make it easy to tighten the belts
• Another minor mod is using Einstein's heavy duty bowden ends. The original designs were weak points and could not clamp onto the PTFE tubing well enough, but with these I can use hose clamps to hang on to that tricky little sucker.

Now having completed it, I have to say this thing is fickle at the moment. One minute things work OK then all of a sudden it will start homing incorrectly or jump a spot while printing if it hits a small plastic deposit Left by the bowden.
Now all of a sudden during the home sequence it will "jump up" slightly after making contact with the last Micro-switch in the home sequence.

I am glad I built one for the experience,  however I would not say this is my favourite at the moment. I am yet to get a completed decent quality print.

Another mod to the rostock - Threaded Rods

I found that just relying on the clamps on the top pulley mounts to keep my belts tight was not all that great. For starers you need four hands to apply tension and tighten the nuts and bolts and its hard to fine tune. Also these are smooth rods so overtime the top could slip down.
Since 3/8" threaded rods are real cheap, I added two at the back corners and one on each side towards the front. Now I can just turn a nut and get the belts as tight as I want.
As this was not in my initial design I had to as small metal plates that I just had lying around to get the rods at the front clear of the movement. If I was doing this from scratch I would change the shape of the top and bottom pieces so the angled out a little towards the front to cater for the rods.
These rods could also be used to attach angled brackets if I want to add more rigidity to the frame.

My next mod will be the relocation of the Extruder. I worked out by suspending it below the top plate about 19cm below the top. It will sit right above the head just clear of the home position and shorten the Bowden tube by almost 50%. Is an easy mod I will try it during the week. I am hoping that shortening the Bowden will improve its response after a retract.

Rostock isTemporarilly out of action

Well the heat resistor in my hot end blew today and I dont have a spare. So she's out of action until the reinforcments arrive. They are so cheap I ordered 5 +  some additional thermal paste to make sure I can keep feeding it :-)

Just before it went, I made another mod to the Rosock. I put a twist in the belt so that the back of the belt runs over the bearings at the top rather than the teeth. I there was a noticible improvement in the smoothness of the movements.  Cant really test it until I get it all back together.
I will have a little break until they arrive.

Rostock Completed and printing fairly well

Well its pretty much done but requires some tweaking though.
The main issue I have now is that I think the hotend cant keep up with the print speed. I am not sure yet. I can extrude full speed all the way through the bowden tube without a problem, but while trying to print at that speed on the longer runs it the Extruder stales every now and then. You can hear it making a loud noise in video.

All in all I am relatively happy with the print quality, I just need to sort out a couple of minor issues.

http://www.youtube.com/watch?v=vzFcKNoxxOk&feature=youtu.be

Rostock 3D - Tuning the extruder

Well I spent some time fine tuning the settings and I am getting there.
In the image below you can see the first print (ahem!) on the left and then after much tweaking and getting the retracts working better with the bowden extruder. There is still a long way to go but its not too bad.
For some reason, its not filling right to the edges. I think that means I am not pushing enough plastic or there is too much slack in the system (its more likely the latter).

Rostock 3D printer - Assembly Complete!

Well this is it. Mechanically complete at last.
I have still to get it printing well but it is now spitting out plastic. A couple of things I have done:

• Mounted my extruder at the top.
• Took advantage of the extra rod length I have at the top and added a spool holder at the top that feeds straight into the extruder. I will eventually add them to all 3 axis around the top so I can store up to 6 of my favourite colours up there

Still to do / Issues:

• At the moment the retract does not seem to work it is actually turning forward when it is supposed to retract. Fixed! Was Firmware. Removed the offending line From Code. Its all to do with the original code that would not allow extrude while now movement.
• The Teflon tubing works its way loose at the top and comes away from the extruder. I will add a steel mounting plate to better secure it. Fixed! Added a grub screw.
• Calibrate it!
• Install the heatbed

But she is getting there.. WooHoo!

Preparing Jhead hot end for bowden feeder

To eliminate a possible snag point at the end of the teflon feed from the bowden where it butts up to the top of the J-head hot end, I removed the existing PTFE tube that is inside the J-head, made a new cap that bolts on and put the feed tube from the bowden extruder all the way into the Jhead for a seamless delivery of filament to the hot end.

This image shows the assembly bolted to the print carriage.
All that is required is the wiring to the hot end and it will be hot :-)

In the future I plan to go two colour and have two Jheads side by side.

Next step is to assemble and mount the extruder over on the side of the printer. and she will be ready for some tests.

Drawing in 2D

This is a video of a test run by drawing in 2D.
http://www.youtube.com/watch?v=QuRplpBZ1g0&feature=plcp
I am still waiting for a couple of bits to turn up from overseas so I can finally add the extruder.

Replaced Top Toothed Pully

While waiting for the bits for my extruder to turn up. I have been tweaking the parts a little. If you look at the fully assembled images in an earlier post, I originally used toothed pulleys that came with the belts at the top of each axis thinking these would be better.  The problem was that I could not really tighten the belts as these pulleys simply had too much drag. Although it worked, if things went too fast it would occasionally skip during a move, so I had to slow things down.

That'll learn me fer thinkin.

I decided to replace them with F6o08zz Flanged Ball Bearings (see link below).

Wow! what a difference. Now the belts are so tight that I can play a nice base riff and the movement is silky smooth. I was able to increase the movement speed by almost 50% over the older setup and I will get a lot less backlash.

I have included a picture of the top part of the axis. There are two of these flanged bearings on each one. They are only flanged on one side so you place 2 face to face. In the image I have put a couple on top of the printer in this photo so you can see the profile.

Now I am just waiting for the mounting plate for my hot end and the PTFE tubing for the Bowden Extruder.

(http://www.vxb.com/page/bearings/PROD/FlangedBallBearings/F608ZZ).