Printing resumes

OK, now the Prusa is working once again (with Yellow ABS this time) I immediately began printing the next set of blades for the VAWT project I am working on, again encountering the malformed leading edge issue I had spotted previously.

As it turns out this does not appear to be anything to do with my retraction settings but more to do with trying to print overhangs so close to the hotbed in ABS, the overhang stays soft and is mechanically deformed by the next layer printed resulting in curling on the leading (or trailing) edge, I have tried several different techniques to resolve this issue none successful as yet and I am communicating with Quentin (the VAWT creator) to see if we can resolve this issue, it is very difficult to tell if this is due to the VAWT model needing tweaking so that it is printable in ABS on a hotbed or if it is my particular printer setup that is causing the issue , I will have to investigate overhangs & warping/curling thereof in the wider reprap community to see if anyone has any other suggestions of how I may solve this.

I have already tried

1)     Inverting the blades to see if the problem was only present on the leading edge (it wasn't) but it also showed up on the trailing edge.

2)     Printing several (3) blades next to each other to see if additional layer cool time would help (a very slight improvement but not significantly better)

3)     Lowering the hot end temps and hotbed temps as low as I can get them without the ABS becoming  unstuck, still no significant improvement.

I may have to resort to getting Quentin to add a support structure to the first 1-2cm of the leading/trailing edge (leading or trailing depending on which is overhanging, which in turn depends on which end you are printing the VAWT from)

Other alternatives I will try are to experiment with active cooling, by either changing the hot bed temps (although my previous tests suggest this won’t work) or by force cooling with a fan, (this would most likely work but would also likely cause the part to warp and become detached from the hot bed so not a good solution either)

Alternatively I could switch to PLA which needs a lot less heat (I will try this anyway just to see)

Anyway regardless of the poor print quality I forged ahead with printing the remaining parts of the VAWT after all I can always repair the malformed leading edge with bits of leading edge from other failed prints by hand with a hacksaw & glue!

More ABS please

Purchased another reel of ABS (yellow this time) as I am getting very close to the end of my 210meter reel of black ABS, this was also so that I could get some replacement hot end resistors on order.

ABS arrived with hot end resistors, and by strange coincidence so did the IMU for the balancing bot (I had completely forgotten about this part, and is the last part needed to start the balance bot project yey)

Set about replacing the hot end resistor and immediately spotted problems, the resistors I had bought were slightly bulged in the center causing me to have to drill out the heater block so that they would fit, after much fiddling I did get the Parcan hot end back on the Prusa and working again.

This issue has highlighted the need for me to get building my own hot ends & heater blocks, this is hopefully coming soon as my local EV dealer has a great workshop with drill press & lathe which I will be visiting  soon (he also wants a 3D printer for his EV projects and has offered the use of his workshop, cool)

Darwin Upgrades

As mentioned in the last post, I have been making some mechanical changes to the Darwin in the hope of making it into a useful printer once again (I had previously butchered it to get the first child working as the extruder stepper on the Darwin had been previously borrowed from the Prusa parts for the Darwin so that I could print the plastic parts for the Prusa (1^st Child)).

1)     Removed X carriage completely drilled out  X ends (motor & idler) to 10mm from 8mm so that I could fit the induction hardened rails I had bought in error for the Prusa to the Darwin, I really need to print better X ends later as they were designed for 8mm rods so this is a fairly major bodge.

2)     Fitted 10mm linier bearings and new custom quick-fit X carriage to X rails (this is when I realized that the belt clamp positions were also different on the Darwin so I drilled 4 extra holes in the carriage to bodge another temporary solution.)

3)     Fitted 608 bearing to idler to replace the “creaking” (yes it was audibly creaking in use) resin cast idler wheel, this required a selection of different sized washers to effect a belt guide 2 of which I had to cut to fit the idler housing, hacksaw job.

4)     Fitted 8mm linier bearings to Y carriage rails and modeled out the holes in both the idler and motor carriage ends to fit using a sharp knife, I will need to come up with some way of securing the bearings to the carriage ends until I can print replacements.

5)     Fitted 608 bearing holder to the Y axis motor end rod (far end from the motor) this replaces a cast resin bush hopefully further reducing friction in the system, I could also print 2 more of these for the idler end of the Y carriage (will do these later)

6)     Reassembled the whole shebang and ran up to Darwin Pronterface setup I had last used several months ago to see if it would move, and yey it lives.

Now I just need to purchase another stepper motor and make a better hexnut nozzle and th darwin should be capable of printing once again.

I still have a whole host of mechanical issues with the Darwin (mentioned in previous posts) and I am planning to upgrade the electronics using  the Gen 3 plus solution (don't want to dump the Gen3 electronics just yet)

I should be able to rewire the extruder stepper so that it is directly connected to the gen 3 mobo, remove the RS-485 extruder controller completely (may try and repurpose this as a filabot extruder controller) and connect the hot end heater and temp probe directly to the gen3 mobo, this should allow me to load the sprinter/marlin (sailfish?) firmware and that will be a major upgrade to the Darwin’s capabilities.

I am also planning to remove two of  the Z axis corners and run the print bed similar to the Prusa (just with 1 motor and a timing belt, rather than 2 motors) this should significantly decrease the friction in the Z axis and I am hoping improving reliability.

I may also add 608 bearings to these two remaining Z corners to improve the mechanical stability and accuracy of the Z axis.

Bowden Blowout!

Had my first Bowden tube failure the other day the tube became detached at the extruder motor end due to internal pressure I guess, and in my frenzy to get it fixed I broke my hot end’s heat resistor, unfortunately I had no stock of these resistors but I did have the old Darwin hot end that I had retro fitted with a new heater block purchased on eBay (it used to heat using a coil of nichrome wire) I had already fitted my only spare heat resistor to this hot end so I thought whilst I was waiting for the replacement resistors to arrive in the post I would fit the old Darwin hot end to the Prusa and see what it could do.

After much fiddling around I managed to get this “working” the quality was poor compared to the Parcan hot end as the nozzle diameter is approx. 0.9mm on this old hot end, also this hot end has a brass hexnut style nozzle so it would be fairly easy to replace the hexnut with one with a smaller nozzle hole, this was all done so that I could test the possibility of reusing this modified Darwin style hot end on the Darwin once I get it back up and running.

In fact I was actually in the middle of printing a new X carriage for the Darwin when it broke, the new X carriage is based on the 10mm lm10uu linier baring derivative of RichRaps great Quick-change X carriage (ref).

I had already printed one of these 10mm Quick-change X carriages but it turned out that the Darwin has 42mm X rod spacing unlike the Prusa which has 50mm X carriage rod spacing, so I loaded Sketchup and modified the X carriage (virtually) chopping 8mm out of the center and bringing the 2 halves back together and exporting as STL.

Printed this modified Quick-change X carriage using the old Darwin hot end (with retrofitted heater block) this worked remarkably well (well at least better than I had expected) and after a few hours of fiddling the Darwin is moving again.

Purchasing for more projects

Bought the parts for a balancing bot (inverted pendulum) ref
got the motors / motor driver board just waiting for the IMU to arrive and then I can get started on the balancing bot project hopefully using the reprap as the system glue to give the project that professional look and give me some practice with openscad.

I have also decided to take the plunge on building myself an EV (Electric Vehicle) found a very local (purely by chance) EV builder and researcher who is keen to get me up and running so I have bought myself a donor vehicle (a Honda Beat) as this project is going to be complex and large I will start another blog dedicated to this.

http://electrobeatev.blogspot.co.uk/

Don't forget your software upgrade’s

Whilst trying to print the planets  for the tiny planetary gear set I found that they would not fill correctly, after reading on this people were suggesting that the extra shells settings were the cause after much fiddling to no avail I finally got the impression (again from more reading) that maybe there was a fault with the software so I bit the bullet and did a complete update of both Pronterface and SFACT to the latest versions and voila the problem vanished.

Print frenzy round two

After my safety improvements (mosfet move & PSU connector upgrade on the sanguinololu) the overheating issues have completely vanished, along with the newly insulated hot bed & moving the entire printer into a heated bedroom rather than an unheated workshop (need to build a chamber for the workshop) the printer is behaving very well build quality and speed are all better and I have taken the plunge to print a complete set of new parts for the 1^st grandchild.

6 x - Vertex – ref
8 x - Barclamps - ref
2 x - Rodclamps - ref
2 x - Beltclamps  - ref
1 x - Y carriage lm8uu bed mount - ref
2 x - Z motor mounts  - ref
2 x - X carriage’s - ref (rich raps universal quick change for lm8uu & lm10uu derivatives)
1 x – Gregs X carriage (a spare for the one I am currently using)
1 x - X motor end
1 x - X idler end

most of these parts worked perfectly and other than a small problem with very thin (and hollow!) walls on the X ends I am very happy with the results, they are leagues ahead of what the Darwin could produce, and all in ABS!

I have also spent some time printing demo pieces to show to colleges such as the tiny planetary gear set (ref), spirograph set for the kids, several holly wands again for the kids.