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.

Bowden issues

The addition of the Bowden tube has introduced some fairly major hysteresis into the system, this required an increase in the retraction distance to overcome the stringing and blobbing that has appeared since the Bowden got put in place.

Carried on with the Atoms of the VAWT (3 required for a complete VAWT) unfortunately my overzealous retraction settings had an undesired effect on the leading edge of the VAWT wing section at the bottom where the print head moves from the wingtip to the centre

Printed all 3 Atoms of the VAWT regardless of the quality issue purely as a build volume test and so that I could tweak the retraction settings to try and eliminate the malformed leading edge issue (and although I saw a slight improvement I think I may need to shorten the Bowden tube as much as possible to avoid or at least improve upon the hysteresis issue)

Chopped out approx. 70mm of Bowden tube and tested, slight improvement in the hysteresis suggesting I am correct in the assumption that the Bowden tube is causing the loss of quality.

As I am still getting issues with bed leveling/flatness I decided to upgrade to a glass bed on top of the heated bed PCB, this cured the leveling and flatness issue completely but introduced a large delay in the heat up time of the hotbed, from approx. <5 minutes to around >10 minutes, this is annoying as it considerably slows the whole process down, I must find some thinner glass, (maybe from an old picture frame)

After much testing of many prints, I remembered the other reason for upgrading to a Bowden tube, speed so I began experimenting with pushing up the speed from 20mm/second to 30 then 60 then 100!

Yes 100mm/second and everything seems to be working flawlessly, wicked!

In fact at these speeds I start to notice mechanical wobble appearing in my y axis print bed, need to shorten the screws mounting the hot bed above the wooden build bed.

I also noticed that I am getting warping again possibly due to the fanning effect of the rapidly moving Y axis.

I am currently finishing the hotbed upgrade to shorten the screws and properly insulate the hotbed underneath so that the hotbed holds its heat better.

Almost finished this last night 21/09/2012 other than the need to re-level the bed properly and fix it in position properly.

If this does not solve the warp issue I will probably need to move the whole printer into a heated room as I am currently doing all my printer stuff in an unheated room and now that summer is ending and winter is on its way it is starting to get cold again.

last year this had major warp implications with the plastic I was using at the time, which I had assumed was PLA but may actually have been CAPA (I am still not exactly sure what plastic this is as It was gifted to me with the original Darwin machine)

It took me a long while to realize that this was due to the local temperature conditions in the room as when summer arrived the problem promptly vanished proving that local temperature conditions in the room need to be warm not cold.

Need to investigate a heated build chamber or at least temperature monitored.

The hot bed should be good enough to heat the chamber assuming it is fairly small and well insulated but I would need to figure out where to connect the chamber thermistor to the sanguinololu electronics set, more web research required here.

I also fell fowl of trying to implement the pronterface control of a fan on small layers recently, as when I looked into this I discovered information (ref) suggesting  that the hotbeds Mosfet on the Sanguinololu board was not rated for use on a PCB of this fine a track width.

Following the advice, I removed the Mosfet from the board completely and rewired it as suggested, basically connecting the hotbed’s Mosfet directly to the ATX power supply and just wiring the gain to the PCB, this means that the Mosfet draws most of its current from the PSU rather than routing it through the Sanguinololu’s PCB tracks.

It was suggested that this is a possible safety issue with the Sanguinololu’s design, At the same time I also replaced the screw terminal power connector with a proper 4 pin ATX 12V PSU socket doubling the copper connecting the PCB to the PSU.
I had noticed also before these upgrades that the power regulator (on the other end of the PCB from the PSU connection) was getting extremely hot and was in danger of meltdown (in fact it was manifesting as the sanginololu resetting itself during prints, which is how I first spotted the problem.