Bowden Extruders are go for launch!

23/08/2012

 

Last night I spent quite some time implementing a Bowden extruder mechanism using parts (ref extruder motor end) (ref nozzle end) I did have to mod the extruder end somewhat as the part was designed for a 16 mm hot end and my current (bought) extruder has a 13mm hot end fitment, so seeing as I am not yet versed in the ways of OpenSCAD I used a stanley knife to whittle down the 15mm hot end plug to a 13mm one and unfortunately due to slicing issues the nozzle end part did not slice correctly (warnings in Pronterface of this problem but I went ahead and built it anyway), as it turned out the Bowden nut hole was missing a corner of the hex nut so again I simply hacksawed one corner off of a nut so that it would fit, both these mods although fiddly (and technically unnecessary as I should have been able to tweak the parts in a CAD package or design my own from scratch) were relatively simple and meant that I could use what would have otherwise been wasted parts.

 

I must start getting my head around OpenSCAD.

Tested the Bowden setup once last night with a very small part (ref belt clamp) and again this morning with another attempt at the first layer of the VAWT bottom part I am still trying to get built.

I discovered during this test that I will need to upgrade my extruder idler to a “Guidler” variety to stop the filament slipping out of the hobbed bolt.

I already have one of these printed in ABS (early ABS test of the new Premium Black ABS I am now using) and again although the quality/ surface finish is not great it should be perfectly functional.

Plan for tonight is to implement the Guidler and attempt a print of the bottom part of the VAWT, this should provide an excellent test of my build volume improvements.

I also took a look at the newly arrived SDSL (SD ram card adaptor for the Sanuinololu set) discovered it uses a “micro” sd card I will source one of these today so I can do some SD print tests at the weekend.

SD Ram card adaptor for Sanguinololu arrives in post (Whoopee!)

22/08/2012

This will give me the advantage of being able to load the stl to be printed into ram that is directly accessible by the machine and not via the USB connection to the PC, I have read that this greatly improves quality as however smoothly you think your printer is printing trust me it is not as smooth as it could be if you were printing directly from ram, I am of the understanding that this can completely remove the surface digital artifacts that appear on some larger prints as these are caused by delays in the PC communicating with the printer via USB, I proved this quite effectively by just loading several other applications on my PC during a print and more or less immediately the printer starts stuttering whilst It waits for the next packet to arrive over the USB connection.

Can’t wait to get this working.

At the same time I will be implementing the Bowden extruder mods to give me that extra build height I so desperately need to complete the Savonius & Gorlov VAWT.

I have also been formulating a plan for a major mod to the prusa that will incorporate a ABP (Automated Build Platform)

I am thinking of a design that incorporates the Y axis as an ABP, I am hoping that the addition of a couple of aluminium tubes with printed skate bearing holders at each end (4 bearing’s in total) will allow me to use the Y axis motor as the ABP motor allowing the ejection of finished  parts using a simple Gcode sent as the last line of Gcode in any particular part printed.

That Gcode will simply rotate the whole build surface by one complete revolution, there would be a requirement for no max end stop to be present on the Y axis and it would also remove the need for a Y axis drive belt (as the build belt would become the drive belt.

The printed tube ends would be studded with teeth much like an old 8mm film projector and the build belt would be peppered with a row of holes that would mesh with these teeth.

There are obviously a lot of technical details to iron out but I think this would be a significant advancement over the existing ABS’s that seem to bolt onto the build plate and require an additional motor/electronics for ejection.

Build volume improvements

20/08/2012

1)     Stripped out the hot bed (again!) in order to reposition the Y bed slider bars below the front and rear bars that tie the triangular ends together (this is to give approximately 20mm extra build height) this also required that I pack the build plate mounts so that the build plate just clears the front and rear bars that tie the bottom of the triangular ends together, this basically just puts the bed as low as it can go without fouling on anything. Also whilst I was rebuilding the build plate I repositioned the mounting bushes (lmu88 bearings in my case) more central as I had rushed this part initially not realizing the advantage of keeping everything central to the build plate, this means that I am now able to reposition my Y end stop to utilize the whole hotbed in the Y direction. (every little helps when it comes to increasing build volume a few mm can make all the difference to a part failing due to it being just slightly too large to fit in your printers build volume).

2)     Began printing parts for the Bowden extruder mods (Bowden extruders are just where you separate the hot end from the geared extruder & motor via a long PTFE tube that connects the two) Bowden extruder mods are being touted as a way of reducing mass of the X carriage and therefore increasing speed and also giving the possibility of mounting multiple hot ends, but they also have the obvious advantage of giving considerably more build height on a RepRap although this does not seem to get a mention in terms of Bowden mod advantages! Strange as I would consider it a great advantage.

The print frenzy begins

19/08/2012

Printed universal size spool end caps (ref Part)

Printed spool holder top mounts with integral handles (ref Part)

Fitted spool mount to top of printer for continuous printing without the need to monitor it closely for filament tangles.

Printed Sanguinololu fan adaptor part  (ref Part)

Fitted Sanguinololu Fan adaptor (stripped fan from Darwin as it was the correct size for this part.

Attempted another go at Savonius & Gorlov VAWT http://www.thingiverse.com/thing:16504

Three tries later (2 fails due to overheating of the x & y axis motors, it just happened to be one of the hottest days this year and this shows the need for heat sinks on my motors.)

Bootstrapped a heat sink to the x axis motor, setup another fan to cool the y axis (this proved to be a mistake as the wash from this fan caused the large VAWT part to start warping again, adjustment of this fans direction cured this temporary bodge fix warp issue until I can find and fit some good heat sinks possibly fan cooled)

Third attempt at Savonius & Gorlov VAWT http://www.thingiverse.com/thing:16504

Proved very successful (more luck than judgment as will be explained later) (Photo) (video on youtube)

Dove straight in to print the other parts to this cool wind turbine blade and discovered that my build volume was leaving a lot to be desired.

Upgrades are the future!

16/08/2012

Last night I completed a strip-down & rebuild of my 1^st Child Prusa printer, and to be quite honest I was stunned by the resultant improvement in print quality to the point where I am not quite sure exactly which of the improvements made the difference but the difference is enormous.

Here is a list of the improvements I made over the course of a couple of days (evening’s).

1)     Stripped out partially melted PLA X carriage and replaced it with my new (not great print quality) ABS X carriage, (which I broke slightly whilst fitting it due to delamination issues mentioned above, but this should not affect its performance)

2)     Stripped off the hot bed and remounted with a center fixing bolt to prevent the hot bed from warping down in the center, this was causing issues with getting the first layer right without constant tweaking of the Z end stop position.

3)     During the X carriage replacement I broke the thermistor (again) and decided to switch to a much simpler thermistor sourced from Maplin’s UK (ref part number) it is much larger than the micro sized glass bead thermistors that are recommended for Reprap’s, this required me to drill out the brass heater blocks thermistor location point hole to 3.5 mm, The Maplin thermistors are quite large in comparison to the glass bead type but they are a third of the price (£0.99 each) and a hell of a lot easier to deal with as they have decent thick leads rather than hair like leads for connection and are therefore much less prone to breaking.

4)     Whilst I had the whole thing apart I thought I would add a couple of electrical connectors one for the thermistor leads and one for the heater leads, this way when I need to strip down the hot end for any reason I can simply unplug the leads, snip the filament, unscrew the 2 mounting screws for the hot end and run the extruder motor (with the heater off of course)  until the hot end drops out.

5)     Also whilst I was rebuilding the heater block with the new thermistor I wrapped the whole block in Kapston tape, I have seen other people do this before on various RepRap blogs and presumed it was just to stop the melted plastic from sticking to the heater block, but I now remember back to the days of the Darwin how insulating the hot end was important in maintaining a constant temperature without putting undue strain on the heater electronics, this may be part of the reason for the sudden quality improvement.

6)     I also reduced the layer height to 3.4/6 mm and increased the temperature to 250 Degrees C (these were going to be my next software tweaks anyway before I decided it was time for a complete strip down.

7)     Adjusted Y end stop switch position to give me full access to the whole print bed size, needed to do this as the last thing I was trying to print before I decide on the strip down was the Savonius & Gorlov VAWT http://www.thingiverse.com/thing:16504 this also demonstrated the need to fix the warping hot bed issue.

Considering the massive improvement in print quality I am not going to tweak anything more until I have taken measurements of anything that may affect the print quality.

 

E.g.

 

Measure the exact temperature of the hot end and hot bed as I am fairly sure they don't exactly match the Pronterface settings and this should give me an indication of exactly what this Premium Black ABS likes to be printed at.

 

Measure the exact length of the idler screws, this should give me an indication of how tight I need to clamp the filament so that it does not slip or strip.

 

Save the default configuration (yes I have just been tweaking the default config rather than creating new ones, I have already done this last thing after the extremely successful print, I immediately saved the config as a new separate one and named it sensibly (Premium ABS Black) this way I can begin to build up a set of config’s for each type of filament I have at my disposal.

Premium “Definitely” ABS Tests

I received my new roll of Premium Black ABS the other day an got straight to it testing with a small belt clamp print test to see how it printed, The quality of this plastic is totally different to the reel I had that I thought was ABS (it is probably HDPE) and has its own set of peculiarity’s.

After printing several test pieces I decided to go for a very large print in order to test possible warping issues, after that test failed for different reasons this is what I learnt.

Warping is non-existent it appears that running this premium Black ABS at 220 degrees C and the hotbed at 110 degrees C eliminates warping completely, as I was attempting to print the Darius self-starting wind turbine which fills the build platform almost completely (can’t build larger than that without a custom build printer with an enlarged print bed).

The reason it failed was due to delamination of the ABS layers from one another, on further reading this may be due to my hot end not being hot enough and or possibly my layer height being too large.

Another issue is that as the hotbed on my Prusa heats up is warps the entire bed downwards, further reading on this issue turned up a simple fix of using the center hole as another fixing point and using a countersunk machine screw to fix the center of the hot bed in place this supposedly resolves the warping hot bed.

One of my ABS test prints was a new X carriage and although  the quality is not great (slightly warped on one corner, as I was running the hot bed at only 90 degrees C at the time, since turned up to 110)  it looks like it would be useable.

I need to strip it down and fit the hotbed fix and ABS X carriage, I have also noticed some considerable flex in the X idler end and I am not sure if this is causing some backlash issues or not but I will probably print a better X idler end soon as well.

ABS? (or is it HDPE?) Die Swell part 2!

(Update : See note in ABS “Die Swell” from hell! for update on the confusion over what materials I was trying to print with)

Ok I persisted with testing this offending roll of (what I thought was) ABS, unfortunately whatever I tweak to try and resolve the quality issues with this plastic I just can’t seem to get consistent results, and eventually getting frustrated enough to invest in a new reel of “Black Premium ABS” it arrived the other day and to my surprise feels completely different to the reel of natural “what I thought was” ABS that I was given.

I am now thinking that this free reel of plastic is probably not ABS at all but could well be HDPE, it has been put back into storage for now until I can be bothered to have another go.

Plastic recycling experiments

I have been keeping an eye out for a cross cut paper shredder that would be powerful enough to shred HDPE milk bottles.

And recently I found one in my local LIDL store for £25 (bargain) it claimed that it could shred paperclips & staples and could cope with 7 sheets of A4 at once, guessing that this might be enough to shred an HDPE milk bottle I took the plunge.

Thankfully I can report that it seems to work a treat, all I need do is make sure that the milk bottles are properly washed and all traces of stickers and or glue are removed (cut out if necessary) as the chipped plastic needs to be as clean as is possible (I am even considering washing it in the washing machine maybe in an old pillow case with a zip).

And then cut the bottle in half down the seam and then each half in half again, so basically quartering the bottle top to bottom, add a couple of extra cuts in the corners just to flatten the quarter of bottle a little more and it feeds fine into the shredder.

Time to start building a “filabot” me thinks!