Latest Build

I have taken a lot of photos, but have not really posted much to the site so far. I was meaning to post more of the build, but got caught up playing around with different ideas and parts for the printer.

From this I have learned a fair bit and recently rebuilt the printer to something closed to my ideal for the Mendel design. I immediately put it to work to build some nice really solid parts to be rebuilt with. Better, faster, stronger.

I plan to take notes and photos for my rebuild. I have a few minor design changes I will be implementing. After some testing I have found that they will likely be beneficial.

It takes quite a few days to accumulate an entire set of Mendel parts printing them a few at a time like I have been with a 0.4mm nozzle and 40% infill. Since I have a few variant parts in the mix, I don’t want to end up printing some extra parts that are in the full build plates. I could modify the plates, but I like to stop and check the progress every set of parts due to some problems I’ve had with certain pulleys coming loose. I will be installing stronger ones in the rebuild.

My goal is to be able to rebuild the entire Mendel, with certain modifications to lighten the bed and reduce lashback on the Y axis, using plastic parts it printed for itself. As a bonus, they’re all being done in the UV reactive plastic I have. Mostly the Flourescent Yellow PLA is being used. It glows very well with the small CCFL tubes I have mounted on the frame of the printer. More importantly (ok, just as important) the parts are very strong and the plastic is quite solid.

This is a before picture, taken while printing it’s new set of parts. I’ve printed some other fun things with some new PLA that I received which I shall share in my next post.

Note that there is normally a (aprox.) 200m x 250mm sheet of glass, or two, clipped on top of the red heated bed platform when it is printing.

Some variation from the normal Prusa Mendel (iteration 2) design can be seen here:

– The x-ends are for the most part, the ones posted by ROTORIT on Thingiverse. My personal modification was to add a slightly undersized 3mm wide hole, within a projection from the left hand side x-end. I used a tap set to thread it for an M3 bolt which depresses the end stop switch. This allows me to dial in a minor z-height change. It would work better if the z-end stop was more securely placed. This is the original object : http://www.thingiverse.com/thing:20104

– The x-ends actually ride on top of a Z axis isolator. This handy, simple device reduces wobble (of the hot end) caused by the rigid 8mm threaded rod being held very stiffly onto the z-motors. Some folks have tried to secure the threaded rods at the bottom with 608zz bearings, but realized that the inherent wobble present in a threaded rod and nut system pushes the x-axis around and creates ridges all the way up the print, mirroring the thread pitch. What these do is wobble with the thread, and act like a sliding shelf that pulls the x-axis vertically with it. It has the additional benefit of saving your hot end/heated bed platform in case the printer decides z = 0 is lower than the bed. http://www.thingiverse.com/thing:20147

– The extruder gears are self-printed from Triffied_Hunter’s Herringbone gears: http://www.thingiverse.com/thing:10707

– Basically anything else you see that is NOT black plastic, but is plastic, is self-printed. I will try to update this at a later date with links to the other items I’m using.

The filament holder on top of the printer, while handy, is adding a lot of weight to the printer, which causes more vibration into the cabinet below it. I find that due to it’s high mounting location, as well as the 1kg of plastic weight in a fresh spool, it ends up making frame wobble much worse at higher print speeds. I just got some 608zz skate bearings in the mail today, so I hope to be able to make a better setup that is mounted externally to the printer.

Another plan for the printer, that is still in the conceptual/part accumulation stage, is to add a set of dual bowden extruders to the printer. This will allow dual material printing, as well as remove a significant amount of weight from the x-carriage. Less mass to be moved by the stepper motors makes it easier for the printer to get the plastic precisely where it intends to.

A more immediate change from the build pictured above will be the removal of the lower platform to the Y axis, bolting the LM88U bearing holders right to the platform that holds up the HBP. The HBP has layers of cork stuck to the bottom, and is mounted on nylon risers above a piece of laser cut MDF. I don’t suspect the heat will be too much for the PLA parts, if it is I will re-print them in ABS. To accommodate this I will also be flipping the smooth rods over so they sit above the base instead of under like they do now. I also have a few Y motor mounts to try that hold the bottom belt more inline with the bed and frame, removing a bearing from the Y axis and hopefully allow it to move more smoothly.
Also in the same vein I will be trying the Y axis as a three-point linear bearing mount instead of a 4 point to reduce binding.