On Wednesday 19 August 2020 01:53:13 Gregg Eshelman via Emc-users wrote: > More perimeters = more strength in FDM printing. For rigid plastics > like PLA that also increases stiffness. Several years ago, Benelli was > designing a new auto loading shotgun and they had a problem with part > of the bolt breaking. They made it thicker serveral times, they tried > different metals, they tried different hardening treatments but the > part would always eventually break. Then they applied some better > analysis techniques to find how the part was trying to flex when the > gun was fired and made a bolt with that part thinner than the first > one which broke. Allowing the part to flex stopped it from breaking, > and the lighter weight increased the cycling speed to the point where > some trick shooters were able to break longstanding records like how > many clay targets they could hand toss into the air and shoot before > any hit the ground. So rather than tying to make the part ever > stronger, and thus less flexible, you need to see what can be altered > in the 3D model to make the area where it breaks more flexible. > The 6 layer wall part is still running. The problem is the concentration of the flex at the base of the wall. There is a filet at the junction of wall and disk, and it was breaking at the exact top of the filet. Going from 3 to 6 on that wall thickness did increase the stiffness some, but getting the wave bearing the right size to remove the roughly 2x needed flex seems to have been the fix.
Makeing all parts at the same printer scale gets a flexure so excess theres 3mm of air between the spline teeth midway between the bearings and with that much flex its bound to break in 5 minutes or less. The first one I assembled yesterday had a fraction of a mm too big a butt end and I beat the bearing up getting it inserted, made another by changing the scale down from a calculated 80.79 down by .14 to 80.65, (In terms of scale per mm in merlin) which also increased the wave about 5 thou, enough that I am not hearing a crackling sound as the splines hop over each other. But that was the only internal spline I had that still fits in the bodies which were made first after calibrating the extruder feed. So I have another flexgear in process and will make a 3rd one that size. Then I'll make another bearing carrier and adjust it to be the same as the one thats working. Then measure the internal spline and adjust to make 2 more that size which does fit the bodies and motor caps both of which have a surrounding flange to hide the spline when they come together at assembly. And that should do it. And I am tempted drill for a lube hole thru the spline face to allow some lube to be inserted with a hypo needle or such. I just need to find a plastic compatible lube on this side of the big pond. Everybody has it, but when you order it, it has to come from some goat herders shack in Ulan Bator, by donkey cart. In the meantime, I am tempted to try some barrel grease I have that made for molycoating rifle barrel bores, its about 95% molysulfide, it should stay where I put it with a q-tip. What it will do to the PLA is TBD. I believe I am fighting with a variation of the cartographers copyright scheme. An error was detectable in a copyright violation copy by looking for a town that only the original map drawer knows is fake. And this error, purposely designed to fail, was this guys copyright detector. Its a very old ploy, and holds up in court 100% of the time. Neither the tpu, nor the micro-swiss hot end kit appeared yesterday. My personal curse for living in a technological vacuum. Long distance shopping. So I took it apart and smeared some of that on the tips of the teeth, and found another potential wear site. Where the bearings are rolling on the inside face is worn noticeably smoother. The bearings are rolling smoothly but I am wondering if I should have colored that area with some of that moly grease now just to slow that wear. That did help with the torque multiply, as it cannor now be stalled by hand despite running at this driver lowest, not much heating, current. These drivers respond instantly to the changes in the dip switch settings, so I contemplating the removal of the dip switch to gain access to the pads for current control for linuxcnc to put max current to the motor if its running, idling back to minimum current for holding when stopped. Can I get an only when moving that axis signal out of motion? And do it without losing a step? I have a oneshot in mind, trigger on leading edge, but send the step so its done on the falling edge, giving a couple u-secs for the current to rise? Sneaky but it might work. Our goal is to make sneaky work reliably isn't it? Or should I junk these and get a tb6600 that incorporates that. Except it doesn't. > On Tuesday, August 18, 2020, 5:23:58 PM MDT, Frank Tkalcevic <fr...@franksworkshop.com.au> wrote: > > the middle of a now thicker and nuch denser 6 wall build. cura > > settings > > > > are for 6 line walls, 15 ipm and 30 ipm. > > 6 line walls/perimeters is a large number. My default setting is 2. > Less perimeters also prints a lot faster. If the part is weak, you > can always increase it later, but it sounds like you are still having > issue with the extrusion flow rate. Not any more. Jury rigged hot end, no more leaks. No sock either. Thanks Greg. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
