I would think a little lube goes a long way. As long as the layer lines never match up, and are able to ācatchā each other, friction should be manageable I would assume. I think you already mentioned printing at different layer heights for this reason.
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And you think something I may have written years ago ā and while possibly āunder the influenceā ā makes any sense? I canāt remember what I had for breakfastā¦
You still havenāt told me what ālubeā would be appropriate.
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shoot any lube will work short term. longer term i think the super lube we use is pretty print friendly, but I can verify tomorrow
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Iāve been using a āwhite lithium greaseā ā sound āappropriateā? Nite-niteā¦
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Went into Onshape and increased the minor diameter of the leadscrews to 14mmā¦ and created new lift blocks to match. New 14mm screws and 10mm for comparisonā¦
Disassembling the left lift assemblyā¦
and new one installed. Tighten the guide rod bolts carefully while manually rotating the screw to find where it still rotates freely without binding or excessive slopā¦ and put jam nuts to lock them into position.
One to goā¦
Later.
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Iāll get ready to reprint. Have you given a good test run on the updated parts?
I didnāt spend much time in my unheated garage the last couple of days. It isnāt terribly cold, 12F this morning when I looked at the back deck thermometer; but a bit colder than I like to work on stuff in the garage (was probably about 35 or 40F in the garage).
I may not make much progress the rest of this week on MPR&P as we have a āParade of cold fronts.ā
Will probaly switch back to my Repeat V5 extruder builds and toolheads for the legacy TAZ as I can do that work in my home lab inside the house.
Iām not altogether sure Iām gonna go with the 14mm leadscrews anyway. Iāve seen some weird binding at times especially on one side that leads to lost steps. I know that Ryan said āgo hugeā but I had far less trouble and far better performance with the 10mm screwsā¦ until one broke. I donāt know whether it was just āmistreatedā or it really wasnāt up to the task. But Iām pretty sure driving a thinner screw compared to a thicker screw requires less torque out of the motorā¦ and the printed leadscrew is definitely a higher rotational friction ābeastā relative to a metal leadscrew to begin with anyway.
So Iām currently playing in CAD to see if I can stick with the smaller 10mm minor diameter of the thread vs āgoing hugeā and simply finding a way to beef up the motor shaft recess area. Simplest would be simply to increase the overall length of the leadscrew, take the D-shaft recess out of the threaded area into a beefier, larger diameter extended area, and then raise the motor on standoffs or a custom spacer. Something maybe similar to thisā¦
Sorry to hear that you really canāt give it your all yet because of the coldā¦ but hoping you can get to it when you can. I know youāve said youād like to take a smallish LR4 or MPR&P to a couple of reprap gatherings. Would really love to see it.
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Tomarrow night -14 here I hope they are wrong again or I will need to find my socks.
Yep, Iād have my socks on for that. Maybe even long underwear 
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Printing nowā¦ a 10mm screw with 14mm diameter extended section enclosing the motorās D-shaft recess. Also changed the pitch from 10mm to 8mm to mimic LR4ā¦ per Ryanās request.
The longer leadscrew necessitates raising the motor by 18mm or so. But there is an added advantage that the new riser block ā with motor permanently attached ā is held in place with the guide rod boltsā¦ and the motor and riser ā and [broken] leadscrew ā can be removed, repaired, and replaced as a unit from top-side. With no change in screw pitch or diameter, the lift-block can stay in place, trapped by the guide rods, and be reused with the new leadscrew.
So, hopefully this will be the last time I totally dismantle to upper portion of the Z-lift assemblies. Any future leadscrew repairs should require only the guide rod nuts be removed and the riser/motor/leadscrew assembly lifted out as a unit.
Iāll print the new parts ā leadscrew, lift blocks, and riser blocks ā and install and test before I update Printables. If anyone (Jim?) wants to give this a try before I update Printables, let me know and I can drop them here in a .zip file.
Later.
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Looks good!
If this doesnāt fix it, it occurs to me that when you zero by running into the top plate you have both a torsional force and a perpendicular force trying to pull the screwās layers apart.
You could avoid (well, reverse) the perpendicular force by zeroing in the opposite direction. You could place blocks between the bottom and travelling plates (for zeroing only) to facilitate that (assuming that you canāt run the travelling plate all the way down to the bottom plate with a tool attached).
I guess this would necessitate no up/down play in the screw, motor, etc. connections, though.
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I think you may be right about the top-plate āimpact driverā actionā¦ trying to separate the layers. The bottom plate would be better and I do have uniform spacers that rest on the bottom plate to de-skew with a tool in place. Thanks!
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Iāll test with the updated files. Send them over when youāre feeling good about them.
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That time it was 1F outside and 35F in the garage.
So I put an old tyvek clean room jacket on the printer and fired off a 40 tooth rack print.
The Core One L is busy with grandkid job at the moment. The Taz are mostly getting disassembled to become repeat printers.
Maybe if it stays above 32F Iāll spend some more time in the MPR&P rebuild.
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Watching the Patriots/Broncos game being played in Denverā¦ started in bright sunlight and clear fieldā¦ snow started about halftime, blizzard conditions, field completely white at start of 4th quarter, canāt see the yard lines even though theyāre trying to clear them. Silly Patriots decided to wear their all-white uniformsā¦ 
EDIT: Patriots white uniforms might have actually helped. Denver QB couldnāt see the defenders clearlyā¦ 
Iām printing test parts while watchingā¦
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We can get all the seasons in one day.
Itās a really, really pretty day out there. Just a bit cool.
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Have to go to the high hills for the big snow.
Itās been since the late 1990s that I had to dig out snow more than a meter deep down on the front range, and typically not over 10 cm down here.
There are no lakes here, so no lake effect snow.
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Spent more time working away.
Cleared off most of the last of the MPR&P V1 from the old table. Thereās an early LR4 beam build with fully printed strut plates. Surprisingly stout.
Hereās what the top of that infernal Ryobi bench looks like. Iām tempted to remove that surface, but then my plan for potentially making a larger MPR&P for RMRRF gets more work, so Iāll likely leave it.
Back on with the slightly thicker 3/4" by 2āx4ā project panel, mocking up the new stubby Y axis.
That is two 40 tooth segments and one 20 tooth segment. So, 100 teeth of rack.
I have extras, for the larger build I may attempt.
I had been using fender washers and coupler nuts on the MPR&P V1 build, these look to expect just standard washers. Iāll come back to that.
Since the EMT is captured by the ends, Iāll need to measure and cut those, which Iāll do some other day. My feet got cold, and thatās when I stop
The printed-in-the cold rack segment turned out fine:
I fired off another one which is almost done.
Now, where did I put the longer 1/4" threaded rod???
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An updateā¦
While Iāve been fiddle-farting around with the design of these printed leadscrews, I decided I need to show that a QUITE MOST PROBABLY BETTER lift assembly could be had using the LR4ās T8 leadscrews (and linear guides)ā¦ if you happen to have them and/or want to help support Ryan by buying new ones.
This modified T8 leadscrew driven lift assembly is quite similar to the printed screw lift assemblies Iāve been playing with but a couple of minor changes are required. I enclosed the bottom plate and added a BB-ābearingā surface for the bottom-end of the leadscrew to rest on.
And, for now, Iāve stayed with the guide rodsā¦
Here it is in action. Itās really noisy with no lube of any kind for now but I want to do a bit more testing if I should decide to get serious about using it.
and Iāve already demo-ed a linear guides version beforeā¦
Best, of course, would be to use both the LR4ās leadscrews AND linear guidesā¦ but that would move it out of the realm of a ājunkbox buildā for most and add a bit to the cost of the build.
So, with that being my āplan Bā, Iām now gonna continue playing with the printed screws and guide rods until Iām either happy with themā¦ or get tired of messing with them. I really want the printed versions to work more reliably before recommending them as the MPR&Pās āyellow brick roadāā¦ but I also felt it necessary to show that there is an less-risk path forward for MPR&P, even if I canāt get the printed screws to work as well as Iād like.
Another thing I want to do is go back and redo some pen and laser testing now. Iāve been air-milling some pretty lengthy multi-hour jobs, such as the Aztec calendar @joegomez1479 didā¦ and it has served as a real ātorture testā for MPR&P. There are so many small XY movements and Z lifts that MPR&P gets really noisy and sounds a bit ācrunchyā at timesā¦ so I want to repeat some testing to insure nothing has rattled loose.
Later.
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