Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Tag: Improvements
Making the world a better place, one piece at a time
The aluminum build platform plates remain both flat and level, but the outline and test extrusions are consistently thin by 0.05 to 0.10 mm in the right rear corner and thick by about the same amount in the right front. That means the rear corner is too high and the front corner is too low, but the whole left side is flat to within my ability to measure it.
The effect is significant, because I’m laying down the first layer at 10 mm/s with a layer thickness of 0.33 mm; the first layer looks exactly like all the other layers in the object. With the middle of the plate at 0.33 mm below the nozzle, the fill can be cramped at 0.23 mm and sparse at 0.43 mm. The long-term Z-min switch repeatability seems to be no better than 0.05 mm, so when the midline goes below 0.30 mm, the higher rear corner really crowds the plastic.
Given that the left side is level front-to-back, the only way a flat plate can appear non-flat is if the X and Y axis rods aren’t quite parallel: the stage rolls or yaws as it moves.
That could indicate a bent rod, but the last time I rolled those rods on a surface plate, they’re perfectly straight. Maybe something horrible has happened, but any stress capable of bending one of those rods will wreck the printer in passing.
Alas, a static platform adjustment can’t fix a dynamic motion, but tweaking the rods to be (more) parallel could reduce the problem. I tried visualizing the possible causes and cures, then decided to stop thinking so much, just change something, then measure the results.
Why my head exploded:
The thickness varies from front-to-back, so the Y axis rods are non-parallel, which should affect both the left and right sides. But the left side is perfectly level and the right side is not.
The thickness varies from left-to-right, so the X axis rods are non-parallel, which should affect both the front and back sides. But they vary oppositely: the front tilts down to the right and the back tilts up to the right. The midline from left to right, however, is level to within my ability to measure it.
I had shimmed the rear X axis rod quite some time ago, so I decided to try a simple adjustment: move the shim from top to bottom. The picture shows the 0.4 mm shim in its original location at the top of the rod; the edge is barely visible. For lack of anything smarter, I moved the shim to the bottom of the rod to push the end upward.
Shazam! The results of a test extrusion in units of 0.01 mm:
39
35
40
35
40
33
36
[Update: Typo in the rear-left was 49, should be 39. Drat!]
Which says it’s give-or-take 0.05 mm around the middle, with the rear-left corner now a tad low; bear in mind that 0.05 mm is about the limit of my measurement ability. It’s off to a good start, anyway, and we’ll see how it fares over the next few weeks.
Methinks if you’re serious about this 3D printing thing, you need a printer with real axis alignment adjustments and enough stability to make them meaningful. Nophead uses custom code that tweaks the G-Code’s Z-axis coordinates on the fly based on an initial three-point probe, which is a wonderful solution that’s not in the cards for RepG. EMC2 could incorporate that in the kinematics module, but at the moment it does just XY leadscrew mapping. It’s simpler, albeit more expensive on a per-machine basis, to get the mechanical alignment right the first time.
Having managed to mislay my dingy yellow kickstand plate, I made two more and this time hit ’em with fluorescent red paint. Ought to be unforgettable for another few years…
In theory, you’re supposed to apply a white undercoat. I hosed ’em down with many drippy, runny coats of red and it’s all good. This ain’t art and they get thrown on the ground, so what’s the point of being fancy?
The backside of the Lenovo N5901 Mini Wireless Keyboard (which arrived with the aforementioned Q150) has a black-on-black power switch with ON and OFF legends (yes, I think they’re backwards, too) embossed in the matte black case: under anything less intense than enhanced interrogation lighting, you (well, I) can’t determine the switch position.
Of course, the myriad certifications / ratings / labels required for compliance with all the regulations are perfectly legible:
Lenovo Mini Keyboard – enhanced labels
Working a dab of white correction fluid into the letters makes them blindingly obvious; the smudges around the letters will wear off in short order.
I should probably add a bit of white to the switch background as well.
It turns out that an ordinary carbide glass drill works just fine on glazed clay pots. Use a low RPM and very slow feed, flood the scene with water, and drill from the other side after the point breaks through.
Glass drill for plant pot hole
The glaze inside the pot already had a flaw that let the water into the clay, from whence it seeped out through the unglazed lower rim. I suppose saturating the clay can’t possibly be good, but I’ve done this to many glazed pots over the years and none of them have ever complained, so it’s all good.
Our Craftsman lawn mower has both a deadman grip for the motor (the Operator Presence Control Bar) and a Drive Control Lever that engages the rear wheel drive. The latter requires a death grip to keep the belt engaged, which means you (well, I) spend about two hours clenching the grip.
Lawn mower – compound leverage handle
I’ve long since flipped the control to the left side and added thick foam padding, but there’s no adjustment that reduces the death-grip requirement: you can change the engagement distance, not the spring constant.
Evidently the Sears engineers have much stronger hands than anyone in our family.
The doodad hose-clamped to the upright part of the mower handle is a basically a hinge that applies force to the tip of the red handle. The hinge axis lies far enough from the handle’s pivot so that holding the hinge against the handle requires very little force; at least it’s no longer a death grip.
Lawn mower – compound leverage handle engaged
It’s not an ideal solution, but it engages and (more importantly) disengages easily. I still don’t like mowing the lawn, but at least I don’t return with a crippled-up hand.
The hinge is actually a lock hasp, so it has a slot that slides neatly over the Drive Control Lever’s tab. I beat both sides into a more-or-less cylindrical form over a piece of pipe, while miraculously not bending the hinge pin.
Evidently the Sears engineers never actually used the damn mower for two hours at a time.
Although those pink clamp platesworked well enough, they did not provide, shall we say, a completely satisfactory user experience. I reprinted new sets in red while varying the extruder speed by 0.1 rev/min, with small tweaks to the overlap between the infill and the loop threads.
First, the big pictures with details scrawled on the back of the lower plate…
At 3.2 rpm, which is only slightly too fast:
Fairing Plate – 3.2 rpm
At 3.3 rpm, a bit overstuffed:
Fairing Plate – 3.3 rpm
At 3.4 rpm, there’s obviously too much plastic:
Fairing Plate – 3.4 rpm
Some closeups, in the same order…
At 3.2 rpm with 0.20 overlap, it looks OK:
Fairing Plate – 3.2 rpm detail
At 3.3 rpm with 0.25 overlap, which pretty much devours the inner loop thread:
Fairing Plate – 3.3 rpm detail
At 3.4 rpm with 0.25 overlap there’s serious overfill:
Fairing Plate – 3.4 rpm detail
In all cases, the extruder left a track while exiting upward from near the middle of the images. Even at 3. 2 rpm there’s slightly too much plastic.
My ladies don’t care about the fine details. They prefer red to pink and the clamps hold the fairings firmly in place…
The Smell of Molten Projects in the Morning 