aviphysics
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Posts posted by aviphysics
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True, BUT usually you don't get that kind of aluminum. Also, these laptop bodies are treated (anodized, maybe other hardening treatments as well) and hardened after machining.
My lasercut aluminum panels are "AlMg3" which is one of the softer, easily machineable alloys. This is worlds apart from 7075 T6 aluminum alloy.
True, but your panels will be thicker than the entirety of some of those devices. As long as you don't drop a panel, it will likely be fine.
I mostly agree regarding construction, accept that I have seen Al extrusion used with relatively good precision in a number of devices. I think there is a trick to designing corner pieces that force everything to line up correctly and perhaps getting precision cut Al stock.
I think a lot of the decision has to do with what manufacturing resources are available. The "Ultimaker way" seems to be less of a burden in that regard (unless the end user is happy to go through the effort that you are with those extrusions.)
BTW, will you plan to use cut outs in the side panels to form other parts, like the UMO design?
One thing I didn't realize is that the additives in Al alloys will begin to pericpitate at temperatures above 230 C. Not a big deal, unless one trys to make an Al hot end.
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That is true, but some aluminum alloys are better than others at bouncing back into form. Consider for example how well the aluminum unibody laptops and tablets hold up. I imagine they see far worse than a desktop 3d printer, unless you drop it.
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Hmmm. Looked up the thermal expansion coefficients of steel and Al and they aren't horrifically different. Al is only double that of steel. Both are the order of 10^-5/K. Even if the frame is heated to 100 degrees above room temperature, the expansion is only 0.01%. Besides, even if the frame doesn't expand, the z axis lead screw still will.
As for thermal conductivity, I have some real doubts a about how much if a difference that actually makes and could be accounted for by blanketing the interior with felt or something like that. It might decrease system energy consumption and warm up time, but probably not a huge impact on performance.
Obviously much of the specifics depend on the precise steel or Al alloy.
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3 mm is already a huge wall thickness for steel
Most machines I know from the workshop have 1, maybe 2 millimeter shells. Only heavy equipment seems to have more, but most strength comes from smart braces, folding or boxing the material, not pure wall thickness. I can imagine that a 3 mm Ultimaker is way too heavy and although I did not do the math, my gut tells me you can get away with less, since the surface area of an Ultimaker is actually quite small compared to other machines.The sandwich idea is interesting, but I am a bit worried how the materials behave together, since they are not properly bonded. Vibrations might become a problem and any gaps will eat away strength. Do you have a plan how you are going to execute those panels?
I think the issue is with the nuts not having a broad enough surface to balance against.
I can only imagine the complications that trying to get the pieces precision bent will cause. IME, bending is not nearly as precise as a cut line. Would make a lot more sense if he were going to be making a lot of them. Then the cost of working out the kinks would at least be distributed.
I wouldn't sandwich with plywood. The problem with wood isn't strength, but dimensional stability (mostly warping). Perhaps a plastic core material, like in Dibond, but with thicker plates. Still seems like a PITA.
Another alternative would be to add steal bands or thin rectangular rod laid flat along the edge, to increase thickness just where you need it. Of course, all that is a lot more work than Al, which would probably be perfectly good.
I had another idea for steel plates separated by a thin grating (like steel cardboard), but couldn't find anything appropriate. I feel like I have seen something like that before, but cant remember where (maybe armor plating or something like that).
Edit: this stuff looks super cool, but I bet it totally doesn't laser cut and probably costs a bundle. http://www.alsic.com/_blog/Structures_and_Armor/post/Lightweight_Aluminum_40_Percent_Lighter_than_Ordinary_Aluminum/
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I get a 404 error from that link.
BTW, there is also a really cool nut holder for the inside side of the rod ends. Just search youmagine or thingiverse for "ultimaker nut holder" or something like that. It is U shaped, so you can put it on without removing the rods. Makes installing and removing rod end covers a million times easier.
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What about putting a sock filled with rice in the microwave and then putting that in your vapour chamber. Then pour a small amount of acetone on it?
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Finally got my GT2 belts and quality rods from Misumi. Set x/y steps to 80 and printed a 20mm cube using default HQ print settings. Final cube came out to 20.005 along the x and y, according to my calipers, which is probably within the tolerance of the calipers.
I had previously been having a significant backlash problem in the x direction, which I had been struggling with since I got the machine.
Getting the shipping grease off the rods was a bit of a PITA. I tried using WD40, which left a gunky residue. Probably should have gone with simple green. I ended up needing to add some light silicone grease (like is used for bicycle chains) to get it moving smoothly; but IIRC, bronze bushings are self lubricating, so you should need anything. I think the problem was from a small amount of residue that the silicone grease spray helped disolve and dilute. The fit of the bushings on the rods alone was just about perfect. Move freely but no perceivable lateral wiggle.
One small issue is that the screw on reptar gt2 blocks doesnt reach the rear end stop. Almost a non issue, unless your not paying attention while jogging the machine.
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Prints pretty well without infill, though the overhang on the ears isn't perfect. I have been meaning to print a max print volume sized one of those. My son loves the little one.
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I imagine the arduino is just sending out a pulse for each step and another line for direction. Seems like there ought to be a controller for any type of stepper motor that would accept that.
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Yes. Very cool technology. It has to look at the previous two steps, measure the time between them and then step 16X faster hoping the next step comes soon after. If the next step comes sooner it advances the schedule I guess. Kind of reminds me of a phase lock loop except on a wave that speeds up and slows down often and dramatically.
It could also always lag by a step. Then it will know what the spacing will be. Perhaps it would also have a time out, in case the next step wasn't going to come. This seems perhaps problematic, but each step is so small, the user might never notice if one motor stepped slightly out of order.
Alternatively, they could just know that going through the pattern in a certain length of time would have the desired effect of reducing noise, and just program it to always do that.
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What are those connectors you are using for the hotend?
BTW I am surprised you have done so much with modding the print head, but you are still using stock tension blocks.
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I was pondering that you might be able to use counter rotating shafts to reduce or eliminate the problem. The gearing could be design so that when both shafts turn the same way, the screw doesn't move, but it does when they are counter rotated.
Sort of like an automobile differential hooked up backwards, so two drive shafts and one wheel. Would need one more gear in there to invert the direction of one of the shafts. Would still only need one stepper motor. I think you might need a differential at both ends.
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I have used helical couplings on several projects and never had any noticeable problem with them. You just don't want to put an axial load on them.
Getting rid of the short belts was about the best thing ever. Was such a pain to get the tension just right.
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That is what I thought. I was pretty sure that both of those are multipart pulleys (though the core might be all one piece.)
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Please remind me where you got your GT2 pulleys from. I am pretty sure it wasn't Misumi, cause they don't carry the right size.
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I don't have a UMO but I gues the first thing to check is if the endswitch is pushed correctly and/or if the wire to the end switch is ok ...
I am guessing that his end stops are either connected backwards or not connected. He should connect the system to Cura over USB and run through the setup wizard. It will help him check the endstops. IIRC, it is not totally clear which endstop is left and which is right, because they don't tell you whether it is from your perspective or the machine's perspective.
Another test would be to remove the short belts, so the hot end isn't driven. You can then activate the homing command from the Ulticontroller and see if pressing the end stop switches stops the motors.
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You need good static pressure and airflow. You will also want a reliable bearing. I went with this one when placing my failed fan http://www.digikey.com/product-detail/en/ME40101V1-000U-A99/259-1566-ND/2757791%20.%20It%20has%20a%20
It turned out to be smaller than the original fan (OD was 40 mm instead of 40 mm screw hole spacing), but it still provides plenty of airflow. I use one of them with the aforementioned Tapir Shroud ( just printed a small size adapter plate ). Would probably be perfect for a dual fan setup ( smaller and lighter than original fan.)
The main caveat to this fan is that it doesn't like unfiltered PWM. This is easily solved with a RC low pass filter. I used a 40 ohm 1 Watt resistor and 10 uF ceramic capacitor. That also brought the max voltage closer to my fan's specs. For dual fan, you would want to use a smaller resistor and larger capacitor. My arrangement should have a cut off in the KHz range, which is probably way lower than needed (I would guess the PWM is at least in the 100's of KHz.) A 1 ohm resistor and 10 uF cap would would probably do the trick just fine.
Edit: Just noticed that marlin's PWM frequency may be far lower than I would have assumed. Some people are posting that it is only 7 Hz in software mode. Not sure if UM is using hardware or software mode. I am sort of surprised that the RC filter I used would have much effect at that frequency.
Ok, looks like the PWM frequency is about 30 KHz (Measured a period of 6.5 div* 5 uS/div = 32.5 uS), so 1/RC should be less than 10,000/s.
BTW, I have seen some posts that say the UM is not grounded, but I can say with good confidence that it is at least ground relative to my oscilloscope BNC ground.
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The resistor has to come "before" the capacitor (if it's the other way round, you have a highpass filter
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(picture source: http://hyperphysics.phy-astr.gsu.edu)
You will change the fan control's characteristics a lot by adding a low-pass filter, because that's not how this kind of control is meant to work. While it's possible to achieve a good regulation characteristic, it will only work with the particular fan you've made the filter for.
Switch out the fan with another one that draws a different amount of current, and you can re-size your low-pass again...
LOL. I didn't see the equation earlier, maybe I was browsing on my phone. I almost always just take 1/RC to be the cut off frequency. I am aware of the equation, but just never actually used it in practical applications. It doesn't even get the frequency totally right (cause it is w not f), but it is almost always close enough.
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That is not normal, but you should start a separate thread.
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Dyanamism is slightly cheaper, but makershed sells them for a similar price http://www.makershed.com/products/ultimaker-original.
Ordering from UM direct is probably the worst option, unless neither Dyanamism or makershed has them in stock, unless you don't care how long it takes to get to you.
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I think I would add a "hot car" test. Maybe using a rig like the bend test and subjecting them to a heated box for 8 hours at the temperature of a car interior on a hot California day. I would say without load, but not totally sure.
The point would be to test what materials will hold up if you leave them in your car on a hot day.
Afterwards, the pieces could be subjected to the bend test, to see if they held up.
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you would probably want to change the design a little to make it out of aluminum. The slots for the nuts and screws would have to be altered to allow for the tool diameter.
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are you using the basic printer window or the pronterface one? I've always needed to set the temperature for both the bed and nozzle using pronterface, never used the basic window when using cura.
I print from SD Card.
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I do have a heated bed. I will have to check that out.
Most machines I know from the workshop have 1, maybe 2 millimeter shells. Only heavy equipment seems to have more, but most strength comes from smart braces, folding or boxing the material, not pure wall thickness. I can imagine that a 3 mm Ultimaker is way too heavy and although I did not do the math, my gut tells me you can get away with less, since the surface area of an Ultimaker is actually quite small compared to other machines.
).
NEW PART DAY: SILENT STEPPER MOTORS
in UltiMaker 3D printers
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Maybe we could move to controllers that support curved paths. Then Daid can have all sorts of fun trying to figure out how to take advantage of that. Of course we would also probably want to move away from STL files at the same time.
I feel like we are currently in a stalemate, where we don't need faster controllers because the current software doesn't need it, and people aren't writing code to handle more advanced kinematics because the current controllers can't handle it. It doesn't help that a lot of printers' output quality seems more limited by relatively poor hardware design than what the controller can do.