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Volkerball posted:It doesn't take super human skills to tell that the gap is .003" wider here than it is over there with decent calipers. I can't really picture his part since he didn't give any details, but 90% of the time, checking it in a few places with calipers will be enough to determine if you have an issue and what that issue is. I would only really do what you're describing if the rails are so flimsy that they actually flex under the force of opening the calipers, and/or there was parallelism callout of .003 MAX or tighter, which is uncommon. Yeah but what I'm getting at is that handheld calipers aren't suited to measuring this particular dimension to the required level of precision. What you're suggesting is mathematically valid, but it doesn't work as well in real life. Here is why: I don't know exactly what sort of rails we're talking about, but I'm imagining two rails or precision surfaces 6 inches or so apart that need to be perfectly parallel along their length, like you'd have in a CNC motion platform or something. I'll take your example of the parallelism needing to be better than .003. If you measure the separation between these surfaces with a pair of calipers and you don't hold them perfectly square to the rails, you'll measure a longer dimension than intended because you're now reading the hypotenuse of a triangle. That is called cosine error. A bit of math says that, in order to not skew the measurement by more than our .003 tolerance, the calipers need to be held at less than 0.18 degrees off of perpendicular. Can you see a misalignment on that scale? I don't think that I can. There are tricks you could use to get around it, like slowly rocking the calipers back and forth several times and taking the minimum value, or holding it against a machinist's square that is held against the rail. But if you're going that far I would just do the 1-2-3 block thing because it's a more robust and repeatable setup.
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Mar 7, 2019 21:52
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Sagebrush posted:Yeah but what I'm getting at is that handheld calipers aren't suited to measuring this particular dimension to the required level of precision. What you're suggesting is mathematically valid, but it doesn't work as well in real life. Here is why: Calipers are calibrated at an accuracy of .001". We outsource calibration, but we are required to do a reference check once a week, and using the OD prongs on a .5000" slot, I consistently measure between .4995" and .5005". If I measure more than .002 from nominal, that's enough deviation to determine that they aren't functioning properly and need to be sent in to get recalibrated. Your concepts here are right, but you're being very conservative with your conclusions from them. It's pretty much industry standard that you be able to make that check. The most accurate way I've found to do it is to not go in perpendicular with your flats. If you come in at a 45° angle, you're causing the blades of your calipers to function more as planes than as a lines, and as you push outwards, the planes squeeze against each other, which forces your calipers to square themselves up. The other thing to notice is that when you squeeze outwards, if your calipers are not square with the work piece, then the force you are exerting is only partially directed into the rail. Some of that force is pushing perpendicular to the rails. With the right amount of force, the blades of the calipers will start to break loose from the surfaces they are pressed against. That's a tell that you aren't seated properly. Should be noted that the accuracy of calipers decreases over distance, to ranges of accuracy more like .0015" and .002", so that's something you would have to take into account for the part you're mentioning where there's like a 6" gap. Also if you're using a $10 set of calipers from harbor freight, just forget about it. And you mentioned the "required precision," which brings me towards the motive behind my argument here. Imagine you drew up a print for a part that is a block with two parallel slots in them. Similar visually to the top of a toaster. If you request a quote for that part, and then request a quote for the exact same part only this one has a GD&T parallelism callout on the two slots for .001 MAX, the second part is going to be substantially more expensive. Accuracy at that level requires more detailed manufacturing and inspection methods, and increases the likelihood of having some scrapped setup pieces. If you're making the part yourself, the difference between those costs doesn't just disappear. It's still reflected in the time, labor, and special equipment you might have bought because you needed it to do the job. Overengineering is a good way to throw a bunch of money away, and it's a super easy trap to fall into. If the part would function up to a TIR of .02" (that Helen Keller could see with calipers) and you're spending all this time trying to ensure that every part is less than .003", scrapping parts that don't "conform," then you're throwing time and money away. Obviously time and money aren't the biggest concerns for hobby machinists, but at the same time, all that wasted time is going to cut into time you could be using making different parts, writing more programs, checking different features, and learning new things. And I think most hobbyists have an eye towards some sort of small scale production, so they may as well integrate lean policies and find those ways to eliminate waste, because it's way easier to do so in the beginning when you're small and haven't developed a bunch of bad habits. If you're gonna do it might as well do it right. Volkerball fucked around with this message at 02:19 on Mar 8, 2019 |
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Mar 8, 2019 02:09
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I was looking for this thread last week and couldn't find it. I posted this in the 3d printer thread instead: I'm looking at a 1000x1000 X-Carve CNC Router. Full 2018 setup with some further upgrades. Does anyone have any experience with these? Is it a good jumping off point for a CNC router? I've been doing more research and this seems like a decent unit to start. What should I be looking at for price of a used plug-and-play setup? Edit: Made a deal with him for the entire setup, with extruded aluminum cart, PC and arm-mounted monitor, a bunch of bits and tools, and a used Dewalt router with a spare brand new DeWalt router for $1800... does that sound reasonable? meatpimp fucked around with this message at 17:27 on Apr 22, 2019 |
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Apr 22, 2019 15:28
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EVERYWHERE 
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Why not get an SO3 XXL for a little less, with beefier extrusions and a larger work area? Tooled out is nice, but unless it's a lot of unused bits it's kind of a crapshoot how much value it adds. I imagine the PC isn't that valuable since it's just running a cnc machine, though the arm and monitor are a nice addition. Either way I'm sure you'll be happy but unless you've already done a bunch of desktop router work prepare for a learning curve and more purchases.
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Apr 23, 2019 02:14
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Ambihelical Hexnut posted:Why not get an SO3 XXL for a little less, with beefier extrusions and a larger work area? Wow. Thanks for pointing that out. I thought the 1000x1000 spec of the X-Carve was the working area. That changes the math for me, a lot. I think the new XXL is the way to go, even though now I'm looking at another computer/monitor/stuff. My question now is -- what do I need to bring a system up from scratch? I'm assuming any recent i5 or better computer is going to be fine? I'll grab a cheap 27" monitor and arm, because 27" monitors are cheap. Is the Shapeoco software going to get me started properly? First projects are going to be simple cutouts and signs to get used to the system and go from there.
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Apr 23, 2019 11:11
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The gcode sender software does not require much of a computer. Doing project design (cad/cam software) is more intensive but I do it on a 6 year old laptop without problems. Shapeoko’s design software is extremely basic but will do simple shapes; once you want more complicated projects you’ll probably want fusion 360 or vcarve. You don’t necessarily do design on the same computer that controls the machine; I use a laptop for both so I can design where it’s comfortable then plug in and run the machine in the garage. But what’s really needed to complete a router is not the router it’s all the other poo poo: do you have a table big enough to hold it, a dust collection system and boot, an organizer for bits, all the bits you own programmed into a tool database in your design software, a way to organize sheet stock and an area to cut it down to fit on the router, a way to hold stock in place while you’re cutting, a triggerable relay so you don’t need to separately turn the router and vacuum on every time you start a cut, safety gear, etc.
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Apr 23, 2019 12:53
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I've got room, a large vacuum system, and time. Just need to put the rest together. I quickly went from a 1200-1500 budget to a 1800 deal on the x-carve to 2300+ with a new xxl and associated parts. Then I realized I was moving way too fast. I bought a cheapo 3018 unit from Amazon and I'm going to play with it to make sure I even like doing this stuff before making a big space/money commitment. But now I've got a bit better idea of what the mid-level goal is, with the ultimate goal being production equipment.
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Apr 23, 2019 19:50
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Cool. I’m not familiar with the 3018 but the problems you figure out on any machine that make the difference between enjoying it and hating it are: Workholding reliably and easily making toolpaths that don’t interact with your clamps. I use painters tape and superglue. Tool changing quickly and easily and adjusting your offset without a hassle. I jog Z up, drop the old tool, put the new one in all the way, jog down to z+6mm, loosen the collet until it drops to stock, tighten the collet, then redefine current z as zero. Touch probe routines and fixed offset tool holders are better solutions. Repeatable xyz positioning by limit/homing switches. Keeping dust down. I have a magnetic dust boot with a collector hose hung above the machine. Managing and cutting stock, and holding the trash from scraps. This really is a pain in the rear end, get ready to dispose of a shitload of plywood scraps. And your work space is never big enough when you need to cut down 4x8 sheets so they fit on the 3x3 router.
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Apr 23, 2019 21:09
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Ambihelical Hexnut posted:Cool. I’m not familiar with the 3018 but the problems you figure out on any machine that make the difference between enjoying it and hating it are: I got one of those 3018s and I'm glad this thread is still active. They run GRBL by default, and I'm sending commands with Candle (grblcontrol). I come from a 3d printer background with gcode where everything is done in positive space, and milling machines and routers home to the far ends so the "machine space" is all negative. I'm cool with this. I'm trying to figure out how to use the various other coordinate thingies effectively. I know G53 is machine coordinates, and they're all negative, and if I ever go above 0 on a G53 move, then I hit an endstop. But how about G54-G59? I have a probe available to get tool offsets, so it seems like this is a thing, right? How do machinists move into different workspace coordinate systems in gcode? Is there a website I can read? I don't want to watch a half-hour youtube just to get the twenty seconds of button mashing I need; I'd prefer to read some complete pedant's explanation for half an hour instead.
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May 25, 2019 08:18
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G54-G59 are modal codes, which means they are active until something replaces it. So if you want to use the workpiece coordinates in G54 in the work offsets page, in the program, you just put a G54 anywhere before the lines where you want to be moving relative to your workpiece coordinates. Then every coordinate you input after the G54 will be relative to the numbers you have for G54 in the offsets page until the program ends, or until you replace the G54 with a different coordinate code.
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May 25, 2019 09:12
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This is long in advance (I don't have the building for it built yet) but I'm doing research on VMCs to put one at home and came across the Fadals; probably around the 3016 one, especially since I've come across people who have wired them for single phase without rotary converters. Is there any good alternatives in the sub-10k price range that will do serious work?
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May 25, 2019 13:52
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babyeatingpsychopath posted:How do machinists move into different workspace coordinate systems in gcode? Is there a website I can read? I don't want to watch a half-hour youtube just to get the twenty seconds of button mashing I need; I'd prefer to read some complete pedant's explanation for half an hour instead. G53 or whatever specific implementation the machine uses is the machine coordinates, which generally will never change more than a few thou week to week due to limit switches triggering slightly differently. G54-G59 are other work coordinate systems. Instead of having to specify all of you code in absolute terms based on what the machine homes to today, you can set G54 X0 Y0 Z0 at the top back left corner of the stock you're cutting, and end up with a substantially simpler program, with a much easier time coding it up in Fusion 360 or whatever you're using for CAM. You also end up needing tool length offsets, which as the name implies, compensates for the fact that tools often aren't all exactly the same length, and as such, some way of compensating for that is needed. Honestly, youtube is the ideal way to learn this poo poo, because if you don't watch some nerd go through a from-scratch setup and code run, you'll miss something important and either explode the tool, crash the machine, or gently caress up the work piece. https://www.youtube.com/watch?v=user?krayvis?videos does a pretty good job of explaining how to work poo poo on the grbl style machines. Methylethylaldehyde fucked around with this message at 21:43 on May 25, 2019 |
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May 25, 2019 21:41
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Ambrose Burnside posted:If you can deal with a small (~5.5x11" ish Y/X) working area a Taig micro mill would be a good fit, it's above and beyond the cheapest "real" milling machine you'll find and will have much better rigidity than comparable gantry-type mini routers which struggle with aluminum. I've got one, you can cut steel at modest chiploads no problem, and with aluminum the issue will be tool deflection before machine deflection until you're running end mills up near 3/16-1/4" dia. my taig worked great in aluminum. You can rip through it pretty fast and it'll definitely hold the tolerances you need for that, and if it's just 2D milling the CAD is pretty easy. The OP has some links. whether you actually need this or whether it'll be cost effective idk
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May 27, 2019 05:07
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Methylethylaldehyde posted:https://www.youtube.com/watch?v=user?krayvis?videos does a pretty good job of explaining how to work poo poo on the grbl style machines. Link didn't work, but I found the guy and watched some of his videos. So, lemme see if I have this right. I make some toolpath that carves a 5mm by 5mm dickbutt on something. I then home my machine. It's now at g53 0,0,0, and my workpiece is way off in the negatives. I jog over to the piece and run G54, then a probe operation. I'm now at G54 0,0,0. If I run my toolpath, it'll carve right there. I could have also set my probe on g55 or whatever and run the same path? How does this relate to tool offsets? Or, to use a more complicated example, I have my 5mm dickbutt toolpath. I probe at a (G54) corner, then move 10,10, then say g55=0,0 and run, then g54 to 20,10, then g55=0,0 and run again? That's pretty slick. babyeatingpsychopath fucked around with this message at 03:32 on May 30, 2019 |
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May 30, 2019 03:28
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I'm looking for a gear motor for a project. I need it to run between 100 and 200 rpm and have greater than 65 inch-lbs of torque, and also not cost a billion dollars. Anyone have sources for this kind of thing? I'm out of my element on this one.
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May 30, 2019 16:54
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Why does it have to be geared? That's a range where a nema 17 stepper motor is totally appropriate, assuming you can set up the proper drivers. You could also look at hobby brushless motors designed for radio-controlled airplanes and stuff. E: oh, you said inch pounds, not ounce inches. Nevermind
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May 30, 2019 17:02
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I’m going to make the family stop at Grizzly on the way home from our road trip because I want to see some small mills and lathes in person to visualize how they’d fit in my space. Is the G0704 (BF20?) still what I should be looking at for a first mill if I have my sights set on a future CNC conversion? I think having some manual experience first would be a good idea. All the DIY info seems to be on Geocities-style sites and mail order DVDs, so I can’t tell if it’s really dated, or just the audience.
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May 30, 2019 17:36
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The audience is dated
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May 30, 2019 20:37
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Ghostnuke posted:I'm looking for a gear motor for a project. I need it to run between 100 and 200 rpm and have greater than 65 inch-lbs of torque, and also not cost a billion dollars. Looks like you might find something in that range as a "wheelchair motor", on ebay or whatever.
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May 30, 2019 23:13
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Ended up grabbing this one for $115
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May 31, 2019 17:31
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What would be the best/easiest way to cut this shape out on a small CNC machine? It's about 4mm thick about 50mm wide. Would cutting it out with waste board underneath and tabs make the most sense? edit: I am dumb, corrected units of measure. Pimblor fucked around with this message at 02:26 on Jun 10, 2019 |
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Jun 10, 2019 02:00
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Pimblor posted:What would be the best/easiest way to cut this shape out on a small CNC machine? Easy answer: it doesnt matter, yea a wasteboard would be fine. Actually the following info is missing: 4 mil...as in .004 inches? Or do you mean 4 mm? Out of what material? How much to do you care if the sidewalls are straight? How much do you care about the surface finish of the sidewalls? Do you care if there is a HAZ around the part (e.g. is it okay to laser or plasma cut it?) What are your tolerances on the size of the part.
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Jun 10, 2019 02:11
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What material? Aluminum? I assume by "mil" you mean millimeters and not the SAE mil (0.001") A part that size in aluminum I would probably stick to a spoil board with double-sided tape or super glue and machine without tabs. It'll get floppy otherwise. Alternately, if your machine is squared up nicely, you can leave an onion-skin layer on the bottom by telling your tool to leave the bottom .010" uncut. That's thick enough to hold the part in place but thin enough to quickly zip out with a coping saw and file off the leftovers.
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Jun 10, 2019 02:15
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"just drill the holes first in some plate, bolt it to a block with the same hole pattern clamped in the vise, and mill away. what's the-" *notices dimensions* ah (i doubt you can use the holes that conveniently for fixturing at that scale; if you don't know someone with wire edm who owes you a favour and are stuck w wee small end mills, i would probably spray adhesive some sheet to a spoilboard and cut it without tabs at the most modest chipload i could manage without the cutter burnishing instead of cutting) e: i assumed mil as in thou i. e. the part is 0.004" thick and you're asking a micromachining question; if its 4mm thick instead you can cut it easily with a couple different approaches via conventional machining, but if you can get them run on a waterjet or laser or plasma cutter i def would, a single-height part w only thru-cuts is well-suited to one or all of those processes depending on your needs Ambrose Burnside fucked around with this message at 02:25 on Jun 10, 2019 |
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Jun 10, 2019 02:22
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Sorry folks, I'm an idiot, I meant millimeters. I blame society.
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Jun 10, 2019 02:25
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In Sweden a mil is 10 kilometers 
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Jun 10, 2019 02:31
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Sagebrush posted:In Sweden a mil is 10 kilometers Turns out he meant the other other other interpretation of mil https://en.wikipedia.org/wiki/Milliradian
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Jun 10, 2019 08:36
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Ok, I fully deserved that. To answer car forums poster, I am using aluminum, about 1/4" thick, I suspect the rest of the questions are more to do with microscopic machining concerns. Does the end result of this look reasonable, I'll use larger stock so I can clamp/screw down the whole thing. The center hole is only critical in positioning.  If it helps this is on a cnc conversion of a grizzly g0704. I just moved up to it and this is my first real project from my old "fisher price cnc" machine which I only ever cut plastic/foam with.
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Jun 10, 2019 12:51
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What feed and speed are you going to attempt when making that full thickness, full width cut? Looks like a half inch tool? On a part and mill that small, I would probably go for five passes at .050 depth leaving about .020 radial stock, and then one finishing pass at full depth to bring it to size. It's a CNC machine so there's no extra operator effort in doing that, and the lighter cuts will be less likely to clog up the tool or cause deflection in the thin stock.
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Jun 10, 2019 15:52
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Yeah, definitely change up that outer profile operation towards multiple fast, shallow cuts; it'll get the job done quicker and transmit far fewer forces to the fixtured stock. If this is a one-off then web + spoilboard is fine, but if you have to run more than say 2 of these, I would do the extra work of making a simple fixturing block with the same bolt hole pattern as the finished plate and amenities for convenient clamping to this mill's vise/fixturing plate- it adds a midprogram pause but it takes all the fixturing stress off the web, which means you can leave a paper-thin web (or no web at all) that, if lucky, will just snap off the finished piece cleanly thanks to how thin metal webs stretch and work-harden in a way beefier stock does not.
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Jun 10, 2019 16:15
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Ambrose Burnside posted:Yeah, definitely change up that outer profile operation towards multiple fast, shallow cuts; it'll get the job done quicker and transmit far fewer forces to the fixtured stock. More or less this. On smaller machines it's better to do light cuts and move the tool fast than to do a full slotting operation at both inches per minute. Something like 0.075 depth and 0.015 width of cut on a 1/4" endmill would work. Depending on your spindle speed and axis speeds, you can cut that in aluminum at over 100 IPM.
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Jun 10, 2019 20:09
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Thanks all for the responses, this is what I've changed it to based on the suggestions I got: Also, to answer, I was planning on using a 1/4" flat endmill and I haven't really changed anything other than setting the spindle RPM to 1000 as grizzly says not to run it at its max of 2000 for very long.    This is a single run part, it's a dust cover for a fuel solenoid shutoff that I plan to run just a plain rod to to shut off the machine manually. I 3d printed the thing to check the real world dimensions, and that'd probably be good enough to be honest, but I'm trying to learn how to make the cnc machine go. edit: I forgot to show the finish pass step of the 2d contour, but it's basically all of the defaults.
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Jun 11, 2019 01:35
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Pimblor posted:Thanks all for the responses, this is what I've changed it to based on the suggestions I got: It looks like you got it done. If you ever need to make 50 of them, machining a block and pinning and bolting that part is a good way to do it. If you ever need to make 500 or 5000 a vacuum fixture is probably a good solution.
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Jun 11, 2019 02:59
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I've gotten it into my head to build a small rotary-style delta robot to learn about the design + serve as a general-purpose 3-axis light-duty manipulator for various microprocessor projects, and I'm sourcing hardware right now, which means picking a joint style. Anybody who's built a delta-style machine ever run into the oddball style of joint used in one of this guy's builds? https://www.youtube.com/watch?v=RM1ytIyH6BQ It's a bit like a magnetic joint, except the tension that holds everything together comes from a taut cord joining the two machine halves instead of from magnetism. Magnetic joints sound convenient and cheap and effectivr, but I don't need zero backlash and I'm not a fan of them being retained solely by magnetism, it puts a rather low limit on the forces the effector will tolerate before falling off. My thinking is that I can just buy the basic cheap threaded steel ball + magnetic cup joint hardware set off AliExpress, and then add tie points to either end of the arm anchors so the magnetic joints are backed up by lengths of steel cable that don't do the constraining work but will make for a secure joint.
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Jun 15, 2019 02:01
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I remember people doing the magnetic upgrade a lot back in the day. The end effector falling off is a feature, not a bug. If you're crashing into something hard enough to knock it off, you're doing something badly wrong, and the whole assembly falls off instead of stripping pulleys or otherwise loving poo poo up
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Jun 15, 2019 03:42
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I feel like I'm missing something elemental running mach 3 that I thought I had down when using linuxcnc/emc2. Assuming I modeled the stock right, do I zero out the axes in the same place I put the stock origin in fusion 360? In other words, when I zero out (touch off?) the machine do I put the end mill in that exact same corner, sneak up on it with a feeler gauge and then put in an offset? I'm grasping for terminology here so I feel like I'm missing some chunk of knowledge that somehow I got by with previously.
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Jun 15, 2019 17:54
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If all the tool path positions in the program are positive in X and negative in Y, then I don't so why you wouldn't.
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Jun 15, 2019 20:15
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Some how I figured it out, and thanks for the check there Volker.  Ignore the blemish there, that was my fuckup trying to get the tabs cut off with the plasma cutter. On to project number 2 (after I reseal the housing with silicone so I'm not dripping coolant everywhere). Is there a better way to fixture this key cap? I'd like to make a few as gifts and such, not mass manufacture, but maybe a few dozen here and there. What I was thinking was 4 quarter inch dowels press fit into a bottom plate, and either held in a vice or itself just bolted to the table.  It looks problematic to me, but this is the first time I've tried to do something like this, any thoughts?
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Jun 16, 2019 14:40
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So maybe it's not so problematic? I need to make the stock a little bigger but it might work? You can see where the tool path is cutting into the bolts, but otherwise should work once I widen it out and should locate right when I flip it over? edit:  
Pimblor fucked around with this message at 15:24 on Jun 16, 2019 |
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Jun 16, 2019 15:02
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Do you have a vise? You should get a vise. Also, for thin tabs like that don't use a plasma cutter; a coping saw will do fine.
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Jun 16, 2019 16:35
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