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biracial bear for uncut posted:You could always go down the MPCNC route. Someone had one of these at flitefest this week in the build tent, cuttin foam board all weekend.
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Jul 18, 2017 16:31
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NPR Journalizard posted:ok, so im about to pull the trigger on buying this and I was wondering if anyone had experience with anything similar. I have also worked with one of these, and can confirm that they're steaming hot garbage. It's like it was engineered by someone who only had a vague idea of what a cnc machine should do, with a topping of Chinese build-as-cheap-as-possible syndrome. They're cheap, but not a good deal.
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Jul 18, 2017 23:04
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biracial bear for uncut posted:There are no limit switches (you basically have to manually tell the machine where 0,0,0 is and pray your Gcode doesn't send it into over-travel or try to drive your tool into the metal bed),  so what happens if it over travels?
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Jul 19, 2017 00:33
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Volkerball posted:
I would assume it rams into the side and burns out the motor driver
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Jul 19, 2017 04:32
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Volkerball posted:
DRDRDRDRDRDRDRDRDRDRDRDRDRDRBRBRBDBRDBRBDBRBDRDBBBRBBZRBZBRBZBBRZBBRZBRBZZBRBBZBRBZBRBZBBBBBBDRBDBRDBRDZBDBRDBRBZR
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Jul 19, 2017 05:18
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Sagebrush posted:DRDRDRDRDRDRDRDRDRDRDRDRDRDRBRBRBDBRDBRBDBRBDRDBBBRBBZRBZBRBZBBRZBBRZBRBZZBRBBZBRBZBRBZBBBBBBDRBDBRDBRDZBDBRDBRBZR I love when that happens except for when it's my fault
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Jul 19, 2017 07:07
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I forget, was this posted here already? https://www.youtube.com/watch?v=BAtb7O_yk8c
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Jul 19, 2017 07:10
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NPR Journalizard posted:ok, so im about to pull the trigger on buying this and I was wondering if anyone had experience with anything similar. I bought a 6040 kit, (the step up from the one you link) and added my own electronics, spindle, and steppers. It works reasonably well.
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Jul 19, 2017 08:01
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Volkerball posted:
It grinds against the hard limits of the machine traverse and the stepper skips steps until the number of steps for the assumed movement are "complete". Depending on the length of the move this can either overheat the steppers or permanently damage the mechanics of the machine (strip the drive screw/rack-pinion setup of any given axis). Open-looped controls are only really useful when you at least have some kind of homing/limit switch/overtravel system in place to stop the machine if something bad happens. Sagebrush posted:I forget, was this posted here already? I hope every single one of the people responsible for the Gcode in those files was fired. Jesus Christ.
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Jul 19, 2017 12:25
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Sagebrush posted:I forget, was this posted here already? That was painful to watch, I couldn't get through 30 seconds.
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Jul 19, 2017 14:05
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Sagebrush posted:I forget, was this posted here already? God drat, about half of those are 'welp, check runout and CLAMP IT TIGHTER NEXT TIME', the others are 'well gently caress, time to get the machine reps out here to see what the damage is this time'. Some of those fuckups are 5-6 figure welps.
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Jul 19, 2017 17:46
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I'll always love the one (at ~1:14 or so) where the part is finished, and the call to home juuuust clips the bolt holding it down. 
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Jul 19, 2017 17:50
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I think my favorite is the one at 2:21 where the initial plunge drives the tool clear through the part, then it dwells for a second like "hmmm...well, whatever" and turns on the coolant.
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Jul 19, 2017 17:55
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sirbeefalot posted:I'll always love the one (at ~1:14 or so) where the part is finished, and the call to home juuuust clips the bolt holding it down. The full video is even better because there were tons of close calls, and just as you were ready to breathe a sigh of relief it fucks up
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Jul 19, 2017 18:12
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Some of those made me duck my head in reaction.
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Jul 19, 2017 20:23
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Yeah, for those of us who don't live and breathe this stuff it's a reminder of the fearsome power behind these things. Like that one where the bed shears the spindle right off, and doesn't perceptibly slow down in the process.
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Jul 19, 2017 20:30
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I like the one where the spindle bends as one of the horizontal axes moved once the bit was in the material.
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Jul 19, 2017 20:50
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I was watching those videos last night and cackling and I don't know why I find them so funny. So goddamn dangerous too
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Jul 19, 2017 20:55
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A good reminder to safety-squint.
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Jul 19, 2017 21:04
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Anybody have a good source for the conduit used in the MPCNC build (specifically something that matches the 1" OD build)? I'm going to print a bunch of the bottom support assemblies to go with it, but am having trouble finding conduit in the lengths I want--I want this build to be big enough to toss a full 4x8 sheet of plywood into and cut a bunch of small poo poo out of (so, ideally, some 5' & 10' pipes). My basic plan is to get some 80/20 off of ebay to frame in the foundation of the thing, get a sheet of Marine-grade plywood mounted as the substrate and have the first program ran on it machine some grooves and counter-sunk bleed holes for turning it into a vacuum table (and have a network of tubing leading to the vacuum pump, and just plug off the sections not being used with o-rings and pennies as required). There is no deadline on this project either, so I have plenty of time to shop around, but everyone seems to be really proud of rigid conduit. Is there an option I'm not thinking of?
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Jul 19, 2017 21:29
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Home Depot? A local electrical supply house? There are several options for fittings so you can use whatever you can acquire locally. E: Grainger may act like they don't want your money, but they're everywhere and have everything. eddiewalker fucked around with this message at 21:42 on Jul 19, 2017 |
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Jul 19, 2017 21:31
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Yeah, Home Depot around where I live is a joke if you're looking for anything that's actually straight. The three closest to where I live don't even carry 3/4" schedule 10 stainless pipe, much less in the lengths I'd want to use. EDIT: Grainger is an online-only sort of thing for me, though I may have to go with them as an option and just eat shipping costs and hope they don't get damaged in shipment.
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Jul 19, 2017 22:15
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I guarantee you there's a place locally where commercial electricians are buying it. In my experience electrical and plumbing suppliers don't get weird about selling to individuals (hvac on the other hand...)
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Jul 19, 2017 22:25
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Mister Sinewave posted:Yeah, for those of us who don't live and breathe this stuff it's a reminder of the fearsome power behind these things. biracial bear for uncut posted:I like the one where the spindle bends as one of the horizontal axes moved once the bit was in the material. I was casually flipping through the manual for one of our Haas mills the other day and saw on the spec sheet that the X and Y axes are capable of producing four tons of lateral force. Yep
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Jul 19, 2017 22:56
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biracial bear for uncut posted:Anybody have a good source for the conduit used in the MPCNC build (specifically something that matches the 1" OD build)? ??? ,,,, I've never ever seen stainless-steel conduit, it's all just this soft crappy zinc-plated stuff...??? --Which works just fine for its intended purpose. But it isn't structural tubing at all. I mean,,,,,,, it might exist somewhere, like a nuclear power plant or rockets or something. But you're not going to find it at Home Depot. You may not know that "pipe" and "tube" are the same shapes, but they are not the same things in the metal supply world. Kinda the opposite, in use. You can buy stainless-steel pipe, but you see--pipe is sized by the inside dimension, not the outside. You may not be able to get it with a specific OD at all, since the wall thicknesses are designed to handle a particular burst pressure, they aren't just set to a specific convenient thickness dimension. And while the inside walls are smoothed, a lot of times the outside wall is not--particularly where the weld seam is. You need the outside surface to be finished here. Also, stainless-steel pipe is going to cost a LOT of $$$$. Metal conduit is for running electrical wires; it's not made to handle internal pressures or physical loads. Pipe is for flow--either liquid or gas. The inside may be finished (smoothed) but the outside often isn't, and the ODs are frequently odd dimensions. Like--a 1" pipe is 1" inside, but may be 1.379" OD... Metal tubing is for structural use. The outside surface is finished, and the OD usually hits a recognizable dimensional unit. So a 1" tube is going to be 1" OD (or probably like .998" or something VERY close to--but smaller than--one inch). ----------- Use 4130 chrome-moly structural tubing instead. I would suggest 1" OD x .083" wall thickness. For comparison--the thickest frame tubes you will find on BMX bicycles are probably .065". Stainless tubing will cost at least twice as much, it is way more difficult to cut and drill and it won't be as stiff as the 4130 will be. You could also use aluminum too, if you could get proper 6061 T-6 tube. It would cost about the same as the 4130 steel, but it would not be quite as stiff. ALL THREE of these will rust from sweat, the stainless or aluminum won't save you from that. To keep the 4130 from rusting you just assemble it and then wipe the exposed steel down with a lightly-oiled rag, and then don't touch it. Also I would warn you--you will pay a LOT more if you buy from an online metals place, than if you find somewhere local. The online places charge a lot for cutting it, and then they have to charge a lot more for shipping it. Any big city probably has a metals dealer there. Ask if they have, or can get "4130 tube, one inch OD and .083 thick". If the local place does not sell by the foot then you may have to pay for a ~20-foot piece--but then, it will only cost half or maybe a third of the prices you see online for the same amount of tubing. edmund745 fucked around with this message at 01:34 on Jul 20, 2017 |
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Jul 20, 2017 01:27
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Sagebrush posted:I was casually flipping through the manual for one of our Haas mills the other day and saw on the spec sheet that the X and Y axes are capable of producing four tons of lateral force. The good news is that the spindle is stronger than a half inch end mill, so it will just snap that tool and go about its day instead of tearing itself to pieces like that cheap rear end machine did. Anyways, always slow down the rapid and use single block on set up.
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Jul 20, 2017 01:39
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I've built stuff using stepper motors up to bigger nema-34's, but so far haven't used any kind of stepper with a gear reduction. Of the two common types of gear reductions (planetary and offset) which one is better? ......Which one is more durable under moderate loads? ......Which one has less backlash? They both seem to be priced about the same at the lower gear ratios. At the higher end (like 100:1) the planetary ones seem to cost more. The planetary ones seem to be a more elegant design, but they tend to hit odd values at the lower end of the spectrum--such as 5.18:1 instead of 5:1 or 6:1. The offset-shaft gearboxes tend to hit even values of 10:1, 16:1 or 20:1, but IIRC they always have at least 6 gear interfaces, where the single-stage planetary drives only have 3 (so less backlash). For the nema-23 size motors there is also places selling plain single-stage worm gear drives (motor + drive is $60) but these don't appear to have any means of taking up the backlash. I've seen DIY robot arms online that used them, but I'd still wonder what the typical backlash and lifetime is like... Do they last longer than the planetary or offset drives? I'm kinda itching to build something, for <$300 or so. I priced out what a 3-axis CNC mill/router would cost, and decent slides would cost $500-$600 alone (they would already have motors, but still). That would probably be most useful but I don't really need it now. And it seems a bit tame. I'm pondering a robotic arm (that could also be a router/mill) but I'd need high-torque motors for that, and there's no harmonic drives that are cheap & new. There is some 50:1 strain wave drives from China-land but I dunno anywhere to get them separate from the products they build them into (the little $200 4th-axis CNC headstocks).
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Jul 31, 2017 00:32
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No idea if this is the right place, but I have a question on CNC programming. I'm looking to make a large stencil for hex maps, which would involve making dashed lines along a hex grid. I've got a good vector image of the grid itself, but I'm unsure if there's a particularly good way to convert it to the appropriate dashed lines via automation, as opposed to sitting down and making a single dashed hex to clone or editing my vector by hand. As I'm looking at a lot of hexes, this could get tedious really, really fast, especially considering consistency is key. As I've mostly done really basic poo poo up until this point (image design for engraving, working with a few different materials - the standard "what the hell do I do with such a cool tool" package), I'd like to try and figure this one out. CNC is an X-carve, but it's in a buddy's shop and so I rarely get to mess with the software. Tried searching around, but I haven't found much in the way of answers beyond actually making the grid itself, which I already knew how to do. Any resource recommendations or guidance would be greatly appreciated.
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Aug 3, 2017 05:22
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Draw the first hex in the pattern (minus the lines/hash marks for the sides where the hex will repeat if they overlap), then use the Array command to fill in the rest of the pattern. Depending on your CAM software, you can tell it to Array such that when the tool-paths are generated it will run in rows/columns while machining the pattern.
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Aug 3, 2017 12:41
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edmund745 posted:I'm pondering a robotic arm (that could also be a router/mill) but I'd need high-torque motors for that, and there's no harmonic drives that are cheap & new. Depending on your budget and planned work envelope I've seen mid-sized robot arms(100kg/1.6m) with controllers go for a couple of grand on eBay, controlling then is a whole pile of fun but you won't waste forever trying to build a rigid arm.
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Aug 16, 2017 10:04
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I'm engraving on my Taig now and again and I want to start using it to augment my traditional repousse work- using it to do embellishment and detailing that I've historically avoided because of how labour-intensive it is, filigree infill and scrollwork and stuff like that- but engraving before repousse is dicey because engraved sheet metal wants to split if aggressively formed, and level raised surfaces are impossible without die-forming. I remember seeing a spring-loaded/auto-surface-conforming engraving tool holder once upon a time, anybody know what I'm talking about? It could do clean engraving across really irregular surfaces within a 0.5" range of Z-height or something like that. (similarly i've been fantasizing about some sort of power-hammer-style spring linkage adaptor that'll turn the mill's rotary motion into reciprocating up-down motion, for CNC repousse/embossing instead of material removal, but hoo boy I bet that'd be GREAT for the spindle and bearings) e: seems like that sort of thing kind of exists already, albeit at such a small scale it's basically an engraving machine with less tool wear, I'd need deeper bossing than 0.2mm. https://www.youtube.com/watch?v=6pDrC9t6h_M e2: this guy's built his own CNC rivet-setter, which seems to be like 3/4 of the way to what I'd want. Pneumatic hammer would be the way to go, yeah. http://www.galtran.com/PRR_L2_Construction_Information/Rivet%20Machine/computer_controlled_rivet_emboss.htm Ambrose Burnside fucked around with this message at 18:09 on Aug 17, 2017 |
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Aug 17, 2017 18:00
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A drag engraving bit seems to be what you're looking for, but they're not super cheap/common http://www.widgetworksunlimited.com/CNC_Diamond_Drag_Engraving_Bit_p/cnc-dmnd_engrv-250.htm e: you can find diamond bits for cheapish on aliexpress - shouldn't be too difficult to make a spring loaded holder for them
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Aug 17, 2017 19:03
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I think that's what I was thinking about, yeah, and the diamond bit holder itself is very straightforward to tackle, found a couple schematics out there already. I'll probably knock one with a 3/8" shank out once I get my Hardinge lathe access back.
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Aug 17, 2017 19:44
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Are you engraving flat surfaces, or 3d?
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Aug 18, 2017 00:57
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Nominally-flat, but with large tolerances- i'd guess as much as 50-100 thou difference between the high and low spots of some pieces. Smaller stuff is tighter, but for bigger pieces the flat 'plane' the sheet is being raised or sunk to is strictly MK 1 Eyeball/"is it flat on the anvil"-level accuracy. I'd hypothetically be interested in engraving rounded or radiused stuff but then we're talking real Z-travel of an inch or less, more than the spring holder would take up, so I'm not worrying about that.
Ambrose Burnside fucked around with this message at 01:11 on Aug 18, 2017 |
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Aug 18, 2017 01:08
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I have been looking at Hiwim rails for a home built desktop CNC and they have kN ratings for dynamic and static loads. Is there a good reference for calculating the sorts of loads generated by the spindle, so I can sort of go back from there and design the whole structure? If I know the spindle loads and geometry I can calculate moments, forces etc. I imagine it would have something to do with the motor torque curve and maximum rotational kinetic energy of whatever you had attached to the spindle. Is there by chance a really good DIY CNC book which assumes you have some engineering knowledge?
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Aug 18, 2017 01:51
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Ambrose Burnside posted:Nominally-flat, but with large tolerances- i'd guess as much as 50-100 thou difference between the high and low spots of some pieces. Smaller stuff is tighter, but for bigger pieces the flat 'plane' the sheet is being raised or sunk to is strictly MK 1 Eyeball/"is it flat on the anvil"-level accuracy. I'd hypothetically be interested in engraving rounded or radiused stuff but then we're talking real Z-travel of an inch or less, more than the spring holder would take up, so I'm not worrying about that. 2L makes some pretty nice spring loaded holders. They're designed for rotating tools, not just scribers or drag knives, so you can get deeper engraving (the catch is that the slower you feed, the deeper it goes, so you have more process variables to control.) 0.4" travel, down to 1/4" shanks. There's enough preload on the spring that force doesn't vary that much with travel. Expensive, though. You can probably make your own fairly easily, it doesn't need to transmit that much torque.
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Aug 18, 2017 02:38
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... so hi, in a fit of craziness, I'm starting to plan out a DIY waterjet cutter (ala that guy who did one off a pressure washer on youtube) purely for cutting foam - the goal is to have 1:1 scale car bodywork plugs by laminating the stuff. Is there any optimization that needs doing compared to a router or the like? I know real milling machines, I know 3d printer stuff, and it's a waterjet so Z droop isn't much of a concern, but ideally I'd like to not struggle with feeding it 4x8 sheets of foam. Would something like chain driven motion systems be better, or would belts possibly be better given the water? And yes I know that a 3000psi waterjet is hardly a waterjet but I'm just cutting foam.
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Aug 22, 2017 16:46
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mekilljoydammit posted:... so hi, in a fit of craziness, I'm starting to plan out a DIY waterjet cutter (ala that guy who did one off a pressure washer on youtube) purely for cutting foam - the goal is to have 1:1 scale car bodywork plugs by laminating the stuff. Is there any optimization that needs doing compared to a router or the like? I know real milling machines, I know 3d printer stuff, and it's a waterjet so Z droop isn't much of a concern, but ideally I'd like to not struggle with feeding it 4x8 sheets of foam. Would something like chain driven motion systems be better, or would belts possibly be better given the water? Look at the Mostly Printed CNC platform. It's probably a good starting point, at least.
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Aug 22, 2017 16:54
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If all you're interested in cutting is foam, why not do what one specialty foam manufacturer i know of did, and rig up a conventional gantry-type CNC router arrangement with a nichrome hot-cut wire in place of conventional tooling? It'll be far simpler to build, much more reliable and straightforward in operation, and will produce cleaner results to boot. Wire tooling is trivial to bend or adjust to get cutting profiles that'd normally require 4th/5th axes with other methods. Safer, too. The company i'm thinking of makes shaped foam panels for building exteriors and they built all their own tooling from the ground up, including a rotary form cutter that let them turn blocks of foam lathe-style to conform to any profile they could bend a wire into by hand. Virtually no machining forces involved and the tooling is very light, so rigidity isn't an issue and big gangly gantry-style setups are more than adequate. Ambrose Burnside fucked around with this message at 17:06 on Aug 22, 2017 |
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Aug 22, 2017 17:00
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