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| NeoTech:
So in casa NeoTech, the crazyness has stirred up under the winter and a new CNC machine build has been planned, parts begun to be sources.. So this is a bit of "so far i have."... So basicly i started to read upon this polymerconcrete thingymajig. And its an awful interesting material. And an awful interesting theory of outcome and use. But one thing.. even tho this material is a epoxy base concrete.. It still a concrete. Something most threads i have read seems to forget. So my approach to this a bit different. Instead of casting in anchors i have decided to cast in a subframe as integral structure. And this is what i have come up with. edit: changed out some of the internal frame after i reevaluated ridigity by reducing internals until it started to flex alot. As seen a series of interconencting 2mm sheet parts are welded into the exposes metal parts that are meant for bolting stuff to. These in turn will be the reference points for the mold as well and later on ground parallell in place. So this is basicly the project, and parts have begun to be sourced. The list basicly looks like this atm. -- Servodrivers: Granitedevices Argon - http://www.roughedge.se/blogg/wp-content/uploads/2015/01/IMG_0466-e1421069123861.jpg -- Servomotors: 1.5kW 130mm framed Quadrature motors from MiGE (china) http://www.roughedge.se/blogg/wp-content/uploads/2015/01/2015-01-20.jpg - Click this link for size reference, this is the motors intended for motion. -- 32mm ballscrews with a 5mm pitch: ordered -- 30mm linear guides from hiwin: ordered -- Mesa 7i90HD + 7i48 Servo card: Ordered -- Misc electronics parts: Orderered. -- BT40 @ 8000rpm Spindle with ATC (chinese): Still haggling. -- 7.5kW spindle servo motor from MiGE: Still haggling. -- Lasercut metal parts for the frame: on hold until all cad is set in stone. And yes yes, i know "buy an old machine and convert instead, bla bla".. not interested in that. The whole project is, how would a polymerconcrete machine be able to behave - and what precision, speed and force would it be able to handle. I plan to make the drawings, parts list and all that available on my website as an openhardware effort when i get that far. |
| DMIOM:
Neo, I'm eagerly awaiting to see this come to life, meantime just a couple of thoughts: The Y rails don't seem to be exploiting the full width of the base - if they were further out (i.e. towards L / R sides of the base) then there might be less tendency for the saddle/table to droop when at min/max X travel - it looks like you could almost double the rail spacing within the same footprint. The Y ballscrew looks to be quite a way below the saddle / rails - when its pulling or pushing, I suspect part of the force will be racking - trying to tilt / lift the front or back of the table - I'd be wondering about getting the ballnut as high as practical (like your X ballnut looks right beneath the table, in the same plane as the rails). I'm not sure of the overall size of the machine; but the table looks a bit out of proportion to me. On my CNC mill, I tend to leave a vice mounted on the right of the table and use the left hand side for clamping-down, fixtures etc. Even if you're using a pallet-style or tooling plate to quick-mount your vice, there may be times when you need that length of table - e.g. using a fourth-axis and tailstock? Dave |
| NeoTech:
Thanks, for constructive feedback. And you are right, there is alot of "height" for the Y axis down to the bottom screw, from the center of the ballscrew to the bottom side of the saddle its about 100mm. whichwill prob, create a problem. Each ballscrew will have double ballnuts, with the flange pointout outward in their respective travel. The same problem actually exists under the pallet and behind the head.. And i havent figured something good here yet. The motor frames is 130mm and they require alot of free space to center well actually, more than one could imagine. This is the main reason im not ordering the laser cut parts yet, i need to reiterade over this when i have the 32mm ballscrews and flange nut in my hand and know how they are in relation to the motors. That palette is 400mm x 400 x 40mm mm palette. The idea of it is to have a quick lock system with 4-5 screwed inserts. (see attachments). The overall travel of this machine would be in the range of half a cubic meter. - And the idea of a 4th and a 5th axis has occured to me, but atm im thinking of it as a module that can be lifted into the machine and locked into the pallette. |
| RotarySMP:
cool project. 1.3kw would seen total overkill for this size machine. The epoxy grantir machines made by Nucky in the cncecke.de forum use 400-800W drives for roughly this size machine with very high performance. What are you truing to acheive through the embedded sheet metal parts? You are still going to need to build forms for casting the epoxy granite. Do you plan to source premixed aggregate, or mix your own. The difference in E modulus is suppossed to be about 2x between a home mix and a mix donebto the Fuller curve. Have you designed in the way covers? Mark |
| sparky961:
You may want to consider a longer (wider) table, more like a Bridgeport-style mill. There are many setups where this length is an advantage. If you swapped your table and the piece between that rides on the Y axis, it wouldn't be much different but it would give a lot more working area for larger parts and clamping support. |
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