Thread: Quite an Unusual one
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08-12-2018 #191
A good way to seal the leaks around a dam before you pour your epoxy is to make up a very small amount of the epoxy and using a small brush or similar just go round the inside of the dam brushing the epoxy into place. it will run into the holes or bridge the smaller holes but because there is not a large quantity behind it, will not run right through and leak out the bottom. You only need to leave it long enough to stop flowing easily before you pour the main epoxy batch - you do not need to leave it for days to fully harden. I made my dam from gaffer tape, stuck to the sides of the rails so that the edge of the tape was above the rails. Biggest problem was peeling it away from the epoxy when the epoxy had hardened. Next time I shall try pulling it away before the epoxy has fully hardened!
I had to strip my first load of epoxy off the rails and start again, but I had already drilled the rails. I put small pieces of Sellotape over the holes and poured the epoxy over the top. I could see where the holes were and then just drilled through the epoxy after it had set. Worked for me!
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08-12-2018 #192
Ok think that'll do. Maybe to be double sure sure I will also use silicone. I imagine that would be frustrating seeing your epoxy flushing in a not properly sealed hole. :-)
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26-12-2018 #193
First time i did it not entirely right. With time discovered new ways and next time i did it welded 6mm or 8mm bar stock, distance 40mm between. Have to check if it was 8mm as it may touch the Hiwin 20 block. Better read my second build log to see how i poured a couple of times epoxy on a 3m machine untill i figure the perfect way. iin short i discovered that the most important part is to make the damned dam longer like 15 cm at least than the actual machine to compensate for the shrink and that way only one bridge is enough, and the bridge must be then outside the machine. So when all dries and shrinks, the bridge will not eat from the actual ways but from the extra length. If you know what i mean
Last edited by Boyan Silyavski; 26-12-2018 at 08:22 PM.
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27-12-2018 #194
Yes thanks. I read that post already. I will follow it. I have a vacuum chamber where I can stir epoxy under vacuum. I am excited to see if it will make a difference in accuracy. Good job btw.
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02-01-2019 #195
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23-04-2020 #196
Hello Boyan.
Nice machine I have to say. Looks very stiff! How is it running these days? Do you have a lot of work for it or mostly hobby stuff?
Anyway I wanted to ask how you went about auto-tuning the axis with double servo motors (Y-axis in my eyes, not the gantry). Auto-tuning is a very nice feature in any servo motor software, but I have not figured out how to tune an axis with double servo motors.
Also how did you go about calculating the servo motor size? Perhaps you have explained this in a post somewhere, but I couldn't find it! :)
Thanks!
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23-04-2020 #197
Thanks!
I have sufficient work for the machine. Not as much as it deserves though. I make some product on it, sometimes for other people and sometimes cut letters for signs.
I tuned the Z and used same parameters on the other axis, as more or less motors a properly calculated for the loads on each axis, working at optimum.
Then one day i figured that if i move left or right motor 5mm, its not a problem as the gantry is like 2 meters. So there is play enough. Then i entered in Samsung software and limited the movement to 5mm each side and tuned the axis like that. With a short movement. I say 5mm just to be on the safe side, it could have been 10-15mm, on such a long gantry this is like nothing, before the other side tries to engage. In Real life if i switch off 1 motor i can move the gantry front/back even with one motor only .Of course autotuning stresses the thing, so better in the short safe range. Check all that range adjustment on the Z firts, so you dont bend something.
The servo motor size Jonathan or Dean helped me, its on the first pages somewhere. But basically 400 or 750W ac servo at 230vac are the thing for a machine like that. I went with 400w as ballnut is geared 3:2 so at 3k rpm of motor i am at 20k mm / min and my motor power is multiplied by 1.5 at that ratio. My motors support up to 6k rpm so ...
As far as i understand the things, Panasonic, Samsung or other brand servos are way better than the chinese ones, so if i was going with China servos would have went with 750w ones, as price is irrelevant also on the chinese servos. No big difference. But remember. All time i am talking about AC servos driven by 230VAC drives.
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23-04-2020 #198
Sounds good that you have work for the machine!
Thanks Boyan, for all the answers.
I like your idea and it makes sense to perform auto-tuning like that.
Myself I have build log (build in real life not started yet) if you are interrested to check it out.
Anyway I was thinking about those servo sizes as well. I will take your advice and get Delta 750W servos! Perhaps also 2020 (plan was 2010 with 400W servos) ballscrews to get a crazy speed of 30-40m/min, depending on what gear ratio I choose (3:2 or 2:1).
Not sure if I ever will need that speed but nice to have some room for experimenting.
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10-07-2020 #199
Hi Boyan. Inspiring. After reading this thread I had to join the forum, just to say how cool your machine is and how impressed with your work I am. Thanks so much for sharing. I am partway through building a beast-sh 1.2 x 2.4m steel and epoxy machine, which I plan to run with similar Samsung servos to you. I am just debating whether to spin the 2 long ballscrews or their ball nuts to eliminate the potential problem of whipping.
Like you I am aiming at snappy ;)
Anyway, I wonder if you would be able to share some of the details of how you designed / constructed that area where the servos, belt drive the ballnuts and attach to the gantry ends?
Thanks again for your inspiring work!
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13-07-2020 #200
Hi,
will take photos
Definitely go rotating nuts. Normally i run it at 8000 mm/min for wood as faster wood will chip. But for foam or 3d jobs i run it 16.000 or faster. And being snappy means no slowing in corners. Especially important if doing deep trochoidal toolpaths. Meaning a very serious difference in time. Not that a 10.000 mm min max speed machine is not enough for a normal work, but if you have an order of say 100 doors or something the difference will be like 4 or 5 more days to do the job. And talking about profiling the panels only. Not 3d job
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