just another plasma build and then some :)

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23 Apr 2020 22:09 #165314 by machinedude
and i very much agree about the internet being a mine field of bad information with out a doubt. but it passes the time on the night shift to make the night go faster :)

it does have to do with the coils in the winding's but has a lot of logic in the background as a result. so why you would go this route and not just use servo's to begin with is beyond me? especially with the price point on the cheaper servo systems.

looks like it will stay as is for a bit and later maybe upgrade to a servo system.
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23 Apr 2020 23:18 #165321 by rodw
There is nothing really wrong with a stepper system if its properly set up. Because your ball screws are the limiting factor with max velocity, you could save your money and apply it elsewhere... In your spare time come up with a moving nut modification before you spend on servos....
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23 Apr 2020 23:34 #165324 by tommylight
Yeah, moving nuts are NUTS ! I did a test a while back on a 2505 ball screw and i could move it at 68m/m without load and with only 24V supply to the drive! But adjusting axial bearings is quite the challenge. Thought of trying angled roller bearings, but got sidetracked. And there is the issue of bolting down the sides of the screw so it does not fly off at those speeds.

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24 Apr 2020 00:37 #165330 by machinedude
i would imagine ball nuts have limits on speeds like bearings do. some ball nuts have a preferred mounting so the ball can circulate properly too. so some care needs to be taken with with the moving nuts in a design.

and back to the original concern i have you still have backlash error and lead screw error. so if you want to remove those you can do it with screw mapping and backlash comp but those add a correction lag time to the system. and not to mention it's just and end position correction. this is what got me on the linear encoder band wagon to begin with. you bypass the error by getting feedback on the actual position. that's the attractive part of linear encoders for feed back.

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24 Apr 2020 01:04 #165334 by machinedude
one other aspect i have to deal with is a heavy gantry. so moving at rotating nut speeds will cause some issues. the cross beam axis of my machine has some good acceleration and when it is cranked up it will make things move in ways you don't want to see things move.

strictly plasma with a super light gantry will run circles around what i have in acceleration and speed. when you have the extra weight it needs extra time to accelerate and slow back down.

i do think once i finish the E.G on the table i can push the acceleration up because the machine base will have a lot more mass to it though. i might get the mold built this weekend and start do that part real soon.

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24 Apr 2020 02:09 #165341 by machinedude
i was thinking DYN4 drives were only 240V AC but they can run on 120V AC i already have these. i was trying to keep things limited to 120V just because i have to much other stuff in the shop :) i guess if i really wanted things to work better i could use them instead of the steppers. im pretty sure the speeds are reduced quite a bit when you run them on 120V but with the 750w motors i could probably get more than enough out of them and get what i want. i will have to look at that tonight while i am at work and refresh myself on the set up of those :)
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26 Apr 2020 20:18 #165689 by machinedude
this molding of the frame in E.G. has been a lot of work. i thought i had just about everything cut out but when i started putting things together i quickly found out i was missing some pieces :) way to many pieces to keep track of :) and it went together in CAD a lot easier than in reality. if i had some extra hand around to help it would have been a lot easier :) hopefully i can pick away here and there this week coming and get things ready to cast over next weekend?
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26 Apr 2020 20:23 #165691 by tommylight
Nice.
Think of us cheering you ! :)
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26 Apr 2020 20:35 #165695 by machinedude
should make for a nice machine base and sub table. in the beginning i thought i could tear the table down if i had to move the machine but that plan went out the window i while ago :) once i seen the frame work on the top i was like E.G. would work so well there the way things turned out because of how it's a bunch of interlocking cells. then as some time went by i figured if i could figure out a way to tie the table top to the frame that would be even better so this is where i landed :) hopefully it's not flat on my face :)
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03 May 2020 02:07 #166457 by machinedude
I think i have A.D.D. :) i was thinking i would be casting by now but just finished the mold and it's to late to get into anything now. T.he Table top ended up getting more involved then i expected and took me all day to get sorted out. i was working til 2:00 am last night but did not get anywhere because i was to busy going over everything 2 and 3 times.

now that it's in front of me this thing is going to take a while to cast. the amount of mixing and working into the mold i am not looking forward too :) working the air out of the mix is probably not going to be much better :)

for the most part i kept things open around the ball screw just so it would not be a nightmare to work on down the road if something should happen. had to create some clearance down the center 3/4 deep for mechanical stuff to clear. i used a hard board for most of the table trying to save some money the plastic is about $80 a sheet compared to $9 a sheet for the hard board. the hard board will need some mold release to be safe but the plastic probably won't the the extra help for releasing from the from the frame.

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