just another plasma build and then some :)

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30 May 2021 20:09 #210731 by machinedude
one of the other issues i was having is getting the rails set on the side of this build. that part got about as sideways as sideways can get when you are trying to get a machine bed flat. they sell expensive laser leveling systems for this sort of thing but they cost several thousand dollars so that was out of the question for me.

i did some digging and seen some people have used a wire method with the wire under tension to get a datum plane to work from and using a loupe to see things better. so i took that and made my own spin of the process.

i was going to use .009 music wire until i started to price it and ended up using Nylon upholstery thread instead since it is cheap and only about .007 in diameter. and rather than using a loupe for magnification i bought a digital Microscope with a 7" screen. the microscope was rechargeable and had better magnification. the contrast of the of the thread color plus the magnification worked well for dialing things in. the microscope was about $100 but worked well and did not break the bank in the process.

i was able to get things flat within about .003 per 30" with a straight edge and feeler gauges which is not to bad. 2900mm long rails basically suck to get straight when you loose your datum point but this got me back on track at least.
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30 May 2021 21:17 - 30 May 2021 21:18 #210744 by andypugh
I have the exact same microscope. I am very impressed, and highly recommend them. Now I can read the print on SMD components again.

(link: www.amazon.co.uk/gp/product/B08G4Y6C65/r..._title?ie=UTF8&psc=1 )
Last edit: 30 May 2021 21:18 by andypugh.
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30 May 2021 21:45 #210749 by rodw

I have the exact same microscope. I am very impressed, and highly recommend them. Now I can read the print on SMD components again.


I have one here too. The price is quite crazy low for what it is.:)

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31 May 2021 08:26 - 31 May 2021 08:27 #210780 by thefabricator03

regular concrete has shrinkage in the mix so if just adding weight is the goal that is about as cheap as it gets. with the epoxy it only shrinks around .001 imperial. any metal dust added would be about the equivalent to the machine setting epoxy for leveling stuff i would think.


What are your thoughts on using a plasticize to reduce the amount of water used in the concrete which should hopefully reduce the shrinkage?
Last edit: 31 May 2021 08:27 by thefabricator03.

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31 May 2021 11:07 - 31 May 2021 11:11 #210788 by machinedude
it would depend on how things are put together? i personally don't think either is good alone. i have seen some builds with epoxy granite with large castings that work fine but the amount of material used to get there is massive and that drives cost of the build up quite a bit.

i have seen people basically do a steel frame and and just use regular concrete to add mass to the frame. the more mass you have the harder it is to get vibrations started. any kind of mass will dampen vibration to some degree i think.

the main difference between regular concrete and epoxy granite are the amount of shrinkage and impact resistance and the amount of dampening.

just to give you an example the cross beam of my gantry i tried with the extrusion and the torsional deflection was pretty severe from the cantilever effect of the spindle center line extending out from the cross beam rails. when i filled the voids and some of the t slots not being used i got around 5 to 6 times better readings with an indicator. the only reason i got this was the choice of filler material and lack of shrinkage. concrete would not do the same because of shrinkage.

if you fill tight spaces stone is not good as a filler material and sand is a better choice by far. large castings are a stone and sand mix. when you add stone the mix does not use as much epoxy so it keeps the cost down. but when you fill something like the voids in extrusion the tighter the pack you get the better off you are.

it put me in the mind set of block work with concrete and mortar work when working with this in this application. different fillers for different applications.

i would probably take the concrete and pour some small test castings to see exactly how much things shrink to start with and then you can see what you will be dealing with before you get into it to deep.
Last edit: 31 May 2021 11:11 by machinedude.
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02 Jun 2021 00:17 #210928 by machinedude
quick video doing some cutting. working on getting the t slot table top started. i was pushing hard at first and snapped my cutter off :) so this is slow and easy. i got more details on this in the off topic section as well. gave the spindle a little more juice from the stock motor

vimeo.com/557837551.
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06 Jun 2021 12:08 #211290 by machinedude

I have the exact same microscope. I am very impressed, and highly recommend them. Now I can read the print on SMD components again.

(link: www.amazon.co.uk/gp/product/B08G4Y6C65/r..._title?ie=UTF8&psc=1 )


actually using these for electronic board repair is a common use for these microscopes. some of these actually have software that will measure part features but i think the software drives the cost into the $300 to $400 price range? i did not play around with the software included with this one so i don't think it does this but other brands have this function from what i could tell.

i did get a chance to run the starter slots through the entire table section and running trough 4 of them 55" long with roughing and finishing passes has a cycle time of around 1 hour and 50 minutes. i did try a standard HSS key seat cutter but it was not working to well so i got something more suitable for aluminum. you need a course tooth count for aluminum so the chip have someplace to go. and this spindle lacks on the low rpm range so carbide is needed to get into the sweet spot which is wide open :) i had to resort to an import since these can get very pricey. so now i have to wait forever to get a cutter.

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