i actually tried cutting aluminum today on this thing and i was surprised by the finish quality and how well it did with modest feed rates and lighter cuts. the drive pulley is the weak link when it gets pushed to hard. the spindle will take a 3 mm depth of cut full diameter with a 3/8 2 flute HHS cutter it just vibrates to much taking that much but cut good at 1.5 to 2 mm depth of cut i had the feed up to 40 IMP but i think it will do 50 IPM and still leave a decent finish. i'm still tweaking things in and have it close but the Z axis is being stubborn. things look pretty good as far as squareness and things being parallel so that's a good thing at least.
i was cutting some plastic as well that was PVC sheet. but that was not really a work out since it's not a very dense plastic. that material was not form a regular plastic distributor and came out of Lowes . so having said that the label said PVC sheet but it seemed light for PVC. i have worked with in the past and this stuff from the home center is not quite the same. i think it's more of a building composite type material made to be lighter in weight?
this was just a quick test on things to see how this machine cuts on something substantial at this stage. depth of cut is .050 and feeding at 30 IPM which is a pretty safe point to start at where i am sitting at now with this thing.
after looking at speeds and feeds for the RPM i have and the tool type and number of flutes what i tested is about the same as what the speed and feeds calculators give me for a max so by the looks that i am on track.
i guess a 2 flute HSS 3/8 diameter cutter is not that impressive numbers wise but if i were to switch to a 3 flute by the numbers i should be able to do 50 IMP with the same cuts. the bigger diameter cutters do better on the feeds but the HP restrictions will factor in to that quickly i think.
just a little bit more info i forgot to add to this test. when i ran this i left out any kind of cutter comp on the tool path just to see how close the machine was dialed in. i was shooting for a 2" wide slot by .5 deep. after cutting i was with in .005 on the width and depth. not to horrible but i will try to mess with things some more to see if i can make things better.
i did get a new set of timing pulley's to try a different drive ratio on my long axis to see if i can get some more traverse speed out of that axis. so since this is a long weekend for me with the holiday i might get to that this weekend.
tried a different drive ratio and that ended up not working but did spot an issue with run out on the ball screw coupling and fixed that and put it back together as it was in the first place. did some motor tuning and got where i wanted to be at least. was not as planned but i will take it regardless i got 400 IMP across the board and can live with it as is now. my acceleration is not that great still but at least it gets up to speed.
i started making panels for a mold frame around the skeleton frame work for more E.G.on the frame. this was a lot more work to sort out than i thought it would be i'm looking at like around 175 different panels to assemble and thankfully this build is far enough along that i can use the machine to do something useful and make it go quickly at least. up until this point everything has been made on a manual mill and if i was to do all this manually i would probably be bat sh@t crazy by the time i was done
been at it but still have a ways to go getting into a wide range of sizes was good to sort out some tuning. i have to say dialing in a 8' table can be tricky. needles to say you have to use a method to measure more than the 1" of travel on a indicator to see a bigger picture of what is going on. so thankfully i have a set of 24" digital calipers that got me about as good as i can get with what i have to work with. this all got me thinking about linear scales and trying to close the loop with those with these steppers and making things even more accurate.
I got curious on the last set of parts i ran since i put pilot holes for assembly. the last batch of parts i ran had 386 holes in the 6 sections i ran which ended up taking a little over 17 minutes to run but the average time per hole was less than 3 seconds i would have been at it forever and a day doing just those 6 pieces manually. it's nice to see your work pay off after 10 months of building in your spare time
this project is turn out to be some work ran out of time this weekend but maybe by next weekend i can start casting the E.G. into the frame if i can pick away at it some more during the week and get it ready by the weekend? i know it's going to take a while casting this so i don't want to cut myself short on time. this is going to be one of deals once you start you have to finish it. but here is some progress of the mold.
well i have a mold but it's to late in the day to get into casting anything. i will have to coat the hard board with mold release and hopefully that keeps things from sticking, was trying to save some money on plastic. the hard board is pretty cheap. the top ended up being more involved that i thought but i got it sorted out today. not looking forward to mixing up this much E.G. but it is what it is i guess
Hi MD - What are you using for mould release? PVA works well. Not the glue PVA but polyvinylalcohol. Glue should be called PVAc. polyvinylacetate is the glue.
https://www.barnes.com.au/mould/pva-release-1lt-1227 cheers Peter
not sure what it is but it is for the epoxy i'm using to their specs. from the manufacturer.
Hi MD - paste wax? spray on silicon? liquid wax wipe on? any clues? Big cast needs a good high temp release. Peter
here is the data sheet. it's a general purpose release agent.
https://www.smooth-on.com/tb/files/ER205.pdf
this stuff is brush on. i think they might have a spray can option but i have the bush on type.
i did see it works from 70 to 500 degrees. but i don't work with enough of the stuff to know if that's good or not? i don't know how warm the batch gets when the hardener reacts with the epoxy?
Hi MD - The epoxies I use can get to 100deg C in a thick section. It says 500F so I've never seen a pour get to 260deg so your good to go.... Peter
Thanks Peter. i know you deal with the stuff a lot more than myself so the feed back was nice.i just looked to see what the manufacture recommended but have no personal experience with different products. i wanted to get to mixing this week end but i woke up late today and go back out to work tonight so that's a probably not a good idea to even try today. i have a feeling it's going to be a lot more than a few hours of work i'm excited to see how it all pans out but don't want to rush myself either
From everything I've read, epoxy granite does not typically get very hot, due to all the aggregate in the mix.
Gerry
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