Discussion in 'Project Logs' started by metarinka, 13 Mar 2006.
Take your time. Good mods take time to finish. But make sure we get to see the results :-D.
long time since an update, I've been squirling away on this case, in fact I've already started my next case and I'm using this one now. I might as well catch yall up to date.
*Here's where the fun begins and plans change on the fly.*
I had to scrap the copper rad, as the I can't buy in tool time or find a manufacturer capable of rolling copper like that and the hand die method I was using bends the soft annealed copper, so until then I'm back to a different design. Some projects just work like that, where you can change the design on the fly to what suites your needs or limitations.
Lets start by buying in time on a VF-2 which is a vertical CNC milling machine accurate out to the 1/10000" or 0.0001" . It also features a 20 tool changer and decent spindle speeds and feed rates. If you have to ask the price Walk outside turn back and look at your house. That will give you a rough idea of the cost of some CNC machines this particular machine cost around $60K with maybe $15K more in Tooling made or bought and other addons.
Don't declare the floppy dead just yet. The controller pictured on the right is still alive and well with only 2 real forms of input, floppy disks and direct computer hookup through parrallel printers ports if memory serves me correct. It's still a good machine capable of quite a bit with a skilled programmer and operator and when I find one I'll let him/her cut my parts but until then It's me left to monkey around on them. So lets get down to buisness I'm a little slow on setting up vertical mills but I had a decent amount of tool time.
the first order of buisness is tramming the vise. If you want a straight cut and true measurements you must know exactly where the part/vise is and the part/vise must be aligned correctly on the axis. It's quite simple, you just run a dial gauge indicator across the vise face and nudge it with a hammer to set it to +/- .0005" over 4" So now over the face of the vice it won't move more than .0005" in the y direction which is much more so than the tolerance of my tooling/parts. Once that's set we can sort out where the vise is
the vise is just sitting somewhere on the table and the machine doesn't know where that is, the easiest way to find it's location is to use a jump edge finder. When the jump edge finder is exactly inline with the part the bottom half will "jump" out and walk along the surface it's on. Long story short you subtract the radius of the jump edge finder and you know exactly where the center of the spindle is in relation to the vise.
Finally, you have to find and verify the height of the tool. Important note: make sure you override the coolant before you start the machine, or you have to deal with puddles. Mistakes like that lead to poo-your-pants moments when suddenly the machine does something unexpected due to a controller or programming error, luckily I'm cleaning up a puddle but sometimes that means buying new tools or new parts when things get detsroyed. I'm using a 1/2" 4 flute HSS endmill. I had carbide tooling but I didn't want to destroy $100+ bits when I made a mistake in my feed rates. In the back of the tool holder you can see the 1/2" aligning pin which comes into play in my program code.
Begin the fun. I had previously cut up roughly 30 1/4" acrylic blanks and then proceeded to manually mill them down to a uniform width 2.253" +.003" if memory servers me correct. Because of the way I cut them they all had 2 good surfaces on which to align in the X and Y axis.
I cut in stacks of 2-3 as any more and the flutes want to grab the material and pull it out of the vise, I'm taking a rather large depth of cut (.1-.25). Which happens to be the tool radius. The parts stick out either side of the vise, so I drop an aligning pin in order to align the part once one side is done the pin comes down again and I align the parts again. This way no matter what the length of my part the final piece will always come out the same length (which is nice as they were just rough cut on a bandsaw)
Here's the pin in action on a half cut part that needed to be realigned. Nothing is scarier than the spindle and solid steel pin flying down in full rapid to .5" above the table and maybe .0005" off the end of the part at those speeds you can't even hit the e-stop before the tool part and spindle are damaged. Just important to make sure you machine is set up right and the code is good.
Here's a sample of the code I used, I wrote it on the fly and it was rather sloppy and impromptu. It would of been more slick and versatile to use a pocketing cycle and some subroutines so that I could vary the length on the fly by changing 1-2 lines of code. It would also shorten the code and be a little easier to work with.
Kudos to anyone who understands this and congrats if you can find my mistakes.
well in all the excitement and rush I forgot to take a picture of finished part although it's a rather unassuming oval, here is a sampling of what is to come next, the bending of the finished parts.
I hope you like this project revival, It's a fun case and I enjoy using the monster and can't wait to take it to lans. CNC machining is interesting and complex skill but if you invest some time and money you can create virtually anything. For instance the guy next to me was cutting a finned tranny pan for his hot rod pickup, quite interesting and crazy seeing how it's one giant block of billet aluminum (hey it's his money)
More to come in the near future. Stay tuned and input is always appreciated
Wish I had money for a CNC...
So do I
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