Now for the Ta Da! moment for the connecting rod with the bronze bearings in place.
With the wrist pin alongside.
There's another piece I started and made good progress on, but it's not quite ready for its photographic session yet. This is a beginner's engine and so a lot of parts are acceptable without touches that might be done on a more advanced engine. One of these is on the crankshaft. The shaft itself is called out as just a piece of 5/16" Cold Rolled Steel. I found a piece of drill rod in that diameter at one of the metal dealers and that became the crankshaft. The way the end of the crankshaft is drawn, this is unbalanced (left side of this picture shows the end).
I've seen various solutions to this; some guys use the square tab for the top and then go into a semicircle for the bottom. That seemed like it would be trading one imbalance for another, so when I saw the idea on the right here, I thought I'd opt for that. It's roughed out on the mill but not ready for prime time.
I spent some time on a problem with my Fogbuster cooling system. It stopped misting the coolant although the air flow is normal. I've done a couple of things to try to fix it and haven't gotten anywhere. I cut out the outline of that sector of circle with no liquid, just the air blowing and while the aluminum chips didn't melt onto the cutter, the metal came out looking like I'm not used to seeing. Shiny but looking ripply. Almost as if it had melted and then quickly solidified. Some of the aluminum cut away was still warm when I picked the pieces up after cutting. I don't think I'll be doing much cutting until I get that fixed. Maybe some of the smaller parts on the smaller machines.
What sort of rpm and cutter dia. are you running on aluminum?
ReplyDeleteThe conn rod and that circle sector were cut with a 1/2 diameter, two flute end mill. My G0704 maxes out at 2250 RPM and the last few pieces I cut 0.050" deep slot passes at 25 IPM.
DeleteI have a speeds and feeds program from CNCCookbook.com, and it always tells me to cut at max RPMs. The feed rate is slowed down from what it says to help with the appearance.
A lot of those tables seem to emphasis productivity AKA making money. The chip load is the issue.
DeleteI do not run constant coolant on the mill, so usually run much slower, 500-1500 rpm using a three flute zrn coated tool. 60-200 SFM. with a chip load around .003-4 or so, about 4-18 ipm. At the lower speeds, there is no smoke from heating up the lube. This is all standard power feed or hand feed. Sometimes a small change in speed or feed can make a dramatic difference in finish, if there is some harmonic going on.
It would be an interesting test to setup a few coupons of 6061, with varying speeds and feeds and DOC. I have taken to writing down combinations that work well , for the various cutters.
A lot of those tables seem to emphasis productivity AKA making money. The chip load is the issue. It's almost entirely what they sell. The software I use is called G-Wizard. By default, it's set to tell you fastest practical speeds but it has a slider to bring it down depending on if you prioritize finish over speed. When I first started using it, I think it went way too fast, so I learned to ordinarily use it at 30% of speed. I've rarely, if ever, gotten finishes that look great.
DeleteThe trade-off is that slower feeds result in more tool wear, and the emphasis is on that optimal chip load per tooth.
The way he has the pricing set up is that if you're using a machine with a 1HP or less motor, you buy it once and then it's free for life. For bigger motors, there's a renewal term. Come to think of it, I think he recently raised that to 2HP. Either way, it's on the honor system.
Looks great, SiG!
ReplyDeleteBeen decades since I made itty-bitty microwave/millimeter wave parts from aluminum and brass, but it was always rewarding to start with a print, make the parts, and then see if they worked as expected.
I've hogged out aluminum for a project box, but that's my only radio use so far. Making a box that way is so wasteful it bothers me, though. Turning a 2x2x1 block of metal into a 1/8" thick shell and the rest a pile of chips just doesn't seem right.
DeleteHAH! I've seen slabs of aluminum the size of a small car whittled down like that to make aircraft and spacecraft parts like that.
DeleteThe little things I made could be held in your hand, so I wasn't "Chips-R-Us"!
That con rod looks nice. Do I understand rightly that the crankshaft is a 3 piece assembly? An assembly fixture may be called for. It turns out that 2 stroke motorcycle engines use a pressed together set of crankpins and side wheels and main shafts. Some mfgrs used to sell parts, others only sold complete assemblies. The built up construction is needed because they use ball bearings for the rod and main bearings, and there's no way to clamp a ball bearing assembly around a shaft. Point, the cranks that you could rebuild needed an impressive array of surface plates, vee blocks, and indicators. And big presses, and, if I recall, mallets. I passed on all that.
ReplyDeleteFrom what I see of that mister set up you have: a common air supply pressurizing the coolant container,then both lines come out of the tank, then on to the mister unit. A needle valve then controls the flow rate of the liquid side. It is actually very elegant in its simplicity.
ReplyDeleteFirst thing to try would to see if it is getting liquid out of the coolant tank, by disconnecting the liquid hose at the mist unit. I would dare say that this isn't going to be the issue, but it will tell you which side the problem is on. If no fluid comes out, under pressure, then the filter on the bottom is plugged or the passage through the housing is obstructed.
More than likely, the mist unit is gummed up around the needle, or the needle itself is corroded. I've seen it hundreds of times on small engine carburetors. Pull the needle, polish it up with some Scotchbrite. Then carefully make sure the passages are clear with a torch tip cleaner. Using a rubber tipped blow gun directly in the needle passage to force any gunk through the jet and liquid inlet.
Probably take less time to do, than for me to type.
The counterweighted crank will probably help somewhat with vibration, which in turn will make it run smoother. Wasting less energy fighting vibration should lower the power needed to run. Efficiency is all in the details.
Looking good, SiG.
Leigh
Whitehall, NY
Ritchie - it's probably a simpler engine than any you've seen. This animation is probably as good a look at it as any of the videos:
Deletehttps://www.youtube.com/watch?v=3EQwegIi5JM
Leigh - let me tell you what I've done. I disconnected the dual hose to the sprayer head and the fluid came out of the hose like any siphon. I had to put a clamp on the hose to stop it from emptying the bottle. It's about a foot above the sprayer head, so it was flowing downhill.
That implies the tank and its plumbing is working. Then I disassembled the sprayer. I put vinegar into the fluid tube's connector (the barbed piece) until the vinegar came out the top and let it sit for 5 minutes. Meanwhile, I took the needle valve and cleaned it off with vinegar. There was just a little white stuff on it that came right off. No soaking, just brush. I can shine a flashlight into that connector and see the light on the top side where the needle valve goes. I don't see anything in the sprayer. I put the hoses back on the sprayer - still doesn't work. Then I cranked up the pressure on the tank (feed to the sprayer) from the normal 15 psi up to 30 psi. Again, no change.
I guess it sounds like I need to go back to the sprayer head.
Yeah, it sounds like the issue is between the needle and the outlet orifice of the spray head.
DeleteLeigh
Whitehall, NY
For completeness - I seem to have fixed it. It worked for a while yesterday, not long enough to cut a big part, but a small one.
DeleteI took the needle valve out of the sprayer, chucked it up in the lathe and cleaned it up. A touch with a file, then 240 grit paper, followed by 320 and 500. There was depressed ring in the needle near the tip - it was gone by the time I held the 240 paper on it, so not very deep. I'd have thought that would have made it leak, not stop up, but I'll keep my fingers crossed and try it again later.
Sorry to "unlurk" but I have to ask: your fluid is above the outlet, and you DID have flow out of the tube - but did you check that your air inlet to the tank is clear? because the mister nozzle requires pressure.. (dont ask me why I thought to mention this :-)
ReplyDeleteWell, I get lots of air at the sprayer and I think it has to go through the top of the tank to get there, so I'm assuming that part is working.
DeleteHere is a design for a fog mister. I cannot vouch for the design and came accross it when I was researching flooded vs mist cooling for machining operations. But one concern I have about any mist systems is the inhalation hazard of coolant chemicals.
ReplyDeletehttp://www.machinistblog.com/zero-fog-mister/
Thanks.
DeleteI know one of the aims of the Fogbuster is to reduce mist that can be inhaled. FWIW, I'm not aware of inhaling it while working.
Flood coolant is more effective for sure. It just has to be a design requirement from the word go and I'd have to tear up a lot of my modifications to switch over to flood.
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ReplyDelete