Machsupport Forum
General CNC Chat => Show"N"Tell ( What you have made with your CNC machine.) => Topic started by: Sam on March 30, 2009, 11:55:51 PM
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Here's one of the parts I have made for my ATV. Made from 7075. Buffing had to be the worst part of it. Those micro scratches from the compound are a real pain to eliminate when your a novice polisher and don't understand what your doing wrong. I think I've finally developed a technique that works good for me, but I still hate doin it. I tried a vibratory tumbler to take out most of the manual labor, but I haven't found that magical formula yet. I've anodized a few 7075 parts with pretty descent results, but don't have any pics of 'em. Next batch I do, I'll snap some.
(http://www.sinistersam.com/pics/l2.jpg) (http://www.sinistersam.com/pics/l1.jpg)
(http://www.sinistersam.com/pics/pockets.jpg)(http://www.sinistersam.com/pics/path.jpg)
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Those look great Sam, what are they?
Brett
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Hi Sam,
The magical formula is to pass the parts onto Ed - he says that he loves polishing the stuff. ;D
Tweakie.
btw. Very nice work.
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Nice job, Sam, may I ask what your buffing process is? I'm sure I can learn a bit - ;)
Thanks,
Dave
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That is the master cylinder cover, Brett. There's a rubber boot that sits into the pocket on the bottom side.
I would be glad to pass them on to Ed for polishing. Only down side is that he would most likely want me to pay the shipping both ways, and pay him for the work. :)
Dave, first off, I wet sand to about 1200-2000 grit. Most people tell you not to worry about sanding to that extreme. "let the polishing compound do the work" they say. That may be true on some parts, but if you want to keep a sharp edge and detail on a part, your gonna need to sand it to a high grit to avoid as much buffing as possible, otherwise the compound and wheel will round everything off. YUCK! So now your wet sanded to a good polish. Go drink a beer. Maybe two. Avoid sitting down at the computer or television, your not done yet. You can definitely see a reflection prior to buffing. I have made a jig for my part to recess into, so I can hold the part firmly and get a good polishing stroke across the entire part surface, without worry of the wheel grabbing it and throwing it across the shop, thereby making it into a half polished paper weight. I made mine from wood, but will eventually make one from the same type aluminum. I would not make one from steel, so as to avoid getting the buffs impregnated with iron, and then the aluminum. That's just my theory, though. Then I heat up the part with a butane torch, getting it really good and hot. Hot enough that if I touch the compound bar to it, it has no trouble in melting. I want it hot enough that the cooling action of the buff wheel does not cool the compound into a solid again. When that happens, the now solid compound damages the part surface, and your back to square one sanding with 220 or 600 or whatever. That's definitely not a good thing. First, I use a sewn cotton wheel with a white rouge compound. Then I finish with a blue rouge compound. All strokes are fairly swift, and only a small amount of pressure is applied with the white rouge, and hardly any at all with the blue. I try to keep the part rotating as much as possable when I polish, to avoid getting grooves into it. After the white polish, there will be micro scratches everywhere. They will be most prominent at a certain angle of light. After the blue compound, there should be no scratches, no matter how you look at it in the light. All the mounting holes and engraving were done after polishing. Keep the buffs raked to a fluff, and never mix compounds on the buffs. Drink plenty of beer, and don't eat the yellow snow. I have no idea if color codes are the same across different manufacturers of compound. I use the buffs and compound from Caswell. I have not used the denim buffs *yet* to have an opinion on them.
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What is your preferred optimum buff wheel speed for, say a 10" buff wheel?
Also; there is an electro 'buffing' method that works very nicely on aluminum. Better with higher strength (>T4 treated alloys) and even gets rid of machining tool marks, but it's a mess of apparatus, power supplies, and chemicals to perform. I don't think Caswell has entered that area yet, but probably will....
Bill C.
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Well Bill, I'm far from being educated enough on buffing to say anything about wheel speed preference. I have a piece of crap grinder converted into a buffer. I think it turns about 3450 rpm, and I use 8" wheels. A 10" would give you a bit more speed, but I wouldn't consider that a problem. I think the slower speeds come into play with delicate materials such as plastics, wood finishes, and such.
If your talking about electropolishing, and if memory serves correct, I think the acids that are used are some nasty ones. I do believe you still have to get the part to a fine finish before you start the electropolishing process, so you may indeed be referring to something else, if it gets rid of tool marks.
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Only mentioned electro polishing in passing Sam. You're correct that it's more trouble and danger than it's worth to do just a few parts now and then.
I usually use the lathe spinning at top speed to polish. The arbor is a long shaft to get the wheel away from the headstock. Works OK but a grinder would be handier. There is always the risk of a knuckle making a divot in a chuck jaw - ouch!
Thanks,
Bill C.
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Thanks very much for the long (and entertaining!) process rundown Sam- ;)
I'm basically doing the same exact thing as you except I do not heat up my parts so that's an interesting tip. It's so true that wetsanding prior to buffing is imperitive to keeping the detailed contours which I had trouble with in the beginning.
I actually do some egraving before buffing but I must admit, using a toothpick and cottom swabs can be time consuming and tedious.
I also use wood blocks to hold my parts, I remember my first aluminum "missile" was a pickup ring for a guitar and the inside cutout caught the wheel and turned that thing into a parallelogram against the wall. Needless to say I won't make that mistake twice ;D
I would like to get one of these pedestal buffers that you can adjust the speed as I think that would be handy. I'm still a long way from being a pro but I'm getting good enough to be dangerous (as read above).
Thanks,
Dave
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Haha..good stuff Dave! I've made quiet a few missiles too! Guitar pickup rings are on my "to do" list also. I will prolly anodize them, when I finally get around to making them next century. It's a shame when you pay $100+ for a pickup, and you get a cheesy plastic ring with it. I too tried the cotton swabs with alcohol or acetone. The cotton always seemed to scratch the part up pretty good. When I didn't heat the part up with a torch, the part would always have what looked like occlusions in it after buffing, but it was really the hardened compound digging in. Heating it up to a toasty temp cured that problem. If you decide to invest into a good buffer at some point in time, Grizzly has a shop fox brand spindle setup for $110. http://www.grizzly.com/products/h3559 (http://www.grizzly.com/products/h3559)
Thanks for passing it along, Bill. I too have used the lathe at 2500 rpm to polish round parts. If you use some Eagle One polish (or similar) for a final buff you can get a great "chrome" look. (http://www.eagleone.com/images/products/Mag_Aluminum_Polish.jpg)The can is actually filled with a cotton material and saturated with oil or polish of some sort. It works absolutely great. Cloth with WD-40 works pretty good too, if you don't mind wearing it and looking like Alice Cooper on a bad makeup day. I too have had battles with chuck jaws. For some reason, they always win and I always loose. That's where a collet system would come in handy for small stuff.
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It's funny you mentioned the eagle one product as it's basically the same thing as what's called "Never Dull" and it comes in a metal can and is a cotton wading filled with the same polish you're refering to. I believe it's the original too.
(http://www.chrysalisacres.com/ShoppingCart/images/large/NeverDull.JPG)
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Sam Nice Part.. I was just wondering if you could answer a couple questions....
What cad, and cam program did you use to make this part.
What process did you use when you made the yamaha logo then how did you flip the piece over and have it all line up...
Finally.... How did you 3d model that piece from the original...
I am at the stage of drawing up a 2d piece in Auto Cad. Opening it up in cam then cutting it out... The 3d stuff or even making the z axis change height during the cut is my next step.. kinda like the U cut in the bottom of the cover..
and by the way my fav. polish is Mothers......
Thanks so much..
Kyley
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I used mastercam for the cad and the cam.
The logo I modified from the standard one. All the curves are arcs, not segmented splines. I sketched most of it, then cut vertically down the middle of the logo, deleted the remaining unwanted half, then mirrored the half to create the full logo. This insured the logo to be truly uniform, and eliminated most of the dimensioning.
I'm not really clear on what your asking about keeping things lined up. When flipped on the cutting table to cut the reverse side, the screw holes lined everything up. After buffing, the holes are countersunk. This removes any defects caused by the hole during buffing.
I modeled the piece from the original by using a good set of calipers to measure the features on the old part.
Eagle One has some great stuff call nano-polish.
(http://econtent.autozone.com:24999/znetcs/product-info/en/US/eag/1031605/image/6/)
I've used it on parts that are now 2 years old, and they still look good with no corrosion. My only complaint with the wadding type polish is that it gives everything a chrome look, instead of a polished aluminum look. It does do a superb job, though.
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OK All you buffers, ;D Yes , I've done my share of buffing, and it is a dirty job, but somebody has to do it. :D
I do my buffing with 8" cotton buffs on a 1 hp 3450rpm pedestal grinder. buffing compound , darker the color , the courser the grit.
Black , brown , red , white. I've never seen the blue, Block sanding is a must on flat parts to get out any waves, Start out with courser compound and work your way down , finishing with the white. Black is more dedicated to stainless which is a real bear.
For your finish hand polish , use blue magic, if you can find it. comes in a tube , or a can. I tried every kind of polish out there including ones mentioned in previous post, and found blue magic did the best job. all the others would leave a slight haze. BLUE MAGIC , did the job. like chrome
On machined parts , I use a scotchbrite wheel to take out the machining marks first.
P.S. Never heated the parts , except with the buffing wheels. :D
And , yes, it can throw parts all over the shop. Stay away from the top edge.
ED
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darker the color , the courser the grit
Good to know info. Thanks.
Blue has no cutting action, and is for use after the white. It's very dry. I always thought green was for stainless. The reason I heat the parts is because... the force required by heating the part with the wheel and compound, always altered the part in some unwanted fashion. So, instead of heat by friction, I use heat by torch after sanding to a fine finish, allowing me to go straight to white, keeping the most detail possible. Try it out sometime, see if it works for you.
Have you tried the flannel buffs? I thought about getting a stone like an Arkansas stone or a fine grit carbide slip stone to see if they would give a good pre-buff finish. Ever heard of doing that Ed? I'll hafta try out the blue magic. http://www.drillspot.com/products/457207/Blue_Magic_500_Metal_Polish_Cream (http://www.drillspot.com/products/457207/Blue_Magic_500_Metal_Polish_Cream)
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Steel molds are stoned with fine slip stones and water or light oil to remove tooling marks. Aluminum doesn't work too well with that type of abrasive since it tends to stick. I've done my share of stoning helicopter blade molds for composite construction with pre-preg graphite construction. They must be smoooooth!
A worker in the lay-up shop placing the pre-preg in one of these molds (about 26' long) left a 6 inch steel scale in the mold that was picked up when the finished and cured blade was xrayed for certification. About $80,000 worth of silly mistake.... I believe he is delivering pizza pies now.
Bill C.
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Sam ,
By the way, I didn't mention how good your part looks. Excellent job. Sorry, this post changed to buffing procedures.
Some years ago I used to buy a emery paste from a local plating shop. you have to keep it damp in a tube. I kepted it in the fridge.
You put it on a buffing wheel and let dry. It was somewhat like a scotchbrite wheel.
Then theres another where you roll the buff wheel in glue, and then a grit. which was made to hard by the cured glue.
Was ok for roughing. Aluminum foundry used it for pressure cookers which were all buffed on a big lathe. T hey were then finished with the red compound. Now those guys got DIRTY.
Ive also used diamond paste for polished steel dies for the final finish.
I still have a pretty good supply of 1" diameter scotch brite wheels and pads. Used to do porting work on Harley heads.
ED