Practical approach to milling sheet metal

ah excellent on this very important flux capacitor part out of stainless steel all that's left is to not out this corner this will be piece of cake with 4 mm carbide endmill just take it in one pass and we will be done and can ship this part so Doc Brown can go back in time ah excellent a quick debur and can go off to the customer that went marvelous he welcome back if you ever had to Mill stainless steel or other sheet metal on a manual milling machine and you tried an approach like I just showed in this very dramatic Recreation um you might have seen a very similar result a lot of heat a lot of uh smoke if you're for example using a piece of wood backing plate uh an absurd amount of bur and the tool life is very bad so I learned this the hard way too I burned up a lot of Cutters doing metal work on Milling machines because often regular shield Metals tool were either not available or we needed a higher Precision on certain parts so we went for Milling this is true for both CNC and me manual Mill in this didn't burn and bur up because my speeds feets were off these were very reasonable speeds uh 2,000 RPM with 4 mm for flute carbide endmill which is suitable for stainless steel but still the result is not very nice and today I want to show you a few tricks or the main strategy that I picked up over the years to do extremely reliable sheit metal Mill both on a manual machine and on the CNC milling machine and especially for the CNC machine if you run a machine with very high speed spindle I will give you some outline for speeds and feeds that will work always I I have used them countless times and I've given them as a recommendation to people countless times and the feedback always was like ooh that worked so uh let first first let's start by looking at what happened here on this smoke machine the overall setup is all okay um we're clamped down with three strap clamps we have a back fence so the our part is straight we have a wooden backer plate um you can use something different here too wood is fine in my book wood or a piece of phenolic fiber reinforced phenolic is also nice for a backing plate I wouldn't use plastic because uh when it melts it gets a real mess um for real Precision work a piece of precision aluminum plate is nice like um the the two-sided parallel mil material uh that's a nice backer but something for if you need for example to make an enclosure and need some precise cutouts and a few whole patterns uh piece of plywood is absolutely fine the cutter I'm using is another topic don't go too big on the cutter if with with sheet metal the bigger the cutter you the more trouble you will get it will start to vibrate this is 2 mm thick stainless it's relatively stiff for the size of piece of material but it's only stiff within reason if we tried to we can use a cutter like this on here and do a small cutout for example if we need the large radius and we don't have access to a CNC mill then we can use a cutter like this to cut create a cutout but in general this is better done with a small endmill don't be scared of smallish endmills a 4mm endmill can do a lot of work and give you great value for relatively little money so sheet metal from a certain material like in this case 14301 stainless steel behaves very different in a sheet form than say round stock or flat bar the the the sheit metal from the from the Rolling process has very different properties and therefore machines very differently as you can see here by the ginormous bur created and the heat created um the the huge smoke cloud that we made was the heat from the cutter burning the Pate of course so a full slotting approach in sheet metal is often the worst case that you can try to achieve what works in my experience the best is to use a high-speed approach we you we max out the spindle of the machine in this case 2,000 RPM and we feed very fast but with a very low depth of cut yes this will take longer but also it will first of all yield a nicer salt and also cutter will last longer and it's overall just a nice result so let me let me show you the general technique since I don't want to waste a whole lot of sheet metal for this demonstration we're just going to take another bite that this cut out for this to work um it's good to have good layout lines so let's say we it's a good idea to to lay it out I'm using the Dr now then I'm just touching off in C on the sheet metal and then I will take1 mm deep Cuts uh relatively fast let me let let me demonstrate [Music] okay I went down 1.8 mm in 2 mm increments I notice that it's working quite well and so I stepped up my depth of cut and now I have 2 mm left and I will over overfeed this I will go down to 2.5 mm so I'm cutting into my waist board into the spoil board below the metal and this approach gave me an extremely clean um cut out and this approach gave me a very clean edge with almost no bur there is a little bit of bur of course this will knock off very quickly with a file or if you feel very fancy with a with a deur endmill but there even the sidew wall is very clean this low depth of cut very high feed approach Works comes more or less from the CNC world it's a high-speed strategy but it works on a manual machine just as nicely and this approach works it's very useful to cut sheet metal but it's also useful to cut other things um can be used to cut hardened materials very effectively with a very good cutor life it can be used for Sheet Metal it can be used for uh if your setup is very flimsy if the machine if you have a a very light duty hobby machine like a SE mini Mill or something like that or a SE X2 uh this approach works very well this usually works better than trying to do a large step of cut and a small step over on a soft machine the like um like many people do adap the strategy a very high depth of cut and small step over that's a different high-speed strategy which requires a little bit of a stiffer machine low depth of cut High feed works better on soft machines in my experience we can do one step better let's say we want the edge to be a little bit cleaner then we would do the the slotting the high-p speeed slotting with a little bit of material allowance like 2 or3 mm and and then we take a climb Milling pass it full depth to clean it up completely as can see when I blow away the when I blow the chips away so when I take a screwdriver you can see the Reflection from the screwdriver blade and the sidewall finish of the sheet metal and that should give you a good idea of how good the surface finish here really is and uh yeah a cheat metal and we cut it dry and and the cutor will last forever doing this I've done this on the CNC on CNC machines in general to Great extent and even in overnight runs and it's just working each time I tried to do a high depth of cut approach on sheet metal it ended in tears okay another view at the at the cut we just took um as you can see with the screwdriver again there is quite the okay surface finish especially considering that it's just cheap metal and not a particular high quality material and if anything just the the nature of the quick deer necessary for a cup like this is worth the extra effort in my mind yes it takes a little bit longer but also you're not dealing with uh a bird that's just annoyingly big to be removed [Music] [Applause] [Music] n [Applause] different machine this is the CNC router or CNT Mill and I just used the same technique very small depth of cut but rather high feet in this case I was spinning the cutter at 12,000 RPM and feeding at500 mm per minute and the result is basically the same we got get a rather clean and very process reliable cut but you might notice that there is quite the nasty bur here and this happened at the very first pass as you can see here in the replay when when the cutter took the first pass it went rather deep into the material that's just caused by the matter that sheit metal especially when you clamp it on a p piece of plywood is rather unflat it's not parallel to the ways of the machine so I would recommend to start above the material like 0.1 or2 mm is enough in most cases then you just take air Cuts until you reach the material and then you will start out with birre cut also another thing that you might notice there is this little clamp holding the cut off um that's that's kind of an important piece of the puzzle if you do when you do this on a CNC machine because if you don't clamp the waist down you do not know what the waist will do it um it often tends to on the on the very last past fold up and then the cutter kind of catches it or sometimes even funnier the cut off gets flung onto the remaining material preferably in an area where the cutter will will next plunge down and bore a hole then you have to then you have a real problem then the cutter will try to to plunge down into this loose piece of stock so um either machine it away completely create make it entirely into chips that's uh my preferred method on internal cutouts or clamp the stock down if it's just like like one piece that you're removing um for work holding as I said said clamps are fine if the part is not too big double-sided tape uh super glue works extremely well I have shown that in the past for Sheet Metal so all all these methods work let's flip it around and and do another try with the CNC with starting starting to cut in the air so you see that we can get a burree result [Music] [Applause] uh second try with starting in the air and by the tool marks you saw that the material was far from Flat that's two reasons first of all the plywood subplate here is not very flat to begin with secondly it's soft so if you clamp it in two places it wants to deform and thirdly this thin sheet metal when you clamp it down also wants to Bow up especially if you're clamping down on a soft material but this gives us a very birth result that I'm not crazy careful to touch without cutting myself so that's the reason why I prefer the strategy for Sheet Metal and on a CNC machine you usually get away without doing a finishing pass finishing clim pass because the machines are repeatable enough so the individual step down Cuts blend nicely I want to talk about the cutter later because there is one important thing about the Cutters you don't need to buy a very expensive cutter for this technique any old cheap carbide ill will do but you have to look for one thing if you want to do this which makes this technique so much better than with uh different endmills you will see we have two carbide ills here um they're not the same diameter but that doesn't matter for what I was want to show you uh approximately same Helix angle same flute count but there is a tiny difference when you look at the end of the where the where the spiral flute meets the front Cutting Edge this endmill here on the right it has an sharp edge and this one has ever so slightly of a chamfer this Edge chamfer makes this technique in with a small depth of cut and a high feed so plausible and so well working and as as long as you stay within the Wii of this corner chamfer the cutter will last forever if you do this approach and you will not really wear the end of the endmill you can get several hours in the cut out of an endmill with this technique and this approach without a problem so if you want to do a cutting approach and metal like I demonstrated whatever you do try to get an endmill with either an edge chamfer like this one or an edge radius in my experience the edge chamfer works better the The Edge radius tend to put a little bit more axial Force into the part then is really necessary for cutting sheet metal so try to get one that has an edge champer why does the the chamford corner of the endmill help us with cutting sheet metal with this highspeed High feed approach well I've have drawn two endmills here uh Center Line Center Line this one has a sharp corner and this is a chamford corner one green is the material and I have drawn in a block of um material the length here the distance here is feet per tooth and on a 90° end that equals the thickness of the chip it's just how much material it removes per tooth per rotation and when you measure that that's the chip thickness when we go over here with the same feet per tooth it feeds the same distance here but when we measure the thickness like this the chip gets thinner over here we have like uh 10 millim and over here it's substantially less it's only like seven means we could feed this endmill way faster than we can this endmill to get to the cha same chip thickness also second effect 90° corner is more prone to chip away because it's well it's a sharp corner then a 135 degree corner on on on a chamford ant Mill there is way more material backing it from behind making it more resistant against chip out or general abrasive wear or too so that's the two reasons why why the chamford corn mod works very well for this technique and a third General benefit of this process with a very shallow depth of cut and the high feet is the endmill has spiral flutes and these flutes when the Tool spins tend to pull the work upwards away from your work holding and the more fluids that are engaged the more of the the pull pulling Force you get and the result is vibration and birth and just the whole mess so if we keep the depth of cut extremely small the effect of the of the Spiral is almost neglectable so that's that's the that's the the main secret behind this technique chamfer corner endmill and the very shallow dep of cut for minimal axial forces so when we look here in the catalog and the cornner chamers on these Cutters for example start at 1 mm below 1 mm they are sharp cornut so that's something you have to look in your tooling catalog or from your get the information from your tooling supplier if you want to try or if you want to benefit from this technique in general the corner Cham for animals are a little bit more robust especially when you do steel and stainless so I hope you enjoyed I hope this is somewhat helpful I often see problems when people try to Mill mild steel or stainless steel sheet metal [Music] and uh it gets all nasty and burned and just not very nice so might be worth worth to try it this way thank you all for watching and I'll be [Music] back

Channel: Stefan Gotteswinter

Views: 62,366

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Id: WzT4HJalwAs

Length: 25min 18sec (1518 seconds)

Published: Sat Mar 30 2024