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- Опубликовано: 12 сен 2024
- In this video I test drilling smaller holes in aluminium using a single flute carbide bit, and exact sized cobalt stub drill bits on the CNC machine and pillar drill. I'm trying to derive the best method before cutting out new plates for my CNC machine.
Pockets Video on tramming pillar drill base: • Square your drill pres...
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UPDATE: I just gone from a zig zag ramping move during an area clear, to using a spiral ramping during an inner profile tool-path and it is cutting a lot better - and quicker!!! Cutting speed is 200mm/min and 1500rpm. Using isopropanol in a syringe as a coolant.
I'd personally use a small bit to create a pilot hole. The center of a drill bit doesn't actually cut so the bigger the bit the more issue that causes. The bit has to push all that material out from the center into the path of the cutting edges so if you remove that material with a smaller bit first there's a lot less work for the full size bit to do.
this and also he's trying to achieve an accurate bore via just a single bit, that's not possible at all
a jobber will cut in an almost triangular shape when you look at it through an electron microscope
it will cut jagged/staggered making the wall of the bore stepped no matter how good your rigging is and and will cut over the size of what it says on the bit
so if you want a hole of a specific diameter it's almost always a 3 step process, drilling, reaming, lapping.
1. drilling below the size of the bore you want by about 90-95%
2. reaming out the hole with the finishing diameter
3. lapping to create a smooth polished consistent finish which can also be used to even more finely tune the bore
I think a 135 degree drill bit has cutting edges on the point.
Savvas, you need to use a centre drill bit first then step up to the size hole you need. For ultimate accuracy drill 1/64 under your required size then ream the hole with a reamer of the correct size, but at an extremely slow speed.
One of the biggest surprises when you learn engineering basics, is that you are lucky to get 5 thou accuracy, but more typically 10 thou error, when drilling scribed and centrepunched holes. There are tricks, but variance is common between holes, using one apparently identical method to mark out.😭😭😭🤣❤️
Hello. I use a centering drill 1.6mm/4mm so i do a mark with that first. Sorry my english. Greetins to you
I had the same experience, my collet isn't precise enough, having a run out of 0.1mm there abouts, enlarging the hole by 0.2mm. The gantry flex lets the spindle slightly rotate around the gantry axis giving oval holes. The stiffness of the x is different compared to the y axis so using an end mill gives oval holes too. I'm ging to order much more precise collets with runout of about .005mm. Drilling a hole with 3mm first works for me, with 2mm/s feed rate and step down of 1.5mm. this is for soft aluminium 1050A.
Thanks for sharing that. Also using a ramping toolpath will help take some of the load off the tool but it adds a lot of time to the cut.
IMHO this is not a bit issue. Your CNC is just not stiff enough for that job.
Axel Sixtysix Yeah I know. But I don't have another CNC machine. :(
Not bad, you own a CNC, so you have all what you need to make better upgrades. I would replace all the plastic parts by thick aluminium ones. You've got a good spindle and electromechanics seems to work well. You just want a better chassis.
This trick can help but this is a short time solution.
I know this is necroposting but I had the same problem. Lots of chatter and annoying vibration even when moving on the X axis (most people call it the Y but I find it easy to imagine the X axis being the long travel and the gantry is the Y)... I found it was my upright plates being slightly out of true and the gantry was actually twisting.
Imagine when you push up on the end of the drill bit and the gantry isn’t getting forced up... it’s actually trying to twist because the spindle isn’t pushing up on the centre of the span... it’s offset and that wants to make the spindle rotate on the gantry axis... but then it says “nope” and tries to force it back in the hole.... which is why you get the vibration and slightly elliptical holes.
I ended up running bolts through my gantry span to hold both pieces of 80x20 v-slot together and stop them twisting apart. I also upgraded from aluminium uprights to steel plate and while it increases the weight it’s actually stiffened up the whole CNC gantry assembly.
I’ve also got a pro tram mini from Edge Technologies. It helps when tramming up. That reminds me... I need to tram up again as I just put a new sacrificial board on. Better do that tomorrow after the skim.
Moral of this story is, the stiffer you can get the gantry, the more accurate the holes you will get. I pretty much gutted my old gantry and my OX is now like a hybrid of OX and Workbee. Oh yeah, the Z axis on my original build was totally loosely-goosed. Gave it the equivalent of the little blue pill and now my Z axis is totally stiff..😂
Neither spacer or your holes are round - if either were perfectly round, the shape of the other wouldn't matter. That's not unexpected really, as even a 0.01 mm cam make the difference between slip fit and a light press fit. Add 0.02mm to the shaft and you'll need a press to put them together.
In the scene where you demonstrate bit wobbling you can clearly see it's not just the tip - the collet is moving as well, which means the machine is simply not stiff enough.
Any bit, mill and drill alike, doesn't cut in the center - it just pushes the material around making it want to walk around that high spot.
I suspect best you can do will be using a smaller center drill to start the hole for about 1 to 2 diameters deep, moving on to a thin stubby drill to make the through hole, then getting in there with the slightly undersized drill or mill and finishing with helical drilling toolpath in one or two passes. First two drills should have diameter about equal to the size of the chisel top of the slightly undersized drillbit you'll be using, and that one should be undersized enough to allow you at least two 0.05mm passes (or whatever you feel conformable your machine can do per pass). In reality you'll probably be drilling 0.5mm undersized, the first helical path should bring you roughly to where you want to be and center the hole from any offset the previous operations introduced, while the last one should give you nice round hole as the bit will have even cutting pressure all the way around.
When you get to the point where your holes are good, you can start dropping some of the steps to see if you still get good enough results. For smaller holes
The power in these HF spindles is very low on anything bellow 6-9000rpm. (their torque increases as their RPM goes up to about 6000rpm, but at 6000 rpm they don't yet have their full power available). The thing with HSS is that it's not suited for high RPM's. (SFM is low) You could use carbide, but then you probably won't be able to meet the minimum chip-thickness before reaching the stiffness limitations of the machine. (although aluminium won't wear out your tool as bad as harder materials) Best way to make holes is to use a 1 or 2 flute in a circular ramp down with a few finish passes at the bottom. The reason why you can't 'climb up' to the correct size without the drill walking is because the drill is centering on the tip and the soul of the drill. That soul and tip require material to center on. It's also a fact that rolled aluminium has some variation in density, which also causes the drill to choose the path of least resistance.
The reason it bibrates is because the feed is to low for the RPMs. Aluminum likes fast feedding. For acurate holes you have to drill first with an undersized drill then finish it by milling around.
Hi. Can you undersized the drill bit and then use a reamer? Great videos.
I wonder if a bit lower speed would help. and a center drill is a must for drill bits!
I think if I do go for aluminium to make future plates I'll spot all the holes and drill those on the pillar drill - and machine the rest.
Doesn't a 118 degree point help. An slow speed with lube.
I need suggesting my product as i need side holes drilled accurate to match the assembly then 6mm aluminum 6061T plates to form a frame structure
Hi savas, I just happened across your channel. We actually have very similar machines. I also went down the ply plates to start and then used the machine to make delrin plates. Am I right to assume that the delrin machine is now making an aluminium plated machine?
If that is the case what’s the problem with the delrin. Mine is only a few weeks old so has had limited wear. Is that going to be problem?
It looks like you are adding adjustment to the x carriage to help tram the spindle. I had this problem too but attacked it a different way. My spindle is supported using a top and bottom clamp approx 120mm apart. I machined the top bracket to an exact 65mm internal dia, and then I used an open builds 71mm bottom mount with an eccentric bushing machined from some left over delrin. By twisting the bushing I was able to dial the spindle to be perfectly square to both axis. Just some food for thought ......
Hi James, yes it is cutting aluminium. I'm just having to learn about correct feeds and tool-paths for that material. There is still slight flex on the spindle, albeit less than when I used the ply plates. Also my design has changed, so yes I am making pivoting plates. I would be curious to see pictures of your mechanism? I think I'm going to spot mark all the holes on the CNC machine, then cut the plates out and finish the holes on the pillar drill.
I think every engineer of any varying experience has encountered this. Unless you are sitting on a major chunk of cash, then it's always going to be a softly-softly approach. But in this case I'd be looking at better methods of holding the item and ramp it a lot more.
i would say the speed is to fast in the cnc machine...the chips need time to get out of the drill bits way..its just too Fast ok man
What's the slowest speed an air cooled spindle can run at without overheating?
Mmmm i do not know that...but i have drill holes in metals in the past and the slower speed and oil and a slow feed gets a better result...but the was on a mill and drill press...never used a CNC air cooled spindle...ok sorry i dont have the answer for you..;-p
My guess, 5,000 rpm. I put a speed control on my trim router that gets down to this speed and it runs cool. I use that speed for my drilling ops.
You are spinning too fast for standard drill bits.
You need to learn how to make a video. Most of the close ups are out of focus. And your audio is "thumping". You talk softly but too close to the microphone.
I like to make bad videos because no one will steal my footage that way.