I have searched this and found a few related posts but no clear answers. I guess all I am asking for is a sanity check. So far I have not been happy with the results and I want to make sure I have the bit entered correctly.
I have a Tapered Ball Nose End Mill 1/4" Shank with 1.5mm Ball Radius 4.82° Tapered bit I picked up from Amazon. I am using the bit for finish pass 3D cutting of an STL file. (Also fyi, I am using Estlcam 11.117 as CAM and controller, but I see there is a newer version out.)
I get that I am supposed to enter 180° for the tip angle on ball nose bits. So, I entered the full shank size as the bit diameter, and the tip radius as tip radius. There is no place where I enter the bits taper–is that ignored? Is the shank=diameter correct? Or should I use the ball size as the diameter?
I see that I halved the tip radius in my tool list, which is part of my problem. Still, I would appreciate confirmation on the diameter question and reassurance that there is no need to enter the bit taper.
I think the angle is what would cover the taper. Something like 175 degrees or something. You could measure the width at the bottom, the width at the top, and the distance between them and then do the math to figure out the angle.
If you are using it for 3d finishing pass, just enter it as a ballnose with radius of 1.5mm. The taper does not matter unless you are trying to do some type of vcarving with that bit.
The taper is 4.82° for an overall angle of 9.64°. (That was not in the graphic but was part of the item description.)
The issue I was having is that if I enter the diameter as 1.5mm based on the tip then the taper does present a problem for deep cuts. Even as deep as 10 or 15mm it cuts well into the side of the object. If I enter the diameter as 6.35mm then I need to use a extremely small stepover value (the minimum is 2%,) and any crevasses narrower than 6.35mm are ignored, no matter how shallow they are.
I am not happy with either solution. I was hoping that someone might have figured out another approach, but I really don’t know what that would be.
Normally those are for cutting molds with built in tapers, no special CAM is needed, or for models that did not include a taper but need one to release.
The only reason I would buy that would be for precise deep carve (super long job time). You could either cut it all the way out and have no sidewall to deal with or just end up with tiny sidewall taper. What you bought was a tiny ball end (that requires a tiny step over) on a rigid shaft. I would input it as such and ignore the taper as it serves you no purpose it will either limit your depth or your width you have to pick one as you can physically not have both.
Also, I read in another post, which I believe was from Christian, that the tip angle is only used in the Carve operations and that the tip radius is only used in the 3D operations. I can’t swear to that because I cannot find that post at this moment. However that is the assumptions that I have been working under.
There is an amazing availability of tapered ball nose bits if there primary purpose is to be a specialized bit to taper the sides of moulds. I am not doubting that they are used for that purpose. But people who do carve 3D models with a CNC also use them–extensively. And you are correct, the process is by no means fast.
The taper adds reach and rigidity to the bit, and they are used for the finish pass of a 3D carving.
Setting the bit diameter to 2x the tip radius does not work. the sides of any cuts deeper than a little more than the tip diameter are cut away as the bit tries to clean out the bottom of the hole.
Setting the diameter to the shaft size also does not work. Any detail smaller than the diameter is ignored, even if the tip itself were actually the perfect size to cut it.
Estlcam and Christian are very clear that for ball nose bits you are supposed to enter 180° for tip angle. The tip radius is what is used for 3D calculations, and the tip angle is for V carves.
I simply don’t see a working solution within Estlcam. It appears that you MUST use a straight ball nose bit to finish 3D carves. Hopefully you will find a bit long enough to reach the bottom, strong enough not to break, and small enough to get in and carve the detail parts.
I think I understand about Estlcam not specifying the bit, but I am not clear on what you are doing that it matters.
Am I correct you have a model with vertical inside walls and a smooth 3D bottom, and you want the unreachable inside vertical corners to be left behind and not carved?
And then are you performing a tool change to come back and do the inside vertical corners or you are wanting to leave them in the finished product?
If you are wanting to leave the sloped sides in the final product then you might benefit from having sloped sides in your model because that would allow you to rough out with a large bit and then come back with the ball nose just for finishing. In that scenario it seems telling Estlcam you have a straight ball nose would be okay.
You haven’t said what sort of things you are trying to do with it. I understand you want perfect representation of your bit but as is it works for 99% of use cases. 2x radius makes it a straight shaft and in deeper cuts you end up with a very tiny draft angle on your walls, which is exactly how I would use this. Or in trying to avoid the angle you will limit your depth. If your model does not include the angle and you are trying to cut so deep the taper gets in the way I don’t think this is the bit for you. You could set the shaft size thinner than in reality you could cut deeper. So if you measure the diameter at the depth of you deepest cut, use that as a workaround or deal with walls tapered matching your bit. I am not seeing how it working in CAM perfectly would make any difference?
As an example, if this was perfect in CAM you would still get limited depth because of your taper at some point if the walls were too steep and the cut was to deep. So that leads me to believe whatever you are doing is just not suited for a taped bit. Without a 4/5th axis you will always get tapered walls and limited depth.
I am uploading a jpeg of the model I am currently wanting to carve, two horse heads and a wagon wheel. It will be about 10" wide. https://imgur.com/a/ddLEdm3
I don’t mind at all if the sides of the areas that are cut away are sloped. I just don’t want that slope to be at the expense of the parts that are to remain. In other words, sloping down and away from a top edge is fine. Sloping up and into the piece is not fine. Estlcam needs to know that my 1.5mm ball nose bit is actually 5mm wide when the tip is 20mm deep in a piece of wood.
For example, in the above model, if I try to clean out the gap between the two dangling straps, then the straps themselves are nearly completely removed by the overcut because of the taper. That can be avoided by setting the bit diameter to 6.35 but then I lose a lot of detail. The wood grain, the belt buckles, and more disappear completely.
The bit pictured in the first post was to be pass number two with a third pass using a bit with a 0.25 radius ball nose. So, if I can’t have the taper for the reach and strength it offers, then I will need to get a 0.5mm ball nose end mill with a 29mm depth of cut, and try not to break it.
There might be a workaround by adjusting the model. I have tried this before when making molds for casting, using OpenSCAD and its minkowski operation. The downside is it takes an eternity to render the modified model. If you have an STL published somewhere I can give it a shot as an example. With the modified model that has tapers built in, you could tell Estlcam that you have a straight ball nose.
What about defining it as multiple tools? Set it up as a narrow ball-end for shallow finishing and detail, or wider for deeper pocketing. Then just be judicious in which mode you’re having Estlcam generate gcode for. Added benefit: tool changes are a breeze!
The problem is the narrow ball end needs to avoid the inside vertical corners or else the wider section higher up will cut too much and ruin the edges of the shallow areas. Estlcam would need to know that those inside vertical corners are not reachable with that bit.
That’s why I said judicious use… You’re absolutely right that there would be locations that one tool definition or another would be inappropriate or downright harmful, but with careful planning it could work.
Thank you for that, both simply understanding the issue and for the offer to help. The model is paid and copyrighted, I do not want to be the one responsible for it escaping into the wild. I will send you a PM with information. I am new to these forums–I am assuming there is a private message function.
That could work, I agree. And that is the out-of-the box thinking I was hoping for when I first posted. I may give it a shot, if Jamie is unable to work the magic he was speaking of.
Otherwise at this point I am looking at buying one of the Vectric products… and I do so much love Estlcam’s integration and the clean user interface. I Do Not want to switch software, I am willing to go to considerable effort to avoid that.
Thanks again to everyone who posted, I do appreciate the help.
A spam bot PM’ed everyone one day and some people got very angry, so PMs have been disabled. You can find some people on thingiverse or twitter or share emails. I think the new discourse forum will have PMs again, because they have an aweseome trust system to fight spam bots.
I don’t know if it will help in this case, but, one feature of EstlCAM is that you can mask the image so that you only machine certain regions at a time. I have used this when I had extreme height variations with very fine detail. (I use a 0.25mm radius tapered bit on occasion…) I can use large bits for the gross features, and then come back with the finest bits and add the detail (like your woodgrain, for example). I’ve not studied your image to consider how effective it would be in your case, but perhaps it’s something to consider.
