Hybrid Mill Design

Hi uli12us,

I'm not sure I follow your description of the Hermle machine. It looks to me like it uses a SINGLE gantry beam with the spindle hanging off the front, like most of the DIY machines on this forum.

As I see it the spindle moves left/right across the gantry, and up/down, as per normal. It is not a fixed gantry with moving workpiece (ignoring the 4th&5th axis for now). The whole gantry can also move fore/aft. This is same as the dmg except that the dmg has a TWIN beam gantry with the spindle in the middle so is potentially stiffer than the Hermle.

The Hermle may look like the spindle is 'fixed' because of the pieces either side but I think these are protection bellows to keep the swarf out and can move as the spindle moves. Let me know if you are seeing something I am not !

All this aside, I think it is generally agreed that for small machines a fixed gantry (with spindle only moving up and down) and a moving X/Y bed is better, which might have been the point you were trying to make as a general comment.

Thanks

Interesting machine Chaz in that video.

Spindle speed looks strangely high for steel but it seems to be working at that feed rate.

Forgot to mention that I'd been looking at double ballscrews, or using back-to-back singles with belleville washers in my machine design to remove (up to a point) the 50 microns or so backlash. Something to think about if you are really trying to max out on performance. I'm undecided on whether to bother . . .

Chaz,
have not been here long, just looked at your initial design .

2 major flaws pop at once:
-the gantry profiles
-the bearing blocks for the Z

Let me explain how i see it and what i mean. I would compare with my design / the violet one/ so its easy to understand, as mine is overbuild also.
-If you take a closer look on the reference machine from the pdf you would see that these are not profiles, the whole gantry is massive cast and braced piece. meaning that your is flimsy in comparison. The only way i see it is make it like my machine- solder a additional reinforcing plates at the gantry beams to tighten all up. Thats why in fact i did not went with that design, cause while on Johnatans red machine it works, for a bigger machine gantry needs serious reinforcing. So i designed my gantry/a typical style/ so its more rigid than the gantry you have in mind. The ideal super machine for me would be combined between both designs. meaning 3 profiles for the Z left right. An overkill. Say no more than 200Euro more on rail and profile


-For the Z i have no doubt. Carriages must be fixed and rails must be on Z , for ultimate strength. plus better 2 rails x2 carriages than 4 carriages and 4 rails. The arm of force, the lever. Now its good to have in mind that for that type of machine and 2 rails with Hiwin 20 x 2 carriages is overkill. So no need for 4.
I bet that the way i designed it /30cm lever arm and 20cm z travel is more rigid than not properly designed Z with 4 carriages.


So why they made that original monster like that. Cause for sure the spindle is much bigger power and weight than what you will use, the gantry is cast and generally is made for hard metal, not aluminum.


I will be happy to explain better if i not clear what i say. Soon i will be able to prove what i am saying, when chips start flying from mine machine.

Quote:

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Originally Posted by Boyan Silyavski

Chaz,
have not been here long, just looked at your initial design .

2 major flaws pop at once:
-the gantry profiles
-the bearing blocks for the Z

Let me explain how i see it and what i mean. I would compare with my design / the violet one/ so its easy to understand, as mine is overbuild also.
-If you take a closer look on the reference machine from the pdf you would see that these are not profiles, the whole gantry is massive cast and braced piece. meaning that your is flimsy in comparison. The only way i see it is make it like my machine- solder a additional reinforcing plates at the gantry beams to tighten all up. Thats why in fact i did not went with that design, cause while on Johnatans red machine it works, for a bigger machine gantry needs serious reinforcing. So i designed my gantry/a typical style/ so its more rigid than the gantry you have in mind. The ideal super machine for me would be combined between both designs. meaning 3 profiles for the Z left right. An overkill. Say no more than 200Euro more on rail and profile


-For the Z i have no doubt. Carriages must be fixed and rails must be on Z , for ultimate strength. plus better 2 rails x2 carriages than 4 carriages and 4 rails. The arm of force, the lever. Now its good to have in mind that for that type of machine and 2 rails with Hiwin 20 x 2 carriages is overkill. So no need for 4.
I bet that the way i designed it /30cm lever arm and 20cm z travel is more rigid than not properly designed Z with 4 carriages.


So why they made that original monster like that. Cause for sure the spindle is much bigger power and weight than what you will use, the gantry is cast and generally is made for hard metal, not aluminum.


I will be happy to explain better if i not clear what i say. Soon i will be able to prove what i am saying, when chips start flying from mine machine.

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Thanks, appreciate the feedback. Agreed on the Z design, it was an idea that wont work. In terms of 'reinforcing' the gantry, this can be done easily. Your purple machine is a good example and the reason why I am staying away from steel is due to me not owning a MIG welder (that can be changed, I used to Arc Weld a bit years ago), but that steel looks to be a pain to get flat based on welding etc. That said, it clearly is and there are other 'things' you can place on top of a steel frame that help with something being flat.

I also wanted to 'play' with something exotic and interesting like something that I can cast or make myself. I researched about casting iron, the epoxy options and even looking at granite.

So ye, I might not be making the 'best', at least it might be interesting (and perhaps risky). That said, I dont have money to piss away, it needs to work.

Hi this looks really cool, I checked the original DMG Mori machine and the design blew my mind! any idea if the whole frame is one piece from cast iron or something of that sort? I wonder if us mere mortals would be capable of building something like that.

anyway it's nice that you are following their design, it seems it is one of the latest advanced technologies. and maybe you can add the B and C axis as well hehehehe

Profile rails come in 2 flavours, those that screw from above, those that screw from behind.

If you screw from above, swarf and grit can sneak in passed the grease wipers on the ends.

Quote:

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Originally Posted by Robin Hewitt

Profile rails come in 2 flavours, those that screw from above, those that screw from behind.

If you screw from above, swarf and grit can sneak in passed the grease wipers on the ends.

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Had this on a previous machine. pain.

Quote:

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Originally Posted by Noplace

Hi this looks really cool, I checked the original DMG Mori machine and the design blew my mind! any idea if the whole frame is one piece from cast iron or something of that sort? I wonder if us mere mortals would be capable of building something like that.

anyway it's nice that you are following their design, it seems it is one of the latest advanced technologies. and maybe you can add the B and C axis as well hehehehe

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indeed. i agree, still like the design.

Quote:

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Originally Posted by Robin Hewitt

Profile rails come in 2 flavours, those that screw from above, those that screw from behind.

If you screw from above, swarf and grit can sneak in passed the grease wipers on the ends.

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Depending on make you can buy top mounting with covers to stop this. Don't mean the Green caps like Hi-win but full metal strip that clips into the rail.
Not cheap put that's what you'll find on many industrial VMC's that use Linear rails.