[peteeng]

Hi Zorbit - Yes its a good read. It (the article) has come up a few times. Given no consideration on cost, carbon fibre would be my material of choice. Std modulus CF will give you 70-80GPa stiffness quite easily and intermediate modulus will be 110-120GPa and stiffer then cast iron at 1500kg/m3 plus really damp to boot. But $$$ do drive the market so until I do the next ALOX tests I'm rethinking the glass fibre stuff at 33GPa. At least I can machine GF vs alox.... Peter

[peteeng]

Hi Ard - That's meaty - is there an english version? Peter

[ardenum]

Hi Ard - That's meaty - is there an english version? Peter

Don't think there is, but the guy has some other publications in machine tool category, some are english.
https://www.researchgate.net/profile/Christian-Neunzig they're available on libgen if you dont want to go throught the 'request full text' process.

[peteeng]

Hi Ard - I found the Uni that published the thesis but google and others won't translate His work is interesting as he does tensile tests vs comp tests... cheers Peter

[peteeng]

Evening All & Sundry - Looking at the evidence it seems E70+ may not be achievable as an isotropic material. I'll still make the plank samples but that maybe a couple of weeks away. So I've decided to dial back to E35 modulus. The CSA Grout should get this, my glass laminates get this and other EG "should" get this. My plan is to make 15mm thick infused E-gLass skins and then these can be shipped and the Maker can fill with local grout. Rapidset in USA and Nanodur in Europe. Or their local equivalents. This means my structure maybe bigger then I had hoped but until a machine is made and stiffness tested we won't know the real answer. I have been through some Eglass/CF hybrid test figures and I think I can bump up the 35GPa a little using some CF. I'm going to call in a favour and try to get a free flexural test done at a lab... So I shall restart Milli's design based on E35....

[peteeng]

Evening All - This is where I'm headed with Milli making slabs of CF and G-10 and machining them... Peter

https://www.youtube.com/watch?v=MnM2FyY3vQc

https://www.youtube.com/watch?v=CWQoV3eIfZw

[ardenum]

Hey Peter,

I was wondering, in your work, have you ever had to glue a rubber/silicone to stainless steel?

[peteeng]

Hi Ard - Yes there are primers for that sort of thing. If its natural rubber then a contact cement is used. If its RTC rubber or silicon then you use a primer and a silicon adhesive... The adhesive supplier will be able to advise on that. Did a lot of that sort of thing with hovercraft skirts and ducting...Peter

[peteeng]

Morning Or Afternoon All - I have been thinking about Milli and trying to rationalise a couple of things. My first concern is that I don't like the table drive down in the muck and prefer a fixed table. Plus looking at the development line seems there is only two possible configs to pursue. If there is another please tell. The gantry/bridge style has the table running away from you if you align the base away from you. The other has the table across you like a conventional mill. The possibility of only having E35 available to build with means the structures will have to be big, Which I don't mind. The rising gantry and carriage has been very stiff...

Geometry wins and a very large part is stiffer and lighter then a small small part (in general) So I have to pick one of these and restart the development... I'll do a block model of each to see how the footprint goes.... unless someone points me in a different direction... Peter

[peteeng]

More thoughts - I think B maybe the one. Will have to get a block model going.... A quick calc says the footprint will be about 700x900mm each. B maybe 850 long, so no real delta in footprint. Going way back the the beginning my thoughts were with A but now maybe B. Peter

[pippin88]

Chip covers are going to be needed whatever design.

You can mould in coolant gutters etc.

Having the rails / screws a few cm higher won't gain much from protection point of view.

Big increase in complexity (dual drive) and cost compared with single screw down the middle of the table.

[peteeng]

Hi Pippin - sounds like your voting for B 2. .. Peter

[Zorbit]

If I was building it I'd go for a moving table design, but with conventional gantry and Z axis rather than the lifting gantry. This would allow me more flexibility with fixturing, not having to worry about the gantry hitting things at the edges of the table when the work is in the middle. Not having to lift the gantry means it can be big and stiff, more distance between the carriages on the Y and Z axis.

[peteeng]

Hi Zorbit - All valid points. I have done deep objects like model boat hulls and bowls (but I'll use the router for these). I have a concern that the lifting gantry design won't work for these. But the carriage and lifting gantry is very stiff... All my built machines and designed machines the Z axis has been the weak link... As has been said many times there's no perfect machine. I'll spend some ZZZZZZZZ's on it... Peter

at 250mm wide the Mazak config would do the job.... but it has a saddle here we go again

P2P Mill from 2 years ago....

[pippin88]

I think it will be rare that a lifting gantry gets in the way / interferes with workpiece

The spindle nose can be set lower than the bottom edge of the gantry. Then you have tool gage length also.

I would chose a stiff machine that can't handle 1% of jobs over a floppies machine that can do the extra 1% of jobs.

Ultimately there will always be many jobs that can't be done with whatever machine you have. 500mm max travel - no use when you need 501mm travel....

[ardenum]

If I was building it I'd go for a moving table design, but with conventional gantry and Z axis rather than the lifting gantry. This would allow me more flexibility with fixturing, not having to worry about the gantry hitting things at the edges of the table when the work is in the middle. Not having to lift the gantry means it can be big and stiff, more distance between the carriages on the Y and Z axis.

This is a common misconception, in a real scenario you can only go as deep as long your tool is.
Lifting gantry is hands down the stiffest config there is and has no issues of a typical VMC nor a weak Z axis of a router. pippin88 is 100% right.

Stay strong Peter, don't regress backwards... Just copy Modig rigimill, I'm actually itching all over to do a small version of that...so I uploaded a mockup a few pages ago...

[Zorbit]

This is a common misconception, in a real scenario you can only go as deep as long your tool is.
Lifting gantry is hands down the stiffest config there is and has no issues of a typical VMC nor a weak Z axis of a router. pippin88 is 100% right.

Stay strong Peter, don't regress backwards... Just copy Modig rigimill, I'm actually itching all over to do a small version of that...so I uploaded a mockup a few pages ago...

In real world situations I have many times had small workpieces held down by many clamps situated around the outside edge of a table. The clamps are often much higher than the work, not a problem with a conventional mill, like the bridgeport vmc I used to run. Creative fixturing can overcome this problem, and is well worth doing for a production job, but is it so practical for a hobby mill that may only be making one part ?

Does the hobbyist / garage machinist need the super rigidity more than he needs an easy to use general purpose mill ? Will the small tooling dictated by the small spindle allow enough tool length to be useful ? Is the rigidity really needed with a small spindle ? It's not going to be a 15hp like the bridgeport.

That's for Petes market research to decide. I look forward to finding out.

[ardenum]

Hey peter, if you hate all the muck and want to protect the bridge+spindle without having it stick out at both ends or limit your X travel, I'm afraid this is the only way... (HMC style)

[peteeng]

Hi Zorbit - Most of my crashes have been with the high hold down bolts on clamps. Agreed
Ard - I have thought about a HMC style but for advanced hobbyists I think its too far from a VMC
Others here's the Rigimill --- its style A
General - seems all the hobby level machines are not stiff enough. So Thats the grail... In my specific case I want to machine composites as most contract machinists don't want to machine composites as it mushes up the lub... and as in most things I aim high....
Mili is a far horizon development project for me. It involves identifying advanced materials and advanced machine configs.. . I have a half sheet (look up YaG) and full sheet router (lifting gantry) to build then I can build Milli... so its a fair way off to breaking ground with Milli. I see another "Holy Grail" sign just up ahead... Peter

Oh I have some quotes on carbon fibre and their not too bad. So a hybrid GF/CF laminate may be the ticket...

[klaas123]

I like the lifting gantry design but would go with a moving table. With a fixed table you are stacking all axis upon each other, less stiff I would assume.