DIY mill from commercial castings?

[Buoyen]

So.. wondering about spindle and motor. Any suggestions? Something that is about the same level of performance, cost and funcionality of the rest of the machine I have described and for the use showed above: small parts in aluminium and steel.

#1: Buying a X2 casting, straight shank ER32, 2 AC bearings etc. Can be combined with either a chinese AC servo-kit or a induction motor+vfd or BLDC+BLDC driver/ESC.
Pros: Cheapest (probably), I'm familiar with ER collet system and like it, can buy proper AC bearings to start with, also familar with the casting since I have a CJ18 lathe headstock for 4th axis and it's the same thing. Can install bearings for high rpm use, will be limited by the belt drive.
Cons: Most work, might not get proper performance/straightness, If I dont get it to work it's wasted money. Might be too small/weak for future needs. RPM limited for aluminium work with 3000rpm motor and 2:1 belt drive.

#2: Buying a complete X2 head unit with R8 spindle. Can be combined with either a chinese AC servo-kit or a induction motor+vfd or BLDC+BLDC driver/ESC.
Pros: Cheap, complete unit so no work with that, R8 is widely available, can make some manual quick change system if I want
Cons: Probably cheap bearings installed - not AC? Might be too small/weak for future needs. Limited rpm range because of bearings? RPM limited for aluminium work with 3000rpm motor and 2:1 belt drive.

#3: Buying a BT30 6000rpm head from china: https://www.ebay.com/itm/Spindle-Bor...B9En:rk:2:pf:0. Can be combined with either a chinese AC servo-kit or a induction motor+vfd or BLDC+BLDC driver/ESC
Pros: Stiffness of the taper is more than I'll ever need. Quite cheap. BT30 is widely available.
Cons: More expensive than #1 and #2. Unsure about the quality of the parts and low run out? Never seen anyone actully have this. Probably cheap bearings. Limited rpm-range, but maybe better than the X2 head? RPM limited for aluminium work with 3000rpm motor and 2:1 belt drive.

#4: Chinese BT30 spindle cartridge: https://www.aliexpress.com/item/ATC-...AbTest=ae803_5

Can be combined with either a chinese AC servo-kit or a induction motor+vfd or BLDC+BLDC driver/ESC
Pros: Proper spindle cartridge. BT30 tooling. Ready for ATC/manual quick change.
Cons: Expencive. Cheap bearings? Needs some kind of housing to sit in.

#5: Chinese high speed spindle ER32, 18000rpm. Just needs a vfd to get it to run. Derated power: at 3000rpm the max output is 750W.
Pros: ER32 is simple. Motor inside spindle so no moving parts. High speed spindle for aluminium work. Simple mount.
Cons: More expensive than the X2. ER not possible with quick change. Cheap bearings? Too weak bearings for steel work?

#: Usovo SK15 ATC spindle. Can be combined with either a chinese AC servo-kit or a induction motor+vfd or BLDC+BLDC driver/ESC. Didn't find any link, but have seen this on ebay.
Pros: Cheap (about the same as X2 head if I remember correctly). High speed spindle, limited by belt drive. Ready for ATC or manual quick change.
Cons: Can't find it for sale now. SK15 is small taper and too weak for steel work. Too weak bearings for steel work?

Right now I'm favouring the X2/CJ18 casting + ER32 "diy" for cost or the chinese ER32 high speed spindle for simplicity (will be exact same setup as my router just a bit bigger spindle).

Any thoughts?

AC servo or induction motor would be 3000rpm and 2:1 belt setup so 6000rpm at the spindle.

The AC servo I looked at: https://www.aliexpress.com/item/220V...AbTest=ae803_5

[skrubol]

Thank you. Agree. What I want to do is something like this, printed in PLA. Can be a problem with available space, but I'll look into it.

I don't think telescopic way covers will work too well in 3d-printed plastic. Seems like the layer lines would lead to a lot of friction, especially when chips get caught in them. Maybe I'm just not thinking about it the right way.
Often they have scissor lift type linkages in them to keep them even and to help keep them straight and from binding.

[Buoyen]

Okey. Yes I just have all this thoughts...Hehe
I dont really know how complex they are.

[Zenji]

3hp chinese spindle?
You articulate in a pillow ball, 30 degrees radially would be enough to do porting.

[Buoyen]

Lifting this thread again.
Abandoned the idea about buying castings.
Startet looking into epoxy granite instead and decided I wanted to build a desktop mill.

I decided though not to design it for sitting on top of a bench, but with a full enclosure and flood cooling.
The machine is nearing completion, but it is not 100% finished yet. I still think it is time to start share something

Dimensions approx 85cm x65m footprint.
Travels 315x165x215 x,y,x. (mm)
Spindle to column 190mm
Spindle nose to table minmum 100mm

Er32 2,2kW spindle with base speed 12500rpm (max 18000).

Ground C5 ball screws on X and Y. C7 on Z.
HG20 linear rails.

Stepper motors.

Washing machine pump for the flood cooling. 80W induction motor.

Did a lot of FE simulations to get the most out of the materials and space. Ended up with a 10,5cm deep column. With Epoxy granite. That means it is not going to be the stiffest out there.

Used my router to make parts, but it is not very accurate so had to do a lot of modificatins after.

Shimmed the rails to get them straight. Bought a ground T-slot table I used for reference.

Renderings from Fusoin 360.

[Buoyen]

First test of the machine by face milling the sub plate.
Video:


Not 100% perfect tram, but very happy with the result. Long extension to reach the sub plate
4000rpm
40mm woc
0,1mm doc
0,15mm chip load

This is how far I have come. Next thing to do is mounting home switches and e-stop.

[Buoyen]

Did some dry test beforehand with different ratios of gravel, sand and epoxy.
This is cast without vibration.
I ended up with something a mixture with about 8,5% epoxy. The aggregate was ca. 50% 10-16mm gravel and 50% 0-3mm sand.

Used some 10mm aluminium strips for rails and motor mounts. A pair of angle iron in the base for mounting to the stand.
Almost all the metal just in this project is scrap that I had laying around and/or got for free.

Cleaned the back side of the aluminium with alcholhol so it would bond to the epoxy. Added som anchors also (screws), but don't know if that is neccessary.
Tried hairspray on the wooden panels so the epoxy shouldn't stick, but that didn't work too well...

Don't have any pictures of the mixing and casting...

[Buoyen]

The finished castings.

Was satisfied with the results. Did stick to the mold and also had some filler in the corners of the mold that was stuck to the epoxy.
Next time a proper release agent and wax is the way to go. And avoid 90 degree corners if I can.

About 25kg pr piece.

The column should have been 2-3cm deeper. That would make the machine stiffer.

Roughed the mounting surfaces for the rails and ball screw mount so they are in the same plane and drilled the holes on my router.

[pippin88]

You can always cast some more epoxy granite on the back of the column.

Rough it up a lot with coarse sandpaper, maybe drill a couple of holes and embed anchors, then cast new stuff onto it.

[Buoyen]

That's true! Smart actually Will test it out now and see how it works.
I'll add this to the list of future improvements.

[Mikeedd]

Very thin and elegant colum you made. I love the simplicity..
Thanks, and keep on posting Buoyen.
Hejsa Norge :-)

Regards Mike

[Buoyen]

Tusen takk, Mike! Hyggelig

An update.
Made the head from two pieces of c-channel and a plate. I wanted to fill the inside to make it stiffer, but needed to fasten some screws from the back.
So made this 3d print so I could cast a cross of epoxy inside and still have voids front and back.

After I completed this I realized it would've been smarter to turn it around. Have all the bolts from the outside and cast everything inside. Well well. Next time I'll do better

With the 3 major components, base, column and head done I startet to mount parts.
Tried to align the rails within +/- 0,01mm sideways and up/down with a ground t-slot table as a reference for the master rail.

All metal pieces of this build is aluminium so I could machine them on my router and almost everything is scrap. So they are not very nice. But it seems to work.

[cncuser1]

Buoyen: interesting project, thanks for sharing.
i have a question about stiffness, I think many do.

Can you take a look at my post in this forum where I did some quick measurements of the stiffness of my X2 minimill.

Would you consider doing something similar so we can compare results?

[Buoyen]

Thanks!

Yes, sure, did see your thread. Nice work!
I'll come back with some numbers.

[Buoyen]

Did a test with random luggage weight.

Not very elegant stand for the indicator. Didn't have anything tall enough for it to stand on. Working on the enclosure at the moment so had some wood stuff.

Force y def x def

2,5kg 0,04mm 0,01mm
5kg 0,045mm 0,015mm
7,5kg 0,095mm 0,045mm
10kg 0,12mm 0,06mm

Just a bit less than 1N/um in Y and 2N/um in X. So a bit lower than I hoped for actually...

Maybe a bit strange numbers. I'll try to fasten the indicator to the table and do it again.

But it is built with a 18000rpm spindle and this should be suffucient for smaller cutters at high speed I think.

[cncuser1]

Buoyen: Interesting result. After the fact the numbers look like they relate to the size of the sections in each direction. And the surface area and method of the column connection to the base.

Is that angle iron in the base? If you could have attached some metal in the column to that you would have been golden.

[Buoyen]

Yes maybe the connection between the base and column needs to be stiffer. Not sure how I'd make this, but my initial thought was to fil the gap with epoxy. But then I need to tripple check the tram of the column first...

I have qllready acquired two pieces of scraped steel. One profile with 3mm thickness that is just a few mm too small so I should be able to widen it a bit an get it around the column.

The other is a plate with small flanges on. 7-12mm thickness.

Both can be glued to the back. What would be more stiff? Unfortunately I'm not paying for fusion so don't have software available.

[cncuser1]

I'd like to give definitive advice but I'm not knowledgeable enough...having said that I'll say that a lesson I learned from my project ( and a poster in that thread) is that the shapes used should be closed, think square or rectangular or a buildup of simpler shapes to give a closed section. NOT a C section and not flat plates, they deform in torsion ( twisting). That was my lesson.

You seem fairly far along in your project so remedial steps are difficult. I prefer metal.

[Buoyen]

Haven't taken the time to upload any more photos.

I have tried to mill some aluminium and uploaded two short videos to youtube here.

This is running a 20mm 2 flute indexable end mill. 5mm depth and 2mm width of cut. 5000rpm and 1200mm/min.
Gwizard proposes 12500rpm and 4000mm/min feed with high speed machining. That's scary.
Without cooling the first run so it's possible to see something. And the second with cooling.

[Buoyen]

Current status.