Solid Bench Top Mill Build (warning large photos)

[RCaffin]

Hi Ian

VP3328D, brushed DC motor, TENV frame, no visible cooling fan (may be hidden). Rating is CONTINUOUS.
See for example Baldor Permanent Magnet DC Motor - 180 Volt DC Motors - 040_DC low voltage motors, DC Electric Motors - Product Detail - Royce Cross Agencies
Actually 120 mm dia x 280 mm long, 14 kg, US$496 /unit on 3rd party web site
Nearest unit on Baldor.com is VP3327D, US$733. I can't find my exact unit any longer.



From my experience of using this beast for production work, I don't think it would get too upset if I ran it at 1 kW for 10 - 20 minutes. That's a far cry from some of the AC motor ratings.

Hi feist92
Could you hang something this size on your rig? Could be a bit tricky?

Cheers
Roger

[Feist92]

Im starting to think a brushed DC motor like whats in treadmills might work. They are listed for a lot of power but like you say they probably wouldnt like to be run at their max for too long.
Yea most likely I remember a thread from way back of a guy who fitted a treadmill motor and a mini mill spindle to a very flimsy looking router thing. Ill see if i can find the thread

http://www.cnczone.com/forums/diy-cn...ndle-idea.html
Start looking from around page 8

[handlewanker]

Hi..... the Baldor at.14 KG is way out for my application.

The build I'm doing is down on the bottom rung (intentional) when it comes to machining small stuff........ interpreted that means it won't be wacking luimps off solid blocks of ally or steel..........mainly small pieces of stuff and short repetition runs that I find extremely tedious to multi set a machine like a manual mill.

In actual fact the bridge mill build I'm currently involved with is a result of the long delay of the SVM-0 I am expecting......I wanted to get into CNC before my ancestors welcomed me home......shook me by the hand....whatever.

The Baldor motor is a bit pricey too, but most importantly it's a bit big for the 3025 set-up I'm working on.

It might suit Feisty's build but he'll have to work out a way to mount it side by side with a spindle too......at any rate, the weight whatever will have to be compensated for the sake of the ball screw and stepper.

Getting closer to the design requirements, and it looks like the motor needs to be mounted on the right side of the spindle to allow the spindle to traverse all the way to the left side for a possible ATC application ....if ever.....it's worth planning for the eventuality now than wish for it later.......not sure what Feisty has in mind for tooling etc......as in R8 (TTS?) or ISO 30.....Morse 3 is an option but it needs to be modified, and I'm warming to that system more and more.
Ian.

[LeeWay]

Here is a nice one.
Price is right, but a bit on the heavy side. I do have one of similar size on my little mill.
3/4 HP 1750 RPM 180 VDC LEESON SS MOTOR

[handlewanker]

Gulp....shipping weight 48 lbs.......must be in a cast iron box......LOL.

Big problem with DC stuff is you need all that AC to DC supply and current feed, whereas with an AC 3 phase all it takes is a VFD and go for broke.....at least the one I have works that way.

For me the jury's still out on the 3 phase motor until I actually see it and evaluate it, but the weight is only 5 KG.
Ian.

[LeeWay]

This is the one I have on my little mill.
It weighs 30 pounds, so quite a bit less weight.
MTPM-001-1M18 | 1 hp Permanent Magnet DC Motor: rolled steel, 56C, 1800 RPM

The motor controller and speed control is all you really need for DC. It is comparable to a VFD.

[handlewanker]

Hi......on a mill?.....that would be OK for a column mill but not Ok for a bridge or gantry type mill where you have a much smaller Z axis than the huge one most column mills have.

Both Feist92 and myself are building a 3030 and 3025 respectively bridge mill type of router and as such the weight of the spindle and motor is detrimental to the Z axis movement......even 30 lbs is way over the top, hence my seeking alternative lighter motors etc.

The current 3 phase motor I'm looking at is only 5KG......costs $59.
Ian.

[RCaffin]

Hi Ian

.as in R8 (TTS?) or ISO 30.....Morse 3 is an option but it needs to be modified,

Morse is fine for a drill, but awful for a mill. The taper will fall out. BAD move imho.
R8 is rugged but you get a very limited range of shank sizes and they are a bit pricy.
ISO30 is excellent, but at quite a high cost for more than one unit.

Mine is ISO-30, but with a good Kennametal adapter to ER25. I ended up with a full set of the collets, including 0.5 mm steps down at the bottom end, plus some small imperials for cutters with imperial shanks (there's a lot of them).

Yeah, the motor is heavy, but a gas strut takes most of the weight. The Z-axis ball screw has no trouble moving the mass of the motor, given the assist from the gas strut.

Those other 180 VDC motors look like fairly good stuff as well: TENV housings, continuous duty, etc, but some of them are a bit low in RPM - eg 1750. I don't like gearing up, but you could I guess.

Power supply: even less of a problem than with a VFD. Mains in, controlled DC voltage out. Various units on the market; I use a KBWT-26, although the control interface is tricky (full optical isolation needed) and there is a bit of RFI coming off - which I am working on right now. Ferrite beads and dual winding chokes ...

Dremel and Bosch motors etc? Forgive me, but that is a different world, where one expects to have to replace the motor every year or two. Who, me, biased? Never!

Type of mill: Yeah, I understand the problem with gantries and weight. Mine is 'none of the above' - it's more of a complete box frame using 40 & 50 mm ground steel rods and 80 mm thick Al end plates. Works for me. Lifting it can be a problem.

Cheers

[handlewanker]

Hi Roger......I understand fully the application of a 3 Morse taper shank.......it grips with a hold that can defy removal.......but, the design I've worked on has a pull pin and a draw bar.......but to ensure full location and sufficient grip without having problems I would fit a restricter collar to the bottom of the Mores taper under the spindle face.........this will prevent it from driving too deeply into the tape and becoming a permanent fixture.....LOL.

The 3 Morse taper shank only needs to have 3/4 of it's length in the spindle taper to be stable, so I would cut off the last 1/4 and fit a pull pin.

It also does not need to have a huge draw bar pressure to hold the taper in the spindle......the restricter collar limits that anyway.

When you consider the TTS system and the need to have an R8 collet on the draw bar (spindle diam and bearings need to be big) with Bellville washers applying huge force.....the simple stand alone shank of the 3 Morse becomes quite interesting.

Without modification the Morse system cannot operate as a milling shank solution.

It's only a might be solution, but has quite good potential.

For all those that are sceptical......valid reasons please not airy fairy won't work criticism....if you please.

BTW, before I thought of the Morse taper solution, I went to ISO 20 for the SVM-0 mill I've bought, as it allowed a PDB application which tipped the scales for me to decide to buy.

I don't think R8 or ISO 30 has a place on this small build, but what other choice is there.

Just had a reply from the Hishine people about the BLDC motors on Ali B.

"IF" I were to place an order for 20 units the price would come down from US$520 + US$155 shipping for one unit to US$470 for 20 units plus $105 for shipping, money up front etc...... which makes it a bit rich for my budget plan.

It does seem that Ali B is a manufacturers' sourcing site......not DIY, one off or retail etc.

Going to a 2,800 rpm 3 phase motor @ 500 watts, I have to wonder just how much torque you have when the VFD pushes the speed up 200%.
Ian.

[Feist92]

I wouldnt use any morse taper for anything other than a drill press. Im still looking into using an r8 taper but shortening the tooling and adding a pull stud with a gripper in the spindle. Should make it quite easy to utilize an ATC. Btw what do you mean by a 3030 and 3025 mill?

[handlewanker]

Hi Feisty, not a mill.....your build is a CNC 3030 bridge mill.....mine is a CNC 3025 bridge mill......routers are in a different league..

BTW.......I quite agree 3 Morse is a drilling spindle taper, but they do make mills with 3 Morse too.......not my cup of tea for a tool retention system

The point is, if you use a 3 Morse with a restricter collar to limit the grip of the taper and a retainer knob and draw bar it's extremely compact and simple.

BTW.....that was not a valid criticism of a modified 3 Morse for mill spindles......unmodified I quite agree, for milling it cannot happen unless you want to have a death wish.

If you are contemplating R8 for a spindle make sure it has plenty of retainer pressure as TTS tooling is known to draw down under heavy milling pressure.......the Bellville washers are at their relaxed state when they need to be applying the max pressure.........the build you have so far is leaning towards heavy milling, whereas mine is small cuts and lots of them.

If you also want to have a pneumatic PDB.....all that clamping/unclamping mechanism has to be carried on the Z axis saddle along with the R8 spindle which does carry a fair weight in itself.......+ a motor.

My main concern now is the motor.
Ian.

[handlewanker]

I wouldnt use any morse taper for anything other than a drill press. Im still looking into using an r8 taper but shortening the tooling and adding a pull stud with a gripper in the spindle. Should make it quite easy to utilize an ATC. Btw what do you mean by a 3030 and 3025 mill?

Hi, re-read your post......you mean using a solid R8 shank with a retainer knob for PDB?

The R8 shank is 25mm diam, so you'll have to have a large spindle body diam.....80mm?..... to accommodate it, big bearings too........that limits your top speed unless you go to expensive matched Ang cotacts.........possibly not a problem.
Ian.

[handlewanker]

Hi, just bought the 3 phase motor, 2,800 rpm 500 watt....$55.....weighs exactly 4.1 KG, so now all I have to do is think about building a spindle.
Ian.

[RCaffin]

the 3 phase motor, 2,800 rpm 500 watt....$55.....weighs exactly 4.1 KG, so now all I have to do is think about building a spindle.Ian.

Inline, or belt drive?

Feist - would 4.1 kg of motor work on yours?

Cheers
Roger

[Feist92]

Ian
I should have elaborated. I have a cheap chinese mill/drill that has a mt3 or similar taper and I hate it. Despite being anal about over tightening things Its forever getting stuck so you have to wack it pretty hard to get it to release which puts a hell of a lot of load on the bearings. I understand that you want to modify the tooling by shortening the taper and adding a stop ring on the bottom and it will probably work just fine Im just imagining it being rather fiddly to get the ring set in the right place and then make sure it dosnt move when tightened up against the spindle. In my mind it will always be a drill taper

Ill post a pick of a 3dprinted mockup I did of the tooling I plan to use when I get a chance. Also I have a plan to keep the pneumatics for the power drawbar fixed on the left side of the machine so the x and z axis wont need to carry the weight. The spindle will just go to its tool change position and in doing so kind of slide into the pdb assembly then release the tool.

Inline, or belt drive?

Feist - would 4.1 kg of motor work on yours?

Cheers
Roger

Yea easily I could probably go up to 10kg if i really had to but that would effect the inertia and slow it down more than im prepared to. I am planning to use nema 34 motors though so it might be ok

EDIT
Just imagine a pull stud in the far end. Btw sorry my camera is so crap

[handlewanker]

Hi, definitely have to be belt drive......side by side......maybe motor upside down, haven't decided yet......this will enable a PDB to be fitted.

I'll also have a VFD to give speed control.......for this build a max of 7,000 rpm would be OK......that will be by trial and error, and the drive will be by 5 groove Poly Vee type pulleys.

I'm still wangling on ways to build a spindle, and the design I'm working on has 12 narrow width (7mm) sealed deep groove radial bearings rated at 11,000 rpm and two ball thrust bearings.....there being no angular contacts......this is so radical and sheer heresy I'll not dwell on it, but by combining it with 3 Morse too the forum will freak out and run me out of town on a rail, tarred and feathered......LOL.

It will be interesting to see how the tread mill motor works out......Feisty still has to build the actual spindle bit.
Ian.

[handlewanker]

Ian
I should have elaborated. I have a cheap chinese mill/drill that has a mt3 or similar taper and I hate it. Despite being anal about over tightening things Its forever getting stuck so you have to wack it pretty hard to get it to release which puts a hell of a lot of load on the bearings. I understand that you want to modify the tooling by shortening the taper and adding a stop ring on the bottom and it will probably work just fine Im just imagining it being rather fiddly to get the ring set in the right place and then make sure it dosnt move when tightened up against the spindle. In my mind it will always be a drill taper

Ill post a pick of a 3dprinted mockup I did of the tooling I plan to use when I get a chance. Also I have a plan to keep the pneumatics for the power drawbar fixed on the left side of the machine so the x and z axis wont need to carry the weight. The spindle will just go to its tool change position and in doing so kind of slide into the pdb assembly then release the tool.


Yea easily I could probably go up to 10kg if i really had to but that would effect the inertia and slow it down more than im prepared to. I am planning to use nema 34 motors though so it might be ok

EDIT
Just imagine a pull stud in the far end. Btw sorry my camera is so crap

Hi.......several posts occurred whilst I was typing..........that tool holder is pretty compact.....reminds me of the ones David Decaussin has on his UMC-10 mill.

I think you'll have problems with side thrust from the tool affecting the axial positioning capability of the holder with just the short taper only.........the R8 has the long body to stabilise it at the top end.

You're intending to maximise the tool cutting potential with the heavy machine construction, so the tooling needs to have a correspondingly rigid capability too.........going to a longer taper and you've almost got ISO 30 which is available off the shelf.....and on EBAY quite cheap too.

BTW, while on the 3 Morse, we used a stop collar on the lathes after we had a 2 ton 8 foot long shaft that pushed the 4 Morse taper revolving centre so hard into the tailstock barrel it froze and had to be cut out.

With the 3 Morse mill spindle you have, try tightening the draw bar by hand with just a knurled round nut instead of a hex nut....whatever........in another life we had a Bridgeport mill with 3 Morse and the guys would always use a spanner on the draw bar........heck of a job to release it, so we made a knurled round nut for hand tightening only.

I propose to have a split collar with a screw thread that you rotate to set the depth and then lock it in position.....it'll position and tighten but not over tight.

I like the idea of the PDB at the ATC position......that would definitely give you scope for a decent power unit without having to trundle the weight around when it's not needed...... if an ATC is not fitted the PDB mechanism could be positioned near the centre of the X travel.

The motor I've just bought with the GL56 frame is 110mm diam X 199mm long overall, which is the biggest power rating in the smallest frame size they carry.......the next size up is the GL63 at 120mm diam X 217mm long.......and the next GL71 at 136mm X 245mm long......Wattage going up accordingly
.
Although they're relatively light, they're physically bigger, so mounting them might be a problem......it's not the weight so much, it's the diam of the body that would make it stick out from the Z axis saddle face you'd have to take into consideration.

With an off Z axis PDB, the motor can be mounted upside down above and in front of the spindle instead of to the side of it .......practical? .....I don't know.
Ian.

[RCaffin]

I could probably go up to 10kg if i really had to but that would effect the inertia and slow it down more than im prepared to

Dunno. I have a little Baldor servo motor driving the Z axis up and down. Now the weight of the big Baldor spindle motor is mainly taken by the gas spring, but the little motor seems to have no trouble at all pushing the mass of the motor up and down.
OK - the motor has a 3:1 reduction to the ball screw, and the ball screw pitch is around 5 mm. The mecahnical advantage is quite high.

Cheers
Roger

[handlewanker]

Hi, I think if the issue of spindle milling power to acceleration on any axis came up I'd go for spindle power any day.

What's the gain in having an ultra light spindle/motor package if it only has limited cutting power but can be accelerated rapidly......most of the time the machine is working away to itself, so reduced rapids probably won't impact on the job finish time.......unless you're really tied to a program that pays if the time saved is in minutes.

With a heavy spindle motor you'd need to have decent steppers to provide the go or you'll lose steps when it suddenly hits the load, or go down the servo encoder path.
Ian.

[Dubbie99]

It's not just Rapids where you need high acceleration, you need it for the cutting moves too. Think of sharp corners. The accel limit directly determines how fast you can go. This machine is going to be great for hsm toolpaths, having lower acceleration limits will impact cutting time hugely.