HGR linear rails for DIY mini VMC

[KidKhaos]

Hi,
why is he selling them?

Have a look at these:
discounted automation products: NSK Precision Ground & Rolled Ballscrews, NSK Ball Screws: 25mm ? thru 32mm ?

Double nut 10mm lead, 25mm diameter C5's with 890mm travel, new old stock for $395USD. That pretty good value, and 10 in stock.

Craig

The ballscrews were replaced for preventive maintenance. They appear to be in good condition based on the pictures I have. I am going to meet up and take a peak at them tomorrow night. He acquired them for nothing and said I could have all six of them for $200 just to get them out of his garage. Wether or not I end up using them for this project I'll get them as long as they are in good condition.
There are two sets, mini mill, and vf2.

[ihavenofish]

All Bridgeport CNC Machines From the Boss series up, have a short travel Y axis of 12" ( 304.8mm ) and a X axis of 18" ( 457.2mm ) all have 32mm C3 Ballscrews with 5mm to 10mm pitch Screws 750W Ac servos work very well with them at 1:1 Ratio or direct mount, so no problem with anyone using 32mm ballscrews if that is what they have

So if they can fit them in there build all is good

link?

I expect 3 things when we see it:
1: the 750 w servo is not an 80mm 2.3nm low inertia model like you find today.
2: the ball screws don't have bearings on the free ends.
3: the motor is not 1:1 on a 10 pitch screw - I don't recall Bridgeport boss's running 1500ipm.

It's also a very heavy machine of course, with ample spindle torque.

I'm also going to go out on a limb that the boss was not, uh, the best performing machine available when it was new, so probably not where you want to draw examples from

Also, sometimes designers have specific goals and pick weird parts: A brand new DMG Mori milltap 700 uses 3232 screws with a belt reduction. Great machine, but, why?!

[KidKhaos]

link?

I expect 3 things when we see it:
1: the 750 w servo is not an 80mm 2.3nm low inertia model like you find today.
2: the ball screws don't have bearings on the free ends.
3: the motor is not 1:1 on a 10 pitch screw - I don't recall Bridgeport boss's running 1500ipm.

It's also a very heavy machine of course, with ample spindle torque.

I'm also going to go out on a limb that the boss was not, uh, the best performing machine available when it was new, so probably not where you want to draw examples from

Also, sometimes designers have specific goals and pick weird parts: A brand new DMG Mori milltap 700 uses 3232 screws with a belt reduction. Great machine, but, why?!

Does this machine have long travels? I considered doing something similar on my router to get higher travel speeds while keeping my screw rpm's low to help combat screw whip and keep stepper rpm's in line.

[ihavenofish]

Does this machine have long travels? I considered doing something similar on my router to get higher travel speeds while keeping my screw rpm's low to help combat screw whip and keep stepper rpm's in line.

The milltap is a small machine, like a brother. 27" x travel. It's just stupidly fast. 2400ipm and 2g acceleration.



not mine, but I have the same one, brother tc225
25mm rails and 2005 ball screws on x and y

$1500 at HGR, in perfect working condition (but very filthy)

Control can be swapped with a few ribbon cables using all the original relay and IO boards, drives, psu's and wiring, although I didn't get the axis servos to behave in linuxcnc so I will be adding new delta asd-a2 86mm motors which are a drop in fit on the x and y (need an adapter plate for the z),

[mactec54]

Does this machine have long travels? I considered doing something similar on my router to get higher travel speeds while keeping my screw rpm's low to help combat screw whip and keep stepper rpm's in line.

Rotate the nut this is what a lot are doing, The Ballscrew than has fixed mounted rigid at the ends no Bearings needed at the ends, and you won't have any whip problem no matter what Ballscrew you use, high pitch you would have to gear them down or use a much larger motor to drive it

[mactec54]

link?

I expect 3 things when we see it:
1: the 750 w servo is not an 80mm 2.3nm low inertia model like you find today.
2: the ball screws don't have bearings on the free ends.
3: the motor is not 1:1 on a 10 pitch screw - I don't recall Bridgeport boss's running 1500ipm.

It's also a very heavy machine of course, with ample spindle torque.

I'm also going to go out on a limb that the boss was not, uh, the best performing machine available when it was new, so probably not where you want to draw examples from

Also, sometimes designers have specific goals and pick weird parts: A brand new DMG Mori milltap 700 uses 3232 screws with a belt reduction. Great machine, but, why?!

The later Bridgeport CNC machines have a 12mm pitch Ballscrew and are 1:1 direct drive 10mm Pitch is not a problem for most modern 750w AC Servos using a 25mm Pitch then you need a 2:1 reduction with the same motor

They only had steppers on the original Boss machines but on later Boss machines they went to servos for the short axis travels they performed very well I have had them run up to 750 IPM , 2 of the axis use a rotating nut so only needed the Ballscrew fixed at one end

[mactec54]

The ballscrews were replaced for preventive maintenance. They appear to be in good condition based on the pictures I have. I am going to meet up and take a peak at them tomorrow night. He acquired them for nothing and said I could have all six of them for $200 just to get them out of his garage. Wether or not I end up using them for this project I'll get them as long as they are in good condition.
There are two sets, mini mill, and vf2.

The MiniMill are a different Pitch to the VF2 the MiniMill is 6mm Pitch

[ihavenofish]

Rotating nut is usually on routers 8-12 feet of travel, where its not practical to spin the screws, but they don't want the slop of a rack and pinion... usually.

My maho z axis rotated the nut. I think it was a hold over from the way they designed their manual machine, I don't see any advantage they way they did it - its only 400mm travel on a 32mm screw.

Ball nuts designed to be spun are kinda rare though. I did look for some for the xzero machines once, cause spinning a 25mm screw at 8 feet was not working out well.

[ihavenofish]

The later Bridgeport CNC machines have a 12mm pitch Ballscrew and are 1:1 direct drive 10mm Pitch is not a problem for most modern 750w AC Servos using a 25mm Pitch then you need a 2:1 reduction with the same motor

They only had steppers on the original Boss machines but on later Boss machines they went to servos for the short axis travels they performed very well I have had them run up to 750 IPM , 2 of the axis use a rotating nut so only needed the Ballscrew fixed at one end

links?

[ihavenofish]

The ballscrews were replaced for preventive maintenance. They appear to be in good condition based on the pictures I have. I am going to meet up and take a peak at them tomorrow night. He acquired them for nothing and said I could have all six of them for $200 just to get them out of his garage. Wether or not I end up using them for this project I'll get them as long as they are in good condition.
There are two sets, mini mill, and vf2.

A quick look through the has catalogue. The mini mill had 3206 screws on the x and y. They were run by 850w 1500rpm high inertia Yaskawa servos that have 5.4NM torque. That's a rather big motor for what is a pretty small machine with a low power spindle and low accelerations.

[KidKhaos]

A quick look through the has catalogue. The mini mill had 3206 screws on the x and y. They were run by 850w 1500rpm high inertia Yaskawa servos that have 5.4NM torque. That's a rather big motor for what is a pretty small machine with a low power spindle and low accelerations.

I'm attracted to these screws because the machines they come out of fall into the range of travel I would like to accomplish. Maybe I could get away with 750-1000w servos? The vf2 has a 30 hp spindle, and the mini mill is 15 though I just can't power something like that. I was thinking a 3-4kw servo to power my spindle. What's that like 5hp? So the result is I won't be able to hog out as much material in a pass I suppose. Man I like that 30x16 xy travel though.

[KidKhaos]

Rotate the nut this is what a lot are doing, The Ballscrew than has fixed mounted rigid at the ends no Bearings needed at the ends, and you won't have any whip problem no matter what Ballscrew you use, high pitch you would have to gear them down or use a much larger motor to drive it

Not a bad idea. I am planning to upgrade my steppers on the router first. The start to miss steps over 150 IPM anyway. I was thinking about buying a set of steppers for the mill build then upgrading to servos later and swapping nema 34 steppers onto my router. I dunno. I've got too many projects syndrome over here.

[mactec54]

links?

Here is one I did this only had the low powered servo drives 48v so not much speed, out of the 750w servo motors, but was not the purpose of this test, it was for Mach3 using just a Parallel Port as a test running 3 axis simultaneous up to 300 IPM profiling a part

[mactec54]

I'm attracted to these screws because the machines they come out of fall into the range of travel I would like to accomplish. Maybe I could get away with 750-1000w servos? The vf2 has a 30 hp spindle, and the mini mill is 15 though I just can't power something like that. I was thinking a 3-4kw servo to power my spindle. What's that like 5hp? So the result is I won't be able to hog out as much material in a pass I suppose. Man I like that 30x16 xy travel though.

The standard MiniMill is only 7.5Hp spindle the supper MiniMill has 15Hp

[mactec54]

A quick look through the has catalogue. The mini mill had 3206 screws on the x and y. They were run by 850w 1500rpm high inertia Yaskawa servos that have 5.4NM torque. That's a rather big motor for what is a pretty small machine with a low power spindle and low accelerations.

Yes the 850W motor is why more than they need but the Z axis needed an 850W so they just used them on each axis they are direct drive to the Ballscrew these motors can run at 3000 RPM 1500 is just the rated RPM

[ihavenofish]

Actually, when you run the mini mill parameters through yaskawas calculator for the X, they wind up with the motor they chose. You are right that has just used that motor for every axis on almost every machine though. The 80mm 750w models are right on the edge of inertia ratio handling. If you tuned down the machine to accelerate very slow (0.1g), they would work ok. IF you swap from a 32mm screw to a 20mm screw, like on the brother, the 80mm motors are well within their inertia rating. That's how much difference the screw size really makes.

Ill say it again though, is he building a 4000lbs machine like the mini mill?

[KidKhaos]

Sooooo I got these lil fellers today..