[genixia]

I've been wanting a CNC machine for a long time, and recently flirted with the idea of a router. My son's robotic team just bought one of those though, so I went back to looking at mills.

This is what I've ended up with. Intelitek Benchman XT.

U.S. made in 2001, it's 800 lb with an epoxy granite base. Motion is linear ways, with servo driven ground ballscrews. It has a 2.7HP 45k water cooled spindle with a 12 slot ATC, and came with a full set of ISO 10 (I think) tool holders and collets. Oh, and it has flood cooling too!

I still need to buy tooling and a vise, but I think this should handle my requirements nicely. Predominantly aluminum and plastic, but it'll cut steel too. (Although speeds and feeds maybe be problematic for steel)

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[awerby]

That's a pretty impressive machine there. Does everything work okay? Given the speed of your spindle, it would be great for engraving on steel, but actually cutting parts would probably be better done on another mill.

[genixia]

Thanks, the machine has great bones. I'm pleased I managed to find one available on my doorstep this side of Christmas.

I saw it under power, all axis and spindle, although not cutting material. The spindle was rebuilt a couple of years back and hasn't seen much work since. I haven't managed to find a power graph yet - I could infer one from the spindle drive settings once I have it under power. I suspect I might be able to get 0.5 ci MRR out of it on steel which would be terrible for a job-shop but would be ok for a small single part or prototype in my garage. As I said, i don't expect to be using it much for steel. If push comes to shove, I'll prototype for form, fit and function in Al and shop out for steel.

[atomarc]

A nice find, but I think for more versatility the spindle may need to be slowed a bit. Its bulk is showing as the overhang of that table its sitting on seems to be sagging a tad..


Stuart

[genixia]

Well, it's vfd-driven, so it's all a question of what speed it develops max power. I'm struggling to find the spindle specs - it's liquid cooled and has air curtain seals, so it certainly wasn't cheap.

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[louieatienza]

Well, it's vfd-driven, so it's all a question of what speed it develops max power. I'm struggling to find the spindle specs - it's liquid cooled and has air curtain seals, so it certainly wasn't cheap.

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At max speed... since torque is usually constant with VFD, speed is proportional to power.

I believe then the company was LightMachines, who made high end mini mills and lathes.

[SCzEngrgGroup]

At max speed... since torque is usually constant with VFD, speed is proportional to power.

I believe then the company was LightMachines, who made high end mini mills and lathes.

With a VFD, torque is only constant up to the motors base speed, which is the motor RPM at 50 or 60Hz, depending on the motors rated base frequency. It also typically falls off sharply at low RPM (<10-20% of base speed). Above base speed, it is constant POWER, which means torque falls off linearly with increasing RPM.

Regards,
Ray L.

[genixia]

Two different answers, and to add to my confusion someone elsewhere suggested that the spindle had 0 torque below its warm-up speed of 15k RPM, which doesn't make sense unless the VFD was deliberating programmed to reduce it. I know that the VFD in question drives to 750Hz to attain 45k RPM which agrees with repair documentation stating that the motor is 2 pole.

I'm inclined to believe that Ray's answer is the most likely. It is highly improbable that the motor could maintain constant torque all the way to 45k. I believe that the spindle manufacturer and model is Centerline 297-040090-ISO10, but haven't been able (yet) to determine its characteristics. Going down that path; Centerline is USA, so 60Hz base speed would be 3600 RPM, and 20% base speed would be 720 RPM. If that is the case, I think going to be really happy. Constant torque from 720 to 3600 RPM and constant power from there to max RPM should work well.

[genixia]

A nice find, but I think for more versatility the spindle may need to be slowed a bit. Its bulk is showing as the overhang of that table its sitting on seems to be sagging a tad..

The bench is straight. The sag is barrel distortion in the lens on my smartphone. The seller's photo in the classified ad had the same problem.