145 spindle control blew (again)

[Frogblender]

Teknomotor Collet Spindles : T-Tool Store, High Quality CNC Tool Holders

George at xzero (he has forum here in cnczone) do sell these spindles.

These spindles look very nice, except for one thing: a power drawbar cannot be added - you will be slave to the wrenches. I couldn't live without my air-cylinder-on-belleville-washer-quickchange-tooling.

[ihavenofish]

These spindles look very nice, except for one thing: a power drawbar cannot be added - you will be slave to the wrenches. I couldn't live without my air-cylinder-on-belleville-washer-quickchange-tooling.

theres 2 things you can do with those spindles. 1 is to mount it and use it directly. the other is to mount it like a motor (you can get it without the er chuck) and drive the r8 spindle. for that youd want to keep to 12000rpm, or belt down to 6k. - or have a dual pulley setup (easy on the 145, not so much on the 200)

they will have a power drawbar version soon aparently - or you can buy the colombo from george - but the price goes up dramatically. the cheapest colombo full kit (5hp spindle, drive, air lines, regulators etc) is in the $5k range.

[tjd10684]

I have always used the wrenches and now that i can get at the spindle flats it only takes me about 2 min from chip to chip to change tools assuming i am not overly concerned about matching depth with 2 different tools. and it gives me time to think about what im doing

[Frogblender]

I have always used the wrenches and now that i can get at the spindle flats it only takes me about 2 min from chip to chip to change tools assuming i am not overly concerned about matching depth with 2 different tools. and it gives me time to think about what im doing

Once you try a quickchange, you will not want to go back to the wrenches. 10 seconds for a toolchange, with perfect height. No thinking required.
And it'll allow me to one day add an ATC (it would be almost-trivial to add one now, if I was willing to give up x-axis travel - which I'm not, which means I need one of those complicated tool-tray-comes-flying-in-from-elsewhere changers).

The biggest downside to a belleville-washer-style drawbar is weak toolholding force. I can't use it for 1/2" bits and heavy/fast cuts in MDF where the torrential clouds of sawdust come off nicely browned, for example, cuz the tool will start to work its way out. But most of my stuff is 1/8" bits in 6061, so it's fine. Air-wrench drawbars don't have this problem, though.

Anyhoo, I'm a believer.

[urbanimports02]

what is the way construction of the z axis on the nm145? is it using the same linear bearings as the nm-200? hiwin or hiwin style if a knock off?

[ihavenofish]

The biggest downside to a belleville-washer-style drawbar is weak toolholding force. .

almost every commercial power drawbar is using bellvile springs, so if its lacking in force, its not the springs fault

i actually did the math last week for a tts specific (not r8 though) spindle design. 3000n pull force is a minimum, about 4-5000 is ideal. 5000 is in the "overtightening" range for a typical cheap steel r8 drawbar. my math is basic, simply converting traditional drawbar wrench torque to linear force.

4-5000 is very easy to accomplish with 4-6 50mm diamtere springs on top of the spindle. the r8 tool needs very little throw (1mm or so), so you dont need a huge stack. this is basically how tormach is doing it.

the mistake people often make is in calculating the force to RELEASE the drawbar, which depending on the spring and throw, can be 1.5-2x the desired pull force. i think my ejection force worked out to 6500n, or about 1460lbs. you need a fairly big air cylinder to release that - or a air over hydraulic intensifier (what im using for my idea).

[ihavenofish]

what is the way construction of the z axis on the nm145? is it using the same linear bearings as the nm-200? hiwin or hiwin style if a knock off?

the 145 is all dovetail. its a fairly beefy one on the Z with a taped gib. its pretty smooth operating and it has counter balance springs. (ive had some less stellar experiences with Z dovetails in the past so i was pleased this one works well).

[tjd10684]

I think i need to tighten the gibs on mine i notice the head trying to jump one way or another when drilling with 3/8" or larger bits oh and with 1/2" roughing mills i could see the head jump my solution for that run was slow down feed increase spindle speed to lessen chip load. that fixed it for that run but i think i need to look into adjusting the gibs

[urbanimports02]

Are the gibs part of the milling head itself or does the head casting bolt onto a plate of some sort? Anyone have pics or Know of an exploded view? Considering a 145 and looking into possible paths to replacing the motor. So far I like the idea of the OP going to ac motor and vfd. That is what is on my nm200 and works well. I would only buy the machine with the idea of changing out the motor first thing. Are you all happy with the control and rapids and all that good stuff? What are your rapids, and is it stable at those speeds? My 200 will lose steps every now and again with rapids down at 65ipm and acceleration at 5! Gets irritating. Looking into new motors and drives to replace the geckos.

[ihavenofish]

Are the gibs part of the milling head itself or does the head casting bolt onto a plate of some sort? Anyone have pics or Know of an exploded view? Considering a 145 and looking into possible paths to replacing the motor. So far I like the idea of the OP going to ac motor and vfd. That is what is on my nm200 and works well. I would only buy the machine with the idea of changing out the motor first thing. Are you all happy with the control and rapids and all that good stuff? What are your rapids, and is it stable at those speeds? My 200 will lose steps every now and again with rapids down at 65ipm and acceleration at 5! Gets irritating. Looking into new motors and drives to replace the geckos.

my nm200 rapids and cuts at 100ipm reliably, 150ipm i can do but once in a while it stalls the the ends of travel.

how is your machine losing steps, what type of program? dont be too quick to blame the geckos and motors. it could be software.

[ihavenofish]

oh, the 145 has a 1 piece head and tapered gib. so you cant tram the machine.

mounting a new motor is a fairly easy task, you just make a plate that mounts on top of the belt drive housing to hold the motor, instead of tucking it inside.

[urbanimports02]

i started a new thread about my nm-200 and control issues so as not to detour this thread. thanks for the info regarding the 145 construction, it is still a strong consideration for me for secondary operations with small cutters.