Calculating What kind of power i need ????

[Biggermens]

I am building this cnc router table and i think i might have over did it and now i am having a hard time finding motors big enought to power this
i understan thare are some formulas the find this out ??

Thomson Linear Guides are 25mm and i have 4 berrings
Thomson Ball Srew is 1inch and 4 turns per inch
the gantry will be about 500 Pounds
and i want to go 90 to 100 IPM

How would i calculate this ??? with aceleration ???

THanks

[Oldmanandhistoy]

Hi,

Have a look here may help you. http://www.cnczone.com/forums/showthread.php?t=8129

John

[Al_The_Man]

There is also many free graphical design programs like Kollmorgen etc.
I did one that had about a 500lb gantry http://cnczone.com/forums/showthread...ighlight=rosta
Al.

[JerryFlyGuy]

It's fairly easy to calculate if you want to do several iterations to find what works best I'd suggest setting up a spread sheet. There are several more questions which need to be answered before you can proceed.
1) Servo or stepper?
2) Reduction onto the ballscrew or direct drive?
3) Time to rapid speed [ how long do you want it to take, if your table is long this could be lower, if its shorter then you may never get up to speed w/ a longer time allowance as it needs to start slowing down before it gets to rated speed]
4) Force at the tool tip [ how much actual lbs force to move the tool through the mat'l at your req'd ipm.

If you post some of this I might be able to figure out roughly what your looking at...

Jerry

[Farmers Machine]

go to automation direct .com and look up sure servo motors and drives they come with encoders and with or without brakes. up to 3 KW call the 1-800 # to speak to tech support and they will walk you thru. Have gotten very good service and parts from these people.

[Mr.Chips]

Originally Posted by JerryFlyGuy It's fairly easy to calculate if you want to do several iterations to find what works best I'd suggest setting up a spread sheet. There are several more questions which need to be answered before you can proceed. 1) Servo or stepper? 2) Reduction onto the ballscrew or direct drive? 3) Time to rapid speed [ how long do you want it to take, if your table is long this could be lower, if its shorter then you may never get up to speed w/ a longer time allowance as it needs to start slowing down before it gets to rated speed] 4) Force at the tool tip [ how much actual lbs force to move the tool through the mat'l at your req'd ipm. If you post some of this I might be able to figure out roughly what your looking at... Jerry

I have often thought about this, and I know I will be very much underpowered with only 116 InLb stepper motors using Xylotex control boards with a 28V 8 Amp PS.
It is a fixed gantry so that is less work on the motors.

1. Stepper 116 InLb
2. Direct drive 1/2" 10 Acme rod. 1 start/turn.
3. Moving table is 30" long. Not sure what figures to use here?
4. Force at the tool tip. ?? Using 1.74 HP router. say 3/8" 2 flute down cut carbide mill. Cutting MDF. Not sure what kind of force this would be.

Given these knowns and unknowns what should be the stepper size?

[JerryFlyGuy]

Chips, that does pose a bit of a problem. Your steppers are rated up too 16-in-lb's but they will not get ANYWHERE near there w/ the lower voltages of the Xylotex power supply [I don't think anyway..]. Can you tell me what your nameplate spec's are for your stepper [ Voltage and amp's] I'm guessing thats a Nema 23 motor? [256 oz-in max] If you have the make/model that might help as well as I can go to the website [possibly] and get power charts from there also!

Now, w/ more knowledge comes more questions

If its a fixed gantry the weight doesn't matter, what is the weight of your table[ the moving part]??
Also, in your first post you'd stated a ballscrew and then in the last post a Acme thread can you clarify which one?

If your cutting MDF then the tool forces are very low, [you can imagine how much force it takes to operate a router in mdf by hand [ not very much ]

Sorry to pose more questions but until the fact's are known its a bit tough to 'tell' anything. It's kinda like looking at a race car and telling someone exactly how fast it goes or how much HP it has w/out even knowing what engine is in the car. It wouldn't be to terribly accurate. Not that you should expect I can work miracles and will have the exact performance spec's from your router either I can get close but.. you know what 'close' only counts in right?

Jerry

[Mr.Chips]

Originally Posted by JerryFlyGuy Chips, that does pose a bit of a problem. Your steppers are rated up too 16-in-lb's but they will not get ANYWHERE near there w/ the lower voltages of the Xylotex power supply [I don't think anyway..]. Can you tell me what your nameplate spec's are for your stepper [ Voltage and amp's] I'm guessing thats a Nema 23 motor? [256 oz-in max] If you have the make/model that might help as well as I can go to the website [possibly] and get power charts from there also! Now, w/ more knowledge comes more questions If its a fixed gantry the weight doesn't matter, what is the weight of your table[ the moving part]?? Also, in your first post you'd stated a ballscrew and then in the last post a Acme thread can you clarify which one? If your cutting MDF then the tool forces are very low, [you can imagine how much force it takes to operate a router in mdf by hand [ not very much ] Sorry to pose more questions but until the fact's are known its a bit tough to 'tell' anything. It's kinda like looking at a race car and telling someone exactly how fast it goes or how much HP it has w/out even knowing what engine is in the car. It wouldn't be to terribly accurate. Not that you should expect I can work miracles and will have the exact performance spec's from your router either I can get close but.. you know what 'close' only counts in right? Jerry

Thanks Jerry,
They are 116 OZ IN Nema 23 One Stack (Soerry I said 116 in lb before)

FLUID METERING CO
BYOBBET, NY 11791

116 OZ IN
POWER MAX II 1.8 STEP MOTOR
MODEL P21N8XC – LSS -NS- 03
CUSTOMER PART NO: 110588
IS(DC): 1.75 A BIPOLAR SERIES
Vs(DC) 65V
PO.48W T:90C MAX
CS:1500 RPM DATE 01066790

Hope this helps.
Hager

[Biggermens]

Originally Posted by JerryFlyGuy It's fairly easy to calculate if you want to do several iterations to find what works best I'd suggest setting up a spread sheet. There are several more questions which need to be answered before you can proceed. 1) Servo or stepper? 2) Reduction onto the ballscrew or direct drive? 3) Time to rapid speed [ how long do you want it to take, if your table is long this could be lower, if its shorter then you may never get up to speed w/ a longer time allowance as it needs to start slowing down before it gets to rated speed] 4) Force at the tool tip [ how much actual lbs force to move the tool through the mat'l at your req'd ipm. If you post some of this I might be able to figure out roughly what your looking at... Jerry

Hay JerryFlyGuy i have some info see if you can help me that would be much apreciated
1) i want to go with servo and gecko drives
2) i was thinking of going Direct drive
3) this i am not sure i never realy used cnc machines before so what do you think is reasonable my table is about 4 feet x 4 feet of work suface
4) i am not sure about that one also i want to cut some 1/4" think aluminium and think plastic ect..

for rapd rate id like to get 250 ipm and for feed rate id like to get 100 ipm i no i no i will not get that in aluminium

if you look at my photo galary i think my machine is built heavy enough for that
http://www.cnczone.com/gallery/showg...r/5656/cat/500

Thanks Jerry
once agine your help is apreciated

[Mariss Freimanis]

1) Power: Watts = Lbs * IPM / 531

Plugging your numbers in: Watts = 500 Lbs * 100 IPM / 531 and you get 94 Watts of power required, which you can easily get from a NEMA-34 step motor. This assumes you want to accelerate at 1G.

2) Screw Torque: in-oz = (8 * Lbs) / (pi * TPI)
Plugging your numbers in: in-oz = (8 * 500 Lbs) / (3.14 * 4 TPI) which gives 637 in-oz needed on the screw.

3) Picking a motor: A Keling KL34H295-43-8B motor wired in parallel (6A / phase) and used with a 72VDC power supply delivers 345 in-oz of torque at 900 RPM when used with a G202 or G203V.

4) Gearing: Screw RPM = TPI * IPM
Plugging your numbers in: RPM = 4 * 100 which gives 400 RPM on the screw. Meanwhile the motor is turning 900 RPM.

Reduction ratio is Motor RPM / Screw RPM. Plugging your numbers in: 900 / 400 is 2.25 : 1. Use a toothed belt and pulley reduction from motor to screw of 2.25 : 1.

This will put 2.25 * 345 in-oz or 776 in-oz on your screw at 100 IPM; you need only 637 in-oz. At low speeds you'll get 1,435 in-oz on the screw for 2,252 Lbs of push. That should shove your 500 Lb gantry around with ease.

4) Resolution: The drive takes 2,000 step pulses per revolution and it takes 18,000 step pulses to move 1" (4 TPI * 2.25 * 2,000). The resolution becomes 0.000055" per step pulse (1 / 18,000).

5) CNC Software: Mach3 tops out at 45,000 step pulses per second. You need 30,000 step pulses per second to get 900 RPM so your'e good to go with Mach3.

Hope that helps.

Mariss

[Biggermens]

Mariss that is some wiked help
i thank you very much

one more question will i be able to jog at 250 IPM ???? with that setup you got
if no what will i need to move it that fast or am i pusshing my luck ???
i also want it to move pretty fast so i can cut fome

I Thank you Very so Much
Bigger

[Mariss Freimanis]

Probably not. 250 IPM would mean 1,000 RPM on the screw and 2,250 RPM on the motor. The motor develops 130 in-oz at that speed and would apply 292 in-oz (2.25 : 1 reduction) to the screw. It would be perfectly happy to develop that speed and torque. Other things would intervene.

The problem would be:

1) Leadscrew whip. What is the critical RMP for that screw?

2) It would require 67,500 step pulses per second; only 45,000 per sec are available from Mach3. That equals 150 IPM.

Mariss