New Machine Build- What size steppers ???????

[Santa Fe Al]

Hi All,

I am just about finished building my Gantry type router. Mostly of wood except for the Z-axis which is all aluminum.

Table size is 24 x 48

Acme screws - 1/2 x 10 - single start. - Single down center of X-axis with double bearing on each end for X and Y axis.

Gantry is approximately 35 lbs plus router weight.

Router to be used is a Hitachi M12VC 2-1/4 HP Variable Speed Router w/ 1/4 and 1/2 inch collets.

I am using skate bearings - top and bottom - for 48 inch X-axis movement using aluminum rails.

Y and Z axis linears are IKO 15 linear slide rails.

I am seriously thinking of using the nema 23 KL23H286-20-8B (Dual Shaft) Rated Current: 2.8A, Rated Voltage: 4.17V (in Bipolar Parallel) 4 wire steppers with a 28 VDC 12 amp regulated power supply - because I have it already.

The big question is: Is the stepper strong enough to do my router justice in power and speed?

Any input will be greatly appreciated. I'd rather hear it now than have to buy more stepper motors after I buy those mentioned above.

Thanks bunches, Al

[ger21]

The 1/2-10 single start will limit your top speed, regardless of what motor you choose. Also, what drives will you be using? Drives also play a part in motor selection.

The 1/2-10 will give you plenty of force at lower speeds with any size motor, but you may find that a smaller motor may give you more top speed.

[Santa Fe Al]

Originally Posted by ger21 The 1/2-10 single start will limit your top speed, regardless of what motor you choose. Also, what drives will you be using? Drives also play a part in motor selection. The 1/2-10 will give you plenty of force at lower speeds with any size motor, but you may find that a smaller motor may give you more top speed.

Hi Ger,

I'm waiting for the new 4 axis Geckos. Hopefully they'll be ready by the time I am, or buy the G250/G251 version.

Al

PS: I'm looking at these steppers instead of the ones I mentioned. I input the wrong ones origionaly.

NEMA 23 BIPOLAR STEPPER MOTOR 495 oz-in, 1/4” Diameter shaft with a flat.

KL23H2100-30-4BM (Dual Shaft) Rated Current: 3.0A, Rated Voltage: 5.1V

[Santa Fe Al]

Hi All,

My main concern is missed steps. In all the threads about missed steps, it seemed as if the stepper motor size had a lot to do with it.

Of course, attempting to move too fast also causes missed steps.

I chose the Kelling steppers because of the new cheap drives from Gecko. I'd rather use nema 34's of about 600 oz/in steppers, but at 6A., I couldn't use those pretty new Geckos.

While I'm at it, almost all of my cutting will be wood - non-exotic or hardwood - and perhaps some aluminum, if the machine can handle it.

I just don't want to do a 20 minute cut in 4 hours, or so.

Al

[Santa Fe Al]

Guys,

More comments / reasoning, please.

Al

[jalessi]

Al
there are a lot of variables that you have not mentioned, such as cutter size, depth of cut quality of finish etc...

Your top speed will be limited by the 10 tpi screws because as the rpm goes up the torque falls off no matter what the stepper ounce rating .

A 5 tpi screw would double your max speed and then a larger stepper would help, because of the additional torque required to turn more aggressive screws.

Jeff...

[jalessi]

Al,

I wouldn't worry about the Keling 495 stepper and the new Gecko G250 or G251

If they perform anywhere near there larger counterparts your router is going to perform a lot better than you expect.

A minimum of 1942 pounds of force will break the largest end mill your router can handle.


2 x "pi" 3.14 x 495 /.1 = 31086 ounces /16 = 1942.875 lbs

Jeff...

[Santa Fe Al]

Originally Posted by jalessi Al there are a lot of variables that you have not mentioned, such as cutter size, depth of cut quality of finish etc... Your top speed will be limited by the 10 tpi screws because as the rpm goes up the torque falls off no matter what the stepper ounce rating . A 5 tpi screw would double your max speed and then a larger stepper would help, because of the additional torque required to turn more aggressive screws. Jeff...

Hi Jeff,

Sorry, I wasn't thinking that far ahead. I'll probably be using 1/4 inch bits most of the time and cutting no deeper than 3/4 inches in increments of whatever depth the machine will be able to handle.

As far as finish goes, I hope I won't be sanding too much.

Everything I know, I read here on the Zone. Sure is a lot of information from many talented people to learn from.

I'm not looking for real fast speeds. Just enough so I won't be lulled to sleep watching the machine work.

If all works correctly and I can get good cuts, then I will probably change the screws to something better.

This is my first attempt and I borrowed heavily from many on this Zone. I'm not a machinist and barely get by in electronics. You can see why I need lots of help.

I'm trying to find out if my ideas are worth anything and will work.

Al

[jalessi]

Al,

Your machine is going to work very well.

Don't worry about it being in slow motion either, it is going to cut PLENTY FAST!!!

You have to much time to think right now, wait until you see it FLY with the Gecko's!

Jeff...

[jalessi]

Al,

The step over distance of your end mill may be between 20-35 percent of the diameter end mill in order to obtain a smooth finish, hence surface profiling and 3d contouring take a lot longer than cutting simple offsets etc...

The diameter of the end mill, spindle rpm. flute count and type of material is going to determine your feed rate.

http://www.endmill.com/pages/training/spdfeed.html

There is a chance that you will not be cutting hardwood and aluminum anywhere near the speed your machine can obtain because of the limitations of the end mill not your screw stepper combo. Spindle horsepower may also come into the equation.

Jeff...

[Santa Fe Al]

Thanks Jeff,

You are a beacon in the night of ignorance.

Thank you for all the excellent information. With guys like you helping out, I will be keeping a positive attitude and will be eagerly looking forward to the machine becoming operational.

Al

[Crevice Reamer]

Formula for Best power supply voltage for a stepper motor: 32 times the square root of the inductance.

The Keling 495s have an inductance of 7 mH. The square root of that is 2.646. Multiplied by 32 = 85 volts required to get the best performance out of the motor. These motors will be seriously underpowered at 36 volts or even 48V.

If you truly want top performance with the KL 495s, Get some Gecko 203Vs and a 72 volt power supply.

The Gecko 203Vs will also run ANY of the Nema 34 motors--and THEY don't all require 72V plus power supplies.

CR.