[VooDooMan]

Hey all.

So I am finally putting my foot down and pushing forward.
I have or just about have ( on their way ) 3 stepper motors from the Asian market rated at
1 x 6.3 amp 5.5 mH 3V 1250oz/in nema 34
2 x 7 amp 3mH 2.8V 1250oz.in nema 34

First one for the Z and the other 2 are for the X and Y axis.
I am throwing Rockford precision rolled screws at the machine ( 6.31 x .200 pitch ) and I also have 3 x Gecko 201 drivers.
I am also making my own floating preloaded nuts for each axis + one shot lube system to loosen things up - hah.
With a C1G BOB from cnc4pc + mach 3 software.
I all ready have a VFD and motor running on the mill.

I will be rewinding a microwave transformer for the 2 required voltages since 2 require 55V and the other at roughly 75V.


My most pressing issue right now is the connection of the stepper to the screws.
Do I or should I gear them down? I have yet to see a RF45 converted to CNC with a stepper motor, - most of the guys use servos, but this was far cheaper for me this way, FAR cheaper.......
its 1250 oz/in holding torque I guess, and any thing above 1000 PPS drops rather drastically, Like you would expect from any stepper torque to speed ratio.
Calculation force that I have using this fellows site http://graetech.com/index_files/Page736.htm
Yields me 2*pi*8.8 Nmeters / .005 ( pitch in meters ) = 11058 lbs force.
That would be at max torque and direct coupled to the lead screw.

Now That torque will never be 100% with the gecko drive as I understand. Some thing to do with the sine wave, making 1 phase 100% and the other at 70% at any one time - Is this correct?
I calculate 875 oz/in the best I can do. at 1:1
And then your friction you need to over come and other factors.

So if some one can reply with the above information and enlighten me I can then continue on and keep a detailed log of all my work, I will give credit to the guys who have helped me along this far - you know who you are.

Thanks every one!

[pete from TN]

I am currently slowly converting a Lathemaster mill to cnc control using servos but there is a fellow named cflocker on here that did one with steppers and a G540 I think. Here is a youtube video...peace


[ame="http://www.youtube.com/watch?v=srPOdLKfDDA"]YouTube - ZAY MIll converstion with NEMA23 and G250[/ame]

[arizonavideo]

The table should be fine with the steppers and direct drive but the Z may be another mater.

With 3mh you should be OK with a single supply voltage for all the steppers.

I do think you may need some lift springs for the Z but you can always do it without them and add one later.

[VooDooMan]

Thanks for the reply Pete and arizona.
I was thinking the same for Z, I can always gear it or like you mentioned use counter balance ( gas springs I have seen used in this application )

Whow now, I am lost........I used gecko drives calculation of 32 square root 3 and 5.5 - They give me the 55V and 75V.
Now you mention I can run all of them at 55V?

Will that not effect my over all speed drastically on 1 of the steppers?

Thanks!

[VooDooMan]

Or did you mean 75V for all 3 motors?

[arizonavideo]

Thanks for the reply Pete and arizona.
I was thinking the same for Z, I can always gear it or like you mentioned use counter balance ( gas springs I have seen used in this application )

Whow now, I am lost........I used gecko drives calculation of 32 square root 3 and 5.5 - They give me the 55V and 75V.
Now you mention I can run all of them at 55V?

Will that not effect my over all speed drastically on 1 of the steppers?

Thanks!

In the video link with the RF-45 clone the Z is not powered. The head is about 200 LBS and they are often sticky like my IH mill. That should be your focus. Without springs or gas shocks you will have to gear way,way down. For the price of some kind of springs you could buy a servo driver and a used servo motor.

The formula is a good idea but just a guide line. The higher voltage will give power at an higher RPM but low speed performance is un effected.

A higher voltage will make your stepper run hotter even when parked. I am running some 400oz 1.8mH steppers at 60V and they don't get that hot around 60 C.

Steppers do vary a bit and the larger ones are known for being slow. A higher voltage may give you some needed speed.

So I would go with 75V. If you could rig a test power supply just to run one stepper it would tell you fairly fast if they will run too hot.

[VooDooMan]

In the video link with the RF-45 clone the Z is not powered. The head is about 200 LBS and they are often sticky like my IH mill. That should be your focus. Without springs or gas shocks you will have to gear way,way down. For the price of some kind of springs you could buy a servo driver and a used servo motor.

The formula is a good idea but just a guide line. The higher voltage will give power at an higher RPM but low speed performance is un effected.

A higher voltage will make your stepper run hotter even when parked. I am running some 400oz 1.8mH steppers at 60V and they don't get that hot around 60 C.

Steppers do vary a bit and the larger ones are known for being slow. A higher voltage may give you some needed speed.

So I would go with 75V. If you could rig a test power supply just to run one stepper it would tell you fairly fast if they will run too hot.

Correct on the gas springs, I think I am going to need to tackle that.
http://homepage3.nifty.com/amigos/60...asSpring-e.htm
^ not quite sure where his lock down screws went for the gib, But since I am using CNC I could leave those out and use small set screws?

Either gas springs and no gearing needed or heavy gearying and no springs. No brainier to me..........

I am looking to push these steppers to the max, in both speed and torque, Although I am not looking for 300 IPM rapids, I have to test this out some how in a mock up - Not easy when all this is new and this is my first go round.

Right I see what you mean about the added heat, Well I have my geckos set at 33% current when idling. So I will rewind my xformer tonight and then hold off on coating it in varnish just in case I have to remove a couple of wraps to lower the voltage, I think I will be ok though.........I will try for 70V

How long do you recomend I run this mock up stepper for and what temp is too hot and or just right? 60-80C?

THANKS!@!

[pete from TN]

That same fella has done the machine with steppers on all three axes and it apparently works. No guesses about Z rapid speeds but it does move and move well. I am currently working on my conversion which includes a belt driven spindle and considerable weight savings on the millhead with added spindle speeds so it might be even more doable with less weight to lift.... Just a thought....peace and good luck

[woffler]

Hi there i have converted mine to cnc i use a 2250 stepper motor on the z axis with a 3/4 x 2 ball screw with double nuts. Ive tested several ball screws for the z and found the one that works the best as you have a lot of travel on the z if you home to the top of the z axis.I tried several springs and all kinds of pulleys and junk on the z and as a result i found that all they do is create drag and cause a increase in backlash .I operate with out any of these things and i can run up and down and hold a backlash of .0002 i use a 4" cogged pulley on the screw and a two inch on the motor .I use 960oz rs steppers on x and y with 203v geckos on all axis.The machine is very powerful will snap a 1/2 end mill in a new york second as i found out by mistake one day.It will run faster than you want it to i run 30 inchs minute cutting aluminum all the time with no loss in steps and great part quality i run several production runs a day with a average running time of six hours a day.I have a secondary spindle hooked to the head that runs at 6300 rpm because the main motor is not fast enough i use it for big heavy jobs and steel jobs.

[VooDooMan]

IMPRESSIVE!!

hats down to your hard work!
Some thing to look forward to then.
2250 oz is most certainly nema 42.......I all ready have 3 steppers rated 1300 oz in at best.

So from what I gather adding the springs will add drag and or cause me backlash issues.
Well The best I can do for my screws all around are rockford precision rolled screws with DIY preloaded floating nuts.

Do you have any pictures of your setup I can browse through and take a gander at?

I bet it snaps end mills with ease. Plenty of torque there is you run at slow speeds.
is X and Y direct connected 1:1 ?

So you are running a 2:1 ratio for the Z AND 2250 oz in. Jesus man that's a ton!
I cant match that or even get close to that with out 4-5:1

Well I think we need to keep in touch, Seems I have plenty to learn from you.

Gluck on future cuts and work......I will be contacting you offline.

Thanks!

Hi there i have converted mine to cnc i use a 2250 stepper motor on the z axis with a 3/4 x 2 ball screw with double nuts. Ive tested several ball screws for the z and found the one that works the best as you have a lot of travel on the z if you home to the top of the z axis.I tried several springs and all kinds of pulleys and junk on the z and as a result i found that all they do is create drag and cause a increase in backlash .I operate with out any of these things and i can run up and down and hold a backlash of .0002 i use a 4" cogged pulley on the screw and a two inch on the motor .I use 960oz rs steppers on x and y with 203v geckos on all axis.The machine is very powerful will snap a 1/2 end mill in a new york second as i found out by mistake one day.It will run faster than you want it to i run 30 inchs minute cutting aluminum all the time with no loss in steps and great part quality i run several production runs a day with a average running time of six hours a day.I have a secondary spindle hooked to the head that runs at 6300 rpm because the main motor is not fast enough i use it for big heavy jobs and steel jobs.

[woffler]

[pete from TN]

Man that is some serious modifications ya got there.... please fill in the details man. Where are you located? It seems like you have an auxiliary spindle setup of some sort? HUGE steppers and serious power to spare, please enlighten us mere mortals....peace

[woffler]

I dont want to jack voodoomans thread go over to mini mill on steroids and ill answer there/ descktop mills /mini mill on steroids.