PDA

View Full Version : Running CNC Router at 25mtr/minute



kmeshal9
29-07-2017, 12:58 PM
Hello There
It took me 3month to build cnc router
I am wondering where did missed
My specs are as follows
Working area:4*8 feet
Actuation:TBI ball screws 3210 2510 and 1610 for xyz axis respectively And hiwin linear guide and bearing.
Stepper motor: 1200oz-in (4.5 amp & 70v) and drive are of 6 amps 80v ac )
Power supply: i have provided 80v and 6amp to each stepper /driver.
I am running my cnc router 6mtr/m
Successfully when drives is set on 6amp
My stepper motor heats like hell
When i reduce current my max speed also get reduced.
Recently my friend showed broucher of some company.
Company is claiming that max speed will be 25mtr/m that seriously gives me an anxiety. This is hard to believe where did i missed. Why i cant achieve this speed.
And one more thing is that they are using rack and pinion.
How this is possible.
My steppers stalls whenever i try to go above 6mtr/m

https://uploads.tapatalk-cdn.com/20170729/b4e7f2ff5c40379276837f92d222bd45.jpg

Sent from my Redmi Note 3 using Tapatalk

Gary
29-07-2017, 07:03 PM
It will be rack and pinion, you can't get that speed with ball screws on a machine this size, unless you have ballscrew with a high lead and large diameter.


Hello There
It took me 3month to build cnc router
I am wondering where did missed
My specs are as follows
Working area:4*8 feet
Actuation:TBI ball screws 3210 2510 and 1610 for xyz axis respectively And hiwin linear guide and bearing.
Stepper motor: 1200oz-in (4.5 amp & 70v) and drive are of 6 amps 80v ac )
Power supply: i have provided 80v and 6amp to each stepper /driver.
I am running my cnc router 6mtr/m
Successfully when drives is set on 6amp
My stepper motor heats like hell
When i reduce current my max speed also get reduced.
Recently my friend showed broucher of some company.
Company is claiming that max speed will be 25mtr/m that seriously gives me an anxiety. This is hard to believe where did i missed. Why i cant achieve this speed.
And one more thing is that they are using rack and pinion.
How this is possible.
My steppers stalls whenever i try to go above 6mtr/m

https://uploads.tapatalk-cdn.com/20170729/b4e7f2ff5c40379276837f92d222bd45.jpg

Sent from my Redmi Note 3 using Tapatalk

kmeshal9
29-07-2017, 08:39 PM
Thanks 4 replying After looking for day
I get it
I am planning to replace my
My ball screws with ball screws with pitch 25 or 30.

Sent from my Redmi Note 3 using Tapatalk

Desertboy
30-07-2017, 07:03 AM
Thanks 4 replying After looking for day
I get it
I am planning to replace my
My ball screws with ball screws with pitch 25 or 30.

Sent from my Redmi Note 3 using Tapatalk

The higher the pitch of ballscrew the lower the resolution accuracy there's no such thing as a free lunch.

Boyan Silyavski
31-07-2017, 07:49 AM
Or you could use rotating nuts on a xx10 screw as the one you have

Anyway, what you are missing is that the company you are comparing to uses Servo motors, not steppers. you also do not state how heavy is your gantry. Also nowhere the acceleration is stated. And that could mean a lot. One thing is sure- you can not achieve real life cutting speed as this with stepper motors in any way and accuracy at the same time.

For your reference i move my 200kg gantry with acceleration 3000mms2 20m/min 2x400W AC servos 230V and 2 rotating ball nuts on 2510 screw. I can hit even 30m/min as my motors can spin faster than 3000rpm up to 5000. Your steppers are good to much lower speed , you probably need to drive them harder with better PSu at higher voltage and so on. So don't compare your machine with an overbuild commercial machine where they simply put some serious servos which are driven at 230V


PS. Machining at high speeds especially more than 10m/min and Hi Speed toolpaths makes that nuts and screw heat very seriously. You must make sure all is perfectly clean and greased properly

Gary
31-07-2017, 08:19 AM
its not just the speed of the motors, its also the critical speed of the ballscrew.
a 25mm diameter ballscrew that is 2000mm long and using a rotating nut has a critical speed of about 1400 RPM.
There is a critical speed calculator on our site in this link.
http://www.zappautomation.co.uk/index.php/ecalculators.html

However motor speed is clearly enabling you to get a higher speed, but by pushing the screws too much, you could damage the screws.
Alos remember, that a servo system has a much higher resolution than a stepper system, so if using servos, you can use a higher lead and not loose out too much on the overall resolution, and then spin the screw rather than the nut.
Also consider the application, may not need a high resolution, if used for wood, thats why a lot of commercial machines like routers and plasma and water cutting machines use rack.


Or you could use rotating nuts on a xx10 screw as the one you have

Anyway, what you are missing is that the company you are comparing to uses Servo motors, not steppers. you also do not state how heavy is your gantry. Also nowhere the acceleration is stated. And that could mean a lot. One thing is sure- you can not achieve real life cutting speed as this with stepper motors in any way and accuracy at the same time.

For your reference i move my 200kg gantry with acceleration 3000mms2 20m/min 2x400W AC servos 230V and 2 rotating ball nuts on 2510 screw. I can hit even 30m/min as my motors can spin faster than 3000rpm up to 5000. Your steppers are good to much lower speed , you probably need to drive them harder with better PSu at higher voltage and so on. So don't compare your machine with an overbuild commercial machine where they simply put some serious servos which are driven at 230V


PS. Machining at high speeds especially more than 10m/min and Hi Speed toolpaths makes that nuts and screw heat very seriously. You must make sure all is perfectly clean and greased properly

Boyan Silyavski
31-07-2017, 08:21 AM
I agree, but now that he has the screws to change them with rack seems a big waste to me.

Desertboy
31-07-2017, 08:30 AM
I have scrapped a few R&P systems from commercial magazine printers and they are always set up anti backlash with 2 pinions with 2 motors, unfortunately I stupidly let this stuff go the the scrap yard.

R&P has another advantage over the ballscrew I've been toying with a dual gantry for an 8*4 setup the idea being I can use park 1 gantry at the end for normal large operations or use both gantries (One a clone) to turn the router into 2 4*4 router's working on the identical jobs.

Whilst you could do this with 4 ballscrews you only need 2 racks (But 8 Pinions lol)

Gary
31-07-2017, 09:28 AM
Absolutely, my point was not to advise a change.
I was only pointing out that there is more to it than just resolution, and you need to also consider the critical speed on the screw.


I agree, but now that he has the screws to change them with rack seems a big waste to me.

Boyan Silyavski
31-07-2017, 10:35 PM
I still think using rack and pinion is mainly for 2 reasons: the size of machine and the ability to put together a long machine from short separate pieces and make it as long as you wish. At least that's how is in my eyes. Maybe also the ability to be hidden and facing downwards in a very polluted environment

kmeshal9
31-07-2017, 11:03 PM
I still think using rack and pinion is mainly for 2 reasons: the size of machine and the ability to put together a long machine from short separate pieces and make it as long as you wish. At least that's how is in my eyes. Maybe also the ability to be hidden and facing downwards in a very polluted environment
I am new in cnc i don't have that much experience
My gantry weighs almost same as yours.
23210 on X
12510 on Y
1610 on Z
How to size servo what specs to look.
What should be rated torque?
I will do whatever it takse to make my machine upto my expectations
Please enlight me more
Thanks in advance



Sent from my Redmi Note 3 using Tapatalk

Boyan Silyavski
02-08-2017, 11:20 AM
Please read very carefully from my second build log post #33 (http://www.mycncuk.com/threads/6619-Quite-an-Unusual-one?p=52452#post52452) and from #133 (http://www.mycncuk.com/threads/6619-Quite-an-Unusual-one?p=64510#post64510) to #140 .

That will answer all your questions. But before that, as was suggested above with a link to a calculator, find what's your screw maximum speed before it starts whipping for given length.

3210 screw is a very serious mass to move and to be snappy opposed to less than 1kg ball nut. Do your calculations, but the way i see it Rotating ball screw nut is the way to go and 400-750W servo motors each side.