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I'll be watching since I also have a 9x20 that I want to convert to CNC. A few questions. Are you going to use 5/8 ballscrews on both x and z? Also are you going to use double ball nuts on either axis?
Thanks,
John B.
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Hello Everyone,
As this is one of my first posts here I should tell all of you a bit about me. I live near Columbus, Ohio, I work in Columbus as a machinist in a die shop. I run a Mazak QT350 every day, wonderful machine by the way! My previous job was making large crankshafts in a production environment. I have been machining for about 10 years.
I am just beginning the conversion of my 9x20 lathe. I decided to convert this lathe to CNC after converting my X2 mill. This lathe was not very user friendly as a manual; change gears really suck! After seeing the maked improvement in capability of the mill, I am looking forward to having the CNC lathe.
First off, thank you to everyone here for posting a wealth of information; it has been invaluable in the conversion of my mill, and the design process of converting the lathe.
I have not made a whole lot of progress yet as I am still waiting on my motors and bearings to arrive. I am finding it difficult to design various mounts without having the hardware readily available for mock up. Since I am without a lathe at the moment, I am going to send my ball screws to my brother for end machining.
I have, however machined out the X-axis ball nut mount. The ball screw for X will mount on the tailstock side, after much deliberation. The mount should also facilitate the use of a double ball nut setup to reduce backlash. I plan on driving the X-axis with XL timing pulleys geared 2:1 for resolution. The stepper will mount somewhere down near the apron.
I think I will mount the Z ball screw in roughly the same location as the stock one; I'll just have to make a gaurd to help keep chips off of it. Speaking of which, anyone know where I can order seals/wipers for 5/8" .2 pitch ball screw? I am using Roton screws and nuts.
The plan for the spindle is to use an old, and hopefully working 1HP, 3 phase Baldor motor with a VFD. I plan to use a v-belt to drive the spindle. I am open to suggestions here though! For threading and RPM I need to get a hall effect switch and make a single point trigger to mount to the spindle for index pulse.
For electronics, I am going to go with the G540, as it will control steppers and 0-10v output to the VFD for speed control. I have 2@ 381 oz/in Keling steppers for the axis motors. The 381 may be overkill for the X, but I know they are set up to run very well with the G540.
I have been looking for a good enclosure for the electronics and have found a few on eBay. Anyone know of any that are reasonably priced, let me know.
In a nutshell, those are my plans for the lathe at this time. Progress will be a bit slow as I have a lot of irons in the fire at the moment, but I will be sure to update the thread as I make progress.
I am open to any and all suggestions and advice on this build.
A pic of my X-axis ball nut mount!
Thanks!
I'll be watching since I also have a 9x20 that I want to convert to CNC. A few questions. Are you going to use 5/8 ballscrews on both x and z? Also are you going to use double ball nuts on either axis?
Thanks,
John B.
Yes, the plan is to use 5/8 X .2 pitch ball screw for both axis. The reason is primarily that I already have a four foot stick that I did not use when I converted the mill; I ended up going the CNC Fusion route there. As I only have three ball nuts on hand, I need to order a fourth so I can have double ball nuts on X and Z. I have yet to complete the design of the double ball nut setup. I will probably do the X first, as that is where I have decided to start. Once my bearings arrive from VXB, I will complete the bearing housing for X.
I will keep this thread as up to date as possible.
Last edited by Cobra92fs; 06-18-2012 at 09:40 AM. Reason: Misspelling
My stepper motors are due to arrive from Keling tomorrow. Super fast shipping at only two days! Hopefully my bearings will arrive as well. I like to have them on hand before I start machining so I can mic them individually. I will post some pics of my new stuff when it arrives.
Unfortunately, It is difficult to get much machining done working 1:00 to 11:00p. Should be able to make a few things this weekend.
I have dreamed up a simple setup for the double backlash nuts. Looking forward to getting it drawn up.
My stepper motors are due to arrive from Keling tomorrow. Super fast shipping at only two days! Hopefully my bearings will arrive as well. I like to have them on hand before I start machining so I can mic them individually. I will post some pics of my new stuff when it arrives.
Unfortunately, It is difficult to get much machining done working 1:00 to 11:00p. Should be able to make a few things this weekend.
I have dreamed up a simple setup for the double backlash nuts. Looking forward to getting it drawn up.
Now that my steppers have arrived, and my bearings on the way, it is time to consider bellville spring washers. I would like to run between 80 and 90 pounds of preload on the ball nuts, as seems to work well for others. Does anyone have any recommendations on what washers to get and from where? I have looked at McMaster Carr's website and they have tons. Though I did not see where they specified how many pounds each washer was. A little help here would be appreciated.
Hi,
On my preloaded ball nuts, I used 9715K89 from McMaster as these are rated at 14lb each and I used 6 of them in a stack to get to about 84lb.
You can find them here:
McMaster-Carr
Hope this helps.
Art
AKA Country Bubba (Older Than Dirt)
80 pounds is on the light side for a 5/8" screw. They would typically be 120-150#. Of course, what's important is ensuring that the pre-load exceeds the maximum dynamoc machining load the screw will ever see, as once the load exceeds the pre-load, backlash returns.
Regards,
Ray L.
Exactly what I was looking for. Thanks, I'll order these at break time.
I'll do some experimenting once the machine is running. I'll make the washer cage so that others may be added in the future if need. I really appreciate the info.Originally Posted by HimyKabibble
On my mill drillI am running about 175 lbs of preload using wave washers on 5/8" screws.
Here's a link to a 9x20 conversion in the Mach3 forum. His is a major project but may have some stuff that'll help you with yours.
9x20 Chinese Lathe Conversion
Seems like I remember there's a space problem with putting a large ballscrew in the X axis on a 9x20. I'm retrofitting an old Denford ORAC CNC lathe which is based on the EMCO Compact 8, the Austrian lathe that the Chinese copied the 9x20 from. It has an 8mm x 2.5mm on the X and a 16mm x 5mm on the Z.
Keep the piccies coming!
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