G4003G Conversion

This forum is dedicated to those Hobbyists Interested in CNC machining & 3D Printing in their home shops. (Digital Read Outs are also topical, as is CAD/CAM as it relates to CNC)

Moderator: Harold_V

User avatar
Dave_C
Posts: 960
Joined: Mon Apr 21, 2008 10:34 am
Location: Springfield. MO.

Re: G4003G Conversion

Post by Dave_C »

Progress:

I finished the mounting system for the zero backlash ball nut system for the X axis on the lathe. Due to space constraints, this was not an easy task. Designing the mount so I could get the spring washers to work properly took a bit of racking my brain and it was hard to find a rack that small. :D

The first picture is a view looking down onto the ball nut mount. It is together just like it will go on the ball screw. You will notice a tiny hole between the two 1/4-20 mounting screws. [actually there are two] The outer one is for the set screw that holds the ball nut from turning and the one in the middle is for ball nut grease. It will force the grease between the two ball nuts and thus flush them as needed.
Top View
Top View
The second picture is just a side view of the assembly.
Side View
Side View
The third picture shows the spring washers with the assemble taken apart. Notice the small 8-32 set screws that keep the washers from rotating. This is necessary as a small amount will be milled away from the bottom of this assembly so as to fit in the available channel depth under the cross slide. The two washers face each other and rest in a pocket that is .040 deep to keep them from binding on the ball screw.
Split view
Split view
The forth picture shows the square slot that keeps the ball nut from turning. The two shoulder screws let the plate and washer move just enough to keep the assembly tight but allows for drunken thread movement.
Split view with reversed block
Split view with reversed block
This area under the cross slide is the most challenging part of the CNC conversion due to space restrictions. You only have about 1.350" of depth under the cross slide before you hit the vee channels of the bed. This assembly I have made will work but it may require me to raise the center line of the ball screw a bit.

I've still got some work to do before I make that decision. I have to start taking the lathe apron apart and do the milling of the channel depth. Before I can do that, I have to have all ball screw work finished and all mounts made that require threading as I only have one machine to work with.

Dave C.
I learn something new every day! Problem is I forget two.
User avatar
Dave_C
Posts: 960
Joined: Mon Apr 21, 2008 10:34 am
Location: Springfield. MO.

Re: G4003G Conversion

Post by Dave_C »

Update:

I failed to mention in the above post that when I threaded the right hand ball nut into the mounting block and torqued in down it was perfectly straight up and down as it needed to be. Couldn't do that again if my life depended on it! Sometimes we just get lucky.

Actually if yours does not turn out that way it is very easy to make it so. Just make your block the extra width of one turn of the thread and mill it down as needed until it registers the way you want it. My thread is a 16 pitch thread so I did have enough material left to make it register if I needed to. (.0625")

Now for the good and bad news:

I mentioned on another thread that I might be taking a teaching position at a Technical school. Well they hired me this week and I start Monday. After 40 years in the trade I figure I can give back something and I love to teach and see others do well.

That means I won't have a lot of time to complete this CNC conversion. I have nothing pushing me to complete it but I will do so when I can.

I'll be back on this thread when I have more to share.

Dave C.
I learn something new every day! Problem is I forget two.
User avatar
SteveHGraham
Posts: 7788
Joined: Sat Jan 17, 2009 7:55 pm
Location: Florida

Re: G4003G Conversion

Post by SteveHGraham »

Pardon me for polluting your thread, but is there some reason you like Ethernet better than USB?
Every hard-fried egg began life sunny-side up.
User avatar
Dave_C
Posts: 960
Joined: Mon Apr 21, 2008 10:34 am
Location: Springfield. MO.

Re: G4003G Conversion

Post by Dave_C »

Yes,

Length of cable and speed. USB should be limited to 5 feet or less. Ethernet can go up to 300' without a switch or router.

Dave C.
I learn something new every day! Problem is I forget two.
User avatar
ctwo
Posts: 2996
Joined: Tue Mar 27, 2012 12:37 pm
Location: Silly Cone Valley

Re: G4003G Conversion

Post by ctwo »

It also seems there is a general trend that Ethernet installs seem to have fewer problems.
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...
User avatar
Dave_C
Posts: 960
Joined: Mon Apr 21, 2008 10:34 am
Location: Springfield. MO.

Re: G4003G Conversion

Post by Dave_C »

I've been off this project for months but am working on it again.

Here is the link to the first video, it only shows the machine stripped down and the Mach 3 computer stand. I will make more videos as I start to assemble all the parts I have made. The ball screws are machined and all I lack is making mounting brackets for the Servo motors.

http://youtu.be/cf_DwCNv68Y



Enjoy for now.

Dave C.
I learn something new every day! Problem is I forget two.
User avatar
Dave_C
Posts: 960
Joined: Mon Apr 21, 2008 10:34 am
Location: Springfield. MO.

Re: G4003G Conversion

Post by Dave_C »

Back in the shop this morning and I finished milling out the channel for the ball nuts! WOW, this was the part I was dreading as there is very little room for error. As you can see from the pictures, the channel hits the milled out relief areas above the Vee's on the ways. Not to worry, There is still .022" between the bottom of the ball nuts and the top of the Vee's. The channel measures 1.358" from the top of the channel to the bottom and is 1.530" wide. The bull nut carrier is 1.500" so that give me .015" clearance on each side.
Channel 1.530" Wide by 1.258" Deep
Channel 1.530" Wide by 1.258" Deep

Looking at the two ball nuts, the front one is threaded full depth to the shoulder, set with a setscrew and locktite. The back ball nut floats between the cut out channel in the second retainer. There are two spring washers, one each in each ball nut holder. The two springs face each other and are recessed into a pocket the depth of the washer thickness.

The trick to making this work is getting the fit up to 1/8 of a turn which gives me .025" compression of the springs for about 100# of pre-load. It only took me three tries to get the pre-load the way I wanted!
Front thrust bearing and mounting block
Front thrust bearing and mounting block
So assembly goes like this. Put the back ball nut on the ball screw first. Install the u-channel retainer with its spring over the ball screw and slide onto the front of the ball nut. Now install the second ball nut and spring facing the first one. As you turn the two ball nuts on the ball screw they will advance toward one another. The two flanges will meet with 1/8 of a turn left to go before square on top. Go ahead and make them square, insert the two shoulder screws that lets the back ball nut retainer float and you are done.
Ball nuts and ball screw in place
Ball nuts and ball screw in place
I'll make a video of this when I get some rest. I'm tired! I should add a note: I removed the threaded part from the back ball nut so that is why you can't see it. Also the little hole between the two 1/4-20 screws is for grease. There is a removable zerk on the cross slide so I can force grease between the two ball nuts thus flushing them from time to time.

Dave C.
Last edited by Dave_C on Tue Sep 02, 2014 8:07 am, edited 1 time in total.
I learn something new every day! Problem is I forget two.
User avatar
Dave_C
Posts: 960
Joined: Mon Apr 21, 2008 10:34 am
Location: Springfield. MO.

Re: G4003G Conversion

Post by Dave_C »

I know someone is going to ask "why didn't you just mount the front bearing into the casting?"

Good question but try as I might, I could not make a setup on my small mill that would let me bore the pocket. The lathe apron is too tall to stand up right, too wide to clamp on the side of the table even when I removed the oiler. My ram will swing to the side but because it is such a sort ram it did not give me enough reach to hit the center of the pocket when I made the swing.

Believe me, I tired real hard to make a set up that was solid and straight.

I'm still thinking on it of anyone has any thoughts!

Dave C.
I learn something new every day! Problem is I forget two.
User avatar
Dave_C
Posts: 960
Joined: Mon Apr 21, 2008 10:34 am
Location: Springfield. MO.

Re: G4003G Conversion

Post by Dave_C »

More Progress,

I got the mounting brackets made for the Z axis motor and the motor is temp mounted. Holes are drilled in the mounting plate for the thrust bearing end and I'm ready to mount the floating end bearing tomorrow.

It is starting to come together!

Dave C.
Attachments
Left end view
Left end view
Right side of Z Axis mount
Right side of Z Axis mount
X axis thrust bearing and cross slide. Back end bearing holder is not made yet!
X axis thrust bearing and cross slide. Back end bearing holder is not made yet!
I learn something new every day! Problem is I forget two.
User avatar
Dave_C
Posts: 960
Joined: Mon Apr 21, 2008 10:34 am
Location: Springfield. MO.

Re: G4003G Conversion

Post by Dave_C »

More progress today,

Just a short video showing the Z axis being tested.

http://youtu.be/CKxG5rH_cPY



Enjoy

Dave C.
I learn something new every day! Problem is I forget two.
User avatar
Dave_C
Posts: 960
Joined: Mon Apr 21, 2008 10:34 am
Location: Springfield. MO.

Re: G4003G Conversion

Post by Dave_C »

More Progress,

I finished the back bearing support for the X axis ball screw. This extension is necessary because of the double ball screws that make up the zero backlash ball nut. I checked the travel with this support in place and I have 7.75" of X travel. I had 6" before the conversion.

I am working on the limit switches for the X axis and then I can mount this back onto the lathe.
Attachments
Front side
Front side
Back Side
Back Side
I learn something new every day! Problem is I forget two.
User avatar
Dave_C
Posts: 960
Joined: Mon Apr 21, 2008 10:34 am
Location: Springfield. MO.

Re: G4003G Conversion

Post by Dave_C »

Starting to close in the front under the apron. The plate that supports the ball nuts for the Z axis is in place and running true. I have the X axis motor propped up and will make the front support plate next.
Attachments
Front of Apron
Front of Apron
Side View
Side View
I learn something new every day! Problem is I forget two.
Post Reply