Anyone own a FRV30-ZX7750 (aka Grizzly G3616)?

[jcdammeyer]

I've gone one of the House of Tools FRV30-ZX7750 which used to also be sold by Grizzly Tools as a G3616. A friend here has a G3617 which has the horizontal mill feature and longer table.

I'm in the middle of converting mine to CNC and would like to find other owners who have the same unit. I've got it far enough along running both MACH3 or LinuxCNC and have now used it to make parts for the conversion. This video shows it moving.

I've also got a Shumatech DRO on the X,Y and Quill Axis. It's been a 10 year project with lots of gaps. This week I finished the RH X axis bearing support and have removed the power feed.

Eventually I'll add ball screws. Next project is mounting an AC servo for spindle drive.

 

[jcdammeyer]

Here are a couple of photos of the X axis lead screw nut (5 TPI, 1"). It's a very rough bronze casting with about 0.025" backlash. I was milling some 1/8" angle iron at 390 RPM and about 5.5 IPM and I the backlash contributed to an uneven cut when the first pass was a bit deep. It tugged enough to move the table.

I'm looking into a ball screw for it but unless I go very small diameter which may whip at high speeds a 25mm or even 20mm ball screw has clearance issues for the nut. I'd have to move it higher which means rebuilding the end bearing holders which I can do but ends up being a lot of work.

I was thinking just making a new bronze nut assembly that lets me take out backlash. I don't think I can actually modify the existing one to attach a second nut that could take out the backlash. Even my drawing for the existing nut is generous in giving it square sides etc. I'm working on a new drawing of the nut. I'll post that when it's done.

I'm looking for feedback and suggestions on how to create only a few thou backlash.

 

[jcdammeyer]

Oh and here is where it goes. There's room for a much wider nut along with more height so a new nut with alignment pins and screws to pull out the backlash seems like the best and easiest approach.

 

[jcdammeyer]

This is what I have in mind. I might also look at adding some flex wave springs between the two halves. Or use threaded studs with nylock nuts to hold the position. Or make it a bit taller and add a bolt that threads through the movable part and us it to press against the fixed part essentially locking it in position.

It's not easy to reach under the table to the center area so it's something that wouldn't be simple to adjust.

 

[YotaBota]

Do you have room for a spring loaded type of nut?

The link shows the idea and once in place shouldn't need adjusting.

 

[jcdammeyer]

Do you have room for a spring loaded type of nut?
The link shows the idea and once in place shouldn't need adjusting.

There's not a lot of room for commercial ACME nuts. It's essentially a 25mm diameter lead screw and the center line of the nut is 20mm from the frame. So there's 7.5mm worth of OD material available.

A 25mm Ball nut has a 40mm outside diameter. I'd probably have to make some sort of mount and tap holes into the casting. But then bolting it down while also having it aligned is the hard part. So it would be better if the mount had the same 25mm pin that would allow it to self align. And if the bearing ends are a bit high then it could pull out of the hole by one or two millimeters without issues.

Once I decide on a ball screw I'll sketch up something that might hold both the ball screw and anchor into the hole. Should be interesting.

 

[jcdammeyer]

Here's the idea for holding the ball screw.
https://www.anaheimautomation.com/manuals/linearcomponents/L011039 - DFU Ball Screw Spec Sheet.pdf
It would be a BSC-AAM-DFUR-25-05 model