MadModder

Houston, we have a problem.  How can I ensure that the X axis rails are parallel to each other?  Just so we're all reading from the same page, let me refresh your memory of what this thing looks like.

Starting in the lower LH corner we have what I am going to call the west side, because that's the way the machine is actually oriented.  The X axis rails are the longer set of rails running east-west, with the Y axis being the shorter set of rails that run north-south.  Keep in mind that the gantry is fixed and the bed moves east and west along the X axis,  The spindle moves north and south along the Y axis rails.

The magenta colored objects that are 50mm from each corner of the frame are the standoffs that hold the frame about 6mm off the base.  Those standoffs are there, because there's a lump in the base.  As near as I can tell, using the edge of a carpenter's square for a straight edge, the east, north, and west edges of the base are flat.  The lump is about 0.008"-0.010" thick, and is centered about 100mm from the south edge of the base, and about 1/2 of the length of the machine from the west end.  Except on the south side, I know those standoffs are in areas that are flat.  The 6mm gap should allow the machine frame to bridge the lump, so the top of the frame should be flat to the east, west, and north sides of the base.  So hopefully, this will allow me to ignore the lump.

So here M'Lords, is my clever plan, at least for the X axis alignment:
1 - I'm going to level the east, west, and north edges of the base.  I've got a precision level, it's not a great precision level, but it's got to be better than a carpenters level.  I've got some leveling feet on order that should make that job a little easer.
2 - After the base is level, I'm going to level the frame to the base.  I'll level it both north-south, and east-west, that'll ensure there's no twist in the frame.  I'm hoping it will already BE level, but... Hope for the best and plan for the worst.  If the frame isn't level, fixing that will involve shimming it level.  Since everything else is somehow related to those side frames, getting them true to the world will make life easier for Future Don.  I got some 5/16" thick float glass that is used to hone wood working tools "scary sharp", this and my 1-2-3 blocks should allow me to bridge over the bed and check that the frames are level - both north-south and east-west.  JBWorxStudio uses the float glass to tram in the spindle of his CNC router, it should work for this too.
3 - Next will be checking that the rails are level, this will tell me if the vertical centerline of the rails are parallel to the top of the frame.  I'm REALLY hoping that the rails will be level to the frame, since the mounting bolts for the rails use the 2 side slots in the 2040 side frame extrusions.  There may be a little wiggle room there, but not a whole lot of it.
4 - Next on the hit parade will be checking the bed,  The bed should be level, it does ride on the X axis rails after all.  But, those linear bearing mounting brackets were fabricated early in this project, before I knew how critical attention to detail REALLY was.  If they aren't level, I'll probably have to slot the mounting holes for now, and make new brackets when I get this thing operational.  I also need to be sure slots of the bed are perpendicular to the side frames. a 6" square fill do for now.

Once I've got the bed level, I can start the process of getting the Y axis rails aligned.

Hi Folks,

 A job that has been hanging around in the background nagging at me for some time! GRP is a very usefull repair medium which is excellent for odd shaped repairs and reinforcing of weak areas of virtually any rigid material. this video is a very basic "how to" for GRP ( glass reinforced plastic) Enjoy!!

Phil, in cool and rather overcast East Yorkshire

Progress has been made, tonight I put the Z carriage back in place. It feels stiffer, before when I pushed on the top of the carriage I could feel it flex - that's not happening now. I even added 15mm to the height of the carriage to compensate for the travel loss caused by the coupler. Here's what it looks like with the new Z carriage and the stiffening plates.

Adding that 15mm in height means that the leadscrew isn't long enough to reach reach the lower bearing anymore. I've got a replacement on order. but it's not due for a couple weeks yet. If by some miracle I get this thing running before then, the lower end can just run wild.

I also took a hard look at the alignment of the X axis leadscrew, both horizontal and vertical. Side to side it looks pretty good, it is DEFINITELY vertically challenged though. From what I can see, it looks like the leadscrew is about 2-3mm too low. With the leadnut block firmly bolted to the bed, I was able to get decent measurements from the top of the bed to the top of the leadscrew, from the top of the bed to the top of the coupler, the leadscrew diameter, and the coupler diameter. After running the numbers, I determined that my 6.17mm thick shim SHOULD have been 4.06mm thick. I'll have to add a stack of washers under the heads of the mounting bolts if they bottom out in the slot before they are able to clamp down. I don't think I've got the extra 2mm of clearance under the clamp that would be required by the thinner shim.

I got the spindle slide and the Z carriage reprinted, I even designed and printed the X axis leadnut block, That should be the last of the mechanical parts that need to be printed - I think!

I took the bed back apart, installed the leadnut block shim, and put it back together. There's a little binding as the leadnut approaches the motor end, it's not as noticeable at the other end. I just centered the leadnut block between the bearings, and I suspect that it's not quite lined up correctly side to side. The T8 leadscrew WILL flex, that's why I don't notice the drag when the bed is in the center of its' travel. When the bed reaches the end of it's travel to the motor end, the non-adjustable end of the leadnut is only a few mm away from the motor coupling. When the bed reaches the end of its' travel in the other direction, there's still about 80-100mm of leadscrew between the leadscrew support bearing and the non-adjustable end of the leadnut. That 80-100mm of leadscrew would explain why I notice the drag at the motor end, and not so much at the other end.

My current plan is to remove the bed and loosen the leadnut block enough that it can move, but not easily. I'll then put the bed back together and run it back and forth a few times, that should let the leadnut block find its' own center. Then, it'll just be a matter of carefully removing the bed, tightening the leadnut block mounting bolts, reassembling the bed, and trying it again. If it still binds after that, at least I'll know that I've got a vertical misalignment problem and not a side to side problem.

Hi Folks,
We are completely knackered! another week of field work, to catch up on what we didn't do last year because we were both ill! Health has returned, and with it just enough strength to reverse the  nature takeover bid, and reach new heights of organised chaos!
Phil, in almost too hotto garden East Yorkshire