Homemade machine, need some tips

[originator]

Helo all, any suggestions on the following plan would be great.

For cost reasons, I intend to use acme 1/2" 10, the main option for the screws are to use Nookindustries.com. They have a black oxide screw for $8.91 a foot. There are 4 23 size 3.5amp bipolars for the project. The machine is primarily for a large format PCB used in an LED sign fab project. Other uses will be routing plexi, so I intend to find some type of PCB spindle for starters. I need these parts asap btw, so leads times aren't an option as there is a PCB spindle by one of the members I'd prefer to use.

The X rails are 1.25. The Y rails are .75. The plan is to machine some stanchions to hold each end of the rails, with bearings recessed in the stanchion to support the Acme screws, with one stanchion designed to mount the motor. My first thought is to simply let the motor carry one end, and the bearings carry the other. I have seen many designs like this. This of course requires either a 1/4" to ~1/2" coupling, or turn down the screws to 1/4 and use 1/4 to 1/4 coupling. Another idea is to machine a bushing to an exact fit on the screw, then drop that bushing in a larger bearing( for example a 1" bore bearing). That way, I have precise fit on the screw which is not a perfect fit on standard inch bearings. For thrust I was going to add collars to the inside and outside on the stanchion opposite the motor. Since the bulk of the load is the bearings and stanchion, I can't imagine the one stanchion not being able to manage the total thrust in each direction. To use bearings on each side, my only thought would be to have 3 total stanchions per side. One holding the motor, one holding the bearing and collars on the motor end, and one hold the bearing and collars on the opposit side.

I'd mount stanchions on the gantry as well for the Y rails. Then mount a plate on the 4 pillow blocks. I am still up in the air on a Z assembly. Low cost is the conern, so unless one shows up cheap, I'll have to machine one.
Originally I was planning to use the 2 pieces of 1030 for the gantry, it may be less hassle just to let the side panels support the Y rails and lose the 1030's. I don't see any strucural advantage to using the 1030's at this point.

I don't have an option for ABL nuts yet.

Well that's where I am at, any suggestions are welcome on completing the project.

[ger21]

These screws are cheaper and should give you more speed. They're good quality, too. http://www1.mscdirect.com/CGI/NNSRIT...MT4NO=15117481

You can get nuts here.
http://www.dumpstercnc.com/leadnuts_acme.html

[originator]

Thanks ger21, that is exactly what I am needing.

[originator]

The dumpster has about everything needed to get it finished, there are a few things left to sort out. One is finding a bearing that will fit snuggly over the 1/2 8 acme screw. I don't have the screws yet, but I heard they are not perfect 1/2 sizes, which means there must be some way found to get it tighter in the bearing. The other issue is that TIm at the dumpster recommended not using a single bearing on one end, while the motor supports the screw on the other. Does anyone know where I could look at a design where the motor is mounted on a plate, then the coupler mounts to the screw which is sitting in a bearing as well, so there is a bearing at each end?