CNCzone Network: RFQwork :: 3Dstuffzone :: Welderzone
Proposed new machine for comment
Here's what I am thinking.
2" x 2" or 2" x 1", as spot purchases allows
3/4" drill rod, a flat ground on one side, drilled & tapped, and screwed to side frames.
1/2-10 acme lead screws.
Please see attached drawings.
Any comments, ways to use the parts better?
Rather than "fish plate" the side supports, I"d be inclined to miter them.
This cleans up the finish for a much more professional appearance (this asumes that you're welding them - bolted joint won't have same rigidity).
The miter fit would also provide more weld area for added.
Weld in stages and stagger from one position to the other to prevent warpage.
Assemble and align techniques
I am planning to bolt the frame together initially.
Most joints will have blocks made from 2" x 2" tube with SHCS bolts at right angles. (1/2" access through hole on outside, 1/4" through on inside, tapped hole in frame)
After the frame is trued I will tack weld and recheck; then a full weld.
I need to leave some joints free for future adjustment and truing.
I have been trying to come up with a good adjuster mechanism but nothing obvious jumps out at me. At this point it is just adjuster screw "feet" under the corners.
Z uprights will aligned by a dial gauge swinging parallel to the rails; tilt as needed to get them perpendicular to the bed – work for no change as is swings from one end of the bed to the other end. I am limited by dial gauge support arm length to about a 15" sample of the bed frame. This would work best if the dial support shaft is mounted directly in the spindle jaws.
I can get the side-to-side adjustment spacing by moving the travel carriages. The bed vertical parallelism will be set by the spacing to a surface plate with Johnson blocks under the rails.
The alignment of the lead screw:
1) Rough align "motor" end, thrust nut and “far” end pillow blocks as much as possible. Tighten "motor" end pillow block and leave the rest of the mounting hardware loose.
2) Move the drive nut as close to possible to the motor end; tighten its hardware.
3) Move drive nut to the “far” end. Tighten “far” end pillow block hardware. Loosen thrust nut hardware.
4) Move carriage back to "motor" end. Tighten thrust nut hardware.
5) Repeat as needed until axis runs smooth.
6) Move to next axis. Y, then X, then Z.
Last edited by mark.browne; 07-24-2006 at 11:43 AM.
Hi Mark, I was looking at your design of the carriage slide ways. It is not a very good idea to have a slide with the guide surfaces spread so far apart, in fact it is very bad practice.
Take for example the standard configuration of a lathe bed ways. The saddle always now runs on a raised vee and a flat. This is so that the raised vee gives a long very narrow guiding surface and the flat just supports the other side and keeps it level. You are using a round bar as a slide way and bearings as a carriage support. The cariage bearing layout should be mounted under the carriage and arranged to give two bearings at 45 Deg to each other on top of the bar and one bearing beneath the bar to act as the keep plate as per lathe and mill slide way practice. This configuration is placed at both ends of the carriage, and should used for all slide way layouts. The bearing layout on the opposite side of the carriage only require a bearing on the top of the bar and one beneath it to keep the carriage stable.
Some lathes (my own Colchester Bantam) had two raised vees, but this required a high degree of slideway accuracy and rigidity in the 'framework' to ensure allignment. I haven't seen this layout on new lathes for quite some time.