Thread: Mel's Odd Idea
Well, here goes. I've set up the sand bags to hide behind, and here's the idea. I won't be building it just yet and am sure that lots will change, but what I'd really like is....
1. A three axis router to cut hard and soft wood, and very light aluminium.
2. A fourth rotary axis for round stuff :confused:
3. A manual wood lathe.
4. Occupying the same space , 'cos that's what I'm short of.
I can do wood, but metal is not for me just yet, so the build will be MDF/Ply/Other at least initially.
Not quite sure how to get the piccies right yet, but here is what I have modelled so far. It's concept really and yes, there are bits missing and I am sure lots wrong.
P1 is a basic workbench with retractable wheels and a manual wood lathe on top.
P2 is the bench modified to allow the lathe to be lowered and raised. This is guided by bearing carriages, but this isn't an axis. I'll probably use an old car jack to lift and lower, with stops at key points.
P3 is the base with what is essentially a Blacktoe build stuck on top.
P4 is the lathe in a position where it can be used as a 4th axis. Of course the lathe will have to modified to be convertible between manual operation and axis operation. I have seen a guy do this somewhere or other (might need help from Bogs here for metal brackets and mounts). Alignment might be an issue, but can only dream.
P5 is the gantry put to one side so that the lathe can be still used manually.
P6 just has a false sacrificial bed in there to mount things on - oh yes, and a computer.
All sorts of things are yet to be decided and probably won't be finally until the saw and drill come out - have to finish a dresser unit and decorate the utility and ... first.
The X-Axis is currently shown as a dual chain drive with the motor mounted at the back of the Y Axis with an axle across it - just like the Blacktoe. I've seen lots of alternatives to this (dual motors, chain or belt across the axis end etc) but the key point is that there can be nothing underneath the bed.
Y axis is also shown as chain again like the Blacktoe. This arrangement does bother me because it puts the motor for an axis on the next axis up and so has to be moved.
Z axis is shown as threaded (or ballscrew) and the motor moves with the fixed part on the Y carriage. I have seen this both ways round. This way seems a little more compact.
I have put in V-Groove bearings on angle or straight as the means of motion. I have been round in circles on this one and have had designs with the cheap skate on angle (pun intended) through round rail and supported round rail etc. I keep coming back to this as a decent compromise.
I know it isn't pretty (yet) but I thought I would put the concept out for your amusement.
If you make the gantry a little higher you will be able to use the lathe for production of spiral turning.
Like the idea of space saving!
I am working on something along those lines but have not progressed as far as conceptual drawings. Space is also what I am very short of. My main concern is that I may end up with a 'Jack of all trades' machine but due to things like the possible hight of a gantry with a very long Z axis then flexing may prove a problem. However I think there is a build around somewhere (the name Art Ransome (spelling) springs to mind) where the Lathe assembly was raised through the 'bed' accordingly. I think his machine was huge though. He was into wooden columns for the entrances to large old American houses or something like that.Tim G-C
“I disapprove of what you say, but I will defend to the death your right to say it.”
(attrib. Voltaire but written by Evelyn Beatrice Hall "The Friends of Voltaire" 1906)
Peter - I think I have worked the dimensions so that it can do spiral turning. I was concerned about the gantry height because of flexing, so have kept it down, but the working position of the lathe when in 4th axis mode can be at router bed height or slightly below or even slightly above. It isn't fixed yet and could even depend on the work piece. I am aiming for a Z travel of not less than 150mm, and the maximum radius of the lathe in the picture is 120mm. OK, this will not allow fancy manoeuvres like turning a wooden crankshaft where the bit has to cross to the opposite side of the centre point, but I think I can live with that.
Tim - Yes I am bothered about flexing. My original ideas had the X-Sides high up like Mechmates, but I couldn't get the dimensions to work properly. I might just try that again. I figured that I could put in a false bed to raise it's height for flat work so at least the Z wasn't reaching down. I am also a bit concerned about my own construction capabilities and have gone for a method which worked great for me on my manual router table. There I took two 18mm sheets of MDF and found their curvature by laying them against each other, which actually turned out to be tiny. I then glued them together with opposing curvature so that they are now my best reference plane. Lots of clamps were involved! I intend to make the table surface this way with two standard size sheets uncut, so I then reference from that hoping it is pretty true being "flat enough" and all four edges are factory originals.
I too have seen a rise and fall bed. It used supported round rail mounted vertically as the guides, but didn't have a lathe on it. And it was huge This is what gave me the idea. I don't think there is anything original in my drawing. It's all taken from various other designs. The gantry height and the Z are very little different from existing designs but maybe the Y height between rails needs to be bigger to give the Z more stability.
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