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Woodturning CAD Page 2 of 11

Symmetrical  profiles - Spline,  Its often not necessary to draw a full profile if both sides are symmetrical, genie finds it much easier to use nice shallow bends than a lot of tight corners,  

With this Spline profile Fig 3.1, some nodes were deleted and the Ref point of the profile has also been moved to the intersection of the red centre lines

The profiles are placed into position snapping to the blue line, hope your not using a black & white monitor :-) Fig 3.2, - this is the reason for relocating the ref point and allows for the Blue line to be used a slicing point or for mirror copying,  When lofting don’t forget the teeny weeny profiles,

Now, either simply  mirror copy along the blue line and boolean add together,  or slice the lofting along the blue line, and then mirror copy along the slicing line, -

Problems - Ref point moving to default location, this will mean that selecting the profile and snap to a line, it will be positioned wrong,

Cause - activating default ref point (local menu or button) - clumsy, occasionally happens on opening file, or moving file to different version (can occur when Boolean is used but unlikely in this case.)

Solution - group the profile and red cross when snapping to the guide, then before un-grouping keep a single copy of the profile on separate layer, then if the worse happens sooner or later it will,  and it proves difficult to realign,  its a simply a matter to making a new profile from the copy, .  This problem doesn’t happen often, but its better to be safe. than tearful

Symmetrical  profiles  - Bezier

The next lofting uses a similar approach to half spline, but uses a bezier curve where  tight corners in the profile can be utilised, Fig 3.4, but there are drawbacks, .the main one being editing the nodes, if you’ve ever tried editing your nodes you’ll see what I mean, can bring tears to the eyes

One thing to do when drawing the profiles is to go into properties Fig 3.5, experiment with the number of segments between controls points,  in some circumstances it can make a difference, the more segments the slower things can get, think of it as quality versus price.  Try it - draw a closed bezier and do some lofts with different segments.  

The loft is done in the same manner as the spilne, except that it’s possible to put the ref point on the ‘virtual’ vertex and snap to an outer guideline, Fig 3.6,  when positioning the ref point, try with  snaps on, zoom in, nearest on graphic, magnetic on,  Sometimes vertex running snap will work. If you haven’t upset Genie too much

Problem -  tweaking the  ‘control points’ of a bezier node, once all the profiles are in position, especially if done on a few profiles,

Cause - none   Blame - its your fault for not getting them right in the first place he he

Solution, - care, pure and simple, there is no magical solution that I know of with bezier control point editing,  just experiment on a few copied profiles to see if the desired shape is possible,  using grid snap with a fine grid, will give indication and possibly something to snap to,

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