I have a curve driven pattern making a spiral staircase. The problem I have is that the top step comes up a short of where it should be. The bottom step is the start of the pattern and the helix is the driving curve. See attached images.
I have a curve driven pattern making a spiral staircase. The problem I have is that the top step comes up a short of where it should be. The bottom step is the start of the pattern and the helix is the driving curve. See attached images.
You may have to play with the spacing since you are following a curve instead of a straight line.
It is equal spacing for 23 steps
Double, double check all your dimensions - there may be an inverted number somewhere or if you're like me and got fat finger disease
Equal spacing is checked
Set your pitch to the height of your cylinder minus the step height....?
Can you post the part?
No soap
Hi Jeff.
I am not sure where your bottom step is positioned from the images. Have you created a pierce relation from the sketch for the stair to the helix path? I created the enclosed image using a pierce relation to the bottom step then curve driven pattern equally spaced. Transform curve, Align to seed, bodies to pattern.
Is this the kind of thing you are after?
Mike.
I am attaching the file
Change the pierce of stair extrude to the mid-point of the stair....
Attached
so, if I put my helix in the center of the step, it will work?
That works and that is stupid
Hi Jeff I've just been doing almost the exact same job! Getting the Curve driven pattern to work right took a while. I didn't use a curve driven pattern to make my treads as on this stair they are all different shapes, but if you look how I patterned the under tread moulding it should work the same for you.
The key is to carefully create a surface. You can use the edge of the surface as your direction and the face as your normal
see how the surface starts in the middle of the body (I generally create the bodies to pattern as extras and then delete them, as it causes a problem if you want just one tread, the pattern feature throws a wobbly, this way there is always a pattern)
The surface is made from the axis and the helix (here extended to a straight wall)
and then positioned using direct editing and trimmed with sketches from the top plane.
getting the face normal right is the important part too
As a contrast you can see the surface I created to pattern the spindles. As I was patterning two bodies at the same time I worked out that I had to go from the center of them combined. Here I used the lower edge of the surface as the pattern direction which is directly between the handrail and the stair going. The cuts were made by offsetting (with zero offset) to get a copy and then using move/copy body, and trim surface.
It definitely took a while for me to get it right, and Im not sure even now how I got it to work, but it's fully parametric and so far behaves itself.
I would look at constructing a helical surface using a swept surface with the twist along path option and using that to control my pattern
hope that helps, happy to answer any further questions.
Rob,
Can you send me your model? That way I can walk myself through it and better understand.
Sorry I can't send you the model I took the pictures from as it was for a company who want to keep their models private but I have made another part with the technique I was proposing. No matter what combination of edges and surfaces I used I couldn't get the curve driven pattern to produce a perfect result, it was close, but not perfect.
Notice the treads aren't perfectly parallel to the top plane, this front corner is 0.2mm low
I probably didn't notice the slight imperfections on my spindles and mouldings on my previous model. The other difference was I contstructed my surface from a Helix, not a sweep like in this case.
I used a 3D sketch and a linear pattern to produce the treads in my previous model. It works but is a little flaky as solidworks is a bit messy and fussy at the same time. Occasionally you have to roll back before the pattern feature and do a rebuild, this seems to reset the 3d sketch. You also have to do a dummy extrude, if you were so much as to hide that dummy body it creates a chain of events where the tread extrude trys to merge result but cant and the pattern fails. Solidworks also sometimes loses the direction of the pattern, i think its just a bit buggy
Anyway it produces perfect results when it works as shown below
I am currently working on developing a general purpose spiral stair model, so I'd be doing this work anyway at the moment. Because the linear pattern is a bit flaky and constructing the 3D sketches a bit tricky the Pattern along curve really appeals to me (It also rebuild 5 times faster). The next thing I tried was the curve driven pattern but with a boundary surface - I read they are much higher quality and the result was acceptable I think if not quite so perfect as the linear pattern
When I select the tread face and the top plane in the status bar it shows an angle, not a distance so there must be a very slight discrepancy
but thats under half a micron out... I think that'll do
I attach the model, It has 3 configurations that show each method. It should be parametric, but I think I suppressed the sketch that sets the height, so you'll either have to switch configurations to alter the height or it should still be accessible via equations, where you will have to go anyway to alter the total angle, etc..
I just checked it before I attached and the linear pattern failed again, see how the direction box is empty, you just have to select the dimension again and it works,,, maybe its when the dimension changes while the feature is suppressed I don't know
All the best hope that helps, these values should be all you need to change to give it a workout, to be cautious maybe switch to the linear pattern config before you make changes
Thank you. I will study it. My goal with all this is to have a design table driven spiral stair. I have implemented it and we are evaluating it now and working out all the bugs.
Cool, I am working on a similar project, I need to produce flat patterns of the curved strings for CNC and also solids of handrails etc to send away. maybe we can compare notes? (All my posts are being moderated at the moment, so taking a while to show up on the forum)
Sure. I am doing the same. I am also working on it being OSHA compliant.
Hi, did you guys get this to work every time?
Come across the same issue (also had the issue several releases ago) sometimes parallel sometimes not.
Change the pierce of stair extrude to the mid-point of the stair....
Attached