Extrusion Problem
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Hello all,
I am new to sketchucation and this is my first post. I have designed a few pieces in Sketchup that have turned out pretty well. I am currently trying to design a table for a customer that has legs that are skewed inwards so that the span at the bottom is 24" and the span at the top is 18" between legs. the legs are 1 7/8 square. What I found I could do was to create the rectangle, draw out the guide lines as to where I wanted the top of the leg to be, extrude the leg, select the top face and move it into the new location where the guide ilnes intersect. This action would skew the leg in the direction I wanted. So far, no problem. Here is the catch.
I also want to have a bead on the outer edge of the leg that has a 1/8" radius. What I did was to create a rectangle that was 1 7/8" square, then create a second rectangle that was 1/4" square pulling off of the outer corner towards the center. I then created a third rectangle within the second that was 1/8" square which gave me the center of my bead. I then used the circle tool to create a circle that was 1/8" in diameter. after that was accomplished, I erased the unnecessary lines to create my profile. Once everything was cleaned up,I tried to extrude my new shape and found it would only push/pull in a perpendicular direction. I could not skew the leg like I had previously done. I have tried several other methods and am tempted to draw the model without the bead, but I would like it to be as accurate as possible. I get similar results by using the follow me tool. Any suggestions? I can elaborate a little if I need to but to at least demonstrate the shape I have attached a PDF to this post which is a screen shot of the footprint. Thanks in advance and I am really enjoying the site!-John Mark Power
P.S. The first thing I tried was to create the leg and extrude it, and then to skew it to the angle I wanted, however I had problems making the top and bottom of the leg level, and not perpendicular to the long faces of the leg. Thanks again!
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Sketchup/OpenGL doesn't like making very small faces [<~1mm].
Try Scaling the form x10 and then making the extrusion.
When you are done re-Scale down x0.1.
Small faces can exist but making them is the stumbling-block. -
TIG's point about the small faces issue is right on, of course. I have a different approach which eliminates the need to scale back down but he's right about the need to scale up.
Your table has splayed legs so instead of trying to draw the leg with the foot flat and the splay angle included, extrude it vertically, rotate it to the splay angle and then cut the foot off parallel to the ground plane with a cutting plane.
I think you'll find it easier to work in SketchUp if you think about how you would make it in the shop. I find this useful for many operation in SketchUp.
Edit to add: Also consider that your bead doesn't need to be drawn with the default 24-sided circle. You can get away with 6 to 10 sides. the detail is small enough that it won't be noticeable that you're using an octagon to represent the round bead.
Edit to add: Here's a quick example.
I made a copy of the section of the leg and moved it closer to the camera so it is more easily visible. I changed the circle to to 12 sided but you can't see that when looking at the leg. This didn't require scaling to get it to extrude correctly. So from the left:
Profile drawn on the ground plane.
Extruded with Push/Pull slightly longer than the final length, made into a component, copied to make the right side leg which is flipped to mirror it.
Legs rotated to splay angle as specified in your text, cutting planes intersected top and bottom and waste trimmed off. -
Thank you both for your quick responses. Dave, I decided to use your method,and you are right, thinking like a woodworker is extremely helpful. In fact, your method is the way I initially went about it, but I didn't know about the cutting plane. In fact, I still don't know about the cutting plane!. I understand the principle of it, but I can't seem to locate this tool and I also cannot find a tutorial on it. It looks like you used a measurement line to create the plane but I tried that and found I would delete the whole face, as I suspected. If you have time to elaborate a little on this process that would be great. I have read many of your posts on Sketchup and thank you for all of the fine work you do. thanks again for the help,
John Mark Power
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John, there's no "cutting plane tool". You draw a plane that passes through to leg at the desired location and angle and then use Intersect Faces to intersect that plane with the leg. Then you delete the edges of the plane and the waste side of the intersect line. Using a woodworking analogy, your cutting plane is a saw blade, albeit with no thickness. Somewhere I think I might have a reference on using cutting planes. I'll see if I can find it for you.
The horizontal guideline was put in as a reference you it would be easier to see that the legs on the right had been trimmed.
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I didn't find the reference I was looking for so I made this quick example.
On the left you can see the cutting plane passing through the leg. Notice there are no edges where the plane crosses through the leg, though. This indicates there's no intersection.
In the middle, I've selected all of the geometry, right clicked and selected Intersect Faces>With Selection. You can see there is now an edge where the intersections have been created.
On the right I've just deleted the face of the cutting plane so you can see how the faces on the leg have been divided. The next step would be to delete the waste at the bottom of the leg and the perimeter of the cutting plane.
One other step you may need to do is correct face orientation after the cut is made. You want to make sure back faces are on the inside. If you are using a default template, the back face color is a blue gray.
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Dave, I think I've got it now! Thank you for the added bit of advice and the tip on reversing the faces. This is a great site and I am grateful for everybody's input on the site. I'll be sure to post the completed table when it is done and hopefully the actual piece once it is built!
-John Mark Power
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