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Drawing a Compound Segment Box Lid/ cutting summary Problem

C

chepler

PRO Member
Hello,

I am somewhat experienced with V2 of WP. I just upgraded to V3 and I have a few issues. Here are the two that bother me the most.

I can't use WP to draw a shape, composed of compound segments, that is wider at the base and converges to a small diameter at the top, for example a 2.5" deep lid for a 7" diameter box. I mean to make it with 12 compound segments (crosscut from the stock board). I think I should be able to draw this shape as compound segments in WP so I can get all the benefits of WP such as board width, board length etc. If I select "compound" I cannot manipulate height independently of upper diameter and the shape shown on the display is not possible to realize in the real world.. To me, the only difference between a compound segment and a stave is that compound segments are crosscut while staves are ripped from the supply piece. WP seems to make further distinctions that I don't understand. The irony is that I have constructed this shape in wood as a prototype and want to draw it so that I can use WP to play what-if in design.

I have two work-arounds. I can draw this if I select "staves" and then take board width to mean board length, etc. I can also draw this shape upside down using "compound" , so that the narrow end is at the bottom of the figure. Still, as I try to learn more about how to use WP, I wonder what I am doing wrong. Its OK if this is a limitation of the program, but its not OK if I do not understand how to use WP for this purpose.

Another issue, while I am at it -- the cutting summary (display and print-out) truncates numbers on the left, so that, e.g., 77.7 degrees shows as 7.7 degrees. I did adjust text size in control panel to be slightly larger than the Windows default. This may be the cause of this problem. Is there any way to change the layout of the summary table to allow nn.n degrees to display correctly?

Doug
 
I'm sure Lloyd will have the correct answer but in playing around I think you can get the correct lid height if you set the lower and upper diameter and then adjust the compound angle. You can see the height change in the lower right of the screen. The steeper the angle the higher it is.
 
Stuart,

I just tried it again, so that I could be more specific about what WP was doing. This time I entered the specifications directly. it worked as expected, although the red crosshatching suggests that the piece would not be possible to realize. This must be the fourth or fifth time I tried this and the first time I got useful results. Perhaps the issue involves using the CTL-arrow keys to change dimensions. (Original reply edited 11/23)
Thanks

Doug
 
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Hi Doug,

There are differences between Staves and Compounds that are more than just cross-cutting or ripping them. You are right in that you can create the identical segment using either Staves or Compounds and depending on which one you use, you may get information regarding board length, etc., that may be of more use to you, but that shouldn't be your only consideration.

The primary difference between the two is the way that details are calculated. Let's start with Compound segments. You'll see that there are three fields where you can input data: Upper Outside Diameter, Lower Outside Diameter, and the important ingredient - Slope. Varying these fields by either entering specific data or adjusting using arrow keys solves for a single variable - the height of the row. Because Compound segments are crosscut from a board, the board is flipped after each cut (exactly the way Flat segments are cut), it is possible to tell you how long a board you will need in terms similar to that of the Flat process.

Staves, on the other hand, use different fields to perform the calculations. For Staves, you specify the Height of the ring and the Upper and Lower Outside diameters and Woodturner PRO solves for the Slope. Since Staves are ripped from boards, there is no flipping of boards after each cut and so the length of stock required is simply the number of segments times the length of the board from which the segment is cut. While this measurement may not be as helpful, it is the only correct measurement that matches the process.

The process you use to cut the segments will help you decide which of the two Ring Types to use. For example, I like to use the 'wedge' approach to cut segments whenever possible. In this method, I attach a long, right-triangle shaped wedge to the miter fence. The angle of the hypotenuse is the Slope in Woodturner PRO. If I have a wedge with a 40 degree slope (for example), I first cut my board to the correct width and lay it against the wedge so that the board will be cut while laying at its intended slope. This means that I only have to change the miter angle to match the number of segments per row (12 segments = 15 degrees) and always leave the blade untilted. The board is simply flipped after each cut just as if it were lying flat on the table for Flat segments. With this method, I can cut perfectly fitting compound segments and glue them in a single step without having to make half rings. If I tilt the blade and use a non-standard miter angle, I always have to make half rings.

I have a few wedges hanging on my wall and each (with the exception of 45 degrees) support two slopes. For example, my 40 degree slope wedge is also a 50 degree slope if flipped over. I also have one that has 35 degrees and 55 degrees. So when I decide to use this method, I always use the Compound Ring Type and then override the blade tilt and miter angle calculations with the miter angle of a Flat ring. The Segment Edge Length calculation is still used as calculated and the Board Length is still a correct measurement.

The one thing I do to simplify the assembly of the ring is to pre-process the board to be cut. Instead of starting with a board that has a rectangular shape, I cut it to be a parallelogram. The angle to cut the the opposing edges is either 90 minus the intended slope. The intent is to cut the wood so that when the board has a wide surface resting on the wedge, the narrow top and bottom surfaces are parallel to the table. The beauty of this is that when you cut the segments and glue them into a ring, the top and bottom of the ring will already be flat and this is a huge time saver.

The best thing to do to try this approach is to work with a board made from MDF.

I hope this answers some questions, but it will probably raise more and if that is the case, please let me know.

With regards to the printout and character spacing, make sure that you have version 3.1.009 (go File > Help > About Woodturner PRO) as I made some adjustment to the font and column widths. My goal was to increase the font size as large as possible to make it more readable, but in the process, some long fields (such as blade tilt) may need some additional tweaking and I'll look into that.

Lloyd
 
Lloyd,

Thank you for your very complete response. I can't reproduce the problem, and I don't really care to reproduce it. I will just try to remember the difference in the way WP handles staves and compounds.

Your wedge method sounds very interesting and sounds like a better way to cut compound segments. It seems very different from the way I do it (sled on table saw) so I will have to learn how to do it -- after I finish my current Christmas presents project. You are right about how difficult it is to get the exact blade tilt. Also, I really prefer to get the blade to 90 exactly and then leave it that way. If I could get perfect segments without the need to sand half-rings, my results would be much quicker and better looking. Sanding half rings affects some feature ring designs like zig-zags. Also, what a joy to glue up the whole blank in one step instead of two at a time, which is how I do it now.

I wonder why I never thought of trimming the boards before cutting. That will now become SOP for me.

Regarding the summary view problem -- I do have version 3.1.009. When I first chose summary view, I was offered a choice of format. I did not know one frm the other, and chose one at random. Now I am not offered that choice again. Does that help or complicate the problem?

Thanks again.
 
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