Author Topic: Dimension Accuracy  (Read 151 times)

M.E.

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Dimension Accuracy
« on: January 20, 2018, 07:37:33 PM »
EXAMPLE: If I draw a line .0001" long and then zoom in enough to see both ends; then use the 'U' command and snap to both endpoints, the dialog displays '0'. This is setting everything that I can find to that .0001 value. If I export a DWG to AutoCad (2000LT), it will arrive at a measurement.  This is the next problem I'm having with the CNC world. I realize that this is not an uncommon problem so, I'm searching for an answer. In the last drawings I sent there were numerous places where lines did NOT snap to an end point. I can zoom in one the examples they sent back to me (like, XXX,XXX%) and see that they are not joined but it shows only a single point  in the 'point selection mode'. This is NOT universal, i.e. not every endpoint is NOT congruous.

Rob S

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Re: Dimension Accuracy
« Reply #1 on: January 20, 2018, 09:01:54 PM »
For the former, under options, general, you need to set the precision to a higher number of decimals, then the units command will show the correct line length.

Possible a bettter way to determine this is to use dimension info, anngle and distance.
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M.E.

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Re: Dimension Accuracy
« Reply #2 on: January 20, 2018, 09:47:34 PM »
Rob, thank you very much for that. It's not an intuitive thing to set the coordinate system to ten from a default of 2! I would never have 'guessed' that. Having said that, I've never needed it and was only curious as to why. All I can add is that I have no formal CAD training.

The other thing that I've been told is that there is some odd 'wild' lines showing up that they can see but I cannot, no matter what I do to try and see them, even in Acad. I will also add that this is the first set of drawings I've done with V2016, and I never had this many problems before. I'm wondering if I should go back to V24. 

Dr PR

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Re: Dimension Accuracy
« Reply #3 on: January 20, 2018, 10:38:47 PM »
M.E.

I used to have a lot of problems with end points of lines not connecting, lines not being perfectly vertical/horizontal, etc. In every case end points were off by a tiny bit. Then one day I noticed the cursor move on it's own!

A mouse or trackball is a digital device - it sends a binary number to the computer - 1s and 0s. When you move it a mechanical device senses the movement and produces a binary number representing the movement. Sometimes the least significant bit is a "0" and sometimes it is a "1". And sometimes this digitizer stops right at the boundary between a 0 and a 1.

When this happens even the slightest vibration can cause the least significant bit to flip from a 0 to a 1 or vice versa, and the cursor moves. Just typing on the keyboard can cause the cursor to move.

THIS IS NOT JUST THEORETICAL! I have seen it happen many, many times while using DesignCAD and other CAD programs.

Let's say you set a point while drawing a line and then start the Point Relative command. While you are typing the cursor may move. If you tell the program to set the point relative to the "Last Cursor Position" - the default - it will do just that, even though the cursor is not where you left it! So the new point will be a bit off from where you thought it would be.

I had a drawing where this had happened so many times that the drawing was totally unusable and I had to start over. I was in the habit of using the arrow keys on the keyboard to move the cursor known distances, but just pressing the keys was causing the mouse/trackball to move.

Now I am very cautious. When I use the Point commands I always select the "Reference Point" option. Then I gravity snap to an existing point that I want the new point to be relative to by the specified amount - the reference point. After that is is irrelevant if the cursor moves because of bit flip.

****

We have another user on the Forum who has a lot of mysterious hidden lines appear in his drawings. They are either extremely short lines at the ends of longer lines - probably the result of cursor creep - or short lines that are co-linear with longer lines. It has something to do with his drawing technique, because most people do not have this problem.

Sometimes you can see these shorter lines by setting Point Select mode (CTRL 1 toggles it on/off) and selecting everything - additional points appear in the middle of lines that should have only end points.

DT posted a macro to clean up these hidden lines. Search the forum for the discussion.

Phil
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M.E.

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Re: Dimension Accuracy
« Reply #4 on: January 21, 2018, 11:27:15 AM »
PR, thank you very much for this information and its revelation causes me to reflect on how I did this last set of drawings: new laptop (Lenovo,) new program (V2016), and a new method of use; using the Lenovo trackpoint instead of a remote trackball as in the past.  Obviously, I won't using the trackpoint again....It will take me a moment to absorb the hidden line situation and other tips you suggested. 

I'm very grateful to you all for taking the time to help me out!   

Lar

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Re: Dimension Accuracy
« Reply #5 on: January 21, 2018, 03:50:48 PM »

DT posted a macro to clean up these hidden lines. Search the forum for the discussion.

It's in DrollTroll's Toolbox in the Tips & Tricks section
http://forum.designcadcommunity.com/index.php?topic=3797.0

Dr PR

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Re: Dimension Accuracy
« Reply #6 on: January 21, 2018, 09:57:15 PM »
ME,

I use a USB trackball for all drawing - actually for all cursor movement, even on my laptop that has a touch pad. The touch pad is almost useless!

Phil
DesignCAD user since 1987