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CAD Intermediate – Linetypes and LTSCALE

Linetypes offer the drafter a means of differentiating drawing content and is an effective means for scope presentation as well. Linetypes along with line weights (we will cover line weights in another post), and line type scale can help improve the quality of your drawing significantly. A well done drawing can present the content clearly by using linetypes properly. Linetypes have been around as long as drafting has been around, (assumption on my part, they probably came along after a generation or two of drafting). There are accepted standards for linetypes that we can take advantage of. There are also special linetypes we can use. We can further expand on these linetypes using LTSCALE and / or pre-scaled versions of linetypes. All of this together provides a great way to define your drawings purpose. Use your linetypes properly in conjunction with LTSCALE and your drawings will not only be of better quality, but also easier to work on and use by others.

As an industry “standard” we see linetypes like “CENTER”, “PHANTOM”, “DASHED”, “HIDDEN” and more. I am not going to break down each type, but we know what these are pretty much used for. CENTER is for representing a CENTER Line, easy enough. PHANTOM is typically used to represent a limit of some sort, like Drawing limits or Skid Limits. DASHED and HIDDEN are pretty much the same but vary in size or scale for that matter. Typically DASHED OR HIDDEN mean beneath something, or implied connection, or even identify scope of work by others. So each linetype we use in our drawings means something and is not just arbitrarily used to differentiate. When working with other disciplines, you should understand what their linetypes are representing. It is beneficial for you to understand why they used a particular linetype. Make sure your linetype is appropriate for your purpose. Review the end result. Does your underground conduit look like underground Piping? Is that the look you are going for? Does your Pipe look just like the ditch running next to it? (See Figure 1) You should be able to manipulate the drawings appearance to identify clearly what is going on. Control is much easier when everyone draws bylayer. See my post bylayer for more on that. Text associated with certain lines helps identify and differentiate as well. Keep relevant information in your drawing to add clarity. Not all line work from other disciplines is needed in your drawing to present your design.

Figure 1

Note: Linetype definitions are stored in your drawing file and are not reloaded each time you open the drawing. If you find that your linetypes don’t match across drawings, you may in fact have a different definition in one of your drawings.

Another aspect of a linetype is the LTSCALE applied to it. Typically each company or even each company’s discipline has a standard LTSCALE. What is LTSCALE? LTSCALE is the scale factor applied to the generation of a linetype. If a line normally has a line for 0.5” and then a gap of 0.25” then repeats, it means that patter repeats at those distances. If you drew a line 5” long it would have 7 – 0.5” segments in it. If you had a scale of 0.5 it would then mean that same line would have 14 segments 12 at 0.25” and 2 at 0.1875” The difference is to make sure the line does not end on a gap. AutoCAD handles all that for you though. You can test this with the DASHED linetype, since the definition of it is as described above. Make sure you start with LTSCALE set at 1.0 and CELTSCALE at 1.0. I highly recommend NEVER changing CELTSCALE to anything other than 1.0. I will discuss that shortly. LTSCALE controls the linetype generation in your drawing and is stored in your drawing. That means it applies to the drawing you set it in only. If you use a scale factor of 48.0 in your drawing and your standard LTSCALE is 0.5 then your LTSCALE would then be 24.0. Take advantage of the scaled linetype definitions like CENTER2 (half sized center) See Figure 2

Figure 2 – What’s important in this sample?

Wait what about Paper space shouldn’t LTSCALE be 0.5? Yes and No. It depends on your environment and how your company standards work or even how your drawing works. If you have a drawing using paperspace and multiple scale factors in your drawing then you want to use paperspace to control LTSCALE set it to the value desired, 0.5 in this instance, and be done, just make sure PSLTSCALE is set to 1. I won’t get into too much discussion on these to avoid confusing this post, or just making it really long. Short explanation is. There are a few variables that affect LTSCALE. (LTSCALE, CELTSCALE, PSLTSCALE and MSLTSCALE). Do a little research and understand the difference. We will stick with Model space for our plot environment on this post.

TIP: Did you know there are different linetype files. ACAD.LIN is typically Empirical, and ACADISO.LIN for Metric. Try and avoid mixing and matching these two. If your drawing is metric you want to use the ACADISO.LIN file, otherwise use the ACAD.LIN file.

CELTESCALE means Current Element LineType Scale. When you click on an entity and look at the properties (see Figure 3.) you will see a Linetype scale for the entity. This is where you can set a custom linetype scale for this entity and this entity alone. The value you input here will be multiplied times the LTSCALE factor of the drawing. I recommend leaving this at 1.0 always. Changing this at the entity level means it is controlled at the entity level. If you set it here and someone else references your drawing into their drawing they will not be able to control how it is displayed in their drawing. See my post on Bylayer, bylayer, bylayer to better understand why that is important.

Figure 3 – Entity Properties

Custom Linetypes are useful as well, but with proper application. You can create your own linetypes and add all kinds of cool linetypes to your drawings. The nice part is once they are loaded they are part of the drawing, so they distribute well. When creating linetypes you can also specify the use of some text or characters to display in your linetype. Be sure to use a standard font file that is distributed with AutoCAD when you do this. using a Custom SHX file will leave your drawings looking incomplete when the end user does not have the SHX file to load. SHX files are stored external of the drawing. Some of the Linetypes make use of the font selected for the Standard text style, so use with caution and understand the impact of a font change can make on your linetypes.

We have covered a lot about linetypes and LTSCALE. I can’t go over each and every linetype available as there are a large number of them that have been created and used over the years. Each line type in your drawing has a meaning or should. If you don’t know the meaning, consult with your design lead. There should be a legend sheet for your discipline that shows linetypes and what they are for. Legend sheets are not just a bunch of pretty symbols, text and lines. They mean something. Your drawings should match what is found in your legend sheets. Consistency is a quality that we as drafters should strive to meet.

On a closing note, your drawing may be used for years to come, and even longer than that. Get it right. Yes we are often rushed to meet schedules, but that does not mean quality should suffer. Poor quality now, means longer delays later in the project. From my experience, project schedules don’t seem to add time at the end of the project; however, they do get extended and run over budget, but that is not part of the plan and neither is poor quality.

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CAD Basics 101 – Drawing Cleanup

Drawing Cleanup is another important aspect of being a good CAD Drafter. Your drawing can start from scratch or from existing drawings. Most of the time it is the latter and we inherit someone else’s mess. This post we will talk about some of the things that can be done to clean your drawing up, before it gets copied across and entire project. How do you clean a drawing? What exactly are we cleaning in our drawing? Our drawing file is essentially a self-contained database. As with any database, it will perform better if it is optimized or free of clutter. Here are just some things that can clutter your drawing.

Empty Text – Text with nothing but spaces.
Empty block references – a hidden block (empty attributes of points)
Nested Block References
Proxy entities or records – Third party custom objects.
Linetypes
Text Styles
Annotation Scales
Wipeouts
Layers
Dimension Styles
Table Styles
Points (Nodes) – use PDMODE and PDSIZE to find these
The List goes on and on…

Here are a few things to consider to help clean up or keep your drawing cleaner.

PURGE COMMAND

PURGE can be used to remove things like Empty text strings from the drawing, Unused layers, block, linetypes, text styles and more. PURGE is pretty much the easiest step to take towards a clean drawing. Keep in mind that you may need to purge a few times because of nesting of objects. If block A has 5 layers defined in it, and you purge block A from the drawing , then it leaves behind the 5 layers. There is an option for purging nested objects, but just know PURGE is a multi-depth process. When PURGE no longer offers anything to purge, then you are done with PURGE.

Tip: If you ever get an older drawing that you think might have empty text strings and want to see just how bad it is, use the QTEXT command and turn QTEXT on. Then REGEN the drawing, zoom extents and see what kind of trash is in the drawing. QTEXT places a box around the contents of text without displaying any fonts. It was used on early releases of AutoCAD to provide faster Regen and redraw times.

SCALELISTEDIT

ANNOTATIVE Scale Factors can be removed from a drawing using SCALELISTEDIT. Why remove scales from the list? SCALELISTS can grow to a massive number of entries, causing more processing on AutoCAD’s part. Every time you reference a drawing or insert a block you have the potential to add more and more entries. There are automated routines out there to help facilitate cleaning these from your drawings. There are a number of tools on the internet to help assist in automatically purging extra scales from your drawings.

 TFRAMES

WIPEOUTS are invisible and often end up driving someone crazy. A less experienced user may open a drawing and plot it. Then notice there is a hole or a portion of something not plotting. They look in the drawing to see and all looks good. They plot again and again. A Wipeout is covering something and can’t be found. The TFRAMES command will allow you to make your WIPEOUTS visible. Review the WIPEOUTS and remove the ones that are not desired. TFRAMES is a Toggle to Toggle a frame to show the wipeout. Sometimes it takes a REGEN to see them, sometimes TFRAMES just doesn’t work. If you find there is no difference, exit AutoCAD and get back in and try again.

How to Find Invisible Blocks

What happens when you have that one block that just won’t go away? This is where you have to do a little detective work. Sometimes it is easy and it is just a hidden block that is nothing more than a block that contains hidden attributes, but nothing you can actually see on the screen. You can use the ATTDISP setting and set Attribute display to ON. ATTDISP set to ON will force hidden attributes to show on the screen, but if the attributes themselves have nothing in them, you still won’t see them. If you set QTEXT to ON and REGEN, then the blank attributes inside the block will show up. Often Third Party software systems will create these for tracking or initializing the drawing. If it is just one and you know it is part of your Software system then leave it, but if you find multiples, you may want to get rid of the extras and let the Third Party software reset itself.

Tip: Another quick way to find out how many times a block is in a drawing, is to use AutoLISP to find them. Start the SELECT command (or any command that you select objects with) and type the following:

(SSGET “X” ‘((0 . “INSERT”)(2 . “BLKNAME”)))[Enter]

Replace BLKNAME with your block name you are looking for. This will add all occurrences of that block to you selection set, note that different space selections will show they were excluded from the selection set. Visit my AutoLISP Teaser Post if you want to play with some more AutoLISP.

Extra blocks

Some other issues that can cause problems is when a user uses the Clipboard copy methods and paste as block. This creates an auto generated blockname that typically looks like A$7EDF1341A. You can easily end up with lots of these blocks that may just be nested blocks. Often times the user may just wish to copy a block from one drawing to another, so they think, copy as block. Unfortunately that is not exactly what happens when selecting copy as block. What happens with that approach is AutoCAD creates a nested block that contains the block you selected and creates a new auto generated block name for your new block. To do this operation properly, simply select a block in Drawing A (it is already a block) simply Ctl-Shift+C (Copy with basepoint); select the insertion point of the block. If INS osnap does not show, then it is probably not a block. Then select the block and press enter. Open up the destination drawing (Drawing B) and simply use Ctl+V (Paste) pick your insertion point and you are done. The only block definition is the one you wanted. If you find lots of Auto generated Block Names in your drawing you will want to check their block definition and if they are just nested blocks, explode them to un-nest them. Then you can purge the Auto generated block. If the block is comprised of entities and such that are desired to be a block, then use the RENAME command to rename the block to an appropriate name.

PROXY Entities – Hate em’

Proxy objects are essentially custom objects (graphical and non-graphical) that were defined and created by a Third party application that is not currently loaded into AutoCAD. Keep in mind that could be an AutoDesk AutoCAD-addon application too. Custom Objects come from Applications like CADWorx or AutoCAD Civil or… To get rid of the proxy you will want to load the correct object enabler for the object. When you see the dialog box stating proxies, you will also see what application it is looking for in the list, so don’t just dismiss it. Review it and find the correct enabler. If you do not want the proxies in your drawing but you want the graphics they represent, you will need to use the enabler’s exporttocad ability. Each enabler does not necessarily provide this functionality. You will need to research it and find out the correct command name to do so. I’ll probably write a post on this later. Once you rid your drawing of them, then you should be in pretty good shape for that drawing. Proxy objects prevent things like Wblock, or Binding Xrefs and can easily propagate into other drawings if you don’t take care of them.

What else?

There are a number of other things, Microstation linetype issues, Annonomous groups, and more that can get in to your drawing and make it a nightmare to just pass on and inherit to multitudes of other drawings, so always start with a fresh drawing and copy just what you want from existing drawings. Save it and check the drawing size. If it gets large quick, you may have copied in something corrupt. Work through what you copied and try and isolate what or where the corruption is. Since things like Drawing Templates or Title Blocks are used throughout projects it is VERY IMPORTANT to make sure these drawings are CLEAN.

AutoCAD Drawing files have become very complex with all the new features that AutoDesk keeps adding into AutoCAD. I did not cover everything here, but I tried to cover some of the most common things. Do your best to avoid passing on corruption or trash in your drawings. This will improve quality and keep your system operating more efficiently.