================================= DOCUMENTATION FOR STACKUP REV 2.0 ================================= This software is intended to be distributed as Shareware. Suggested donation is $15.00. A great deal of time and effort has gone into the development of this program as well as many years of Engineering experience which aids in the concept of the program. I hope to be able to develop other Engineering applications specific to the Mechanical Design community. Given the time required to develop these applications, it would be impractical to continue development of them without some measure of compensation. My main aim is to enhance the productivity of my brothers and sisters in the industry. Since I am over 40, however, my days of working for free are long gone. IF YOU CAN USE THE PROGRAM Send check or money order to: W.C. Bowling 1742 Hanley Ave Simi Valley, CA 93065 OTHERWISE... Please delete it from your files or get it to someone who can use it and is willing to contribute the $15.00 NOTE: There is a version 1.0 of Stackup which is written entirely in Amiga Basic. There are lots of bugs in the program for which I accept all blame. I recommend that you do not use Rev 1.0 unless you are very careful with your results interpretation. All known bugs have been fixed with Revision 2.0 but I am sure that someone will find something I have overlooked. Please notify me of any problems you encounter with this program so that I can repair them post haste. ----------------------------------------------------------------------------- ******************** STACKUP REV 2.0 ******************** You have sucessfully UNArc'd STACKUP.ARC since you are reading this file. Before you continue, you should make sure that you have placed each of the files on a floppy and that they are in the root directory. Make sure that the floppy is empty since there is a Disk.info, Editor.info and a .info file in the archive. Once you have familiarized yourself with the workings of Stackup you can put the files anywhere you want but for now, be sure you have everything on one floppy which is otherwise empty. For Stackup to work properly you need, as an absolute minimum, the following files: EditMast Editor * Note: These files will allow EditStack you to launch Stackup StackupRev2 from a floppy with EditMatl icons. Editor.info * Disk.info * .info * In addition to these files you should have the sample data files: MatlProps MasterDim StackFile Lastly, there is Stackup.doc which is the file you are reading (I hope!) The sample data files will help you familiarize yourself with how Stackup does its thing. Once you feel comfortable with Stackup you should save these files somewhere other than this directory since we KNOW that they are good working files. This program is in modular form. After you have launched the program by double clicking on the Editor icon you will see a menu which gives you a number of options. Selection of an option will cause its particular module to be called and run. This has minimized the memory requirements for Stackup and enhanced its speed. Unfortunately, Stackup does not use much of the Amiga's wonderfully designed operating capabilities. All of the prompting is on the screen and selections are made by keystrokes (touch a key) or other keyboard entries. Stackup was developed on an Amiga but it was designed to be used on almost any PC. The program is highly specialized in nature and will be of tremendous use to Mechanical Design Engineers. For some reason most companies (author's included) use IBM or compatible PC's for this type of work. This is why the program does not require a mouse except for startup if you want to go that way. Stackup does not (as you probably know) mandate Workbench startup. You may launch the program from the CLI. Make sure the stack is set to at least 7000. Be sure you are in the directory where Stackup is residing when you launch the program. From the CLI type: EDITOR and press the key. You MUST launch the program with Editor. Don't try to launch by typing StackupRev2 or EditStack or ANYTHING other than EDITOR. **** WHAT IS A STACKUP **** You may call it something else but a stackup is a dimensional tolerance buildup study. If you still don't know what a stackup is, read on. Nearly every mechanical system consists of large numbers of separate, individually dimensioned parts. No part can be manufactured EXACTLY to a given size. Because of this, tolerances are applied to the dimensions which define the part. A liberal tolerance allowance gives the manufacturer a better chance of making the part per the designer's requirements and significantly reduces the cost of the part. When the part is used with the system, however, the liberal tolerance allowance may cause big problems in terms of excessively tight fits or bad operating clearances. How can you, the designer, make this determination? Do a Stackup! If you still don't know what a stackup is then it should be abundantly clear to you that you have no use for this program. Please delete it from your disk or give it to someone who can use it. **** WHAT THIS PROGRAM WILL DO FOR YOU **** Stackup will show you what the maximum and minimum values of the tolerance buildup are for the area under study. It will also do a temperature compensated calculation for the same area providing you define the thermal co-efficients of contraction/expansion. Once you have defined the stack relationship you can go back and change any of the dimensions which go into the stack and the area under study will change accordingly. You can change your material selection and the change will be immediately incorporated. This capability will significantly reduce your iteration time and allow you to do a better job of dimensioning your parts. Design time and hardware fabrication costs will decrease substantially. **** FUNDAMENTALS **** Stackup is designed to be used with a 'Loop' type tolerance study. You will still have to do the layout and set up the stack. It would be unwise to try to automate the stack layout since the visual aid provided by the stack layout would be lost and obvious errors may not be located. Always begin the stack on the left side of the area under consideration. By consistently starting on the left side, you can be sure that you are interpreting your results correctly. Positive resultant numbers indicate a gap. Negative numbers indicate interference. It makes no difference which way you travel across the stack as long as you start on the left side of the area under study. **** STARTING THE STUDY **** The first thing to do is look at your system layout and determine what areas you want to evaluate. You will need to make sure that all of your operating clearances do not close up excessively. Shims will have to be sized. Springs which are pre-loaded will have to stay that way. Make sure that interference fits don't get loose or too tight. Pick your first area of study. Let's assume that you are looking at an operating clearance. You can identify this gap on the layout and you will see that it has a right side and a left side. We'll say that the gap is bounded by two parts, each of which is located by its relationship to other parts in the machine. What you are going to do is work your way through the machine starting on the left side of the gap and ending on the right side. Moving sequentially from part to part, identify the first dimension as one (1) and indicate the direction of travel (l or r) through the stack. Identify the second dimension as two (2) left (l) or right (r) and so on. You will eventually get to the right side of the gap. The layout for your first stack is now done. Stackup uses three data files for its calculations. To keep apples with apples and oranges with oranges the files are individually created and edited. The master dimension list is the file which contains all of the information about the dimension as it is found on the drawing which defines it. Each dimension has a maximum and minimum value which you enter into the master dimension list. The part name, drawing number, drawing revision letter, material code and drawing location for the dimension are all in this file. These dimensions have a dimension number associated with them. The dimension number is not necessarily the same number as the number you used in the stack layout since it is probable that you will use the same dimension more than once. Stackup allows you to do this by assigning dimension numbers to the dimensions and asking you for this number when you create or edit the stack file. The dimension identification you used in the stack layout is actually the item number you will see when you get to the stack file definition portion of Stackup. The stack file is the file which contains all of your stack relationships as defined in your stack layouts. All you have to do is supply the dimension number and the direction of travel for each item number. Let's say that your first stack layout had seven (7) dimensions. You would have labeled them as one through seven and each of the labels would have been either a left (l) or right (r) dimension depending upon which way you were going through the stack. Now let's set up a table which shows which stack item number goes with which dimension number (defined by master dimension list) Stack 1 ------- Item No. Travel Dir. Dimension No. -------- ----------- ------------- 1 r 15 2 r 7 3 l 8 4 l 13 5 r 5 6 r 9 7 l 10 You would use this table to enter the information required by the stack file portion of Stackup to establish the stack relationship. You will be prompted for dimension numbers and travel direction for each of the item numbers in the stack. Follow the prompts and you will have no problems. You will, of course, need to have the master dimension list created so that each of the entries in the stack file definition has a number to reference. You may create these files in any order you desire but each must be created before you will be able to compute the tolerance study. The last file you will need to create is the material properties file. This file provides the information needed by Stackup to do the temperature compensated tolerance study. Each of the dimensions in the master dimension file has a material code associated with it. This code tells Stackup that the thermal co-efficient of contraction/expansion for the material corresponds to the information in the material properties file. You MUST have a code for each dimension in the master dimension file and there MUST be an entry for the code in the material properties list. This sounds like a real pain if your system doesn't see any temperature changes but there is a workaround. Use a material code of one (1) on all of your parts and use anything you want in the material properties file. When you run your tolerance study just answer no when you are asked whether you want to do temperature compensated stackups. If there is a temperature change in your system you should use the material properties file as it was intended to be used. You may find some real surprises when you look at the temperature compensated study. Let's say that dimension number 1 is made from Inco 718 and you know that its thermal co-efficient (Alpha) is 2.2 E-7 or .00000022. If your part is operating at -370 degrees F then the Alpha DT is 2.2 E-7 x (70-370) = -6.6 E-5 or -.000066. This is the number you use in the material properties file. PLEASE note the sign. The negative number tells Stackup that the system is colder than ambient. If you are warmer than ambient then the number will be positive. Once you have all of your files created you can do your tolerance study. Look at the results and use your good engineering judgement to try and make the tolerances just as liberal as is possible. Edit the master dimension list and see what happens to the stacks. If you don't absolutely need a tight tolerance on a dimension, don't use one. Stackup uses specifically named data files. Once you have established a set of files for a mechanical system it is STRONGLY recommended that you save the data files in another location. It would be best if you had one disk with all of the program files and data files for each system you analyze. Keep the disk with the stack layouts. All keyboard entries are case sensitive. When you are prompted for a key stroke (Touch some key) it must be lower case. Data which goes into the files may be either upper or lower case but when numerical input is required, make sure you use numbers. Be sure to enter lower case 'l' for left and 'r' for right when you are working with the stack files. Planned future versions will include, among other things, a statistical study of tolerances used on all dimensions in the master dimension list. This will help with cost analysis of the machine as well as showing the designer what sort of tolerancing he/she is tending towards. I hope you find this program to be as useful as I have found it to be. If you would like more information on tolerance studies or example layouts of stacks contact me at my BBS: MECHANICAL ENGINEERS' BBS Simi Valley, CA 805-522-4435 ATTN: Sysop or write to the address above.