Programming of CNC Machines. Ken Evans
Operation Sheet
The purpose of this planning document is to identify the correct order for operations to be performed and the machine to be used. For example, suppose you are required to produce the part shown in Figure 1-7. You would first saw cut the rough stock into blanks and then turn the part on a lathe to create the five-inch diameter and rough turn the diameter for the hexagon. Next, you would use a milling machine to cut the hexagon and drill the bolt-hole circle. Before any inspecting the part for accuracy, you would deburr the part.
The operation sheet is particularly useful when many identical parts are machined (production run). The operation sheet is similar to directions or a how-to approach. The process needed to manufacture the finished part has been decided in advance and is documented for future use.
When small batches of parts are to be made, there may not be an operation sheet. It is the machinist’s responsibility to study the engineering drawing or blueprint and decide the necessary steps to machine the part. The operation sheet can aid in this decision making process (Chart 1-1).
With CNC machining, multiple part geometry features can be performed in one setup. In some cases, when using a CNC mill turn center, a part might be machined to its completed status without ever using another machine. This is very efficient and another advantage of the use of CNC equipment.
To complete an operation sheet, study the engineering drawing or blueprint; then decide on the steps necessary to machine the part. Document the machining process and refine any problems the process has. Then list the operations in the correct sequence in which they will be performed.
The top section of the operation sheet is for reference information and includes:
• The date the document is prepared or revised
• The name of the person preparing it
• The part name and the part number (from the engineering drawing or blueprint)
• The quantity of parts to be manufactured
Because some parts require a large number of operations, it is possible that more than one operation sheet will be needed to document the whole process. The top section also includes a sheet numbering system (Sheet _____of _____). This information must be included. Other information included on the operation sheet header is the material, the raw stock size for the part, and the operations list.
CNC Setup Sheet
The CNC setup sheet is the document that tells the machinist what tools are to be used and any specific information related to tools. For instance, it may be necessary to have a certain amount of tool projection/extension for a drill to be able to completely machine through a part. This document is where the operator/CNC machinist finds this information. In Part 5 of this text, you will be introduced to CAD/CAM and how you can develop CNC setup sheets within the CAD/CAM programs. Many companies today are going to “paperless” factories, wherein these documents will be on the intranet in electronic form. The CNC setup sheet has two sections (Chart 1-2). The top section is for reference information and includes:
• The date the document is prepared or revised
• The name of the person preparing it
• The part name and part number (from the engineering drawing or blueprint)
• The machine being used
Note: If more than one machine is to be used to manufacture a single part, separate setup sheets are completed for each machine.
• The CNC part program used in the manufacturing process
• Workpiece zero reference points for the part (program zero)
• Work holding devices
Note: If more than one device is needed, the operation number(s) and process are also included.
The lower half of this form lists the tool(s) by number, description, and offset. There is a column for comments, remarks, or explanations, if needed. Specific tool requirements, like minimum tool length projection/extension, can be entered in the comments section.
Chart 1-2Process Planning CNC Setup Sheet
| Date | Prepared By |
| Part Name | Part Number |
| Machine | Program Number |
Workpiece Zero: X __________Y __________Z __________
Setup Description:
| Tool Number | Offset Number | Tool Description | Comments |
|
|