Computer estimation: Precise estimation
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Computer estimation: Precise estimation
Article Introduction
In recent years, computer-aided estimating has come to the forefront as a means to take the estimation out of the quoting process.

Article Description
A good business quotation always fetches a lot of business. But offering a good business quotation requires a lot of understanding and indulgence. The profit or loss of any business depends on the accuracy of the quote. A higher quote than your competitor can kick you out of the rat race whereas as low quote that offers you low profit will not allow you to survive in the competitive world. Today, the Computer-aided estimation is all set to change this. Unfortunately, the industry has neither a standard definition of what an estimate is, nor standards that measure the results provided by an estimating program. Before selecting a software program for your own estimation, it is important to understand the approaches that the software uses to construct a computer-aided estimate.

What is computer-aided estimating?
When people talk about estimating software, they usually refer to one of two groups of software:
- Quoting software: A software that simply helps determine a price where the estimator manually calculates or guesses the time a job will take.
- Estimating software: A software that not only provides a quote, but also estimates - using speeds and feeds - the actual time a job will require. Time is the factor that differentiates between quoting and estimating software. And time is the dominant factor that determines the accuracy of an estimate, making the difference between profit and loss.

Within the estimating classification, some software systems are standards-based, some are engineering-based, some exhibit genuine intelligence by emulating actual machine motions, and others are evolving from one form to another. Intelligent simulation attempts to determine how long each operation really will take, as opposed to how long it should take. And now, automated feature recognition has entered the picture. Having the capability to account for rapid travel and idle times defines the difference between standards-based, engineering-based and intelligent-simulation estimating systems. The latter system tells you that it will take one minute - not that it should. Intelligently simulated estimates attempt to include every significant event, as opposed to interpolating average times and indicating what should happen. The term estimating still sounds like a guess, no matter how sophisticated the software is. In fact, some computer-aided estimating software programs are true engineering-based, process-planning, and profit-predicting systems. Today, just as speed and accuracy are demanded on the shop floor, predicting profit before a job gets to the shop is a critical phase of manufacturing. It begins by computing an accurate price for each job.

Benefits of computer-aided estimating
An exciting transformation in computer-aided estimating has emerged. Many shops have the capability to receive a request for quote (RFQ) electronically, with an accompanying drawing. The estimating program can automatically recognise the part features and develop a suggested production method for the part. The estimator can review the information, accept or modify the process as needed, and send the customer a price for the part - all in a matter of minutes. The customer can then accept the quotes cost - having reviewed the e-mailed information - and can reply with a confirming e-mail. Upon receiving the confirming e-mail, the estimator can electronically forward the information from the estimating system to the shop management system, and to the part programming system for processing on the shop floor. Realise, as well, that this opens up the estimating process to a whole new department that has always asked, "If I make this change, how will it affect the cost of manufacture?" Now, design engineers using estimating/design tools as described above can make changes to the design, and reprocess the part in the estimating/part recognition system. There, they can see the instant impact of their design changes on part cost. Those who have treated quotes lightly in the past "because it is just an estimate" may find themselves losing the job before they begin their quoting.

Remember, when it comes to estimating, you dont care that it should take one minute - you need to know how long it will take. In an estimate simulation, the software attempts to include everything significant that occurs, as opposed to what should happen. The simulation process must factor into its calculations many issues: How many types and shops use styles of machines today? How many different vendors? How much time is lost by lead-in and lead-out? Rather than providing generic standards for turning or drilling, intelligent simulation will recognise perhaps 60 independent machine types for those processes.

What was said earlier merits repeating: When buying estimating software, remember that each time you send a quote to a customer, you are betting your business on the accuracy of the times in the estimate. Today, most CAD/CAM systems integrate with a solids package or have an internal solids drawing capability. Combined with that capability, feature recognition now is taking part design in a new direction. Solids packages enable feature recognition by other software - no more visualization, no more isometric views. Clusters of software packages that use solids will revolve around a technical database. This supports a consistent method of programming and manufacturing. In that technical database will be relationships of features to manufacturing methods. For example, a database entry for a 1/4"-20 tapped hole, 3/4" deep in 6061-T6 aluminum, may specify that a 0.125" center drill be used to spot the hole prior to drilling, and then a 0.201" diameter drill be used to drill the hole. When you machine a part out of 316 stainless steel with a certain finish, the technical database can suggest that you machine using the specified speeds, feeds and tools that you previously determined are appropriate. Additionally, knowing the material can provide the part weight, the center of gravity, and possibly highlight other challenges that significantly enhance a computer-aided estimating systems ability to create estimates automatically.

Feature recognition and estimating
It wont be long until an estimator - knowing a part was designed in a solids program - will click on a pull-down menu and choose recognise features. When the software recognizes a shaft adapter, and the estimator selects the machining center to run the part, the software will suggest a center drill, a drill, a face milling operation, a contour end milling operation and a burnishing operation. Thats the set of work instructions based on the features it saw. The estimator will be able to drag and drop and rearrange any tool or process, based upon his knowledge of the facility. Feature recognition in computer-aided estimating is already in the marketplace.

Its available for turning and milling, as well as fabrication processes. Consider a simple part, linked from a solids package to estimating, and then to a CAD/CAM system. The identified features from the solids technical database are matched with the estimating programs technical database. With this data, the estimating program knows which tools to use. By automatically reviewing the machine parameters and the part, the estimator may find that the initially selected machine is unavailable, or otherwise not optimal for the job - perhaps it has insufficient tonnage, tolerances or size limitations. Therefore, the estimator - who is always in control - could select another machine.
Posted : 10/21/2005

Computer estimation: Precise estimation