How do you estimate the cost and time of CNC machining projects?

Material cost estimation involves knowing the type of metal and its quantity required for the project, as well as its grade and availability. I use a matrix for material and tolerance considerations is two-dimensional chart with the material types listed on the vertical axis and the tolerance requirements listed on the horizontal axis. Each cell in the matrix would represent a specific material and tolerance combination and could be used as a quick reference guide for selecting the appropriate material and tolerance for a specific project. Then is use a form of risk matrix for complexity of the design, the type of machine used, and the skill of the operator. The two values gives me a modifier for my estimate.

For material cost estimation, it's not enough for you just to consider the requirements of the serial number, chemical contents and physical performance. Based on the required serial number, you need to take many factors into consideration, like rod , tube, plate or shaped-profile, normal tube or seamless tube, cold drawn or hot treated; Ground material surface or normal surface? For some special sizes, is the right size available in the market or you have to buy a bigger size with unavoidable waste to meet the tolerance of maximum external dimensions？

Material selection will also help to choose right Machine tools and cutting tools, I found that material with harder property affects the Machinability of the parts which affects the Cutting tool selection such as carbon insert or in rare cases diamond insert. So, selection of right material would also impact on pricing of the material, that's the reason choosing the right material is vital.

One thing I found is that, selection of right Machine tools will majorly impact on machining time and number of set-ups required to machine a part. For example, a part with few complex features and uncertain shapes would take 3 to 4 set-up on 3 axis milling machine, whereas same part with 5 axis milling machine would take 2 set-up. Set up cost reduces the overall cost of the final product. Plus, a fasteners for mass production is more suitable with swiss type multi spindles machines rather than 2 spindle or 3 spindle lathes. The cycle time can be reduced by more than 50% if we select 8 or 10 spindle lathes. All in all, selection of the right Machine tool could make huge difference in lead time, cost of the parts.

In the machining step, you need to consider the RIGHT machining solution for the part. That means it's not the more advanced machine the better. Instead, the optimal balance between fewer set-ups of machine type, fewer/simpler jigs/fixtures, higher machining efficiency and lower costs is the first choice.

In Addition, Proper use of ATC (Automatic Tool Changer) will enable us to switch between different cutting tools quickly & will contribute by reducing downtime (Tool Change time) and increasing productivity.

In the realm of CNC machining, precise cost estimates are vital for project success. Amid the myriad factors influencing project costs and timelines, certain key elements demand focused consideration. Here, I offer my insights: Complexity of Fixturing: Complex parts often necessitate custom fixtures, increasing setup time and costs. Streamlined designs can simplify fixturing, expediting setup and potentially reducing costs. Toolholders and Tooling Accessories: Optimal toolholder selection can impact ccuracy, surface finish, and tool lifespan. Documentation and Reporting: Comprehensive documentation and reports across project stages, from design to quality control, enhance transparency and accountability. Best regards, Rey

I've been in the industry for 50 years and estimating for 25 of it. The most critical factor is the initial approach and innovation of the machinist, and how big his balls are. In these times, the approach is very similar from shop to shop using the methods that those of us in the CNC industry have pioneered. Weather it's the shop that does 14+ million a month, or 2 million a month. The fact is, selection of who's material ( what mill producer or forging house) pays a big part in final results of certain geometries and repeatability. Not all materials are created equal. They have slightly different chemistry and they do not react equally to the exact machining process of a similar grade of material resulting in scrap.

In my experience we also need to consider set up and fixture design. Because there is a big difference between contained state and free state of each work piece or part. For example a brass bushing has a tolerance of .0003” in roundness and the process is boring it on either CNC lathe or milling or cylindrical internal grinding. When you check it mounted on the fixture with a dial after processing it checks good but after removal and using another method to verify the called feature the part turned out to be oval so we changed the design of the fixture and corrected the problem.