Posted on Sept 12th, 2019 | By WayKen Rapid Manufacturing
If you've ever ordered parts from a CNC milling services, you may know that custom machining costs a considerable sum of money. Upon looking at the total quote, some of the clients gasp and have a lot of questions regarding the pricing of the milling shops. Well, this article aim is to explain what a CNC milling job price consists of.
The Importance of Cost Calculation for Milling Services
First of all, it is important to speak about why an accurate estimate of the machining cost is important. After all, there are a lot of different elements that contribute to the overall cost of a CNC milled part. The importance of consistent quoting by the CNC milling services ensures trust between the client and the manufacturer, makes it possible to understand where the minimum price is (when you don't get any profit margin but are able to work and pay your employees salary), allows the manufacturer to control the profits and estimate the necessary resources for each job.
Stock material is the most basic cost. You need something to mill from, right? With CNC milling, choosing the right stock is usually easy. You look at the geometry of the final part (mostly, the form and the maximum dimensions), choose a standard stock type (most often a block or a plate for milling operations) and add a couple of centimeters in thickness to the maximum dimensions of the final part. Some milling services make it possible to upload your model of the final part and a milling cost estimation program will find a suitable stock for you.
The tooling consists of all the jigs and fixtures, loading mechanisms, tool holders and of their similar elements that are required to fix the base elements of the milling manufacturing system. These costs are highly individual and cannot be estimated automatically. The good news is that the majority of tooling in CNC milling shops is flexible and will fit 80% of the parts that come through this shop but there are always 20%. Since the cost of tooling is high, it is recommended to change the design of the part a little bit so it can be manufactured without the extra purchases.
Cutting tools, as well as cooling liquids, are consumables. Cooling liquid is recycled by the modern milling centers so its cost is negligible. But the percentage of cutting tools in the total of the milling price can be quite costly. Why is that? The answer is simple. This depends on the material. For example, tools for CNC milling acrylic or other soft plastics will be usable for a lot of operations because those materials are soft and do not damage the tool insert. However, harder materials, titanium alloys being on the top of that list, will wear the tools faster.
Apart from that, some CNC operations require specialized tools. For example, diamond machining inserts are much more expensive than carbide ones. CNC milling services usually have a set of recommended tool inserts for each material and will include those in the total.
This part of the machining costs is the most understandable. The work is carried out by an employee who has a per hour rate to his CNC services. If your part is large, additional loading and unloading rates may be added to the quote. It should be noted that the machinist is paid for preparation time as well since he sets up the fixtures, tunes up the cutting tools and so on.
Machine tools, especially 5-axis CNC milling centers use quite a lot of power and some are mounted with pneumatic systems additionally, which further enhances the use of electricity. Apart from that, companies have to take depreciation costs into account. All of that comprises the rate of a machine tool per hour. Naturally, if the part has to be processed on multiple machine tools (milling and turning both, for instance) then all the rates are added and multiplied by the processing time.
Different parts have various quality demands. The better the precision and surface finish of the part, the more complex features it has, the more it will cost. So, some CNC shops add a tolerance coefficient when online quoting the jobs. That makes clients more careful when choosing the quality of their parts, saves time and increases overall business efficiency. In addition, when a batch of parts is ordered, you can insert a percentage of faulty parts. The lower the percentage, the more often the machinist will have to check each corresponding part and the more expensive the whole job will be.
We are living in a global world and it is often that a client from Europe orders CNC milling china services. Despite having a lot of different transport companies, shipping still costs money. Usually, machine shop managers let you choose from multiple methods of shipping with different price ranges, you have to include the weight and dimensions of the final part, of course, because shipping a small 0,5 kg shaft is different from shipping a whole set of injection molding dyes. If the shipping is free, then its price is just hidden into the profit margin of the total but the majority of CNC milling shops specify how much you'll pay for shipping. Some companies can even offer to send your order to a side shipping company that you trust.
Profit margin is never shown to the client but its coefficients are included in each part of the whole price. If the profit margin is zero (for shops where business is hard), it means that all the money from the milling goes to cover the expenses and pay the salary. Basically, the business has work, pays its people and gets just enough to make ends meet but it doesn't grow or develop. On the other hand, with a large profit margin, the milling shop gets a lot of extra money for each order but the demand is definitely lower since fewer people are ready to pay more money.