Introduction
How does the supplier calculate the cost of machining parts? Are there any practical tips to save costs of CNC machined parts? Wow, they are attractive questions and we suppose all machined parts buyers and other people who are involved in CNC machining are interested in answers to these questions.
Generally speaking, the calculation of CNC machining cost is pretty complicated. Because it depends on a lot of factors. And all the machining parts should be customized according to drawing or the print. Thus, compared to other manufacturing methods, calculating the cost of CNC machining is more complex. That is to say, there is no fixed standard formula to apply in estimating the machining parts cost.
- Introduction
- What will affect the CNC Machined parts cost? (8 factors)
- What we need to calculate the cost of machined parts?
- 10 practical tips to save costs of CNC machining parts
- Tip 1. Choose the right raw material and consider its machinability
- Tip 2. Find the right and high-efficiency machining equipment
- Tip 3. Allow a radius instead of a 90° corner
- Tip 4. Specify tolerances but don't overuse tight tolerances if possible
- Tip 5. Minimize the cavity depth of deep pockets to save machining time
- Tip 6. Avoid thin wall design if possible
- Tip 7. Use standard hole size and threads if possible
- Tip 8. Avoid surface finish/multiple surface finishes if possible.
- Tip 9. Choose laser engraving instead of CNC engraving
- Tip 10. Order big quantity per time if possible
- Conclusion
What will affect the CNC Machined parts cost? (8 factors)
Even so, we still can share some secrets on what we will consider in quoting for CNC machining parts. In general, we consider the following 8 factors.
1. Raw Material Cost
The unit prices of different materials are different. When it comes to the same material, the heavier the material blank is, the higher the raw material cost is. Note: here we consider the material blank weight, not the final machining parts weight.
2. Set-Up Cost
No matter you need 1 piece of prototype or a bulk quantity of mass production. The machined parts manufacturer must take the same or even more time and effort to set up the machines. This is a fixed cost and it’s necessary.
3. Machining Time
One of the mechanical part costs is the machining cost. While the machining cost depends on machining time. The longer the machining time is, the higher the machining cost is. And machining time is usually the main determinant of CNC machining costs.
4. Tolerance Requirement
Tighter tolerances required more precise machines and tools to achieve it. Then tight tolerances raise the cost of machining. As it would increase the machining time, quality control level and parts scrap rate.
5. Fixtures and Cutting Tools
If any special fixtures and cutting tools are necessary for this part, we must consider the cost accordingly.
6. Order Quantity
According to point 2 and point 5, these costs need to be shared equally among the order quantity. Then you will find the unit price of a small quantity would be higher than that of a big bulk quantity.
7. Surface Treatment
Surface treatment will issue extra costs accordingly.
8. Special Design
If there are some special designs, for example, thin wall thickness, deep hole or thread depth, high requirement of surface roughness, then we should consider special processing steps and machining speed accordingly.
What we need to calculate the cost of machined parts?
As a machine shop specialized in processing precision machined parts, before quoting to customers, we need not only the technical drawings but also the specific material, surface treatment and quantity of parts. Because these four factors are the basic elements of quotation.
From the technical drawing, we can get the information of raw material blank, tolerances and whether there are any special designs. Of course, in most cases, the designer indicates the raw material type, surface finish in drawings too. That’s much helpful.
Without any of the four factors, it will be difficult for us to quote a reasonable or correct price.
How to save costs of CNC machining parts?
What is CNC Machining?
CNC means Computerized Numerical Control. And CNC machining is a manufacturing process in which pre-programmed computer software dictates the movement of factory tools and machinery. People can use this manufacturing process to control a range of complex machinery, from grinders and lathes to mills and routers.
We know that 3D printing is a kind of additive processing. While compared to 3D printing, CNC machining is a kind of subtractive processing method of mechanical parts. This means we use different CNC equipment to manufacture the parts according to drawing by removing material. CNC machining can manufacture metal parts, plastic parts, ceramic parts, etc.
10 practical tips to save costs of CNC machining parts
In professional parts procurement, customers are not only satisfied with the reasonable price to buy CNC machining parts. They have been always interested in finding tips to save costs or reduce the cost.
From the first part of this article, we are clear what factors affect the cost of CNC machined parts. In this part, let’s see how we can minimize the cost. Here Top Leve Intl. would share with you 10 practical tips to reduce the cost of your project.
Tip 1. Choose the right raw material and consider its machinability
The choice of raw material for a machined part affects the cost in two ways. One is the cost of the raw material itself, another is the machining time.
Machinability means the ease with which a raw material can be cut or machined permitting the removal of the material with a satisfactory finish at a low cost. The higher the Machinability is, the faster a material can be CNC machined, lowering the cost.
Tip 2. Find the right and high-efficiency machining equipment
There are so many types of CNC equipment for CNC machining. Are we a good supplier to you if we use the most advanced and the most expensive equipment to fabricate a simple part for you? Not really like that. It depends on the part design. We should use suitable equipment to make your parts at a reasonable price. The most suitable is the best!
Do you know that? The working cost per hour of different types of CNC equipment varies to their processing capabilities and efficiency.
For example, if you have a part to turn, both automatic lathe and CNC lathe can meet the tolerance. Then you will get a better price from automatic lathe rather than CN lathe. Another example, the work hour cost of a 3-Axis CNC machining center is lower than that of a 5-axis CNC machining center. However, if you have a complex part that is suitable to make by a 5-axis CNC machining center, then you will get a better price from the supplier who has a 5-axis CNC machining center. Why? Because the 5-Axis machine can fabricate the parts by one-time clamping in a shorter time though its working hour’s cost is higher. But the 3-Axis may need three clampings. In addition, the 5-Axis can control better accuracy of the part than the 3-Axis due to it needs fewer clampings.
Tip 3. Allow a radius instead of a 90° corner
If you know CNC milling tools, you will find they have a cylindrical shape and will create a radius when cutting the edge of a pocket. If a 90° corner is required, we have to process it specially with extra time and tools. Then it increases the machining time and cost.
So if the 90° corner is not functional or necessary. Please allow a radius in internal vertical edges and external vertical slots instead of a 90° corner.
Tip 4. Specify tolerances but don’t overuse tight tolerances if possible
As mentioned above, the manufacturer needs tolerances indication in technical drawing. That’s because if there is no tolerance indicated, then the manufacturer would make parts according to a general tolerance standard like ISO 2768. Because this is sufficient for most non-critical features. But for some functional or assembly dimensions, general tolerance may not precise enough. Thus you should indicate the specified tolerance range. Then the supplier will fabricate the parts and control the quality as required. But please specify tolerances only when it’s necessary.
Top Level Intl. has good processing equipment and 15+ years of manufacturing experience. And we can achieve the tight tolerance accuracy to ±0.001mm. Even though, we still sincerely suggest our customers not overuse tight tolerances if possible. Because tight tolerances would raise the cost of CNC machining. As we may need to slow the machining time, use special tools, introduce other processing methods and manual inspection one by one.
Tips to save costs:
- Specify tolerances only when it’s necessary.
- Don’t overuse tight tolerances if possible.
Tip 5. Minimize the cavity depth of deep pockets to save machining time
As we mentioned above, CNC machining is a subtractive processing method. It processes the machined part by removing excess material to achieve the dimensions and accuracy required by the mechanical part drawing. Then if the mechanical part has a deeper internal cavity, it will take a longer time to remove the excess material. Longer machining time takes more cost.
So please minimize the cavity depth of deep pockets if possible to save machining time. This will save costs for you in such conditions.
Tip 6. Avoid thin wall design if possible
Thin walls commonly happen when you place holes or threads very close to the edge of the part.
For thin wall machined parts, we have to use special processing technology. It usually needs slower processing time and special-designed fixtures to achieve the safety and accuracy of the wall. Even so, there are still some possibilities to have part scrap or wall deformation. Accordingly, the processing time is prolonged and the cost is increased. So avoiding thin wall design can reduce the cost for you.
On the contrary, it’s more stable to make thick wall parts. As it’s not necessary to make special fixtures to support the manufacturing. If possible, we suggest you design the wall thickness of metal parts ＞ 0.8 mm and plastic parts ＞1.5 mm.
Tip 7. Use standard hole size and threads if possible
For standard holes and threads, we can machine them fast and get good accuracy by standard drill bits or taps. However, if they are in non-standard sizes, we must machine them with customized drilling bits or taps. Based on this, some extra costs are increased potentially.
Tip to save costs: You can design holes with a diameter that is standard and commonly used.
In this way, it’s easier for us to buy the GO/NO-GO tools involved to control the quality and you can also buy the matched screws easily in the market. For hole diameters up to 10mm, you can design an increment of 0.1 mm and for those above 10mm you can design an increment of 0.5mm.
Tip 8. Avoid surface finish/multiple surface finishes if possible.
Sure, surface finishes improve the appearance of CNC machined parts and protect the surface again corrosion, rust, etc. But the surface finish, especially the multiple surface finishes also increases the cost of the parts.
Furthermore, multiple surface finishes, especially multiple local surface finishes required much extra cost. Do you know the detailed reasons？Click here, you will find answers in another article named Surface Treatment of Metal Parts.
Tips to save costs:
- Choose the as-machined surface if it’s sufficient for the function;
- Only apply multiple surface finishes when it’s absolutely necessary. No matter they are multiple whole surface finishes or multiple local surface finishes.
Tip 9. Choose laser engraving instead of CNC engraving
If text or logo is necessary, please choose laser engraving to achieve it instead of CNC engraving. Because laser engraving is quick and cost-effective. However, CNC engraving works in this way by removing much more materials. That takes more time and increases the cost.
Tip 10. Order big quantity per time if possible
With a big quantity order, the machine shop can buy bulk raw materials at a better price. And no need to be troubled by a material supplier’s MOQ.
For big quantity mass production, CNC machining equipment would keep running for the manufacturing of the same item. That maximizes the production efficiency and then we can cut the cost for you accordingly.
As shared in the first part of this article, we consider set-up cost and cost of fixtures&cutting tools as well as raw material cost. Therefore, when these costs are shared equally among the order quantity. You will find the unit price of small quantity order would be higher than that of a big quantity.
Frankly, order quantity is a significant factor that affects the unit price. For example, you can enjoy a much better unit price for 10,000pcs per order than that for 2000pcs, even you repeat 2000pcs 5 times.
Conclusion
Calculating the cost of CNC machining parts is very complicated. However, in this article, we shared what factors will affect the cost of CNC machined parts. And also suggested 10 proven tips for you to know how to save cost in CNC machining. If you keep them in mind and apply them to your active projects, they will help you to reduce many unnecessary costs.
If you are interested in more tips or looking for a CNC machining service supplier, feel free to get in touch with us. We are always open to you!
