CNC machining is a key necessity in today’s manufacturing sector. High quality CNC machined parts are utilized to create high quality products all over the world. These parts must conform to the design specifications specified by customers and following industry standards to function accurately and efficiently.
Parts not conforming to the required specification and design will cause unexpected problems, resulting in enormous downtime and costs. For example, an aerospace part which is out of accuracy may cause an equipment to malfunction during flight, endangering many lives. Similarly, defective brake discs or calipers may result in automobile accidents, or the costly recall of thousands of vehicles.
Manufacturers fully understand the importance of producing quality parts in a timely manner. Failing to do so could result in the loss of customers and new future orders.
So, what does it take to produce quality parts in CNC machining?
#1 Review Your Machining Project
First and foremost, you need to have a clear assessment of the project you want to take in. Ask yourself these questions:
- What are the different sizes and complexity of parts?
- What are the materials to be machined?
- What levels of precision will you need in making these parts?
- What are the cutting tools that you will need?
- Do you require costly fixtures to clamp your machined parts?
Performing this review allows you to select the most efficient and cost-effective method to achieve the desired results.
#2 Consider the Best Machine Type
Do you have the right equipment and machines in your workshop to do this job? If not, you will need to consider the best fit for your project while evaluating the wide range of CNC machine types available in the market.
High quality CNC machines may cost more. However, they can achieve extremely high accuracy and tight tolerances. CNC machines manufactured with good overall mechanics, quality Ball Screws, and Linear Roller Guides or Solid Box Guideways, hardened, grinded and then hand-scraped to perfection are capable and proven of delivering long-term accuracy and stability.
Do assess if the market demands the very same type of machine that you are looking for — this will give you a hint on what’s practical and useful for your machining needs. Finally, consider the delivery time of the brand and type of CNC machine, so that you are not forced into buying second or even third choices.
#3 Automate with CNC Controls
As computer systems are used to control CNC machines, many operations of the production can be automated to increase production and decrease unproductive times. Identical or mix of parts can be machined with higher and more constant accuracy levels. Repeat orders can also be set-up in shorter times, while emergency orders can be more easily slotted into your production schedule.
#4 Optimize with Machine Software
Reputable CNC machine manufacturers often provide specially designed software in their machines which control various parameters and provide error alerts and reports. Such software enables your knowledgeable machinists to evaluate machining processes, take proactive or corrective actions to ensure that part quality is not compromised, and optimize production efficiency by maximising your machines capabilities.
#5 Ensure the Right Materials are Used
The type of materials to be machined will influence the levels of performance and cycle times. Factors such as the durability, the load to bearing, and overall machine structure will affect the precision that can be realized.
Material properties and tooling behaviour under the required machining conditions will also influence machine tool factors. These include the maximum spindle speed and feed rate, most effective motor power, and spindle motor torque.
#6 Use the Right Feeds & Speed
Use the right feeds and speed during part machining as these factors affect the surface quality of your parts and the lifetime of your cutting tool selected.
If you set your speed too slow, you may experience both lower efficiency and possible damage to your tool. If you set your speed too fast, you may encounter accuracy and contour issues, as well as the faster wear out of your cutting tool — this results in higher production costs. Consider the “Golden Middle” as doing so will secure good part quality, longer cutting tool life and also constant and save production runs.
#7 Choose the Right Cutting Tools & Tool Holders
Use the right cutting tools and the recommended cutting settings first to achieve your desired quality surface and accuracy. Thereafter, you can fine tune the cutting parameters to achieve your desired output and production cost.
Avoid using blunt tools, wrong (dimension) tools or tools that are not suitable for the machined materials — doing so may result in rough edges, cutter marks, raised marks, or even burn marks on the finished product.
Do also avoid using the same tool for roughing and finishing in series production runs as this can result in lower quality finishing, and possibly higher wear and cost.
#8 Adopt Proper Part Clamping
How you clamp the material or individual parts to be machined is dependent on the number of operations to be done and whether you need to machine on more than just one surface.
If there are multiple operations (e.g. milling, drilling, tapping) to be done, it is always best to clamp your part in a way that allows the various operations to be performed in one setting.
This can be achieved in “clever” and effective fixture designs, which are costly, or by using an additional Axis in your machine (e.g. 4th Axis or CNC Rotary Table).
If your material or part needs to be machined on all five sides, a Multi-Axis Machining Center needs to be considered. These can either be a 3+2, or better, a 4+1 Axis configuration. Full 5-Axis capabilities should be used if you intend to machine Mould & Die or very complex shapes and contours.
#9 Ensure Effective Chips Clearance
Chips produced by the production process need to be cleared out of the machine effectively, otherwise they can badly hinder your machining processes. They should never accumulate at the cutting area and must be cleared by using effective coolant or air pressure.
When chips are not cleared from the cutting area immediately and effectively, they may be dragged around the cutting tool and make contact with cutting area and the cutting tool repeatably. Resulting in higher wear, possible damage to material area surfaces and in the worst case, cause breakage of your cutting tool due to its increased load. Avoid that chips remain all over the work piece and ensure that the surface quality of your machined part is not affected.
After you have ensured that sufficient coolant or air blows chips away from your progressing cutting area, you can effectively dispose of the chips by using conveyors inside the machine. There are various conveyor designs available:
- Standard hinge type conveyors are all-rounders for various materials.
- Scrapper type conveyors are recommended for steel casting material.
- Drum-Type conveyors are mainly for aluminium material, and will ensure that the fine chips are filtered out of your coolant system.
#10 Manage Your Manufacturing Environment
Beware of the influence of external sources of debris and pollution — these can potentially create very negative effects during machining and can result in very costly damages to your machine.
Examples of these include:
- Dust from grinding or worse, nearby foundries
- Shock waves created by presses or stamping machines
- Electrical fluctuations due to an unstable power network
- Welding operations near CNC machines
Beyond these, unstable and changing temperatures in the workshop will affect your machine’s accuracy, while unclean (humid) and unfiltered air supplied by the air compressor and air-pipes to your machine will affect its functionality and effectiveness.
#11 Hire Skilled CNC Machinists
The expertise and experience of CNC machinists play a critical and important role in producing quality products. Skilled CNC machinists with good manufacturing knowledge and mechanical aptitude will perform, set-up your machine, and handle your operations with care and significantly reduced errors.
#12 Conduct In-Process Inspections
Conduct quality inspections when the part is still running to immediately identify any issues and adjust your CNC machine tool to achieve the required tolerances. You can conduct “In-Process-Measuring” by using high precision work probes — these allow you to immediately check specific dimensions, or do so after the operation is completed and before the part leaves the fixture or machine. You can then adjust your data if required, and re-work.
In-Process checks on your tools will also prevent worn out cutting tools from being reused — these are dangerous as they have the potential to break during the process. Cutting tool checks not only helps you to confirm that your drill or tap is ok — a tool live monitoring system informs your operator when your tool must be replaced. Tool laser measuring systems can even measure tool wear in terms of length and radius.
#13 Implement Quality Control Measures
Quality systems are an integral part of manufacturing. Implement effective quality control systems throughout the entire operation — from the start of the project to the end products.
Your stringent work procedures should ensure compliance in material inspections, process checks, dimensions, tolerances, and specifications of the final products. These will avoid non-compliance products and match the high quality required from your customer, which in turn enhances your standing and productivity levels while reducing costs. Ideally, manufacturers should also be ISO-certified.
#14 Conduct Regular Preventive Maintenance
Adopting a regular maintenance protocol helps to keep your CNC machines in good condition. Frequent calibration is recommended to prevent your machine from operating out of specification or generating potentially damaging vibrations.
Such maintenance checks can also help you to avoid experiencing technical issues at the wrong time. Schedule such preventive maintenance checks at least once a year – better twice a year.
Ensure your expensive machine tools, which make the money for you, are receiving the care and attention they deserve. Do not try to save a few dollars by using cheap lubrication oil. In the machine operation manuals, there are all the details of which brand of oil and which specifications are required. To try to take short cuts and buy cheaper non-conforming oil may result in void warranty and near future expensive repairs.
Get the Free Preventive Maintenance E-Guide [Checklist] Top Preventive Maintenance Tips For Your CNC Machine Tools
Producing quality parts often depends on a complex combination of CNC machines, software, tools and processes, and skilled machinists. By managing these different parameters well, you will be able to deliver quality and consistent machined parts with the right levels of accuracy demanded by your customers.
To continually produce quality CNC machined parts, you need to invest in higher quality CNC machines. Doing so helps you to meet the constant demands for higher productivity, ever changing parts, increased complexity, and need for consistent product quality.
In order to meet or exceed the increasingly stringent demands of manufacturers, you should also mandate that your CNC machines stay in tip-top condition. Learn how to do so by reading our article on CNC Machines – The Ultimate List of Dos & Don’ts
Wish to learn more which CNC Machine is suitable for your CNC parts?