Aluminum has a relatively low hardness. This makes aluminum machining parts to be a generally fast and easy process; however, aluminum part deformation is one of the major concerns in the prototyping industry today.
For this article, we refer to aluminum and all its alloys as aluminum. Aluminum is one of the most important industrial raw material. Many of the products that you see today are manufactured with aluminum. Having a relatively low hardness and a large thermal expansion coefficient, CNC machined aluminum parts can be manufactured in relatively less time and cost.
At the time, people who are not directly involved in aluminum machining services have misguided views. They tend to believe that in order perform CNC over aluminum, it is enough to have a sharp, balanced tool, run it at maximum speed, set it up at medium feed and slice it up against aluminum and it will cut like butter.
However, that is not the case. Machining aluminum requires high precision and accuracy since the soft aluminum parts are prone to deformation when being machined into thin plates and thin-walled parts. With CNC aluminum parts prone to high deformation, several steps can be taken to reduce the deformation of aluminum.
Stratified multiple machining
In the case where there are multiple cavities on the aluminum parts, it is quite easy to cause a twist in the cavity due to the uneven forces acting on the part by the CNC machine. Aluminum prototype manufacturers adopt a strategy of multiple layered processing methods. Via this method, all the cavities are processed at the same time.
This results in parts not being finished all at once but are divided into several sections and layers and then processed layer by layer. Stratified multiple machining is one of the proven techniques to machine aluminum with material deformation.
Symmetrical machining
One of the major reasons for part deformation is due to the heat build up over a concentrated location. Therefore, it is important to avoid heat concentration over a localized region. For aluminum rapid prototyping parts with large processing allowance, symmetrical machining is used. Under symmetrical machining, both the sides of the material are worked together, and each surface is processed at least two times until the final dimension is reached.
Selecting an appropriate cutting parameter
The cutting force over the workpiece can greatly be reduced by selecting proper cutting parameters, and this is what aluminum machining services takes special care of. If the cutting parameters are bigger than the normal parameters will lead to excessive cutting force. Excessive cutting force results in deformation of aluminum as well as adversely affecting the durability of the cutting tool.
As compared to all the other cutting parameters, the cutting depth has the biggest influence over the cutting force and the heat generated. To counter this, high-speed milling is used by many top aluminum CNC services. By effectively reducing the cutting depth, increasing the speed of the machine and the feed, the overall efficiency can be increased, and the heat generation can also be lowered. This results in lower part deformation and quicker material turnarounds.
Precision grinding cutter teeth
To avoid part deformation, the roughness of the cutting edge for the cutter teeth should be lesser than Ra=0.4µm. Before the use of new blades, it must also be made sure that fine oil stones should be used to gently grind both edges of the teeth so that to eliminate any burrs or slight zigzag patterns at the cutting edge. Doing so will not only minimize the cutting heat but also greatly lower the part deformation.
Two-times compression of thin-walled parts
To perform rapid prototyping over the thin-walled parts, prototype manufacturers clamp the parts into place. Though clamping is an absolute necessity, the clamping force is known to cause deformation. To avoid part deformation while doing thin-walled aluminum machining, the part must be unclamped before finishing. This releases the pressure buildup in part and restores the parts to their original shape.
Thin-walled parts needs high precision and care as they can easily deform underwork
Once applying the force for surface finishing, a supporting surface is used to clamp the thin-walled aluminum parts so that the parts do not deform under the clamping forces. If handled properly, the workpiece will be held into place by supporting piece compression force. This method requires an experienced operator at the machine to ensure that the part deformation is to the minimal or not at all, something that Wayken is a pioneer in.
Strict control over the tool wear
Over time, cutting tools tend to wear away. When tools get worn, the workpiece surface roughness increases exponentially and so do the temperature. An increase in temperature, therefore, results in the deformation of the parts. To avoid part deformation, the tool wear standard should not be more than 0.2mm. The temperature of the workpiece should also higher than 100 degrees since high temperatures can result in part deformation.
Using the right approach
It is important that the aluminum machining services use the right approach for the right finish. For instance, finishing machining requires surface quality and higher machining accuracy. Therefore, to make sure that your prototype does not deform once finishing is carried out, the cutting thickness of the cutter teeth should decrease from maximum to zero. Using any other approach will result in poor surface finish and a high chance of part deformation.
Final words
Though machining aluminum is one of the easiest aluminum rapid prototyping technique, it still requires high expertise from the operator as part deforming is a huge problem for aluminum due to low hardness. To meet tight budgets and strict deadlines, it is essential that your prototype manufacturer has the needed equipment and expertise to cater to your needs. We at Wayken are aware of the aluminum part deformation and make sure that none of our clients miss their deadline or cross their tight budgets due to their prototype manufacturer handling their product unprofessionally.
