The Z-Axis Assembly, Step 4

So from the picture below, we can see two types of Z-axis assemblies and the Y-Axis CNC Machine Gantry behind the Z-Axis assembly.


Just like the last discussions, when building or designing a CNC machine, it is imperative to understand the forces that are derived from its movement. By so doing, you can modify your design and also establish that it will meet the requirements of your design. In any case, for you to design and as well build your machine to meet your requirements, you need to acknowledge the forces that are involved.



Forces that are on the Z-Axis Assembly



Let’s translate the above picture.

The dimensions are explained by the following:

D1 = the vertical distance between the upper as well as The lower area of Y-axis linear which bears rods and rails.

D2 = the distance between the upper and lower sets of Z-axis linear bearing which is vertical.

D3 = the spindle’s length attachment plunge arm.

D4 = the Z-axis assembly’s width

D5 = the horizontal distance between the Z-axis linear bearing rods and rails.

D6 = the plunge arm’s thickness

D7 = the gap between the cutting force (approx., a tip of the cutting tool) and 1/2 D2.


Now we have an understanding of what the labellings are, let’s have an analysis of the forces and moments.


Forces and Moments on the Z-Axis Assembly

Building a CNC router machine can be simple or complicated. Certain people over think and others just create it and check whether it works or fails. I think it’s best to mix the two concepts. So let’s understand what’s happening first.

The above image explains how the Z-axis assembly are assembled this is shown in a front and a side view. Take a look at the front view and observe that the Z-axis assembly is moving to the right while riding on the Y-axis linear that bears the rails and rods.

The plunge arm is at max Z travel and is as well cutting into a material as-as well as it goes from left to right. This action that is cutting creates a cutting force that connects the movement of the Z-axis assembly.

The cutting force is a variable of spindle RPMs, the number of flutes on the cutting instrument, the rate of feed, and the material that is being cut. You can know more on the most proficient method to calculate cutting force here. When setting up a CNC router, an essential choice to make is the sorts of material you might want to have the capacity to cut, which was talked about in stage 1.

For the primary time, just understand that there is a force in the other way than the Z-axis assembly is moving. Right now let’s see what happens due to this cutting force.


The cutting force makes a moment, which is explained in the image above as Moment A.

A moment is only force applied at a distance. We covered moments in more details in Stage 3.


Moment A = D6 x Cutting force.Z-Axis

Moment A torques the diving arm in the opposing direction of the cutting force, which torques the entire Z-axis assembly.

Br> This very moment results in resultant forces which are applied to the Z-axis linear bearing rails/rods and the Z-axis linear bearing themselves. (Yellow arrows)

As D5 and D2 increment length, the resulting forces reduce. You can see that when you are making a design or building a CNC router, it is vital to maximizing the horizontal distance between the Z-axis linear rails (D5), and the vertical distance between the Z-axis linear bearing block.


The Plunge Arm

D2 affects while cutting along the X-axis as well. See the image below.

The cutting force brings about another moment; Moment B.

B moment is the result of the cutting force being duplicated by the distance between the cutting strength and ½ D2.

Z-AxisThis moment will apply forces with a result on the Z-axis bearing. As the distance between these bearing (D2) increments, these effects will reduce. That is the reason it is best to maximize D2.

As a policy of thumb when setting up a CNC router, D2 ought to never be any less than half portion of the length of the plunger arm. Additionally, you want the thickness of the plunger arm (D6) to be sufficiently thick to not flex under your greatest cutting force.

The flex will rely upon the most extreme cutting force you are designing your machine around, the thickness of the material (d6), plunge arm length (D3), and the material it is made of.

If you require help calculating your cutting power you desire or the measure of deformation a particular material and size will have, you may get in touch with us. We offer free design consultation and other engineering services.



Remember the following when you design or set up a CNC router:

Maximize D1, diminishes the forces because of torque caused by the cutting force in the X-axis.

Maximize D2 diminishes the forces because of torque caused by the cutting force in the X-axis.

Maximize D3, yet still, permit your desired Z-axis travel.

Maximize D4, diminishes the forces because of torque caused by the cutting force in the Y-axis.


Different Contemplations

In later areas of the building, a CNC router guide, we will talk about other features such, for example, lead screws, motor placement, linear bearing and so on.

Do not forget that you may get in touch with us with any questions in regards to CNC machines in general or your design. We will help out any way imaginable.

The motor mount that is utilized in the above image might be purchased pre-fabricated from ebay or banggood for an assortment of router spindles.



So now we have taken a look at the initial four stages when setting up a CNC router machine,

Step 1: Key design Choices, HomeMade Hobby CNC Router Machine

Step 2: The Base and X-axis frame Design Understanding

Step 3: The Y-axis Gantry Assembly and Design Understanding

Step 4: The Z-axis Assembly and Design Understanding

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Right now let’s keep on one of the most critical features when designing or setting up a CNC router machine system, the linear motion system.