6. Large format CNC (computer controlled Machining)¶

This week we worked on bigger scale designs and used the CNC Machine to cut it.

about group assignment¶

What is CNC Machine?¶

A computer numerical controlled (CNC) machine uses a program to control the operation of machine tools such as lathes and mills. It takes a raw material (metal, plastic, etc.) and cuts, grinds, drills, turns, mills, and/or shapes it into parts that meet exact specifications.

Feed rate and rotation speed¶

The time consuming to cut the designs we want differs by changing the feed rate and rotation speed of the spindle.

As far as we increase feed rate and speed we would get less time? Actually, no. This is not as intuitive as it seems.

Let’s state a rule: as much material eaten by the machine as we finish faster. How much material eaten by the machine is considered by the volume of the chip load, and the sound of the operation.

For feed rate, as we go faster as we get bigger chip load and more noise. That means it would finish in less time. For rotation speed, as we spin faster as we get smaller chip load. Aha! It means it eats less material. So, to take less time we decrease the rotation speed.

Safety requirements¶

We should wear safety glasses to protect your eyes from flying fragments. Also don’t forget to protect your ears by soundproof headset.

Other things you must do is to wear suitable footwear and ensure that you raise the sleeves of your clothes.

When the machine is working, make sure that you are behind the flashy line in the ground.

There’s also an emergency stop button, if anything wrong happen you can stop the machine right away.

Limitations¶

We should say that, CNC is a powerful machine, but it has limitations. It’s a 2.5 D machine, that means it is not fully free to make 3D designs as 3D printers. It can only engrave along the z-axis.

Another thing is that your precision is related to the diameter of the spindle you are using. For example, you cannot operate the machine on a design contains some 2mm details if the spindle’s diameter is 4mm.

Due to spindles, you cannot go with highly feed rate without any limits. You are restricted with the strength of the spindle and the material you are cutting. If so, the spindle will breaks and it’s fragments flies away. So be careful!

Cutting phase¶

Before starting the cutting operation, we had to make the wooden panel stable (the type of wood we used was MDF)

some informations:¶

You can notice some parts of the numbers is not cut properly. This refers to that, the width of the toolpath there was smaller than the diameter of the spindle. So the software doesn’t allow the spindle to go there. This can be solved by choosing a proper spindle and editing your design.

Alignment in cnc machine¶

Aligning most CNC machinery can be critical for proper performance. If your goals in aligning CNC mills, lathes and gantries is to ensure accuracy or simply to prevent machine tool wear, a laser alignment system is the most precise way to do this. Alignment in setting up a new machine, working on sub-assemblies and even day-to-day machine tool applications cause workplace stress to compile because the more responsibilities you have, the more likely you are to make mistakes. Aligning and measuring projects may follow a well-conceived alignment process, but the very machine you are working on has multiple components that must be in specification to prevent errors, and if several people have access to your CNC machine, there is higher likelihood that the machine will fall out of alignent.

profile Toolpath¶

Profile Machining is used to cut around or along a vector. Options provide the flexibility for cutting shapes out with optional Tabs / bridges plus an Allowance over/undercut to ensure perfect edge quality.

Profile toolpaths can be outside, inside or on the selected vectors, automatically compensating for the tool diameter and angle for the chosen cut depth.

When working with open vectors the profile toolpaths can be to the Left, to the Right or On the selected vectors.

Clicking this icon opens the 2D Profile Toolpath form which is shown at the right; the functions in this form are described on the following pages.

If you have vectors which are nested (like the letter ‘O’), the program will automatically determine the nesting and cut the correct side of the inner and outer vectors. In addition, the program will always cut the inner vectors before the outer vectors to ensure the part remains attached to the original material as long as possible.

Pocketing Toolpath¶

This option opens the Pocket Toolpath form for machining 2D pockets. These toolpaths automatically compensate for the tool geometry - both diameter and angle , Specifies the depth at which the pocket toolpath is calculated. When cutting directly into the surface of a job the Start Depth will usually be 0. If machining into the bottom of an existing pocket or stepped region, the depth of the pocket / step must be entered.

vacuum machine¶

The Vacuum machine in CNC machine helps us to clean wood from dirt, which helps to make it easyer and move the router faster

Final shape¶

After experiments and some attempts, we made sure that the appropriate feeds is (120) and the good speed is (14000)

My own work on CNC¶

dog bone¶

Dogbones are a great way to allow vertical plates to be inserted into horizontal plates without out having to worry about the radius left from the cutter. Depending on the thickness and size of the part will affect the size of the dogbones needed.