Don't worry,, this has happened to me.Hello Friends,
Now we are facing a problem:
While we were milling a part, the z-axis suddenly took deep cut and spoilt the part and then the connection of the lead screw with the handwheel was gone when we checked. So we opened the assembly and found out that part no. 67105 (CNC COUPLING) was broken. Now I needed to replace this part.
I want to understand why this part broke and does this part breaks often, so I can keep a few in my inventory?
The sudden z axis cut was about 1mm.
I will tell you what we were doing and what exactly happened so you get a better idea on what might have happened:
We are doing a part production for which we designed the part and generated the code. We were using 5mm end mill cutter ( 2 flute as well as 4 flute). the maximum cut size was 0.75mm. Material is brass and the spindle speed = 2500 rpm with feed rate of 250. For making this perticular part, we need to use 3 tools. 1st 5mm tool for roughing and finishing, then 3mm tool for further finishing and finally 1 mm end mill cutter for final finishing. While using the 5 mm end mill cutter, there are always vibrations and a bit too loud noise, compared to 3mm and 1mm cutters. but we successfully produced about 25 parts.
Then because of the vibrations while using 5mm end mill (though the material to be removed was very less because we turn the blank first so that the cutter has to remove minimum material), I reduced the maximum cut size to be 0.375 mm. Vibrations were still there but little lesser. Thus we successfully made about 25 parts and then one day evening while we were doing last part of the day ( 8 nos. already finished during the day) using 5mm cutter, it suddenly took a deep cut, so we stopped the machine at the end of the 5mm cutter program. Then we tried to take the z-axis up, we noticed that the connection between the handwheel and the leadscrew is not there and by rotating the handwheel the axis is not going up.
It is then we opened the assembly and came to understand that the part is broken.
I guess this should give you fairly a good idea on what we were doing and what exactly happened. Kindly guide us on this, so we understand sherline machine in a better manner.
Sometimes, z-axis used to move a bit too tightly. Kindly also guide us on exactly how to keep is smooth moving like x and y axes.
We are planning to use the machine for about 9-10 hours of operation per day. I hope that's not a problem?
After I got the new part from sherline dealer:
We removed the broken part from the motor shaft which a bit too tight fitted. After removing the same, we noticed that there were some marks and burrs on the shaft which we cleaned by using a very find sand paper lightly, taking care that we do not alter the diameter of the shaft. Then we slide in the new part, which slide in easily. Fitted in the screw and done the whole assembly for the z-axis.
Then we dis not know what to do next, so we well lubricated all the 3 axes and made sure that z-axis is moving smoothly up and down and then did a work piece but almost at the end of the program, the z-axis again took a little deep cut than desired at some points and then the program stopped at the end of the program.
When we investigated the matter, we found out that the lead screw was disengaged from the top. we engaged it again but now the up and down movement of the saddle was little tight, so we tried to adjust the saddle screw and the 2 small screws at the side. We stopped at this stage because I do not intend to again break the same or any other part or harm the machine in any way, so I am seeking your help and guidance.
What I could understand is as below. Please let me know if my understanding is correct or not:
The main saddle screw is provided to engage the spindle with the saddle but as it may put load on saddle and in turn on leadscrew, the 2 small screws are provided, so by adjusting the same, the load can be balanced and the lead screw can be kept straight. The up down movement is to be adjusted using the lock which is provided just above the saddle. Is this correct?
I want to understand what causes the lead screw to disengage from the top and what can we do to prevent the same. How to run the machine in correct manner so as to get best from the machine?
I tried to search in the book and on sherline website and also on google on this but could not find much help.
You may please write to me on my email address at email@example.com.
Thank you all,
Soon I'll put a video teaching how to make a 67105 (CNC COUPLING) coupling with detail.
The result is perfect.