Operation always cuts into my design

[choonlong210194]

Hi i have a question! 

I tried using "3D adaptive clearing" to clear out the material on the curved surface of the chair leg design. 

But the result always ended up like this:

the highest point of the model is also the top of my stock. 

I tried using "Contour", "Parallel", "3D pocket" operations for this part but the result is always the same. The bit will cut about 2mm below where i wanted it to stop.

Bit i used: 8mm Flat-end mill.  

Appreciate if anyone could help me with this problem 🙂 thanks!

[seth.madore · Accepted solution]

Looking at your Setup and your toolpaths, a few possibilities spring to mind:

1) Your tool has pulled out of your holder and it's cutting 2mm deeper than it should be

2) Your defined Stock is not correct; it's 2mm thicker than expected

3) Your WCS origin (at your machine) is not established correctly, and it's sending the tool 2mm deeper than it should be

What is your machine and control?

[programming2C78B]

you'll also want to use some stock to leave and smoothing.

[choonlong210194]

Hi Seth 🙂

Thanks for the reply! The 3 pointers you suggested make sense. I guess i will have to tinker with the machine after i get back to the workshop on Monday~

Come to think of it, i realized only encounter this issue when i attempt to cut a design with rounded corners, or any convex/concave surface. The extra 2mm dip doesn't seem to happen when I'm just doing ordinary 2D cuts. 

Below is an example of me trying to do a parallel operation for the finishing pass of the plate. i used a 12mm ballnose bit for this operation. It also has the same problem of cutting below my intended depth.

Same issue for the round plate shown below:

On the other hand, straight forward 2D cuts seem to do just fine. As you can see from the photo below, the top of the stock levels with the top of my intended design.

I am just wondering if i did anything wrong or is there anything i am missing out when it comes to machining 3D profiles. I hope this information provides more context to the problem i'm facing ~ haha

Oh ya to answer your question, the machine i'm currently using is Stepcraft M1000 and i'm using UCCNC for the driver.

Thank you for your help 🙂

[choonlong210194]

Hi there!

Thanks for the suggestion! I'm not planning to do a finishing pass on the surface, do i still need to use stock to leave and smoothing? I am planning to the sand and smooth out the surface manually later on using a sander.

[programming2C78B]

Sure, if thats what you want to do. I'd just use a 3D parallel with the endmill instead then with a 20% stepover if you just want to sand it after. Then you're just removing cusps instead of a full staircase. 

[choonlong210194 · Accepted solution]

After some troubleshooting, it turns out that there is a problem with my probe haha. Apparently the 'click' inside wasn't secured properly, resulting in it shifting everytime when i tried to zero the z-axis using the probe. It shifted about 2mm and hence all my cutting depth is off by 2mm. So it's not a software but a hardware problem~

Anyway thanks for your help! 🙂 Appreciate it.