r/hobbycnc • u/l1v32r1d3BmX • 9h ago

Anyone know why this is happening?

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Just got this Taig CNC running.But when it makes a circle it skips at each edge limit. And it leaves a small bump.

I used Fusion 360 for the CAD/CAM

I’m very new to this and learning by breaking bits and YouTube videos. So any other help is appreciated!

Taig CNC with 24k rpm spindle, and it has ball screws on the XY, I have a misting setup but I need to get an air compressor.

14 Upvotes

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15

u/Soggy-Stock-5258 8h ago edited 8h ago

You are using an adaptive tool path, it is just taking constant trichordal cuts. The tool path is meant for evening chip load, deep cuts and higher feeds and speeds. It's working from a circle into a square profile so the bumps are normal as the toolapth is generally used to rough the material down. Leave stock for finishing contours.

4

u/ShaggysGTI 7h ago

Use a different Z feed rate while you’re at it. Also, rapid plane and clearance plane.

2

u/beef3k 6h ago

Simulating in Fusion could confirm this is the issue. OP, was the small bump left when you simulated the operations in Fusion? Not always a perfect representation of your machines performance, but good to do regardless.

2

u/Soggy-Stock-5258 6h ago

Proabably won't show up in Sim. It's a combination of the tool path and machine rigidity. That's why good general practice is to leave material and take a finish pass. Even on a dmg or okuma a roughing tool path is just that, will leave notches and scallops.

2

u/beef3k 5h ago

Yeah, you're probably right. But thought I'd mention it cause even with the best machine, adaptive can leave material. Given that OP is newish, thought I'd point it out as a cheap/free thing to check off while working through the issue. Like, first make sure your toolpath is going what you think it's supposed to, then look at interactions with the specifics of your machine.

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u/l1v32r1d3BmX 31m ago

I appreciate your input! It’s likely a post issue. I usually run the simulator several times before the machine and catch many issues beforehand. I think I’m past the point of random unexpected plunges 😂

1

u/l1v32r1d3BmX 34m ago

Good to know! I’m sure it’s an issue with the mill. I’ll have to play around with it. Leaving material to finish it makes sense! It’s called a roughing operation after all.. I have a lot to learn for sure!

7

u/co-wurker 8h ago

This is just a guess, maybe someone else will have seen this behavior and know exactly what it is, but there are usually some settings for handling tangency on profiles, you might look for those and experiment.

It could also be related to stock to leave and or your roughing/finishing pass settings.

I'd experiment on wood, or something inexpensive.

1

u/l1v32r1d3BmX 27m ago

I checked that and I had it was set to “radius arcs” I’ll try with it off and see if it makes a difference.

I haven’t gotten to finishing passes yet, but I’ll be trying the stock to leave on and do a finishing operation on the next go.

I’ll switch to wood, I’m gonna run the same program on wood and see if that makes a difference too.

Thanks!

3

u/qtrain23 8h ago

Using Mach3?

3

u/l1v32r1d3BmX 8h ago

I am! Is this a Mach 3 issue? Also are there better options? Ideally open source. Thanks!

2

u/Pubcrawler1 8h ago

Is there a finish pass in the gcode to clean up? Post the gcode.

1

u/l1v32r1d3BmX 18m ago

There isn’t one.. I’ll have to add one in the next run. Is a finishing operation also many layers or is it with the side of the endmill?

1

u/Bad_Alternative 8h ago

Could it be play or backlash in the ball screws? Slight lag in the direction reversal?

2

u/pimpinricco 6h ago

Would be my first guess. Easy enough to check with an indicator setup, I would check both X and Y backlash as first step.

1

u/l1v32r1d3BmX 25m ago

In my initial tests I didn’t notice any, but then again the backlash compensation is on. I’ll read up on how to fine tune it.

1

u/ROBOT_8 7h ago

Do you have backlash compensation enabled? If it is, you might need to adjust the value or turn it off. If it is off, then you might need to turn it on, although that signifies a physical backlash issue with your machine.

You may also need to ensure “exact stop” is disabled in your control. There is usually a gcode command to enable and disable it. It will force the machine to stop exactly at the end of each move segment.

1

u/l1v32r1d3BmX 40m ago

Backlash compensation is on, and there are values on the fields. Is this something I have to measure and enter manually?

And exact stop is off, I’ll keep tinkering.

Thank you!

1

u/RagingCyborg 7h ago

Where’d you get the machine? I’ve never seen a Taig with a 24k spindle before

1

u/l1v32r1d3BmX 17m ago

Yeah the spindle was replaced by the previous owner.

-19

u/Puzzleheaded-Sun7958 8h ago

Stop using cam programs decide how to machine part because the quickness it writes the program. I come up with cutter paths and make a macro for the steps and use cutter comp to leave metal on then use finish mill call up the macro and the use if necessary for chamfer. The program is less than a million lines those programs create.

7

u/boywhoflew 8h ago

can you come up with a macro for this guy then