Either I broke something in Fusion or my CNC is broken/cutting incorrectly

[Anonymous]

Hello all,

Background:

I am very much a beginner to fusion 360. So I've been in the forums and all over youtube to get me to where I am now. What I am creating is a very simple wooden pot stand. I had a version created that was working ok.

Somewhere between the design of the piece and cutting it out, something is going wrong and I am stuck in a mental loop and can't find my issue.

My current issue:

What is happening is that the lock-and-key component in the center of each part measures ~18.02mm wide but when it cuts it produces a space that is only ~16.7mm wide. I had a working version where everything was sliding together as expected, but now I can't get it to cut correctly. 

What I need:

1.) I need to know what the issue is/what mistake I am making that is causing the issue so that I can get better at this and be able to fix it next time. 

2.) If someone looks at my model and says "ew" or "oh god" feel free to give me an example of how I should've done it. 

Thank you in advance to anyone who takes the time to provide help and advice!!!

[davebYYPCU]

I am not a CAM expert.  Not found anything amiss in the Design Section.

Do not use the Move Command.  There are other ways.

If the slot is not cutting correctly then the rest of the outline should also be in error. 

1.5mm oversize, have you checked that?

So it comes to specified cutter 1/4" and actual cutter - not 1/4"?, 

Machine controller adding cutter compensation?

Few things to check.

Might help....

[jhackney1972]

I cannot see any error in the toolpath.  I do not know what Post Processor you are using it could be the culprit.  You mentioned you would like to know anything we see that could be a trouble spot.  Well the big thing is the sketches for the main bodies.  They are not constrained at all!  You do not have even dimensions on key points like the width of the base of the legs.  This sort of thing is going to come back and haunt you.   Also you want to avoid a lot of Moves.  You are working with components so it is easy to drag them around and then use the Align command to flush their faces or even an assembly joint. 

Good luck on the toolpath.  Post back here if you can when you find the error, I would like to know.

[Anonymous]

Hi John, 

1.) Thanks for the reply. Is there any way that you would be willing to redraw that design as you would have done it? If possible record the screen or just send the file so that I can see what/where the constraints belong in this situation? If no, I understand! Just wanted to ask.

2.) I'm still learning and that was my first try to get something on "paper" but I welcome the help and will work on redoing it with constraints added. 

3.) From both forum replies I've gotten it appears that I'm really doing something wrong with moving objects around, to not use the "Move" command, what should I use to drag the component/body if not the move command?

4.) Attached is another picture showing the actual cut out/product. What's really interesting to me is that the area that i am pointing to is the correct width but then it pulls back in and the rest of the slot is not wide enough. 

5.) Here is a link to the post that I have been using: https://cam.autodesk.com/hsmposts?p=techno_cnc_router

[davebYYPCU]

That looks like a different tool path than the file you supplied,

the bottom right corner with a ramp cut, (Machine or post error) is not in the file I have for review.

You did not answer the question, is the error all the way round?

What is this measurement when cut?

10.875?

[Anonymous]

1.) The rest of the outline appears to be correct (I'll remeasure everything tonight and let you know for sure)

2.) The cutting diameter of the actual cutter is 1/4" (6.40mm as measure by my caliper)

3.) Is it possible something is messed up in my included manufacturing tool settings?

[Anonymous]

I just sent a picture of one with the same issue. I was trying different configurations and that was just one of the few I had tried to cut out.

Give me a few minutes and I'll go cut one out with the file I posted to make sure I'm giving you the correct information.

[Anonymous]

Attached are 3 images showing an overview as well as close up photos of the noticeable issues I'm seeing.  I also labeled the dimensions as requested. Let me know what you think!

[Anonymous]

Also, here is the exact file and setup I just used to get that cutout. 

[davebYYPCU]

Ok, so yes the part is too big all the way round, 

9 3/8 is coming out 9 9/16.

Those steps in the outline is backlash in the table or spindle mechanism. 

Major machine problem.  Warranty will cover it.

This means that the spindle pushed left has enough play in it so that when the machine is pulled right - it will not line up on the same start position.  Looks Ok top to bottom, but still you have a cutter compensation error thrown on top of this machine problem.

That machine will waste a lot of your time until the backlash is fixed.

[Anonymous]

Well that’s disappointing but I appreciate the input. I got it used, but was told it was all functioning well.

How can I work out what is causing the cutter compensation issue?

Is backlash a fixable issue or am I looking at a complete rebuild?

I’ll have to contact the cnc company tomorrow and get it worked out? 

[davebYYPCU]

Might be just freeplay, loose bolts, motor, pulleys, leadscrew, Ballnut anything similar not rigid, and your looking for less than a 1mm.  The amount of step in that outline, but just in the left right directions of the cutting you have pictured.  You can see that the top bottom directions are not doing the same.  

Cutter compensation, well that is being done by the toolpath, (blue Line is the centre of the cutter)  You are not getting size for size from Fusion - to timber.  Fusion is probably sending the right Gcode to the machine controller, which, may also have some settings making the cutter stand a bit further way from the Fusion outline.  (Double Compensation)

Might help....

[davebYYPCU]

Step up my timeline for how I would do what you have done. (Design side but not CAM stuff)