Unexplained Z down ramp in Vectric

[rgobell (rickgobell@gmail.com)]

I am using Vectric with my Shapeoko Pro XXL. I’m running a rather simple file that includes a V-Carve, Pocket and Profile tool paths. The V-Carve and pocket tool paths operate as planned but the Profile tool path is not running correctly. The profile path starts at the proper depth but as the path continues it continues to slowly plunge until it starts diving into the spoil board and needs to be stopped to avoid further damage.

I’m very perplexed by why this one tool path is operating erratically. I believe I have my machine settings and post processor settings correct:
“Shapeoko Pro XXL - Carbide Motion/Carbide Motion ATC (inches) and I’ve been saving and running each tool path independently.

Any thoughts or insight into this issue is greatly appreciated.

[WillAdams (William Adams (Carbide 3D))]

Upload the G-code?

Screengrabs showing how the toolpath is set up in Vectric?

(also the job itself, Vectric is complicated)

[rgobell (rickgobell@gmail.com)]

Okay will do.

Cutout_1-Cutout.gcode.nc (7.4 KB)

[rgobell (rickgobell@gmail.com)]

[rgobell (rickgobell@gmail.com)]

[rgobell (rickgobell@gmail.com)]

Coasters.zip (138.3 KB)

[cheu (Charles)]

Might be a tad aggressive given that you haven’t used any ramping. Thunderstorm hitting…gotta run but I took this screen grab for Will.

[WillAdams (William Adams (Carbide 3D))]

You are cutting a slot just as narrow as the tool:

at least as deep as the diameter of the tool.

where possible avoid slotting and add geometry and cut as a pocket

Making vacuum hose adapters

While cutting up vacuum extension wands for this is expedient, it’s a bit problematic given that Shop Vac recently filed for bankruptcy, was bought at the last minute, and production hasn’t caught up. I need a receptacle for the Sweepy 2.0 dust fitting — one option would be to purchase one from Woodcraft, but Carbide 3D sells blocks of HDPE: which looks to be just barely big enough for things to fit. Measuring the hose fitting I get a diameter of ~63.5mm — offsetting that twice we arrive at…

and/or

Adding geometry to cut as a pocket with a finishing pass

One technique which is often suggested to avoid slotting is to add geometry around a part which one wishes to cut out and cut as a pocket down to tab depth — here’s one technique for that. In this case, the project is a bevel gauge which will be cut out of 0.0625" (~1.5mm) thick aluminum: [bevelgauge] Due to the narrowness of the angles, an 0.03125" endmill has to be used, so after importing and scaling the file (we will be cutting out one which is 3") we select the perimeter and offset it tw…

and consider leaving a roughing clearance and taking a finishing pass.

Best Bit for full cut through

One which has a cutting flute length equal to or greater than the thickness of the stock — pretty much any tool should work. Big thing is the toolpaths — if cutting out, rather than just cutting a slot: [image] Offset to the outside by endmill diameter plus 10% or so: [image] [image] [image] Then cut as a pocket: [image] down to tab height or the penultimate pass: [image] then move the contour down to below the pocket and start cutting at the bottom of the pocket: [image] and…

Ensure that feeds and speeds are appropriate to the tool and material.

[rgobell (rickgobell@gmail.com)]

Will a too fast feed rate cause the bit to plunge?

[WillAdams (William Adams (Carbide 3D))]

Yes, please see:

Feeds & speeds | Shapeoko CNC A to Z

and

Toolpaths | Shapeoko CNC A to Z

and

Cutters & collets | Shapeoko CNC A to Z

[rgobell (rickgobell@gmail.com)]

Thanks much guys, this information is helpful! Looks like I have a little bit of reading and research to do in regards to speeds and feeds. I will make some drastic adjustments to this profile cut.

I thought I was making progress in my CNCing skills but it’s clear that I have a lot to learn. This hobby can be very humbling at times and this is certainly one of them. I appreciate everyone’s input.

[CullenS (Cullen Simpson)]

I use Vectric with a pro XXL as well. As the others have said, probably aggressive but I guess it depends on the material. On most wood I use 1/2 the diameter as the pass depth.

[Fifinella (Keri-Ann Price)]

Just check this … possible?

[cheu (Charles)]

Sure. This is not a sudden one inch plunge. It is a ramp of the plunge. The plunge is perpendicular and gradual to the z axis. I never use that long of a ramp, but I absolutely use ramping whenever possible. The depth (in your example) itself is limited to the 0.51 inches of the cut depth, and is further restricted by the parameters in the 1/8" endmill found in the tool database. If you check the “show advanced toolpath options” you would see the number of passes it takes to finish the toolpath.

[rgobell (rickgobell@gmail.com)]

Thanks everyone for your responses. I’ve determined that my issue was caused by the bit slipping down.

I’’ve taken the extra step of cleaning the collet and shaft with denatured alcohol and tightening the bit with double wrenches. After doing so I’ve made a few cuts with no issues. I’m mad with myself that I didn’t notice the bit slippage earlier.

I guess the lesson here is to keep the collet clean and tighten your bits with two wrenches.

[SBarrett14 (Scott J Barrett)]

I have found that a .25" depth of cut on this size bit can cause a bit of deflection. I usually set the path at .1" as my max…more cuts, but no problems…