Engraving help

[Adrian]

I’m surprised nobody has suggested: is your machine trammed properly?

Martin did mention it early on but the OP insists everything is flat and square with zero flex anywhere.

[Truck trudeau]

Everything in those last pictures was done with vcarve toolpath just experimenting with different speeds.

Tomorrow morning I will get a good pictures from different tool paths and label everything and upload it for you. I will also try it without the mat and clamped down. I’m even going to get some video so you can see exactly what’s going on.

I’m not sure if it’s perfect but I know that it’s flat. When I first got it it was all out of square but Im pretty sure I got it dialed in. When I do the spoilboard board with a 1 inch surface bit you can barely see any tool lines it’s about as perfect as I think you can get this machine. Flex…. Yeah there’s flex! I think that’s common with the shark? I did not know about that before I bought this thing.

There could be something very simple that I’m overlooking and I hope that’s what’s going on here…

[martin54]

I will also try it without the mat and clamped down.

As I said in an earlier post edge clamping can cause the material to bow upwards in the centre. If you are going to experiment with a different hold-down method then something like the CA & painters tape method people use might be a good option. I built a vacuum fixture for holding thin sheet material but it wouldn't be worth you going with that option just for experimenting

[Truck trudeau]

Well I did quite a bit more testing and the machine seems to be vibrating…. You can see it, I don’t know why…. I understand that resonance is a thing but not this bad. The couplings are tight and every bolt or screw I could find is tight…. It’s clean and oiled…. This thing is making me crazy

[Truck trudeau]

OK pretty sure I found the problem…. The motor for the long axis has some excessive shaft in and out play…. Like well over an eighth of an inch. I took the motor off and you can push the shaft in and out with your finger. Not sure if something is binding intermittently in there or why some cuts are clean and some cuts are not but that’s got to be the problem. Checked both other motors and you cannot push the shaft in like that. Looks like there is some sort of spring washer at the back of the motor stater but I don’t think it’s supposed to be so springy…. So not sure if anyone has any experience with this problem but I will let you know once I get a new motor. Also the part that pisses me off the most is that there is three regular looking screws and one different coloured longer screw holding that motor on…. Maybe someone already was dealing with this problem

[martin54]

Is this a new machine or one you purchased second hand? From what you have said in your last post it sounds like you might not have purchased it new.
Do you have any play/backlash on the ball screws or lead screws on the machine? sorry not familiar with them so not sure what you have fitted. Any movement of the motor shaft shouldn't be transferred to the shafts as they should be locked in place by the bearing blocks at either end of the shaft.
Any binding would be more likely to cause lost steps rather than what you are seeing

[Truck trudeau]

Brand new machine. But I suspect it was an open box or something like that. I installed some shim washers in the back of the motor to prevent it from pushing in. There is a long thread about that online It’s some sort of defect but that problem is solved. I’m still going to get a new motor ordered up first thing tomorrow. Now there is no play or backlash at all in all 3 axis. I ran another test and there is really no difference…. It’s still vibrates. If you slap the router like you are slapping a mosquito The whole thing vibrates…. I did not know that about this machine. The long screw does seem to have a tiny bit of flop like it’s not perfectly straight but other than that I can’t find anything else that could be causing this problem…. On Longer straight lines there is no problem it’s the quick turning and stopping and starting on the small lines….

[martin54]

Think I would be contacting the manufacturer if it was a brand new machine, especially if it has some known issues that have now been fixed
OK so now you have checked that there is no backlash in any of the 3 axis have you looked at the spindle or router that is fitted? Run out on the spindle or router could be causing a problem, if it's a desktop type machine what is it supported on? The vibration could be caused by whatever it is sitting on. Lot's of different reasons for the vibration of the actual machine & lots of different ways to try & reduce it

It might also be something to do with how your machine control system is set up to handle changes in direction, try a search for constant velocity & exact stop for more info, I don't know anything about the shark control system & how it works.

[Truck trudeau]

I’m going to call them tomorrow and see what they say. To be clear when I say the whole machine shakes it’s the gantry and the spindle that shakesthe actual table doesn’t move. It’s on a strong bench that doesn’t move

[Truck trudeau]

Ok I have a vibration problem but my original problem is still there…. Thanks to your help I understand it better but not completely. Have a look at the attached pictures. The top test is v carve and the bottom test is quick engrave. I understand why the quick engrave is more thick, and I understand why all of the lines are not perfectly straight (vibrations) but I don’t understand why v carve makes those little lines protruding from the letter edges leaving dots... The quick engrave does not do that…. Also the quick movements to make those tiny lines contributes to the vibrations. Does anyone know how to solve that particular problem? Like get rid of those little lines?

Thanks

[Rcnewcomb]

Until you fix the vibration problem nothing else matters. Solve one problem at a time. Keep careful notes to ensure repeatability.

[Truck trudeau]

I could not disagree more. You can see on the tool path preview that it wants to draw those lines that are making those dots that’s a crystal clear problem that needs solving. It wouldn’t make any sense for those lines to be there doing what I’m doing. Does anybody know about why those lines are there?

[Truck trudeau]

Just to be clear I’m talking about these little lines in the close up pics. You can hear the machine going out of his way to make these lines which turned into dots. This is a clear and present problem regardless of what else is going on.

[Truck trudeau]

Sorry for the excessive posting but one more thing…. It does not have those lines in the quick engrave and look at how much cleaner that looks. The one below is quick engrave the one above is vcarve

[adze_cnc]

It would seem that deep down you don't have a full grasp on the difference between the "Quick Engrave" and "V-Carve Toolpath". To re-iterate "Quick Engrave" is meant to be used with some sort of dragging tool. Any path it creates will just be at one depth (the "Depth / Pressure" setting).

The "V-Carve Toolpath" as the name might suggest is for cutting with a V-shaped (effectively conical as it rotates) cutter. It is designed to have the v-shaped cutter ride between vectors. As the distance between vectors widens out or narrows in the edges of the conical tool follow along raising or lowering as needed (the flat depth can put a limit on how deep the lowering can go).

One other thing the "V-Carve Toolpath" can, and does, do is that it sharpens corners. It does this by raising the tool along an angle to the vertex of corner's vectors (see the following image):
 

Top of a V-Carved letter "A" preview in 3D. The two angled parts of the toolpath pointed to by the red arrows are corner sharpening.

 
With a v-bit that has a properly specified included angle angle the corners cut as nicely pointed. Any engraving bit with a properly specified side angle will come out reasonably pointed but not 100% pointed because the flat area of the bit will still round the "sharp" corner.

When corners are appearing as in your images there are some thing that can go wrong such as:

• improper bit angle setting
• telling the program that you are using a v-bit (no flat) but are actually cutting with an engraving bit (flat). The preview will show crisp corners but the corners will cut rounded.
• machine vibration especially present on speed changes
• your controller is set to use "constant velocity" rather than "exact stop". The former can cause the actual cutting path to deviate from the real toolpath the latter will do its best to keep them the same