Straight cuts nit straight

[Angelp357]

Anyone have any idea why these are not coming out straight? could it be the feed rate or depth of cut? Any suggestions would be appreciated. Thanks.

[Kayvon]

What's the material? It looks like a slightly soft foam, which means the foam itself might be compressing (and briefly warping) during the cut.

[Rando]

And, of course, does the GCode actually say to move in that serpentine manner, or should they really be straight?

[Angelp357]

The material is poplar and yes it's gcode is set to make a straight cut at .25" x 2" for each cut.

[Rando]

In that case, it looks like the bit is likely deflecting due to heavy cutting forces. If I may assume the cuts are "full slots" meaning the intended width is the same as the bit width. If that's true, then slow the cut and lessen the depth of cut. Since it's just wood, start with 1 x Diameter of the bit (aka 1D) as depth of cut; if that works fine, move up to 1.5D and potentially 2.0D. Watch carefully and you will be able to see the gantry and z-axis carriage bending under the strain of the cut. Something in the 60 IPM feedrate should be a good starting point. Find something that works, and then adjust from there to get faster/deeper.

And if you're really cutting a 2" deep slot in one pass, yeah, that's the problem; sharks flex too much for that aggressive a cut.

Hope that helps,

Thom

[Angelp357]

Thanks Rando I will try that. And just to clarify, the .25" x 2" I was referring to is the height and width. The depth is only .25".

[Rando]

Thanks Rando I will try that. And just to clarify, the .25" x 2" I was referring to is the height and width. The depth is only .25".

Yeah, without the DOC, SO and RPM designations, it can be a guess sometimes .

If it's only 0.25" deep, then feedrate speed is the likely issue, assuming you're running a normal RPM.

Of course, just like "is the computer plugged in", there are a bajillion prerequisites, but it sounds like you have those down already. For example, it's not moving in the clamp/hold-down method, right? Yeah, I thought so .

Thom

[Kayvon]

Since it's just wood, start with 1 x Diameter of the bit (aka 1D) as depth of cut; if that works fine, move up to 1.5D and potentially 2.0D.

I've always used half the diameter for cut depth as my rule of thumb. Too much give in the plastic of the gantry for me to want to try deeper than that.

Thom is much more knowledgeable than I, however, and I'm using an older baseline Shark.

[Rando]

Since it's just wood, start with 1 x Diameter of the bit (aka 1D) as depth of cut; if that works fine, move up to 1.5D and potentially 2.0D.

I've always used half the diameter for cut depth as my rule of thumb. Too much give in the plastic of the gantry for me to want to try deeper than that.

Thom is much more knowledgeable than I, however, and I'm using an older baseline Shark.

I was basing that on some wood work I did the other morning. Maybe it's just that it looked so easy compared to what I normally see .

Kayvon is right: The trick to being successful with these machines is to understand where its limitations are, and work within what is possible. Many of the things I'm doing now, I was told I was crazy to even try. But with careful observation and experimentation, and a good amount of time, I'm getting results that are well within expectations.

So yeah, if you have a really old machine with plastic gantry-plate and such, then you're going to need to be even more careful and gentle with the cuts. If the 1D cut is too much, go shallower.

Regards,

Thom