Pockets not flat

[Crosetti]

Hello there!
Strange cuts have been occurring & I don't know why. Is it the machine, is it the program?
Pockets are not flat & v-carves just are not right. I have tried different strategies as in offset, raster, climb & conventional with no luck.
1st pic is uneven pocket
2nd pic is a funny corner & where it should have carved a clean grove, the tip of the V bit made its passes in two different areas leaving the space between the passes raised (green lines are where tip of Vbit passed).
3rd pic is just random non-level sections

Suggestions?

[BillK]

Your router might be slipping in its clamp. Definitely looks like a Z problem to me. Tighten the router clamp, put a reference mark on it to see if it slips again.

[Crosetti]

I put a reference mark on the router when it slipped a while ago & it hasn't moved. But I'll take a closer look at the area when I get home.
If it's not the router moving/slipping, what could it be on the machine that would produce this?
Thanks Bill

[tonydude]

Make sure your router bit is square to your bed.

tony

[Sam]

Another possibility is that there may be slippage somewhere else in the system. I would check your motor/lead screw couplings to make sure they are tight.
Yes, it *could* be the program. If you want to post the code for the letter E, we will have a look.

[Eagle55]

Slippage is always a possibility but I think your problem is going to be more closely related to either a dull (or not keenly sharp) bit or feed rates that put stress on the gantry assembly. Slowing down the FRO is likely to help both or either problem. I have a 1/4" carbide 4 flute end mill that I have used forever that used to produce silk smooth flats but now doesn't do quite as well. I have an 1/8" that I rarely use that does superbly because it is still razor sharp. Feed rates are much more critical on the shark than some of the steel frame versions of CNC. I have seen many great projects that turned out mediocre because the operator likes "computer fast" action rather than top quality projects.

Roger

[Crosetti]

So... I ordered the aluminum gantry back & a aluminum clamp from sam. we will see....

Feed rates are much more critical on the shark than some of the steel frame versions of CNC. I have seen many great projects that turned out mediocre because the operator likes "computer fast" action rather than top quality projects.

Roger

I program & operate a 4'x8' welded steel CNC @ work (i now have to find somebody to teach how to run - which makes me sad - cuz I just don't have the time to cut) & am used to running at 200 - 400 ipm. So yeah, I might be expecting too much & pushing it too much. I run the shark @ around 70ipm / .25 end mill ... & slow down depending on wood hardness.

[Eagle55]

Yes, I'm gonna say that is the problem. If you design it for those speeds I would try adjusting the FRO on the control panel down to 20-35% and see if you have better results. I haven't really considered the aluminum back panel upgrade yet but may in the future. Its an entirely different world at the $4000 level compared to the $20,000 - $100,000 machines out there. Not a bad choice for home or small shop, just a little bit of a challenge.

Roger

[Crosetti]

Well, slowing feed rate down smoothed out my cuts. Then I purchased the aluminum gantry back & a clamp by Sam & I can push the feedrate back up now with a smooth cut.... Awesome upgrades & well worth it!!

[Eagle55]

Thats a good report to get, I will look at doing mine at some point too. I have seen many situations similar to yours and nine times out of ten most people think that if the machine can move that fast it can cut that fast.... will its just not designed to be able to do that. A few key changes here and there can make it a much better machine than it originally is, but in the mean time it can do good work if you do it at its own pace. Glad to hear that and other reports about that particular upgrade.

Roger