Multiplex Poplar, Feed & speed issue

Olivier · February 19, 2024, 5:30pm

Hi there

I ran into some issues that I can not seem to resolve, hope any of you can point me in the right direction. I have cut like 100´s of items in 15mm thick Poplar Multiplex without issues.

Recently I swapped my PC and reinstalled my tools like Fusion 360, ESTLCAM, etc.
At the same time, as I could not find 15mm A grade poplar multiplex, I bought 18mm instead.
Since then things went wrong. No matter what I do the cut fails as the machine wanders of, or the bit starts to burn. Waisted some serious amount of wood but still haven´t found what I do wrong.

Some examples;
a 3mm bit (from the tools I have used since the beginning), at speed dail 2, it burns the edges as you can see. This cut is stil “ok”

same tools, suddenly it wanders of:

same tool, wanders of again:

One cut went well, the next one wanders of again as you can see

I just bought 2 new bits at Sorotec (single flute, 6mm 22mm DOC).
The bit started to burn, so dailed back to 1,5 and after some passes it started to wander of again, so increased speed dial but it jammed anyway (and burned once again)

Now for my settings, I always used a cutting feed of 15mm/s, 3mm/s Z speed at 3 - 5mm DoC with a 3mm flat end mill (single flute). The same settings applied for my new 6mm single flute bits.

I ´ve tried so far slowing down, gearing up, changing the router speed… start to wonder if something went wrong with my LR setup.

pony1023 · February 19, 2024, 11:30pm

I’m only going to beat everyone else for the #1 thing over time that causes frustration. You verified the grub screws are still tight? Or used threadlocker?

Although not covered by most of your issues, the wandering off is almost always belt related. Grub screws, skipped steps, etc.

The other stuff I’m watching to learn.

pony1023 · February 19, 2024, 11:36pm

Posted and thought of one other question.

I heard changed from 15mm to 18mm. But same vendor? Same product? Thickness is the only change?

The reason I thought of this, is the number of topics lately, using some sort of manufactured product, that the adhesive for the layers, was the cause or appeared to be the cause. Aka can you run a test on standard poplar to compare?

Olivier · February 21, 2024, 10:05am

Well actually I did check it all before posting my issue, but did not mention this as I wanted to hear all potential issues:)
It is tight as hell, but without threadlocker.
I do not notice any skipped steps, but ofcourse, I might have missed that in the noise.

That´s difficult to say, I bought it in the same store but they could have gone with another vendor. but TBH I was thinking the same. Something iw off with the new sheets I bought.

Good news: I completely re-designed it in Fusion, created a new toolpath and used the shapeoko speed table… and it ran flawless. So now I wonder where it went wrong to avoid it a second time.

note, shapeoko mentions a feed speed of 2500mm/M and my postprocessor has the save values of max 900mm/M, so it overwrites my speeds. Wonder if it is worth the try to bump it up twice the speed or keep it as is.

Olivier · February 22, 2024, 1:29pm

ok, so I think I might have found “a” cause of my issues. It seems that Fusion 360´s post processor is not respecting the max cutting feed for some reason.
Played around with settings and tried again. With new issues

Started the job, and the spindle positioned itself in the middel, went down and wonders of once again. Tried again, same story. Swapped the bit for a brand new one, and it started to cut fine. So I figure ok, the bit was wasted …

this is what the initial bit created:

up close where it started (and went wrong) :

So I let it cut the full sheet and after 40 minutes I am off to lunch. Once back I mounted a new sheet to start cutting once more…

This is where I really get annoyed, it wanders of again :@ after cutting fine before.
This happened:

Let me blow some dust for better detail:

Nothing I can see that would cause an issue. And highly doubt my 40 minute old bit is to blame as it was still shiny as new.

After try few times, swapping back to the old bit, and back to the “new” one, there seems to be enough space cleared for the LR to do what it is supposed to do:

As you´ll notice at the bottom it is making a perfect cut… and now it is running fine for like 20 minutes.

I did notice in the experiments that the issue lays in the X direction, there it stutters like it is unable to cut trough the material and then wanders off (makes sense as it finds a path with little resistance at some point).
The starting position is in the middle of the X & middle of Y at cutting depth of 5mm with a single flute 6mm.

Does it sound like a weak spot on my LR, or just twice in a row a bad piece of wood at exactly the same spot?