Problems with soft wood

Goliath CNC Bugs/Issues
1

I am not able to mill on soft poplar plywood with a thickness of 1 cm.

I used this sheet for milling:

and this milling bit from amazon:

I tried different settings for forward speed, depth per pass and rpm on the router. However, I was not able to get a clean cut on the poplar sheet.

I tried the following combinations on rectangular test cuts:

  • 18000 - 24000 rpm (number 3 - 4 on router), 1000 - 2000mm forward speed, 3 mm depth per pass (several tests with different combinations of the aforementioned settings): cut went mostly ok, but the bit burned and left burns on the wood, sometimes small sparks could be seen.

  • 18000 rpm (number 3 on router), 1500 mm forward, 5 mm depth per pass: I tried this setting because I wanted to increase chip load on the bit (mitigate the burnings and cool the bit) - however the cut failed completely, with Goliath moving away from its track - have a look at the following pictures:

5mm_depth_marked
5mm_depth_marked1920×1920 155 KB

IMG_20211222_232557
IMG_20211222_2325571920×1920 156 KB

I then wanted to cut the actual project, a big squirrel, but the cut also failed, although I used settings which worked ok before → 18000 rpm (number 3), 1500 mm forward speed, 3 mm depth per pass.

IMG_20211222_232650
IMG_20211222_2326501920×1920 93.9 KB

You can see that the cut started out good, no burnings can be seen. but after a while the wood started burning and in the end Goliath lost its track and gave me an “obstacle on the surface” error.

I continued the cut several times, but the machine was not able to continue.

I also shot a video of the process - Goliath trying to mill the sheet, loosing its track and starting to shake

goliath.zip (2.2 MB)

I don’t why it seems to be hard for Goliath to mill soft woods - I had good experiences with hard wood (beech), so I thought that milling poplar shouldn’t be an issue

Did anyone have similar experiences and can give me advice to my problem? Which bit to use and the correct settings therefor?

Thanks,
Best Christian

2

Hi Christian
The video was sounding bad obvously the goliath trying hard to cut but failed. The soft wood should not be a problem as you have noticed. I bet the router bits are not of high standard I guess. A good bit should be able to cut through smoothly - if there is chatter then there is something not right. If your goliath original bit is not too blunt try with thst bit. (May be on a smaller art)
I wish Springa should be able to send us spare bits or atleast recommend a good place to buy.
I bought 4 bits for 40 pounds from SpeTool
SpeTool Router Bits Carving Set for Wood Profile V Groove Engraving Solid Carbide 1/4 Inch Shank
But I have not tried them yet.
Plywood has lot of glue in them and destroy the bits fast.- I read some where.