Low cut quality

I have a very wobbly cut edge, which I cannot explain. I cut MDF at 3mm passes with 1000mm and the quality of the edges leaves much to be desired. The edges have a wavey pattern to them. I use the standard tool (6mm).

Anybody notice the same problem?

Hallo ich habe das auch schin gehabt abet nur auf eine Richtung aber was noch mühsamer war das es zu teils runungen mehr eckig als rund kommen :thinking:

Not recieved the machine not able to help really.

What rotation speed do you use? (should be adjustable at the spindle)
Is the edge of the cutted material burnt?
How does the milling bit look like? (Debris, colored because of heat impact, sharp cutting edges,…)
Is the milling bit deep enought pushed into the collet? (milling bits normalle do have a mark indicating how deep you should insert them into the collet)

Have you tried to reduce the speed of travel by half not sure what 1000mm means. 1000mm/min.

Just test a little bit.

Yes, 1000mm/min
No, the issue isn’t burnt or anything like that. It has a wavy pattern, almost as if there is some oscilation somewhere. Perhaps in the wires connecting to the sensors? Strangely enough it doesn’t happen for all parts either.

Used all recommended settings from the manual.

Hello, could you please send us a picture of your cut to support@springa.tech?

I had to same problem, when the machine was cutting it was running jerky. This was my first attempt. More to follow, any recommendations?

i can’t make mine operating yet so i don’t really know what are Slingshot term this look like the spindle is not spinning fast enough for the feed speed or is the final pass on climbing , also i see your entry start are probably set wrong

Recommended spindle speed per the book is 20k, but that’s not an option, you either use 18k or 23k. I believe I ran this at 23k. All the setting were pre the manual 3 mm deep cuts and 1000 feed speed. There is no setting for final pass to climbing. The Entry was the default set by inkscape.

For plywood we recommend a speed of 20.000 rpm and a feed 2 m/min so we think the value you’ve set could be too high, try to reduce them and let we know how it goes.

It is exactly like this for me yes. I had a feedrate of 1000mm/min and a 20k rpm feedrate. @Lucia do you suggest increasing the feedrate?

Hello, what kind of material are you working?

Might want to check your brushes on your spindle. I had the same issue with mine. Here is what my brush looked like when I removed it.

Hello, supplied with Goliath there are two reserve brushes and you can easily make a replacement following the instructions on the operating manual page 22. If you need more information please contact us at support@springa.tech

Hi, I just encountered the same issue as you but cutting plywood. i’ve been adjusting the settings but still random wobbly edge. I notice the entire machine would move that way. did you ever figure out what the issue was on yours?

Hello Louis, as described in the email we’ve sent, we recommend to follow instructions indicated on our guide about cutting parameters, you can find it clicking the following link:

We also kindly ask you a picture of cuts and your log and project file.

No, unfortunately I did not. Haven’t done many projects since as I was waiting for the firmware to mature bit. Will pick that up now I think.

For plywood (exterior grade) I use a small bit ( about 3 or 4 mm diameter, smaller is better), two flutes (cutting edgdes), a feed rate of max. 1200 mm/min and a router speed of about ‘2’.

The standard milling bit is quite big (6 mm) and has only a single flute which causes more vibrations. I yuo want te use that bit for plywood I would first reduce the feed rate to 300 or 450 mm/mi and increment it in small steps of 150 mm/min until you’re happy with the quality vs the total cutting time…

In general, I also add about 12,5 to 15% to the size of my milling bit so my parts are more correct in their dimensions (in case of “outline” cutting operations).

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12 to 15%… ouch. Thats a pretty bad accuracy then.

I’m kind of curious if springa is working on any solution for this. It stands to reason that if the accuracy really is 0.1mm for the positioning, this level of vibration should be detectable? If its really 0.3-0.4 mm wobble as you mentioned, it should be comfortably inside the nyquist sampling limit. Unsure how to actually deal with that, but it might be an interesting avenue to persue.

Well the 12 to 15 % is about cutting accuracy which is also related to the type of material your are cutting away and the way this is happening (feed rate, rotation speed, “depth of pass”, type of bit, etc.).

Goliath is not as rigid as a beefy portal gantry type of CNC-machine so “smoothness” of the milling proces is what you need. Producing saw dust is preferable above producing wood chips, double flute above single flute, upwards above downwards, low feed rate above high feed rate, etc.

Disclaimer: I have been measuring my parts with a measuring tape of (Euro) class II.
Normally, every CNC-machine needs some calibration. Currently, Goliath has no such procedure, so it needs to be done “on the go” by tweaking your bit diameter.