[Dave18]

Hi
I have a routout cnc Z90 that I got second hand and yous Vcarve pro with Mach 3 mainly to make Plaques and various shapes from MDF. Quite new to this and don't know if I am doing something wrong. I amusing 9mm mdf and use small 3d tabs to hold the shapes in place but when i remove the parts they have gouge marks / indents where the tabs were so have to sand realy hard to remove these resulting in slightly misshapen parts. Is there anyway of getting better edge finishes? I use a 3mm spiral upcut bit.
Thanks Dave

[Wackamazoo]

I have a simmilar problem. For me I think its becuase the gantry is not as stiff as it should be and the bit wobbles a little. The gouging is only a couble of thouthands but definitly noticable. I have taken some steps to stiffen my gantry and the gouging is reduced. I will need to redesign my gantry supports to make it stiffer.

W.

[4nelsons]

I have the axyz 4010 and my tabs come out awesome on 9mm mdf.

[dias11]

Hi,
I am having the same problem with gouges when i use tabs at Vectric Aspire. I wonder if the problem is at Vetrics post processor or at my machine gantry.
I read that you had that issue long time ago.
Did you solve the problem ? Do you have any suggestion ?

My machine is High z 720 with Winpc Nc usb.

best regards

[gfacer]

The tabs, 3d or regular, linearize any curves they might be placed on, and this can cause gouges if the linear moves don't match the curves well. I get the limitations for 3d tabs, but its a bug they should correct for regular tabs....but no I have not filed any type of bug report, just an observation I've had. Check the g-code and I think you'll see just this.

[islaww]

Dave...
Divots in the part next to tabs is a deflection issue. Either the bit or the machine. Bits will always generate more chatter when a vertical move is introduced. Feeding your 3mm bit beyond its (or the machines) capability is one cause of the problem. Machine components that cannot control the force generated by the bit is the other.

I would run the same toolpath in the same material with a 6mm or larger bit. You didn't post yours, but this assumes that your feed/speed is appropriate. If the divots disappear, the bit was deflecting, if not it was the machine. Cut feedrate in half and repeat.

[dias11]

Thank's for your reply.

My apologies, i should have post photos and informations for my problem. I will post next days (maybe tomorrow) after doing some tests.
I am working with MDF and wood and today was the first time working with aluminium. I have also the divots problem with 2d tabs at wood , so i have always to sand.

Todays milling at aluminium was with
6 mm two flute spiral HSS bit (cheap ebay bits) at
6 mm/sec feed rate
at about 15000 rpm
1 mm depth step
material 6061

i have only some months expirience with cnc machining. I have spend a huge amound of time, reading and searching. I understant the theory but i havent try or solve everything yet.

Best regards
Chris

[4nelsons]

I do aluminum all the time. I cut lots of .080 aluminum. I use a single flute up cut end mill at 20000rpm @60ipm with my 5 hp. 2 passes. First pass .060 depth to leave a thin onion skin for my vacuum table to hold material as I cut multiple signs out of 4x10' sheets. Last pass about 100ipm at .020 and my parts don't move and no tabs required.

Sent from my SM-N900W8 using Tapatalk

[4nelsons]

Sorry that was with a 6mm bit. Lately I just leave an onion skin for final pass and it seems to work better than tabs.

Sent from my SM-N900W8 using Tapatalk

[dias11]

Hi, i am back again with some results.

Attachment 293408


At the attached photo you can see various cuts of circles (50 mm dia). Using the 3d tabs i have only one defection located left and right of the tab which is also the starting point of the process.
No matter the size of the tabs the defections exists.
It comes to single line when i use lead in - lead out method, this is logical.

The results are fine when i use smooth ramp or circular lead method.

So the problem was solved but i still dont understand why everytime the bit moves down to z-axis collides with the object.

some thoughts:
For sure there is not problem of table's vibration because the movement at z axis has no resistance at this point. But i also hear squeak while bit going down.
For sure my router does not spining conical because the diameter of the circles are constant when measuring them.
The post processor seems to be fine.

May be, there is vibrations of the material when the bit spindles with 17000 RPM inside it ? Its that possible ?

Do you have this issue when you cut with your machines ?


Regards
Chris

[RTP_Burnsville]

I also get a small gouge almost always when the tabs are used. My router is a Camaster stinger so machine or work piece flexing is not the problem. I am still using an older version (6.5) so the issue may have been solved in a later version.

Robert

[ger21]

It's not a software issue. It's a tool deflection issue.

[FastFarmer]

It's not a software issue. It's a tool deflection issue.

For sure; especially with a 6mm and the amount of stick out you have to cut your tests.

You can calculate deflection and it should be taken into consideration when planning your tool paths and speeds.

[jmpluk]

If it can help someone
When I have to cut letters or small pieces, I use a base board and this put the material to be cut, to prevent small parts move and deform I use adhesive double-sided tape between the base and the workpiece , make the cut in two passes leaving for the last one millimeter, so that the thrust of the drill does not move the piece and the tape has sufficient strength to prevent movement of the piece when making the final cut, thus cutting him perfect.
;-)

[Jon.N.CNC]

Hi, i am back again with some results.

Attachment 293408


At the attached photo you can see various cuts of circles (50 mm dia). Using the 3d tabs i have only one defection located left and right of the tab which is also the starting point of the process.
No matter the size of the tabs the defections exists.
It comes to single line when i use lead in - lead out method, this is logical.

The results are fine when i use smooth ramp or circular lead method.

So the problem was solved but i still dont understand why everytime the bit moves down to z-axis collides with the object.

some thoughts:
For sure there is not problem of table's vibration because the movement at z axis has no resistance at this point. But i also hear squeak while bit going down.
For sure my router does not spining conical because the diameter of the circles are constant when measuring them.
The post processor seems to be fine.

May be, there is vibrations of the material when the bit spindles with 17000 RPM inside it ? Its that possible ?

Do you have this issue when you cut with your machines ?


Regards
Chris

1800mm/min @ 17000rpm is slow @ very high rpm. That bit will be hungry which won't help deflection.

30mm/sec is more like 6-8000rpm