Clear Pocket Profile Pass issues- please assist

This forum is for general discussion regarding VCarve Pro
Post Reply
madaras
Posts: 23
Joined: Sun Mar 12, 2017 10:10 pm
Model of CNC Machine: shopbot standard gantry 4896

Clear Pocket Profile Pass issues- please assist

Post by madaras »

I'm having consistent issues regarding pocket toothpath. Currently I'm using a 1/2" 2 flute end mill and keep coming up with a .002" deeper cut on the profile cut last pass. When using a 1/4" end mill I get the same although about .001+ deeper. The issue is consistent across a 21" x 48" job. I resurface my work top twice now ending up with same results. Any ideas?

User avatar
FixitMike
Vectric Wizard
Posts: 2173
Joined: Sun Apr 17, 2011 5:21 am
Model of CNC Machine: Shark Pro Plus (retired)
Location: Burien, WA USA

Re: Clear Pocket Profile Pass issues- please assist

Post by FixitMike »

It sounds like machine deflection. It doesn't deflect so much on the profile pass because less material is being removed. Does the difference go away if you recut the pocket? Another possibility is wood movement after the pocket is cut before the last pass. It happens.
Good judgement comes from experience.
Experience comes from bad judgement.

madaras
Posts: 23
Joined: Sun Mar 12, 2017 10:10 pm
Model of CNC Machine: shopbot standard gantry 4896

Re: Clear Pocket Profile Pass issues- please assist

Post by madaras »

Thanks for responding. I've had the same thing happen on other projects. This time I ended up skipping 'last pass' and making a separate profile cut. Both pocket and new profile cuts were level, clean, no issue. It only happens when I use 'last pass'. I have not used 'first pass'.

User avatar
IslaWW
Vectric Wizard
Posts: 1402
Joined: Wed Nov 21, 2007 11:42 pm
Model of CNC Machine: CNC Controller Upgrades
Location: Bergland, MI, USA

Re: Clear Pocket Profile Pass issues- please assist

Post by IslaWW »

Are you using a down spiral bit?
Gary Campbell
GCnC Control
ATC & Servo Controller Controller Upgrades
GCnC411 (at) gmail.com

User avatar
martin54
Vectric Archimage
Posts: 7339
Joined: Fri Nov 09, 2012 2:12 pm
Model of CNC Machine: Gerber 48, Triac PC, Isel fixed gantry
Location: Kirkcaldy, Scotland

Re: Clear Pocket Profile Pass issues- please assist

Post by martin54 »

Is your last pass in the same direction or are you reversing the direction for the last pass ?

User avatar
WaltS
Vectric Wizard
Posts: 500
Joined: Tue Sep 13, 2016 7:44 pm
Model of CNC Machine: ShopBot 2418 - Spindle - ScottP Spoilbrd
Location: Virginia USA

Re: Clear Pocket Profile Pass issues- please assist

Post by WaltS »

I had this same thing happen recently on two plaques I made. Last pass profile cut of pocket was deeper than pocket. I recut the pockets and the same thing happened. Used a 1/4" downcut endmill. Never had that happen before. Still scratching head.

LittleGreyMan
Vectric Wizard
Posts: 1012
Joined: Fri May 15, 2015 1:10 pm
Model of CNC Machine: 3 axis small size machine
Location: France

Re: Clear Pocket Profile Pass issues- please assist

Post by LittleGreyMan »

Have a look at the G-code. Even if you're not G-code fluent, it's pretty easy to check if the depth of the pocket is the same as the depth of last pass profile.

I am pretty sure they are the same as Vectric programs are very reliable, but you may have encountered a specific case, who knows.

If they are the same the issue comes from the machine controller of from a physical problem on the machine.

I'd bet it's the second case. So forget the software and think of the physical causes like the ones Mike, Gary and Martin mentioned. You may also have a loose collet or lose steps on the Z axis.

Change parameters, perform some tests to identify the culprit. The first thing to do is checking Z0 before and after the cut. If it has changed, your bit has slipped in the collet, you've lost Z steps or your material moved (depending on your Z0 reference: machine bed or material top).
Best regards

Didier

W7 - Aspire 8.517

Post Reply