Depth Problem on Machine

Discussion about the CNC Shark Pro Plus HD

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BayouWolf
Posts: 8
Joined: Wed Aug 20, 2014 5:14 pm

Depth Problem on Machine

Post by BayouWolf »

I'm trying to do some engraving on some 3/4" pine with a 3/8" 90 degree V bit, but it's not running at the right depth. I noticed that the table has a slight bow across the X-axis, so I attached a piece of MDF and flattened it in hopes of compensating for the bow. When I re-ran the piece, it seemed to be running fine. But, part of the way into it, it started cutting deeper by about 1/16". The G-code seems to be fine, and the bit is secure in the collet. I'm currently at a loss for what else to try. Any help is really appreciated.

Also, if it helps, I'm using the touch plate to set Z0.

basecircle
Posts: 488
Joined: Fri Apr 08, 2011 2:14 pm

Re: Depth Problem on Machine

Post by basecircle »

Hi Bay Let me throw this at ya.You already did the resurface of the spoil board. That is good.And you are using a touch probe (Do ya have virtual Zero?) that works great on warped boards.Take a look at your pine lay it on a flat surface feel for the rock flip the board do the same (Do ya got bow?) if so Plane it or sand it flat.If ya have it flat you will get a better engraving.Also how deep are you engraving?Hope some of this helps.It is basic and you probably know most of them if not give em a try.Also I sometimes use a oversize board and screw it down in 6 plcs. Good luck Let me know if any thing helped Basecircle

tonydude
Posts: 1581
Joined: Tue Aug 17, 2010 9:23 am
Location: Buffalo,NY

Re: Depth Problem on Machine

Post by tonydude »

Is the router slipping in the clamp? Try putting sanpaper around router and put the router back in. Sometimes the router slips.

Tony
Buffalo,NY

"What will matter is not what you bought but what you built; not what you got, but what you gave”

Aspire 11.015, photo vcarve, cnc mako shark extended bed with the new upgraded HD 5 gantry with Led pendent.

rungemach
Posts: 460
Joined: Mon Aug 02, 2010 8:24 am
Location: Sarasota, Florida

Re: Depth Problem on Machine

Post by rungemach »

You may want to check to see that the machine returns to the original z zero point when the part is finished.

If the machine is now lower than the original z zero, you may have lost steps. The "usual suspects" for lost steps are running too fast, or binding in the affected axis. For an increase of depth in z, you can do an air cut to test whether you are losing steps, as the up move of z works against gravity and the inertia of the z axis to get it moving in the up direction. Any binding or trying to retract too fast can cause lost steps. This will show up as a change in the original z zero point at the end of the job.
Lost steps is when the machine can not keep up with what the controller asks it to do, and some steps are lost. The controller has no feedback to tell it this has happened and assumes the machine is following perfectly.

for ultra critical fine lines with a v bit, you may also want to plane the top surface of the work using the shark. That will assure that the work surface is coplanar with the router travel at all points.

Hope this helps

Bob

BayouWolf
Posts: 8
Joined: Wed Aug 20, 2014 5:14 pm

Re: Depth Problem on Machine

Post by BayouWolf »

I can't run Virtual Zero since I'm still running 1.5, but the upgrade to 2.0 does sound enticing (The Haas machine I was trained on a few years back makes me miss some of its features). There is a slight bow in the wood, but it's so minimal that you'd need a feeler gauge to measure it. I also have considered using a larger board and screws instead of clamps.

The router is very secure in the clamp. I made sure there was no wiggle room when I tightened the clamp.

I'll reload the file and try an air cut to see if anything happens. I doubt it's moving too fast, as it's running at 25ipm.

Also, I just tried running another simple program with cross hatches at 1/16 deep. It started off fine, but then the cuts started getting shallower until the bit was running above the surface. I'm starting to wonder if the control box might be the problem (it often takes me several attempts to get the control box to communicate with the computer).

basecircle
Posts: 488
Joined: Fri Apr 08, 2011 2:14 pm

Re: Depth Problem on Machine

Post by basecircle »

Hi Bay You say your running a .375 dia v-bit.Is it a full 3/8 dia or a 1/4 shank? Basecircle

BayouWolf
Posts: 8
Joined: Wed Aug 20, 2014 5:14 pm

Re: Depth Problem on Machine

Post by BayouWolf »

The V bit is 1/4" shank. It's the same Amana V bit that came with the machine.

jeb2cav
Site Admin
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Joined: Thu Sep 30, 2010 7:04 pm
Location: Kentucky
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Re: Depth Problem on Machine

Post by jeb2cav »

This feels like it is mechanical. I would go ahead and loosen and reset the set screws on the z axis lead screw/motor axis collar. A while ago one of these was just loose enough and resulted in the behavior you are describing. Be sure that the set screws are positioned against the flat parts before tightening.

Not ruling out control box entirely, but if you haven't done this, try it and check after.

BayouWolf
Posts: 8
Joined: Wed Aug 20, 2014 5:14 pm

Re: Depth Problem on Machine

Post by BayouWolf »

Okay, I just checked the set screws on the Z-axis. Even though they were already snug, I loosened and re-tightened them. I ran another test piece, and it's still acting the same way. Any other suggestions on how to fix this? Also, the reason why I'm suspecting the control box is because I've worked on a lot of computers over the years, and I know how easily wires and circuits can be damaged.

jeb2cav
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Re: Depth Problem on Machine

Post by jeb2cav »

Have you checked to see if the tool is at the same height at the end of the job for z0? I'm curious to know if the tool is now 1/16" lower than it was when you set z0 prior to the start of the job. After the job, jog the gantry to the place where you're seeing an increase in depth of cut and see if z0 position is reasonable at that location.

If you reposition this whole job in a different area of your table, do you get the same outcome?

The lead screw nut is perhaps the last mechanical thing to check on this - lead screw lubricated, etc.

A control box oriented test you can perform is to swap out cables and perform and air cut. Put the z cable on the x output and vice versa. You may want to either create a simple job or use the 1in square file (although that may not be enough movement to duplicate this) and see if after the swap, you can duplicate the error in output from the control box on that channel.

If you can duplicate an error in movement with the cable swap - your only option is to contact NWA and send it in for repair.

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