Loosing my Z while cutting

[les_linton]

Having a bit of a problem loosing my Z while cutting 3D files.

I'm using the free Vector Art 3D Machinist software and some of the files that you can purchase there. I have been on the phone and emailing with James Booth (Carve3D)and we think we have eliminated the software as the problem.

My roughing cut appears to be ok, but when I start to do my finishing cut it appears to start ok, but within about an inch or so it starts to loose the Z position and is eventially not cutting any material.

1/4" end mill, for roughing cut. 1/16" ball nose for finishing. Zero tool with plate and then brought tool down on a piece of paper to be sure of zero position before starting. Shut off machine when I was no longer cutting material and moved to exact "surface" location for original zero and did move Z "0". Used numbered drill bits to find offset. 0.118 above the surface of the material.

Will be on the phone with ShopBot in the AM, but was looking for any thoughts that you might have.

PRT 96
3.4.1 Software
Colombo 5hp spindel
Precise bits 1/16" ball nose with stop collar (checked against new for distance out of collet)

Thanks,

Les

[richards]

Les,

I'm not exactly sure of the process you're following to zero the 1/16-inch cutter. It seems that you're using a Z-Zero plate to set the height of the 1/4-inch cutter and that you verify the position by touching a piece of paper when at 0.0 height. Then, when you inserted the 1/16-inch cutter, you set the height to 0.0 and then raised the cutter to a height of 0.118 off of the surface of the material.

It seems that you need to establish a common z-reference point for both cutters. If the 1/4-inch cutter cuts away the original reference point, the 1/16-inch cutter would have no vertical reference point. But, you could use a removeable block for both cutters as long as the removeable block could be positioned in exactly the same place when each cutter was zeroed. Another method would be to reference off the spoil board, raise the height to the original thickness of the material and then do a ZZ. That would work with both cutters.

[les_linton]

Mike,

I'm using the Z-Zero plate at a location on the part that is not being cut for both tools. The problem is that while running the part file it is somehow loosing the position of the Z-0.

The .118 is how far off the substrate that the tool ends up when I check it after running the file. I do a mz,0 at the location that I originally had zeroed the cutter and it is that far off the workpiece.

I just downloaded the latest software and am currently running another test. Hoping that this resolves the issue.

Les

[les_linton]

Never Mind.....

Software update resolved the problem.... not to mention smoothed out the whole process.

Les

[Ryan Patterson]

Les,
Do you have a PRT or an Alpha. What speed are you using for the Z? Is the bit slipping? Have you tried it by cutting air? I have not had this problem with the Alpha but have had this happen with the PRT. I corrected it by using a lower speed for the Z. Adjusting the ramping could also help.

[Brady Watson]

3.4.1 Software

Download the latest software 3.4.23 (http://www.shopbottools.com/files/Setup_sb3_4_23_PRT.exe) and try it again. This will narrow your troubleshooting a bit.

-Brady

[robtown]

Overall, while 3d carving on the PRT with your feed speed set too high for x,y will cause this as well, as Z tries to keep up the x and y moves it loses steps.

[jsfrost]

Sounds like part of a problem I am trying to resolve. I had thought the bit was slipping. Good looking relief, but a gradual slope in Z. About .020 rise over the long side of a 4 x 5 oval with long side in Y. 3.4.23 is in my pocket, maybe it's time to put it in the machine.

Rob, how fast is too fast? I am presemtly cutting a 1/4 deep relief with 1/8 ball. I start cutting slow, then kick XY to 3 IPS, Z to 1 IPS after a few raster cuts.

[robtown]

Jim,
I lost z steps going 2 ips the z speed doesn't really matter, z can't go fast enough to keep up resulting in lost steps. I'm using a PRT by the way...

[paco]

Any of you (who have Z problem) are holding your part with vacuum? I recently founded that my MDF spoilboard is "swelling" when I use the vacuum through it. It's moving up to 0.025" (over the time of 3-4 hours) then going back down to where it was (or so) the next day morning!

[les_linton]

I'm not sure that anyone caught this, but the software update took care of the problem and smoothed out the motion on the machine.

So, per Brady's post... install the new software.

Thanks everyone,

By the way, for those that are like me and not up to speed on 3D, the 3D Machinist is pretty cool. Ya, you've got to buy the files, but there are a couple of free ones so James can set the hook.

Les