First try at 3D cuts

[Gilrock]

I'm brand new to using a CNC router. I bought and assembled the 4'x4' CNC Pro machine from cncrouterparts and I bought the prewired Nema 34 electronics. I'm using configuration files for Mach 3 that were provided by the company. I initially had an issue with the Z travel being 2.4:1 but that turned out to be their config file wasn't updated for the ball screw version of the Z axis. So they gave me the new value and I verified it with a dial gauge. I've had no problem doing 2D cuts. I've cutout several gear parts for a wooden clock I've been wanting to make. But I tried starting on the Gingerbread house project from vectric's free project area and the detail doesn't look right on the first pieceI tried to cut. I'm using Aspire to create the toolpaths. If I had to describe the result I'd say it looks like what you'd see if you did a gaussian blur over the image.

Most of the details don't look like they have the depth I see in the photos of the example project. It looks like edges get rounded over like the y axis starts moving before the z axis completes the move. The electronics I bought have a smooth stepper board pre-installed by the way. I'm mainly talking about the finishing pass also. I did the roughing pass with a 1/4" down-cut EM bit and the finishing pass is a 1/8" round-nose bit. I had already slowed down the toolpath from the example file because they had it originally at like 3"/sec which seemed really fast. I think I cut that in half. After not liking that result I tried doing another one slowing it down even more but I had a different failure very early in the cut where the Z axis looked like it didn't retract all the way and started cutting deeper than it should. But that didn't happen the first time since the baseline depth appeared good across the part.

I didn't build the Z axis section because it came preassembled. I just don't have enough experience to know what to look for. Is there a setting somewhere that is causing it to average between points? Because as it's moving across doing the raster cut I don't really see the Y axis slow down when it gets to the spots where it needs to move Z up and down?

By the way why is it so horrible to try to type in this window once you get this much text. It keeps flashing up to a higher point where you can't see what you're typing.

Thanks for any help,
Gil

[Gilrock]

I'm surprised no one knew this. I emailed cncrouterparts and got a reply in one minute that pointed me to the answer. Since it wasn't a Vectric related issue this probably wasn't the best place to go for help. I've been looking for a more general cnc woodworking forum.

[ChrisInEstes]

Hi Gil,

I'm glad you got your problem worked out.

I do have a tip for you when you have more text than the forum handles well... I open up my email program or MS Word and type my text, then copy & paste it into the forum body window.

Chris

[Rcnewcomb]

I've been looking for a more general cnc woodworking forum.

A great resource for general CNC information is cnczone.com

Some good wood working forums are:
SawmillCreek.org
LumberJocks.com

[ssflyer]

Out of curiosity, what was the solution?

[Gilrock]

Sorry I didn't reply sooner. I thought I would get an email if there were replies. Guess I'll check the settings to see if there's a way to be auto-subscribed to threads you create.

Anyways I did discover the cnczone forum and was working through the problem there. The original suggestion I got from the manufacturer turned out to not be the real issue. We thought it was a constant velocity issue causing the rounded corners. It took me 3 days of troubleshooting and I finally found the problem. I had previously verified my Z axis was repeatable using a dial gauge but all my test moves had been 1" moves in the down direction. I hooked it up again and discovered small moves against gravity were not working. It was looking like a backlash problem in the Z axis. After I told cncrouterparts what I had found they recommended I remove the thin metal dust cover from the back of the z axis ballscrew assembly and although I was skeptical it turned out that fixed the problem. The attached images show what my first two attempts look like that had the issues and the second image shows the detail I was getting after removing the dust plate. Notice in the first image how the area near the window and the curls down the sides. Once I figured out what was causing the problem it explained a whole bunch of problems I had run into.

Thanks,
Gil