Saxophone - Sixth Project, You Be the Judge

In our previous project-posts to this forum we’ve pointed out the mistakes we made, this time we want you to do that. Tell us what we did wrong, or what we could have done better. We’ve got thick-skin, be critical we’re trying to get better and we need guidance.

We have taken what we have learned in our previous projects and are attempting to make something nice for Granddad, who retired a few years ago and is enjoying his retirement playing saxophone in a local Big-Band named “Talk of the Town”.

This project is similar to our third project, but we are hoping the knowledge we have gained since then will lead to even better results.

Using Photoshop I put together a PNG image that was 2175x2175 at 300dpi (7.25” by 7.25”).

The stock material is .75” thick pine, cut to 7.25” by 7.25” and then stained. It was mounted to the wasteboard using three strips of 10lb 3M/Scotch outdoor tape.

We used MeshCAM’s ability to import the PNG image and interpret colors as cutting depths.

The frustrating step (took us several attempts) was selecting the Region to Machine. Really wish there was a zoom or even better a “Select Entire Region” option. But we’ve learned this step is necessary and we need to manually select the entire area. If the pink line/box goes outside of the yellow area MeshCam will attempt to cut something that isn’t there, and if the pink/line box is too small it leaves a ridge of unmachined material around the outside of the stock material. Notice the pink line placed around the outside of the yellow area, that is harder to do than it should be.

We’re getting more familiar with the various Toolpath Parameters, but our knowledge is rooted in reading the MeshCAM help file and basic trial and error. We decided to use EndMill 102 for the roughing pass and EndMill 112 for the finishing pass. Using EndMill’s allows us to rely on the “Don’t Machine Top of Stock” feature. Not sure what our reasoning was, but we selected the BallMill 111 for the Pencil Cleanup. I’m still on the fence regarding the Pencil Cleanup, on a few projects it seemed to do more damage than good.

After saving the toolpath we then loaded the file into Carbide Motion and zeroed to the lower left corner. We could slide a sheet of paper between the bit and the top of the stock, but could feel the paper dragging against the bit.

Here is what it looked like after the Rough Pass (using EndMill 102).

Here is what it looked like after the finishing Pass (using EndMill 112).

Here is what it looked like after the Pencil Cleanup (using BallMill 111).

It’s not what I was hoping for, I’m second-guessing the background music staff and notes. It would probably look better without them, but focusing on what was already done we determined the top of the stock/wood was not perfectly flat and that is why part of the design was missing, but we think we can fix that problem. I went back to the original Photoshop file, and made a new image with just the background notes, this time with a little darker color.

Loaded the SaxophoneFix.png into MeshCAM and made

Then in Carbide Motion I loaded the new project, used the same X and Y starting values, but lowered the Z .03mm. Which produced this result.

So it got better, but clearly this (Photoshop) design is flawed and we need to start over. We’re going to remove the background-notes, and make his name a little bigger but not cut as deep. But what we are looking for from this forum are discussions about our actual CNC process.

So now it’s time for you to be critical and critique our process. What would you have done differently? What settings do you disagree with? Did we pick the right bits? Etc.

We are going to make another attempt next weekend, hopefully with some new advice to try out.

I’m thinking for your text a V-engraving bit would be a good choice if you can get one this week—you can get by with a ball-end mill, but cutting a V-groove by setting up your design so that the cutter is only going to make one or two passes tops through a very narrow channel of pencil-milling would look very sharp. I can see if I can come up with some demo text to show you what I mean when I have a chance on Thursday or Friday.

I’d be curious to see how your resulting piece looks with a bit of sanding and the stain applied after you’ve done the mill work :wink:

Are you talking about something like this Dremel Bit

I bought this from lowes, but now the big question… what settings do I use when defining the bit in MeshCAM?
Here’s my best-guess…

Those will do for engraving bits—but what I’d really recommend is something like this:

As for how to enter it into MeshCAM, I"ll need to think & work on that a bit to offer any kind of best-practice. Ultimately you may need to change your image you’re using as well to accommodate the draft-angle of the cutter. You’re likely going to have to “lie” to the CAM a bit about the setup in order to get it to produce the paths you actually want.

I’ll try to give you a work case when I have a chance over the next day or two.

You have it almost right, ColdCoffee. The tapered tool is defined in MeshCAM with the tip diameter and taper per side. The tip diameter will usually be a guess, but “pointed” tools rarely have a tip diameter smaller than .13mm / .005"


When I look at the categories list it shows that the last post to this thread is two hours old. When I click on the category to see the posts the last one listed is by ColdCoffee and it shows it posted 1 day ago. If I scroll to the bottom, no other posts, if I use the page button in the bottom right corner to go to the bottom, same result.
If I hit the refresh in the URL box I briefly see another post below the day old one from ColdCoffee and then it goes away. I have seen this symptom of missing recent posts before and after a day then they show up. I am on an iMac with the latest updates to OS X and am browsing with Safari. Does anyone else see that very recent posts are ‘missing’ for a few hours before they can be read?

Update: Made another pass and I am very pleased with the results.

Now I want to learn how to CNC a brass part to fit inside the saxophone cutout.

But I’ve got to learn how to do that and currently I am having problems. I’ve attempted cutting aluminum, and while I was somewhat successful the part was unusable. My last attempt was with Lexan, but the results were the same (just got them much faster). Not sure if I am doing something wrong or if I am encountering a bug.

Update: The brass was probably going to look awesome, but after a few attempts with aluminum we decided I don’t have enough experience to get this right on the first attempt. So we made a lexan saxophone insert instead.

And on our 2nd attempt we got it right, and the part fit so well it just snapped into place.