Newbie looking at 6040 (China CNC) for polypropylene 15mm sheet

[Snapper]

So I just used the probe and by hand found the center of one of the button holes in my case.
Was then able to chamfer the edges.
Not bad, not great. Was a hair out on the Y. X was perfect.

I just added 0.025mm to the Y and it is near perfect.
So Zeeflyboy your method works... :p

The real test would be machining around my part top and bottom now with out much, if any step in the surface finish once flipped and had the same operation done.

I guess the best way to do the flip is to leave 0.0something on the bottom of my stock and then flip, then remove that last 0.0something and chamfer...?

How deep is your case to cut in one pass? I don't think you will ever get this machine to flip a part and cut from both sides without leaving a step, but you should be able to make it small enough to sand and polish out.

Just to give an idea of the machines repeatability I zeroed in on the reamed hole mentioned above, moved my coordinate system over to the vice, milled out a part that was ~1hr machining time, came back to the reamed hole and it was 0.045mm out in Y and 0.02mm out in X.

You should be able to get the results you're after without probing everything. If this is something you're going to be making multiples of it would be well worth your time in making a proper jig.

[JOGARA]

How deep is your case to cut in one pass? I don't think you will ever get this machine to flip a part and cut from both sides without leaving a step, but you should be able to make it small enough to sand and polish out.

Just to give an idea of the machines repeatability I zeroed in on the reamed hole mentioned above, moved my coordinate system over to the vice, milled out a part that was ~1hr machining time, came back to the reamed hole and it was 0.045mm out in Y and 0.02mm out in X.

You should be able to get the results you're after without probing everything. If this is something you're going to be making multiples of it would be well worth your time in making a proper jig.

I have worked out that I don't need to do the flip on the outside.
I will just use the super glue method to stick my stock onto some sacrificial that I can reuse.
Adds a bit of work removing the glue but it has worked since day 1.

Flipping the part and milling the rest would have meant not spending time on that but it works, don't fix it.


At the moment I can make 2 cases at once. I'd rather not go beyond that as it is more setup and I just need to start making these things now.
Can't spend any more time trying to make it better for batch production...

I have got it to around 3 hours total per pair of cases (not including the rear of the case, though a pair of those are 30 mins.
I can probably get it down 10 mins just with less cautious lead in and lead out distances.
Most of the time is spent with my 6mm roughing bit. That takes out 95% of the material and totals nearly 2 hours of 3.
I have found that I can cut 2mm depth quite well at 75% of the feed it is currently doing (currently 1mm DOC) with my 6mm rougher, so putting adjusting that will result in less time too. Not much but another 10 mins off.

In total I a have 100 of 2 different case designs to make. At this rate I can make around 6 every day.
But for vast majority of that time I will be working on other things (tumblring, PCBs, Anodising, Finishing etc) while keeping an ear on it so it is not that bad.

[Snapper]

Just looked back through the thread for pics. I have a suggestion.

First, it looks like your buying custom cut plates? If so, order them cut to size, they always come cut slightly oversize, so rather than milling all that away from the edges, you would just be trimming a mm or so off each side saving you in both material costs and machining time.

Second, you could make a fixture plate for accurate location after flipping. Carry on machining out the guts inside on your vice, in the pic below the three holes circled you could drill out .1mm undersize, hand ream them to size, then use dowel pins in these holes to locate into the fixture plate. These dowels will also pretty much hold the part in X and Y, with a bolt through one of the big square holes and a large washer just to keep everything dead still. Then you can profile round the edge and chamfer or radius your top edges. When it comes to do the square hole which you have a bolt through, just have a pause in your toolpath and move the bolt over to a different hole. This would then also give you the ability to pull a case off and put a new one on without having to rezero, you could also run a toolpath on all your cases in a row, saving you the need to keep changing tools. If you have more than a couple of these cases to make, it would be well worth the price of a 10mm slab of ali and the hour or so it takes to draw up, machine and fix in place. And also far preferable to dealing with super glue.

(Ok it won't let me upload a pic for some reason, but there's only three holes I can see so you should get the idea)