CNC circular picture frame - questions

[JoSchmaltz]

I am planning to make circular shadow box picture frames for my laser cut maps, somewhat similar (but better) than the ones I jigsawed and routed:

so I decided to look into CNC’ing these out of 20mm MDF. I designed this in Vcarve 12:

I realize I will have to adjust the bits used in the toolpaths to what we have or what I get, (I know we have a 6mm 4 flute, end mill, lets assume we have the 2nd one I used in the design, a 1.5mm end mill). I have also learned the hard way to screw the piece to a sacrificial board with the screws clear from any toolpaths and use tabs to keep the whole things stable while . I am currently not fussed about processing time, so I am going slow with 2mm deep passes

But have a few questions:

I have used a “profile toolpath” for the inner and outer profile cut:

• is the a CNC the right tool for a 20mm mdf ? or rather a router with a circular jig?
• I dont seem to be able to set the pass depth if I use a profile toolpath as opposed to a pocket toolpath?
• what is a safe total depth for lest say a 1.5mm endmill?

The design is for the mini CNC with a job size of 170x170 to test. is there any design changes needed for the big CNC?

Lastly: I want to be able to scale the design so that the outer diameter of the frame changes - while other dimensions should keep the offset from the outer diameter fixed. A simple scale will scale everything - can anyone point me to how to achieve scalability of a design with certain fixed offsets (I found this video, but I dont think it works for circles?)

Any other suggestions welcome - and thanks for all the advice yesterday specifically from @dannz and @fin_wells (and for the consolation)

[scday94 (Sam Day)]

Ive had some really good results with one of the moulding tools in Vcarve. rather than the discrete profiles paths, you add a cross section drawing for it to cut, should work nicely for MDF I would imagine. This might be the tool you are already using.

Pub style sign

One of the first actual projects I’ve managed to finish while at the space. This was a pub style sign of an inside joke that I with a colleague at work for a retirement present. The start of the process was doing some test cuts with @Archie on the Big CNC to work out the best way to cut the custom mouldings. We weren’t initially sure which contour we would use for the moulding so we were testing curved and square corners. [058CD3D2-EC4D-4EFC-90C7-0CE85E007ACA] [D3C93484-6890-42B7-847D-4664D…

[dannz (Dan Law)]

is the a CNC the right tool for a 20mm mdf ? or rather a router with a circular jig?

Both could do the job, depending on what you want to do. With the router, the profile will be according to what bits are available, with the CNC, you have more flexibility and, as Sam said, can define a profile.

what is a safe total depth for lest say a 1.5mm endmill?

Standard 1.5mm endmills have flute length of 4.5mm, which is then the absolute limit. You might find ones with longer flutes. They may be prone to breaking though. For 20mm depth, you probably need 4mm diameter or greater.

Why do you want to use such a small diameter endmill? Your design doesn’t seem to need it (?) Use e.g. the 8mm on the big cnc and no need for a tool change.

is there any design changes needed for the big CNC?

No, but bear in mind that the big cnc has different endmills.

I want to be able to scale the design so that the outer diameter of the frame changes - while other dimensions should keep the offset from the outer diameter fixed. A simple scale will scale everything - can anyone point me to how to achieve scalability of a design with certain fixed offsets

Use the circle tool in vCarve to alter that vector. Just adjust the diameter of the circle rather than using scaling. That will retain the centre point.

[JoSchmaltz]

Yeah, this is what I am after:

I was thinking about getting this bit: https://www.amazon.co.uk/gp/product/B0BJ8PBYL7/ref=ox_sc_act_title_1?smid=AIF4G7PLKBOZY&th=1
- do you think this will work on the machine )and how do I add it to the tool library?)
see more detail here: CNC circular picture frame - questions

[dannz (Dan Law)]

Why do you want to use such a small diameter endmill?

?

[JoSchmaltz]

Ok, understood. My thinking was why use a 6mm bit if I only need the cut, but understand this gives more stability for the cutting set up. Thanks!