proxxon KT70 CNC ?

[john constableParticipant @johnconstable10725]

Thanks guys I’ll check those out. I was worried about spindle with the proxy on but actually it goes up to 20000 rpm which is around router speeds. I’ve seen several 4th axis projects for this using a rotary tabLe but I must admit preinstalled software including the 4th axis would be one less hurdle.

[john constableParticipant @johnconstable10725]

Wow. Arc kx1 is about 4.5k without software! That wont be happening be happening any time soon!

[john constableParticipant @johnconstable10725]

OK, so I was getting comfortable with the proxxon mf70 cnc machine and adding my own controller and 4th axis. I just checked the spec and the millable area is only 7x13cm which is just a little bit too small for me. A lot of money for quite a small capacity. I'd really like a minimum of 10X20.

So, your suggestion to get a chinese overhead router is now under serious consideration….

There are loads of 3040 tables. Very few have reviews and the prices vary wildly and start around 300 quid (no good surely?) and some for several K which look very similar. There are also gantry type and pillar-drill type (some of the latter have a 4th axis).

So, please could I have your thoughts on gantry vs pillar type and can anyone recommend one or point me somewhere I can get reliable reviews?

Then there's still the self-build option, daunting as it is.

cheers guys.

[john constableParticipant @johnconstable10725]

maybe the x limit is the size of the table so I could widen it? presumably y limit is related to throat depth and harder to increase.

[JasonBModerator @jasonb]

Travel is 150×70 so extending the table won't help you. spec here

Also bear in mind that you will loose somewhere in the region of 250mm or more by the time you have mounted a rotary table at one end and the tailstock to support the work at the other so you need a table of 500mm or more to machine your 10" bits of wood

[John HaineParticipant @johnhaine32865]

John, all I can suggest is that you do a lot of reading! You might start here and here. First thread has some links to machine suppliers, and also mentions a self-build design that was published in MEW that you might use as a starting point.

Then there are the CNC forums that I mentioned above – they are full of posts on the Chinese routers.

A "pillar" type machine is really a vertical mill. They tend to have limited working envelope unless the machines are very big when they get expensive and heavy. If you want to machine tough metals like steel they are the way to go. But to get a bigger working envelope with a cheaper/lighter machine the gantry router works better but is much less rigid.

Loads of people build them and there are lots of components and materials available to make it easier such as linear bearings, rails, leadscrews, steppers and so on. A good supplier is Zapp Automation. Google "build your own cnc router".

[john constableParticipant @johnconstable10725]

Thanks john. Mills now moved to bottom of list due to range vs cost. I joined a cnc forum which is scarily massive but as you say lots of specialist advice and experienced. Window shopped for self build components and their are loads and they’re fairly cheap so looking at that today. Cheers.

[Another JohnSParticipant @anotherjohns]

Posted by john constable on 25/06/2018 10:01:42:
Wow. Arc kx1 is about 4.5k without software! That wont be happening be happening any time soon!

I have a KX1, which I got without controller, and added my own.

I run LinuxCNC on it, which is free and rock solid.

For engraving, LinuxCNC will read in a bitmap file (jpg, etc) and engrave.

I do use "CAMBAM" for CAM, but others use Fusion 360 for CAD and CAM, which is free. I did use the free DXF2GCODE for a while, but went for CAMBAM.

I use a little Sherline CNC rotary table which was not free, but does work well.

All in all, a great little machine. It just runs all day, doing what I ask of it.

John.

[john constableParticipant @johnconstable10725]

Thanks, John. 4.5K for KX1 is waaaaaaaaaaaaay outside my budget. I found the sherline rotary table plus stepper but thats over 400 quid too.

[John HaineParticipant @johnhaine32865]

Is this link Of any interest?

[john constableParticipant @johnconstable10725]

I like it. Sound-looking machin and we’ll presented kit. I’d have to uprate the spindle as I think 60000 is too low?
The major problem is capacity which wouldn’t get close to my 8″ spindle objective especially after adding a 4th axis.
I found another but can’t post the link at the moment.

[john constableParticipant @johnconstable10725]

here it is.A bit more money but larger and c/w 4th axis:

[JasonBModerator @jasonb]

John, out of interest what are your CAD skills like? You would need to be able to draw out these spiral shapes as a little spindle like that could only use small diameter cutters so your profile would need to be cut in many passes unlike using a large barley twist type cutter that could be moved in a simple spiral by simple Gcode.

[john constableParticipant @johnconstable10725]

sorry – that's complete with, not clockwise!

[john constableParticipant @johnconstable10725]

Posted by JasonB on 27/06/2018 12:21:57:

John, out of interest what are your CAD skills like? You would need to be able to draw out these spiral shapes as a little spindle like that could only use small diameter cutters so your profile would need to be cut in many passes unlike using a large barley twist type cutter that could be moved in a simple spiral by simple Gcode.

Hi Jason. CAD skills not too bad. Use Visio for 2D and sketchup for 3D and at a pinch I can use Autocad.

 

Would it not be possible to rotate the work and introduce the cutter, moving it at a chosen speed (like thread cutting on a lathe)?

Edited By john constable on 27/06/2018 12:45:02

[JasonBModerator @jasonb]

A lathe uses a tool th ewhole width of teh "v" of the thread much like a router-lathe uses a cutter the whole pitch of the spiral typically 60mm for a stair spindle as I said in one of your other threads.

With a small Dremel or engraving spindle you probably won't be able to use a tool much over 1/8" dia so the profile will need to be built up with a series of passes along the helix, you could work out the co-ordinates and manually move the cutter for each pass but with 4-axis CNC and the right program it will do all that for you.

Simple G code will move the cutter a set amount along the work for a set rotation and give the spiral movement but without a full width tool you will simply get a spiral groove much like that shown in the Quorn photo.

 

EDIT

Profile on the left in read is basically a barlytwist cutter and the shape has been produced buy using a helical cut in one pass as per a router lathe or any other method that can use a full size cutter. If you only have an 1/8" tool then you will need to make multiple passes as shown by the group of circles, the closer they are together (stepover) the smoother the resulting surface.

You may bet away with 0.5mm stepover so on your 2" spindle with 60mm pitch double start that would be about 380 passes, which would be easier to let the CNC work out rather than you manually set the tool for each pass.

Edited By JasonB on 27/06/2018 13:36:39

[john constableParticipant @johnconstable10725]

That's a shame. It's going to be a deal breaker for me. I thought I would be able to just control the spindle speed with one stepper motor and sync it with the movement of the rotary tool rather than having to carve it out of a block. I think I'll just leave this project to one side for now and hope something changes.

[JasonBModerator @jasonb]

It will do it but not just a case of one simple spiral cut along the length of your workpiece. Hopefully one of those suggesting using a CNC Router will chip in and say whats involved better than I can. Anyone?

[JasonBModerator @jasonb]

This is a good example of how one of those small gantry routers will go about cutting a spiral.

[john constableParticipant @johnconstable10725]

 

this is what I'm after. I realise it'll take more than one pass but I never really expected anything else. Obviously this is a bigger budget machine but it illustrates the principle of what i want to achieve.

 

Edited By john constable on 27/06/2018 21:09:46

[john constableParticipant @johnconstable10725]

[john constableParticipant @johnconstable10725]

ha! Finally got it!

[JasonBModerator @jasonb]

John, that is a legacy mill that I mentioned in the very first reply (though CNC not manual) to your first post about this we have gone full circle and not got very far.

The Stepcraft one achieves exactly the same result just has to take many more passes due to the low power spindle and small dia tool it has to use. The one in your video starts off with a large dia barly twist cutter.

Other good thing about a gantry router is that it can be used to cut the pockets and close fitting contrasting woods for inlay work on your boxes, carve textures and features and could even cut things like wooded hinges.

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