Adventures in Hardware Store CNC

[unfy]

I've mentioned it in the AL melting thread a few times... but I figured it'd deserve it's own thread.

The above pic is the first cut ever done on a home built CNC-mill machine.

It's built out of wood (mostly pine, 2x4's, 1x2's, etc), some under mount drawer slides, a trim router, and some ebay stuff.

If I had to guess, I have less than $200 into it.  I'll have to compile a complete bill of materials for it - but it was done with as generic stuff as possible (as much hardware store as possible, else common ebay fodder).  None of the "recycled this for it, or found these on sale dirt cheap" etc.

The purpose of this machine is to learn, mostly.  It's under powered and far too sloppily built for anything 'production'.  I'll eventually build or buy a better machine heh.

It can obviously engrave / mill wood.  I've not done any other materials.  Plexiglass and aluminum are on my list of hopeful materials as well.

Anyway.  For other thoughts - maybe clamp brass into reloading blocks and have it auto chamfer case mouths ?  Or even possibly trim to length if you trust it ?  Drill hollow points ?  I dunno.  I'll have to spend time exploring what it can or can't do etc.

[Mali]

Looking forward to your info on this.

[SS_N_NE]

Making CNC stuff is fun and useful. I built a plasma cutting table that will hold a 4x8 piece of steel sheet. A few more dollars than you project but still cheaper than commercial stuff.

The big issue with machine tools is rigidity and repeatability. You will need linear slides and ball screws to get to that level of accuracy. ($$$$$...but eBay is your friend)

Getting your brass set up for chamfering will be a challenge...the brass shape varies...the mill doesn't vary...results will be awful.  Maybe a floating tool that pilots on the case mouth? The cases will have to be trimmed to length first. A mill could do that pretty accurately...but the clamping/changing starting might not be too much faster than a typical hand or drill operated trimmer/chamfer tool for reloading.

I bought a small mill to CNC but instead went with a 4600# machine...which needs an expensive 3 phase converter...which quit working....sheesh....

[unfy]

CNC machine has indeed been fun.  And it was really relaxing to be sitting out in garage with materials, tools, squares, and marking implements.  Just casually plodding along and fabricating it by the seat of my pants heh.

Eventually I'd like to get up to a 4x8.  Perhaps not with a plasma cutter attached... maybe just a high speed spindle of some sort .  Granted, water or plasma... or any spindle/head is easy enough to incorporate.  Do you still use your plasma table ? There any chance of pics ? Or maybe a tour of it in person ? Hehe...

Small linear slides, even the little hiwin's off ebay are a tad painful in $$$ yeah .  The supported round rails (sbr10,12,16,20,25,50, etc) are definitely cheaper but from what I understand the bearing blocks on those require a some screw stuff for tension - which is a bit scary.  And obviously not as nice as the linear rails.  No personal experience, though.

Chinese ball screws are surprisingly not terribly expensive.  At least not as scary as the linear slides heh.  My next build will be the supported round rails and either the acme lead screws or the chinese ball screws.  Just continuing the learning/experience situation as well as what the $$$ situation is at the time.  I'd like to build a fully usable solid little machine (square steel tubing based) that I will end up keeping 'forever'.


Brass work.

See, depending on what's done... I'm not entirely sure if it'd be as difficult as you suggest.  Would some rubber grommets / glands be good enough to keep the brass in place ?  For chamfering I don't imagine slippage (spinning slightly) in their blocks as being a really bad thing ?  Perhaps the cutting tool could be mounted to a semi-flexible rod / straw ?

I just don't see chamfering as being a high precision action, personally.  You're just touching the edge barely to knock edges off ?

Is the setup slower or faster than doing it by hand ? I dunno.  Possibly not.  Is there anything to be gained from a relatively quick setup and then walking away to do something else ? A few min later come back to empty & refill block ?

Length milling - that might be more of a concern.  Do you index off the case head such as the bench mount case trimmers ?  Or do you index off of a rod that sticks into the case mouth for length against the primer pocket / webbing area (some hand held tools) ? I would assume the case head is prolly a better answer since you need overall length, not just powder chamber length.

Honestly, I dunno how much to keep discussing these things - it's neat to day dream, but I'm not to the point of actually *trying* stuff yet so it's kinda... mental masturbation ? Heh.


Nice Mill.  Jealous .  shooter has some lathes.  Makes me jealous, too

I need my own place with my own workshop / garage .


This weekend I have plans on initial heating of the melting furnace.

I'd like to get a metal crucible welded up, if I can.

I'd also like make some stupid **** out of wood - primarily a box to throw a small air compressor into to quiet it down.  I've drawn up plans that include baffles for air in and air out so it can breathe yet still hopefully be quiet.

Wouldn't mind attempting some plexiglass on the CNC just to see how it behaves.

Playing with attempting PCB hole drilling with the CNC will have to wait until next weekend.  I really want some thrust bearings to show up so I can hold my lead screws captive along their long axis.  This will help eliminate some of the deflection I've got at the moment.

Basically - I dunno how much time I'm gonna get to play with it in next few days


Oh, I'll be spending some time each night messing with BlenderCAM now.  Or watching tutorials on youtube, etc.  Given that I have some experience doing 3D level editing for some games, I figure this might be more up my ally for this kind of thing.

[SS_N_NE]

Here is pic of plasma table...part of it...covered in motorcycle parts and industrial computer is mounted on the corner of the table to run the machine (imagine a cell phone could do the job these days).

[SS_N_NE]

Brass work.

See, depending on what's done... I'm not entirely sure if it'd be as difficult as you suggest. 

Where I work, I operate a Hurco CNC mill. The machine will move the table to .0001".  Getting a part to repeat in a holding system is the difficult part. Usually you just let the machine whittle away some extra material not needed in the part. My experience in brass is that it is not very precise. Trying to set up a thin wall "tube" that is not especially precise in a repeatable fixture would be tedious. The machine doesn't care about the part, it just cuts where the computer runs the table and spindle height. All the hand brass tools I have float on the case mouth and just follow regardless of variations (to a usable degree). Even with my .300BLK cases made from .223 a Lee Deluxe case trimmer takes about 2 seconds to load in the press and five or so turns of the handle to knock off .030" of excess length I leave from cutting the .223 neck off the case and maybe some growth from the reform. The trimmer also chamfers inside and outside with floating cutters. Think it was a $25 tool that just drops in the Lee press (breech lock system).

Length milling - that might be more of a concern.  Do you index off the case head such as the bench mount case trimmers ?  Or do you index off of a rod that sticks into the case mouth for length against the primer pocket / webbing area (some hand held tools) ?

I will offer that the case head is a fixed surface. A rod type cutter I have for .308WIN has a pin on the end of the rod that bottoms on the clamping head surface. A stop for the cutter. For CNC it just means you would set the tool touch off on that pin end and cut to zero (or any offset that gets your needed case length until the pin touches something to stop it.

I will offer that brass is an odd metal to machine. Standard drills and cutters are not of correct geometry for brass. The grand effect is often that a standard tool will bite into brass and just pull its way thru the material...generally a non-desirable result. Usually the bit will pull the part of its fixture if the tool gets too much of a bite. Shallower cutting angles work better for brass or very slow/light cutting.

In CNC the machine just does what you tell it to do. There is no regard for flex, backlash, fixture or part movement or any other movement in the system. The heavier the cut or faster the cut, the harder the material the more flex involved and power required.


But, playing with low cost machines is fun and definitely educational. Cutting soft materials and drilling things like pcb holes doesn't take much more than a Dremel motor mounted in a MDF wood machine.  Plasma/laser is easy since the tool doesn't have any pressure on it.