New Machine Build- JF's 36" x 48" Solsylva build for tangential knife cutting.

[jfmonod]

The main problem that I have found with CNCZone is the number of people on here who make building these things look easy. Spend enough time on this forum for example and you start to wonder how hard it could possibly be ? And down that road lies madness.

A bit of background. I'm an architecture student and I have exactly zero experience machining anything. I build models out of basswood. Actually until last night I had never even taken a drill to anything but wood.
Long story short I run across the Solsylva stuff, I see a few examples on Youtube, I recall an experience watching one of my models get cut out on a Zund machine, and I figure I can do this. And I buy the plans.

So here's what I want to achieve. Build the rack and pinion router table with the aluminum gantry straight out of the plan book but make it cut model materials like chipboard and cardboard. This requires a knife rather than a router. (see this machine for inspiration: http://www.comagrav.com/oscillating_...ial_knife.html )
This knife needs to rotate around its axis (parallel to z) so that's a 4th motor, size unkown. I also want to be able to swap a router on to this and create 3D contours on site models. This is a lot of routing so I want it to be fast. So some 425 oz-in steppers on x,y and z should just about do it.
Until I figure out what motor size I need to turn the knife (not a clue but probably not big) I'm holding off on sourcing the motors.

First off these materials come in 36" wide sheets so I need to increase the y axis. No problem according to David Steele. I figured I could use 4 foot racks everywhere. DS lets me know in a very informative email that I'm better of with 3/8" leadscrews on the y if I want to avoid excessive backlash. But now I need to cut my leadscrews from a 6' length.
Interesting thing, the 6' x 3/8" screws at McMaster do not come in plain steel. The 1/2" ones do. So 1/2" at 10-2 is cheaper than 3/8". However I am sure that that difference will be offset by the cost of 1/2" leadnuts and bearings. So 3/8" or 1/2" ? Decisions, decisions. Whipping isn't really going to be a problem over 4 feet and apparently neither is z axis drop.
David evidently got good results with 1/2" 10 - 2 ACME Precision rods (in the drive systems comparison table in the plan book) so I'll just go with those. Maybe it's overkill ? What do I know ? At this point the anticipation is making my palms itch.

Summary: my final machine spec will be something like a 36" x 48" cutting surface with racks on x and ACME Precision 1/2" 10-2 rod on the y and z. Then I'll be putting 425 oz-in steppers on all 3 axes.

This leaves the cutting head design. I'm still stuck on that. But this can wait. Like I said, I'm getting antsy. I need to start building something.

So on Friday I went and got all the aluminum from our local Alro Metal Supply here in Sarasota. Total 112 $. On Saturday I went and got the hardware and gas pipe. On Monday evening I chopped the 3/8" x 6" aluminum plate for the gantry ends and put in the order for the bearings. And last night I broke out the Craftsman benchtop drill press I got specifically for this purpose a year ago (50$ on Craigslist), checked the supplied templates for accuracy (they are way more accurate than I am) and started drilling the y gantry end plates.
Halfway through making the 5/16" holes I get over enthusiastic, push too hard, stall the bit in the aluminum, yank the chuck straight off the arbor and bend the bit into new and interesting shapes.

Open fridge, extract beer, close fridge, drink beer, go to bed.

Today I receive delivery notification that the skate bearings have arrived and so am flush with a renewed sense of purpose.

Need new drill bit.

[gmfoster]

Its like everything else in life you just go 1 step at a time. Then once in a while you have to back up turn a little and then go i step at a time again.

Mach is supposed to support this type of cutting or at least they were working on it a few years ago. And there have been several pictures of the knifes built over the years. Not something I know anything about but I know you can find some ideas as have seen them. Good luck!

[louieatienza]

jfmonod good luck and have fun with the build! Looks to be a really cool project.

As for making things look easy, (at least in my case) I selectively "edited" out the boo-boos!

[Grunblau]

Originally Posted by jfmonod Open fridge, extract beer, close fridge, drink beer, go to bed.

Spoken like a true Architorture student

Good luck on your project! Tangental knife sounds cool, I think once you have the ability to mill something you might end up changing your model building methodologies. You might even consider moving to 1:1 scale!

[fatal-exception]

Any progress on the tangential knife? I want to build one, but would like to know what features it should have before starting on a design.

Thanks,
Paul

[jfmonod]

Hi. Wow. I haven't been on here in a while.
I noticed an interesting phenomenon when trying to do a side project in one's free time.

Free time with no project --> Nothing to do, people leave you alone.

Free time with project --> More work than you know what to do with falls out of the sky and nullifies your project.

I now have a small stack of aluminum parts which will one day be finished and assembled into a machine. But not today.

As for features. What I had in mind was basically the Solsylva table with a 48" gantry and 60" table giving me a 36" x 48" cutting surface. I was going to make sure that it worked with a router first of course, and then for knife cutting I was going to figure out a way to stick a Foredom Wood Carving tooltip with a straight blade in it on the z axis.

The Foredom thing can take a 1/3 HP motor which can be mounted on the gantry with a flex shaft going to the tooltip. The tip is a 6" long x 1" diameter piece which should fit in a 1" ID captive bearing. Then it needs an off axis stepper of as yet undetermined size to rotate the knife around the c-axis (parallel to z).
The reciprocating wood chisel action has an 1/8" stroke and can go up to 15'000 strokes/min. Ideally it would stay around 5000 because of heat buildup in the chisel. It will take a straight "Exacto" type blade so normally I should be able to get through cardboard etc with this.

But like I said, it's on hold for now.

Good luck with your build.

JF