Making Skins #74 - Brisbane Australia

[Surfcnc]

Not this time anyway Tony.
Thanks for the nice words.

Regards
Ross

[shaper]

G'day Ross

Some good stuff there, I really like your locating jig, elegantly simple but very effective. Looking forward to seeing your first shape off the machine.

[Surfcnc]

Today was an "interesting" day, sure started off poorly, recovered somewhat then finished with a total fail.
Nobody said it was going to be easy

Initially something went wrong with my Z height, still not sure what though as subsequent tests with the same setting went well.
It was however 4 seconds of total destruction as the 12mm cutter ripped up the blank too fast and too deep !!

Sorted that then had to upgrade my hold down spikes to some two inch nails instead of some soft wire.
After that things settled down and I was able to machine the bottom of a surfboard as a test.

IMG_2532.jpg

I got a bit of video for those who are interested.
Note due to previous movement and some subsequent re-machining the cutter is only cutting the tail part of the blank.

http://www.youtube.com/watch?v=UevjM8qLDF8

...and yes the EPS foam does make quite a mess, the foam dust coats the rails and rollers and it sticks to everything as it is electrostatically charged.
Still beats sanding a surfboard though

I finished my day totally unable to produce the gcode for the deck of the board.
Done it before but today is a no go for some unknown and yet to be determined reason.

Regards
Ross

[AuS MaDDoG]

Hi Ross,

Sounds like you had some good and some not so good fun today, all part of the learning mate! just hard when you do not know why things go wrong sometimes though.
I cut some little shapes out of some 19mm old pine I had lying around for a friend today. Some rough cuts and a not so nice noise I eventually found it was the allen key set screws holding the spindle mount to the X had started to come loose.
Tightened them really tight, much better but some smoke and still rough cuts for my liking so I think I am back to the drawing board to find the right cutters to use, feed rates and spindle speeds.
Or maybe I should start cutting foam

Oh and I think your setup and what you are doing with your boards is awesome mate !!

Cheers
Tony.

[shaper]

Nice work Ross, stoked for you

Keep posting your progress keen to see a final product. The hold down looks like it works well, though I couldn't help but notice a couple of tear spot in the middle right of the stringer

[Surfcnc]

Hi Tony

Good to hear you are cutting stuff up and working out the bugs.
Simple things can take some real time to find somethimes,
I have seen you tighten things up and I am surprised anything dared to come loose

Fun day for me but more to do.

Cheers
Ross

[Surfcnc]

Hi Jed

Until I got the holdown sorted, there was some ugly stuff going on
The cutter centering did not work quite like I imagined, so that first deep cut was exactly one cutter width left of where it should have been.
Moving the 12mm cutter 6mm right in the Y axis on the shapebot.properties fixed that.

Had another accident on the mid RHS side too, but in the end I re-machined the whole thing with a 16 stepover value and it was better than a production shaping machine by a good margin.

Thanks for you interest,

Ross

[shaper]

Hi Ross

I guess that's the bonus of having your own machine, the production machines just do big wide cuts quickly trying to churn out volume but for backyard guys like us, a decent stepover value's still going to get the job done faster than a planer, surform and sanding block with the added bonus of far better accuracy

My shed's basically done so I'm close to getting back to work on my machine also.

[Surfcnc]

Jed

A man needs a shed, especially if it is going to have a giant machine in it.
That's a milestone achieved, can't wait to see what you build.

Boardcad

I found the cause of my deck gcode problems. The boardcad configuration file shapebot.properties had become corrupted somehow.
After replacing it with a new file and transferring over my settings it happily produced code for both the bottom and the deck very reliably.

No time to take it any further for the moment but the issue has been put to bed, which is a great relief.

Regards
Ross

[bozona1]

Ross

Very nice work you're doing and very educational to follow. Keep it up.

Jed

Speaking of sheds and machines have you ever seen this?

http://www.youtube.com/watch?v=RT5l3Q5oYZc

[Surfcnc]

Hi all

Today I consolidated and finished up the deck of the surfboard blank that was cut a few days ago.
It moved around a bit and was not as accurate as I would have liked.
Considering it was a first go to get the feeds and speeds dialed in and generally test how things went, it was a great success.

Here are a few pics of the board covered in foam dust and later cleaned up.

IMG_20120109_111635.jpg
IMG_20120109_113131.jpg

Here is the Mechmate ripping into the foam on video.

http://www.youtube.com/watch?v=BUWjqCgmubc
http://www.youtube.com/watch?v=7GFSWH69sL8

Lastly the hold down was still lacking and the resulting shaped board had errors nowhere near acceptable.
So like Kobus started thinking about vacuum hold down.
I jerry rigged up a piece of plywood and some closed cell self adhesive tape.
Even with this rough implementation, it worked very, very well.
In fact I had to dail down the suction as it marked the foam.
Watch what happens in my one handed phone video how it sticks to shaped EPS foam.

http://www.youtube.com/watch?v=wAnuRHKGIvM

Lots of room for innovation and improvement with my processes but still felt good about how far I got today.
Frankly still a bit stunned about the power of the vacuum hold down on the uneven foam surface.

Regards
Ross

[KenC]

it only need little vacuum to hold a workpiece the size you are working on...
I would suggest you double-side tape a small piece of fomica which is >3X larger than your suction cup that would hold thing down without suction mark on your foam.

[Surfcnc]

Cheers Ken

Good idea, will keep that one in mind.
I have some 1mm tape that gets used as hold down quite regularly.
The remaining VHB tape that holds onto the racks, it is only used for special occasions.

Reduced the vacuum to 10 Inches Hg and the marking was no longer an issue.
The marks were occurring at around 20 inches Hg, far too much vacuum.
My trial blanks are very soft, blown around 2004 when the EPS technology was still getting the formula right in the surfboard world.
If I can get no marks at 10 Inches Hg with the soft blank, the new far more dense ones should be fine.

Still working on a better system to hold the blanks but need access to some plastics that are not available here over the December break.

Regards
Ross

[Red_boards]

Looking good, Ross.
With foam that light you'll need veneer to limit denting, and be sure to glass on a dropping temperature (late afternoon), to limit out-gassing issues. We're heading to 40kg/m3, which is probably 2-3x what you have.
I'm learning from your hold-down issues. Spackle is another way to seal so vac pads don't pull air. Water it down with clean (distilled) water to mayo consistency so it goes on smooth.

Why have you used the Boardcad cutting path, rather than exporting the dxf to a more reputable CAM program?

[Surfcnc]

Hi Red

The CNC cam programs are not as sophisticated as you might think they are.
In short the issue is the blank is modeled accurately in the Boardcad app while the CNC cam apps the blank can only be modeled as a block eg x, y and z.
Even when wire cut blanks or foam blocks are used, more time is required to cut through the extra air or foam in the respective models.
That time is best spent cutting the model surface itself a little more slowly to produce a better finish.

More tellingly the cam apps will produce only a raster toolpath pattern.
This means that the gcode will follow an axis or a specified angle but not flow along the natural outline of the shape like the specialist code does.
Over time as I looked at how the typical CNC software worked I had to rule it out and instead opted to torture myself with the specialist code .

The blanks I am using a pure rubbish and only suitable for testing.
My recent investigations lead to these guys as an EPS blank supplier http://www.coreindustries.com.au/.
The density and compression strength is quite amazing and seems for the moment ot be displacing XPS in the blown or wire cut blank market.
They have missed the mark by not supplying a specialised fish blank though.

As ever I am open to suggestion and if you can get an alternative solution together.. I'm all ears as their is no denying blocks are cheaper than blanks !!

Regards
Ross

[Surfcnc]

Made me think Red

Quick calculation on the foam density of my softest blank.
Shaped volume 27.3 l or 0.0273 m3 x 850 grams shaped weight = approx 23.2kg /m3.

Regards
Ross

[Red_boards]

23 kg/m3 will dent even with veneer (I've had 5 at that density). Use hard foam inserts for leash and fin plugs. Be careful pouring epoxy into the plug holes because it heats up when pooled and melts the foam

Good info on the CAM issue, thanks.

This means that the gcode will follow an axis or a specified angle but not flow along the natural outline of the shape like the specialist code does.

The best (most accurate, best finish) boards I had cut were done across the rocker.

[Surfcnc]

Cheers Red

None of my current crop of blanks will see any glass.
They are destined to be destroyed in my experiments on feeds, speeds, cutting depths and hold down.
While this will not relate to you most likely, the stringer cuts and the end plunges that cut off the excess timber are far trickier than the foam itself.

I like your hint of glassing on a lowering temp.

The gcode Boardcad produces is a good enough approximation but not great.
Zoomed in you can see wobbles in the cut lines.
Using an open model approximation of the bezier curves when converting into a NERBS surface supposedly improves the modeling.
So far I have not played with that (will though).

Already I have found the bottom cuts better at a lower stepover value than the deck.
The domed deck spreads out the toolpath and causes less recutting of the previous passes.

The EPS also accumulates most heavily in the middle roller on the Z slide, if you are doing any thinking on wiper brushes.
Eventually it spits off a ribbon of compressed foam as it builds up.
I cleaned the Z slide with compressed air quite successfully but get the impression the wipers would need to be pretty stiff to work as the bond is strong.

Regards
Ross

[Surfcnc]

Who would have thought that reading the instructions actually works

Jed you might be interested in this.
The open model approximation of the bezier model produces far better Gcode.

Deck.jpg

Bottom.jpg

A significant improvement on the deck code in particular.

Regards
Ross

[shaper]

Cheers Ross

I'll send you an email on that one as the tool path looks MUCH cleaner. I haven't looked at BC lately but know they have a beta version out at the moment.

[rowenich]

Just figured this would be appropriate with this build log.

http://cncrouter-info.blogspot.com/2...come-more.html

Very cool surfboard made from bamboo i believe.

[Surfcnc]

Hi All

I have been working on my foam hold down system recently, it sure is crawling along but I am slowly getting there.
The objective for my supports was to have them rotate around a point on the top plane of the support.
First up it occurred to me that i needed a ball joint that I found and extracted from a machine support leg.
The hex nut at the ball end was also sanded down to allow the top to rotate through a larger range of motion.
IMG_2560.jpg

Then I machined a half moon in the top support and a mechanically fixed bottom retainer with a push fit lip
IMG_2558.jpg

This is the support being assembled with the bottom retainer in place
IMG_2562.jpg

Finally my wobbly support fully assembled
IMG_2564.jpg

The plastic is UHMW poly and is self lubricating, so the joint rotates nicely.
The top will get a piece of sandpaper glued to it to trap the foam in place.

I am currently experimenting with a vacuum hold down system that uses some commercially available 2.5 bellows vacuum cups.
The cups grip the shaped foam beautifully easily bridging the cutter striations.
To find these was a great effort as the cost from most suppliers was through the roof.
Eventually I found a supplier that sold into a large packaging market and held stock at a fair price with good availability.

Now to patch these bits together into a working system !!

Regards
Ross

[AuS MaDDoG]

Nice work Ross !!

Cheers
Tony.

[Surfcnc]

Hi Tony

Got to love the Mechmate if you can imagine it (and design it) you can have it.

Vacuum Hold Down.jpg

This is one of three units needed, missing one vacuum cup mount as I am still short some parts as I work on my solution.
Been a while since I have done some alloy so had to put my alloy head on - so different to timber and plastics.

Regards
Ross

[Kobus_Joubert]

You sure that is not for a breast feeding mommy ?

[Surfcnc]

Ha Ha, in all the time I was making it never thought of THAT
But now you mention it, I'll ask around and see if there are any takers.

Regards
Ross

[Kobus_Joubert]

MM = MOTHER's MILK not Mech Mate

[TechGladiator]

Ross;

THATS IMPRESSIVE.. Nice job. I think I am going to have to steal your idea for a little project I am going to do. Very nice.. Did you cut that aluminum with your MM?

Best regards,
Miguel

[Surfcnc]

Hi Miguel

Yes the machine made these.
As a rule use a fairly high feed rate, cut with very shallow passes and always use a cutting lubricant of some sort.

I have found dry cutting is an instant pathway to failure.
Others using something more fancy than a two flute carbide end mill might have other solutions though.

Regards
Ross

[TechGladiator]

Ross: What kind of bit are you using to cut the aluminum?

I was planning on trying to use this gizmo to see if it made any difference to the cutting. All it requires is compressed air and it will cool off the bit. I am not sure if enough tho. I don't mind using lubricant at all, but i was trying to keep any fluids from the machine, although the amount of lubricant to cut small pieces like that cant be that much.