SpudFiles

Gun Freak wrote:

We explained to this same guy the difference between "shít" and "sheet" and he was so conscious of the fact that wanted people to know he was referring to a "sheet" of paper that he would say "sheeeeeeeeeeeet", most amusing

Damn, just damn

In case you don't know it yet he earns his living making drugs

More on heightmaps that evilvet mentioned.

"Inspired by the inimitable greybeard's experiments in the cnczone 3D for Crazies thread, I photographed a object submerged in a tray containing water and blue food colouring. I then used a drawing program to filter the bitmap to just show the red channel as a greyscale image." -CAMBAM (I'd call it the MSPaint of CAM software)

link

Yeah, that's one of my favorite examples on the site.

Bear in mind, a height map that:

• * Has perhaps only three levels rather than fifty or more
  * Has one of it's levels at zero, i.e. penetrates the material
  * Is made twice, the second time as a mirror image

Will produce you two clam shell halves. It's not 3D CAD CNC but it is 2.5D and works very nicely for making 3D parts.

A quick demo herewith



Edit: BTW to put CamBam in with MS Paint is a bit harsh. It will do pretty much anything the DIY hobbyist would want included pocketing, and 3D profiling.

evilvet wrote:Yeah, that's one of my favorite examples on the site.

Bear in mind, a height map that:

• * Has perhaps only three levels rather than fifty or more
  * Has one of it's levels at zero, i.e. penetrates the material
  * Is made twice, the second time as a mirror image

Will produce you two clam shell halves. It's not 3D CAD CNC but it is 2.5D and works very nicely for making 3D parts.

A quick demo herewith



Edit: BTW to put CamBam in with MS Paint is a bit harsh. It will do pretty much anything the DIY hobbyist would want included pocketing, and 3D profiling.

Gents, sounds great. So you machine an example part. You realize the sear has a clearance issue. You want to trim off .015" or .016" off one wall of a pocket. Oh, and the pocket should be .025 deeper. How do you work these issues? Maybe the pivot pin location has to move a few thou one way or another. You find the endmill plunges too hard and has a tendency to break off or load up. How do you address that? Being the guy that runs the USG Factory, I am asked to jump hoops. I see limitations with what you propose. Oh, and almost 97% of our parts are not mirror image. Maybe you guys can help me see it your way with better examples. Thickness on a 2D part does not make it 3d or a surfacing job.

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USGF

True, true, all you say is true. I am not suggesting a $3000 home made unit is going to compete with a Bridgeport mill. Back at the start JSR was looking at a 3D printer or converting his Sherline, neither of those options is going to produce something with repeatable five thou tolerances.

Over here in DIY Land I don't have those issues, the things I make are simple, often regular geometric shapes. Replacement parts for things the kids break on Nerf guns, a cam for my chicken feeder, even a part to replace a bit on the grille of my wife's car.

Just the same there a plenty of folk out there making all sorts of things that would be well within spud gun tolerances.

I think evilvet makes a very good point, in a nutshell there's a difference between pissing around in your garage and having to meet customer deadlines and specifications most of the "DIY" solutions aren't perfect, but they're good enough for those using them - most of whom are as interested in the process as they are in the result.

In the meantime, something's come up, we'll see where it goes...

JSR,

Wanna see where this interest goes...

If I can beat on the horse for a few more minutes. If you take it that simple bitmap to z height conversion programs are all that is available to the DIY crowd, this is a mistake. There is great software for cheap if not freeware. I have seen many Sherline or Taig class machines do really intricate and dimensionally accurate work. The hobby crowd has the time and love that makes this possible.

I simply do not want JSR or any other aspiring CNC machinist to start with a router when milled results are desired. There are a few times we use router type code, esp when making large wooden thermoform molds. They have their place.

@Evilvet, I am sure you have seen many of USG Mike's creations. These do require +- .005 or better in many places. But it can be done on lower end machines. I did it for may years before going pro.

evilvet wrote:I am not suggesting a $3000 home made unit is going to compete with a Bridgeport mill"

Not in productivity but excellent precision is attainable. You want a part that looks good, fits good and works well.

USGF

@USGF

On the subject of mill vs router, I am coming to the point where the limiting factor in precision is the spindle itself; my ball screws are the best I can afford, double nuts to eliminate as much backlash as I can manage, top shelf stepper controllers and sinusoidal drivers, fully supported rails etc, the whole nine yards.

Where I think I am getting let down is the spindle, not much point going to all this trouble if the spindle and chuck is sloppy. Even my best Bosch router at $300+ has a bit of spindle vibration.

Do you have any suggestions as to a DIY spindle, say a 24v motor with PWM controller for speeds in the 15k RPM range? I am thinking that may be an option with a suitable chuck.

A few links from a favorites folder that might help with home brew spindle ideas:

http://www.haythornthwaite.com/Spindle.htm

http://www.homegunsmith.com/cgi-bin/ib3 ... 21411;st=0

http://www.cnconabudget.com/

http://www.cnccookbook.com/img/OthersPr ... rawing.jpg

http://vincechanblog.ca/cnc/cnc.html

Thanks, much appreciate the great links.

Off to see the local aluminium fabricator tomorrow. They make all the CNC pick and place stuff for the plant I work in and I think I can get "mates rates" on the build.

I did some testing today, hung a 20kg load from a pulley in the man cave and had the ballscrews running at 3m / minute luffing the load no problem.

Basic frame plans herewith FYI

Evilvet,

Frame looks great. Since the overhead portion is stationary, I guess the correct term is bridge machine. I looked at the Chinese spindle you propose using. There are a lot of write ups on these, mostly positive, some complaining of poor bearing life and vibration issues.

I'd think the air cooled model would see higher temps, course this depends on duty cycle. Hot running spindles have shortened bearing life. Also, I'd think the air cooled units, having a fan inside, make more noise. Really research the seller as the units are made by a lot of vendors, not all are made to "world class" standards.

Other than that, I think it will be a fun machine. I look forward to progress photos. I cannot promise prompt service (ask JSR) but if you are in a bind to machine something for your machine, we can certainly have a look.

We can currently machine parts up to 60" X 30" on a mill. 21" diameter on a lathe

USGF

but if you are in a bind to machine something for your machine, we can certainly have a look.

Thanks, I might just take you up on that as I progress, thought freight from US to Oz might beat me.

Had a good result with the fabricator, they can make my frame from the Bosch-Rexroth or 80/20 style aluminium section. In both cases this is a 80mm x 40mm section with a honeycomb internal as part of the extrusion. It is extremely rigid yet lightweight and bolts together with T-slot bolt and nut meaning they can ship it to me flat pack. He had a frame in the shop he was making for a local college that was 12' x 6' and running a 3phase 3Hp motor that was as solid as a brick dunny, you could hit it with a sledgehammer and not get a vibration.

I hear what you are saying on the spindle; the thought of sending $500 to an eBay merchant in GwangZhou leaves me cold but when I look at my options locally, that figure is closer to $2k. I looked at the options that Gippeto suggested but they are spindle only or too light for what I need; I still need to add a motor and VFD driver so I am happier with the bundle deal.

Photos to follow as soon as the frame can be agreed.

Cheers