On Tuesday, February 01, 2011 11:36:45 am Mark Wendt did opine: > Comments imbedded below: > > On 02/01/2011 10:22 AM, gene heskett wrote: > > On Tuesday, February 01, 2011 09:39:56 am Mark Wendt did opine: > >> Okay, here's some pics of the hold-down bed and the cutting head. > >> > >> First, an unadulterated pic of the hold-down bed: > >>> http://farm6.static.flickr.com/5217/5407421436_d806332728_b.jpg > > > > I am having trouble visualizing exactly where the bamboo strip lays, > > and have the saw blades been removed while you do this work?. > > Gene, that's the bare vacuum hold-down, going the length of the Z axis. > The bamboo strips are 3/8" wide, and about 1/4" thick. Once it's all > draw filed and scraped in, I'll be placing a rubber-type gasket on top > of the hold down. And yes, the blades are currently not on the > spindles. Damn things are sharp, and they get in the way of my depth > gauge that I'm using to determine the flatness of the hold down. When > the blades are mounted, if you look at the cutting head from the > direction the pictures are taken, the saw blades form a "V". The saw > blades will track down the center of the strip, and cut a tapered > triangular section from the rectangular bamboo strip. > > >> Next, with Gene's tape measure... ;-): > >>> http://farm6.static.flickr.com/5011/5407421544_6c86112d0d_b.jpg > > > > Sorry, I meant crossways so I could get an idea of the width of the > > surface you are cleaning up. My bad for not saying so. It also > > appears that you are pretty space constrained around this machine. > > Sorry about that. The hold down is 3/4" wide. > > >> Quick and dirty view of the cutting head: > >>> http://farm6.static.flickr.com/5293/5407421640_9da64c20c4_b.jpg > >> > >> And last but not least, the entire cutting head: > >>> http://farm6.static.flickr.com/5254/5407421742_99bee52187_b.jpg > > > > If the surface being cleaned up is that nominally 1" wide face that > > looks like it has a row of holes in its top surface, then the > > grinding idea is probably not feasible because its alu& wider than > > the drill doctor wheel. That leaves the thought of mounting the file > > to the bottom of the carriage, and using the x motor to do a drawfile > > action if the file is sharp enough to cut with the light touch of > > just skimming the high spots. If you had a nema 34 motor that could > > be swapped into the x drive temporarily, that might work. Or it > > might be overkill because it would flex the frame with its power. > > Yup, that's the surface that's being cleaned up. > > > Two other thoughts come to mind, one is that since I can see > > adjustable legs that appear to be supporting the relatively light > > crossbars this track rides on, how solid is this floor? > > Those legs aren't supporting the crossbars, the crossbars are supporting > the legs... ;-) Those legs actually mount to the bottom of the > aluminum extrusion so as to keep it from sagging from it's own weight, > and/or the pressure of the cutting. I should mention, the machine > weighs about 700 lbs. > > > Another thought might be to rig some rollers that would resemble a > > belt sander, with the belts backing platen being the lowest, active > > sanding area and wide enough to cover the track, but I'd say the > > construction time for that, effectively making a 'stroke' sander out > > of the carriage, would exceed the time it would take to finish > > scraping it with the file. > > > > Considering the relative lack of precision in the thickness of the > > backing media of whatever the belt might be made of, I don't see that > > as arriving at the desired final result. > > > > How are you 'marking' the high spots now? And how much error now > > remains? > > I've got the hold down bed marked off in 1" increments the entire > length. I keep a log of the measurement at each 1" station. Based on > the measurement at station "0", I determined using the depth gauge as > it's run down the length of the bed, how much I need to take off at each > station. So, I draw file and scrape a bit in each area, run the depth > gauge back over the area I just scraped and note how close I've gotten > to the "0" measurement or whether I need to stop draw filing and > scraping. If I can get to less than a half thou at each 1" station, I > happily stop draw filing and scraping there, and move on the the next > are that needs to be filed and scraped. The areas that match the "0" > measurement, are marked on the side of the hold-down and on the base the > hold down is mounted to so I can see those areas from either the side, > when I'm measuring or above when I'm filing and scraping. > > The sanding drum gave me the same kind of problems you mention above > with the sanding belt. > I was afraid of that too. and of course would be highly dependent on the quality of the shaft and its bearings its turning in. The dremel with its rubber mounted output shaft, even on the cable driven hand piece, would be an absolute disaster. I can remember the first dremel I ever wore out back in the 50's while building a 15 second 1/4 mile flathead 49 Mercury engine, the cutter wheel chuck was rigidly mounted to the motor armature and one could to .001" accuracy by hand with it. Todays version may have 3x the motor power, but it also has a chuck running in its own rubber mounted bearings that can be pushed .020" in any direction by hand. No way in hell can you carve a PCB trace that is truly precise with that, and it amazes me that folks even try.
Anyway, if you have 70% of it done now, nothing we can suggest will get you finished enough faster to be worth stopping and building a new method. Sometimes the tried and proven methods do get the best results. -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) <http://tinyurl.com/ddg5bz> Real programmers don't bring brown-bag lunches. If the vending machine doesn't sell it, they don't eat it. Vending machines don't sell quiche. ------------------------------------------------------------------------------ Special Offer-- Download ArcSight Logger for FREE (a $49 USD value)! Finally, a world-class log management solution at an even better price-free! Download using promo code Free_Logger_4_Dev2Dev. Offer expires February 28th, so secure your free ArcSight Logger TODAY! http://p.sf.net/sfu/arcsight-sfd2d _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
