I will admit to having some considerable reservations about relying on deliberate distortion to get a flat surface. I would prefer to get someone to polish the surface FLAT at the start.
My bias.
Cheers
Roger.
I have some reservations myself Roger but this build is about finding out what can be done and if I screw it up someone else can learn from it. The latent stresses were more of a concern before I read about prestressed concrete. Basically steel rods are put under stress so the concrete is preloaded which improves the strength. Wikipedia has a good article about it. So the main thing I am concerned about is creep over time were my machine becomes more and more relaxed causing it to move. I have done the carbon fiber coating on the backside of the X axis gantry to lock the gantry in place as much as possible.
I am using 20 layers of carbon in the short side with flat being covered with 8.
I then covered the ends where it will attach to the z axis riser with peal ply so I won't have to do any post layup sanding, just pull the peal ply and add additional layups.
Going back to my setup I bonded 1/8" x 3/4" angle iron to the side of the gantry. I will use this to push against for correcting my flatness. This was then covered with JB weld on the outside to prevent any galvanic interaction with the carbon fiber. Probably not as big a concern as the aluminum inserts but I am doing everything I can to prevent it.
You can see where I have coated the angle iron and if you look at the edge above it I used a flapper wheel on my angle grinder to put a radius on it so that the carbon layers would not lift.
I covered the angle iron with peal ply to keep from having to do a post cure sanding. This worked great.
The holes were filled with paper and then taped to keep as much epoxy from filling the holes as possible. Post cure, I will drill the carbon layer out to reveal the holes.
The next step will be to fabricate the jack screw plates, (22) required, and mount them. Next is another dry run to see how close I can get to 0.0001" flatness.
If I can get the flatness but I have creep then I will hone the linear rail surface flat.
Thanks for reading, more to come.
No problems at all about running the experiment. Experiments are always good. (Professionally I am an experimental physicist.)
My wondering is about the material. Is this synthetic quartz (ie made with some sort of resin) or natural sawn quartz?
Hum - natural granite is widely available, but natural quartz in blocks? I dunno.
Anyhow, we do know that natural granite can be amazingly stable. I believe high end CNCs use it sometimes.
I was interested in the epoxy granite thread and this material is a factory made version of this. I originally was planning on using aluminum but even using pieces from the local Alro supply was going to be $3.00 a pound. While shopping for counter tops with my wife I found a local supplier with pieces of quartz counter top left over from jobs for $10 a square foot. I took a few samples and found it was fairly easy to work with. I then modified the design I was working on to use this material. So the good is that it is cheap and weighs less than aluminum and has better vibration dampening than cast iron. The bad is it has 1/3 the bending strength of aluminum. I ran a stress analysis with carbon fiber covering the quartz and was impressed with the results. My plan is to check results with reality when the current layup has had time to set. I don't know this yet but my guess is that the larger the piece the more the carbon fiber will help. So that's a summary of how I got where I am and what I know about the material. I will continue to post my results good or bad.
Cheers to you.
It has been cold in Michigan so I have let the composites sit a bit and worked on the design and frame construction.
I don't like sweeping chips so I have designed in a tray, shown in blue, to collect everything that falls down the chutes.
Here is the frame with the chip tray in place. I am using 4" steel v wheels riding on angle to track inside the frame. I still need to finish the design for the end but it will be two wheels riding on the concrete.
I am using 1" square tubing x 1/16" for the scrap tray frame. I found some 7/8" key stock which I pressed into the support brackets so the frame could slip together/apart when I need to work under the machine.
I will have a 2" gap all the way around the perimeter to allow chips to fall into the chute. Hopefully this keeps things clean.
The green way covers will help move the chips to the tray. I am attaching them to my table so as it moves back and forth the chips will move to the end scrap chutes. I am using springs to attach the two ends together (see bottom view).
By the time the frame is done it should be warm enough to go back to the composites. I hate heating the shop to 75 when it's in the 20's outside.
Haven't posted in awhile but I have been working. I switched to the mechanical components while the weather warmed and have completed some of the way cover roller mechanism.
Rendering of the way cover roller assembly
Plates are complete and I am working on the bearing spindles.
The steel frame and guards are mostly complete but I still need to weld in angle iron hold down for the quartz sub table.
I need to tap the inserts in the end pieces and then I will bond the sub table together on my surface plate. Missing in this picture are stub pieces that will go between the outer and inner plates. When all are bonded the sides will be covered with eight layers of carbon fiber.
Rendering of table reinforcement without top plate.
I plan on getting the sub table completed and then I can paint the frame and move the mill into its final location to anchor it down. At that point I can level and bond the table top to the sub frame. The linear ways bolt to the table top.
Thanks for following.
This is my setup on my surface plate. The table mounting surface is face down. The right side is my master side and I used two blocks for spacers for distance and squareness. The dimension between the to outside surfaces with the blocks was within 0.5mm of the design dimension. The only real critical dimension is between the two inner rails. I used the 12" calipers to set that dimension, worked well. The third rail from the right is held square with the large square. I want these surfaces dimensional correct and straight because I will mount the angle iron piece for jacking the table surface straight there. Bolts will be threaded up into the linear rail mounting inserts to pull the table down. Holes will be drilled between those holes to jack the table up. More to come on that when I mount the table.
I applied JB weld to both the end piece and the rails.
Used a stick to radius the corners. I will have to add chopped carbon fiber and epoxy to make the radius larger before the fabric is applied.
This is my dad giving me a hand with the project. He turned 85 last week. Thanks for the help Dad.