One would think by now, there would be no more mods needed for the MKI, yet I found another.

Cutting lite ply and phonelic has been a challenge for me on the MKI phlatprinter. Hard woods leave the roller at an angle and hit the cutting bit slightly raised from the surface of table making accurate depth choices difficult.

While this is not a problem for FFF because it bends and flattens out by the time it reaches the cutting bit, plywoods on the other hand do not bend and there is a gap between the table top and the material being cut at the point where the cutting bit approaches the material.

It occured to me that I could eliminate most if not all of that angle by simply adding some plywood to the top in front of the roller. I first tried 1/4" MDF but it was a tad too thick and rose above the feed roller, so I bought some 1/8" Masonite and cut out a piece to fit in front of the feed roller. I sanded a 45 degree angle into the edge that butts up with the roller to keep it as close to the roller as possible.

I then screwed the Masonite to the table top and cut a slot it it with an 1/8" bit, removed the Masonite and put it on my table saw and cut out a 1" slot for the bit opening.

The hard surface of Masonite makes a slick surface for the material to move over and I can now accurately setup up my cut depths since there is very little open space between the plywood being cut and the table top at the point where the bit comes up from below.

By changing the constants.rb file to remove the 40% overcut setup for FFF, I can now specify the exact cutting depth I wish to make and use the shorter shanked 1/32" bits to cut the plywood.

After installing the mod, I cut out a Bevel Cutter courtesy of mrbubbs (http://phlatforum.com/viewtopic.php?f=67&t=1354&p=13118&hilit=bevel+cutter#p13118) using a .043 bit with a multipass script applied.

I used 1/16" Birch for the project with a sand weighted upper roller and two strips of painter masking tape on the roller side of the Birch piece at 10 ips. My X axis moves at 500ips on the rapids and the Birch ply moved effortlessly across the Masonite and was nearly flat against the top where the bit makes its cuts.

Likewise, I tested the movement of FFF and Depron across the Masonite and it works flawlessly as well.

It is an inexpensive mod and can make cutting those lite ply firewalls, control horns, etc much easier. Attached files

 

Flash, do you know if they have masonite at home depot? Is the other side, really rough?

 

Yes, I purchased mine from Home Depot. Lowes did not have it. And yes, it has a rough side on the other side.

 

Thanks, I will probably do this mod. Think they call it something else then. Maybe "hard board"? I noticed it next to the 2' x 4' mdf.

 

Yes, could be called that. Probably is... Masonite was probably a brand name from my memory years ago.

But that is the stuff. It was right next to the MDF like you said.

 

The thickness is very close. If it could have been 3/16, I think it would have been perfect, but 1/4 is too much and 1/8 is not quite enough so I opted for as close as I could get and it does the trick none the less.

And the hard board is under $5, so its an inexpensive mod and if I spill anything on it, or do something stupid like cut parts on it, which I have been known to do in a hurry, it is easily replaceable, unlike the main MDF top there now.

Now if only I could find a way to remove that slight droop in the center of the top where there is little support. I suspect I would need something metal that is thin enough to serve as a brace, yet strong enough not to bend as weight is applied to it. Its pretty tight quarters in there.

I noticed this very slight droop when I was installing the hard board. It has always been there but now with the top closer to the top of the roller, it became more obvious.

I suspect there is some minor depth inaccuracy nearer the center. So maybe another mod could be in the works to address this. If anyone has some good ideas for a solution, lets hear em.

 

I cut out 10 sheets of FFF today with no problems.

I did add sand balast to my upper roller for better grip and I have two rollers forward of the drive roller. Don't know if that might be significant or not, but I am not seeing any slippage whatsoever.

Since all of the grip is on the back roller, I don't understand why the hardboard being too high would have any effect. The front roller(s) is just to keep the foam down on the hardboard and it is so smooth that there should be little if any friction there.

Just curious why FFF would be an issue. If anyone else trys it, maybe they can post their experience with it.