CNC Shark Forum

It's not just a matter of milling the table flat. The Sharks sag in the middle of the work space (the Pro Plus HD less than the Pro Plus). So if you mill a "flat" table, you actually get a dished table. But if you attach a dial indicator to the router, the table will register as "flat" since the router sag will match the resulting dish in the table.

For the best compromise, adjust the table so all 4 corners of the work area are at the same level. Place the the work in the center of the work area to get the least variation from perfectly flat. Set your Z zero at a point about 1/4 of the way across the work area in both directions.

In another thread, it was calculated that for the Pro Plus, the sag at the middle of the table that is the result of deflection in the steel guide rods is about .028". Of course the Pro Plus HD will be much less since the guide rods are supported.

The person who designed and built the enclosure for our Rockler store Shark made a miscalculation that actually turned our to be a low tech solution for supporting the gantry weight. The solution probably needs some tweaking, but here it is:
He designed a cutout area in the center of the enclosure that the Shark would fit down into. This insured that the Shark would be secure. We have been using this enclosure for about 6 months now. About three weeks ago, I noticed that the bottom edges on each side of the gantry were resting on the top edges of the cut out section. The cutout area was too deep so there was constant contact between both surfaces. This is a bad thing if the gantry is resting on a surface that is not flat. But, when looking at the setup, it might be a good thing if the surface could be flattened and on the same plane with X Y travel. Some WHMW plastic, or solid surface material would provide a good low friction, flat surface.
...Time for me to start tinkering.
Love those low tech solutions,
Bob

I bolted 3/4 in slats as my sub base and machined flat and parallel with the machine- your are limited of course to 25 x 25 because that is all that will cut but the rest is useless except for support anyway. Its about $25 bucks worth of wood and bolts, much less if purchased in bulk- see pics attached. Rockler should scrap the aluminum extrusion design- I also have an old 1990 era Pheonix CNC router with a 22 x 22 X 1 1/2" thick MDF top- Stayed flat and solid, I used it for years until the electronics died... Pics attached of modified shark table and old Pheonix table- ( I added the T-slots to the Pheonix)

Hi Bob

For what its worth, regarding the gantry sides resting on something flat..
When I first tried to eliminate the flex on the lower rods of my pro, I put bearings on the bottom of the gantry side supports and had them riding on metal plates ( to keep the friction low) I didn't work very well, and I ended up converting to fully supported bearings. If the gantry sides rub on anything, you may be in danger of losing steps due to extra friction.

I bolt my sub bases and fixtures down with plastic bolts, with the heads recessed into the board. ( I think consultingwoodworker suggested that a long ways back).

The vectric forum does not speak highly of the infamous "double sided tape", especially with fibrous substrates like wood. Corian and laminates may work better with tape, I always clamp everything..

The slat Idea that 2big pictures above is a great way to maintain the ability to get at many of your table slots, and also can help tie adjacent extrusions together.
I will be converting to a slat arrangement at my next sub base replacement cycle. Thanks for that idea.

another Bob

Bob

Taking the idea from 2big, I made a new slat type arrangement for my top.
Although my top uses 1030 extrusion, the concept applies to the Rocker extrusion tops as well.

Using 1 x 3 red oak, I positioned the slats to span adjacent extrusion sections with countersunk holes for the hold down bolts. The holes are made in pairs, next to each other and spanning two extrusions.. This helps lock the extrusions together so they do not flex up and down independently, as well as give you a surface to plane off to get the last bit of level and flat. On the 1030 extrusions, this leaves one slot uncovered in the center for clamping purposes. If you have bolts in at least 3 places along the length of the slat, it will help make the table more rigid as well.

The gaps between the slats can be routed to take a few thousandths off of the slats in the gaps to make the slat gaps parallel to the router axis as well.

I made some spare slats to save time when the inevitable "oops" happens and one needs to be replaced.

Bob

Good looking clamps, rungemach. I have been using some wood versions almost identical for a year or so with my Shark.

And for anyone interested in the above slat solution, the slats can be cut and drilled on the Shark too, if you don't mind laying them out diagonally.

Also, wouldn't half as many slats that are twice as wide be just as useful given the clamp range? Might save on the nut/bolts required.

You can use wider boards, you just give up clamping versatility as the clamping spans get longer.
I guess the important part to me was to try and get bolts into slots adjacent to each extrusion seam.

I cut my holes and pockets on the cnc. I just did half a length and turned it 180 degrees to get the other half, did not go on a diagonal.

As my table top is 36 inches long, I put holes at 3 and 13 inches from each end, giving me 10 inches between holes. If you set up the clamps to provide fixed stops at the end and sides, you can put slats in for the hole cutting pretty quickly. Then have the cnc do the holes and countersinks for half of the slat before turning it around and doing the other side.

If your machine has two widths of slats you will have to take that into connsideration when you figure out how wide your boards will be and where your open slots will be.

So the slats are doing 3 things. providing a replaceable surface to plane true to the machine,
strengthening the top lengthwise,
and holding the extrusions from shifting up and down relative to each other.

Dont try and save on bolts, they are needed to provide good clamping force along the slat to gain the strength from the assembly. Ends and center would be a minimum.
A man-made composite type material might be better for the slats from a dimensional stability standpoint if you have wide temperature and humidity variations in your shop.

I countersunk 3/4 dia holes to fit washers. 1/2 inch deep in 3/4 thick material came out right for half inch long 1/4-20 bolts.

bob

I am new to this forum and just received my Shark HD. I have read all postings for leveling and am very confused. Can someone give me a simply way to make a stand for the machine that will work??????

See the answer in your other post
Cheers
Wolffie

No CNC is "flat" straight from the factory. There could even be minor shifts during shipment or installation, so most will recommend machining the base after installation. The new Virtual Zero option seems to solve these problems.