Pine Slab Preparation
CNC Pine Slab Preparation can be done in a couple of ways. I will discuss with you the techniques used for preparing a pine slab for an engraving. The simplest way is a commercial planner that can accept the large slab material. Planning both sides flat certainly makes life easier except for the cost of the equipment to do so.
Most of the material used falls between 20-30 inches in width, a homeowners planer will not suffice for this operation. Finding a sawmill to do this step is an option but now another cost is incorporated as well as time. I will walk you step-by-step through how we do this operation in our own Little Little Wood Shop.
Aside from all the personal safety equipment available in the marketplace, we’re going to mention machine safety. Making sure all persons are protected is always first priority, then there’s the equipment. Poor preparation can result in a very poor outcome, injury or unfortunately something worse if not careful.
These large pine slabs need to be secured so as to never move for correct flattening on your CNC machine. Also if something came loose the results could be disastrous for an expensive piece of equipment. Please take your time in making sure safety is always adhered to in your own shop.
The first step I take is a visual inspection before I even purchase my material. What are the effects in the slab itself? Are there too many cracks where it’s checked from drying? Will the knots pose a problem or complement the piece? How will the effects in the material look with a particular engraving? Most importantly, is the thickness of the slab consistent throughout?
The thickness consistency will determine ultimately the milling time involved for getting your slab ready. If we start out with material that’s fairly flat then the milling is significantly reduced. Now if the material exhibits multiple inconsistencies, the process will take longer.
Knot holes and cracks are remediable depending on placement in the material itself. They can either be filled with wood filler or cut off if they fall right . Cup, bow, crook, and twist are not effects that are useful or easily milled. A cup creates a high or low spot depending on how the material is placed, cup up or down. Bow’s create a low center spot with two higher ends like a rocking horse leg. The twist should be saved for the dance floor and never milling. The inconsistencies won’t allow for safe secure fastening. Slabs that are crooked have a slight arch to them. If thickness is relatively consistent then this can be worked around. The negative aspect with crooked material is it shrinks down the milling area due to its arch. There’s other effects but I find these to be the most common ones.
This is pine we’re talking about so some cleaning will be necessary prior to securing it to the equipment. A heavy duty scuff pad for removal of loose dried material is helpful as well as a putty knife for any pine sap. This sticky excretion will get everywhere so try to remove as much as possible first. To avoid this gooey resin all over your machine a piece of plastic sheeting can be placed on top of your spoiler board and taped. If you choose not to have a live edge then now is the time to remove any bark.
After all above steps have been taken for CNC pine slab preparation, securing must be done properly. I’ve mentioned in countless articles I personally don’t like or use clamps. I block and screw my slab material directly to my spoiled board. Mind you I don’t use any screw that will go into my factory spoiler board, only the one I’ve installed.
Arrange the blocks around the slab to prevent it from sliding side to side. Extra material to be cut off anyways will be screwed directly to the table to prevent shifting/sliding end to end. The last thing I check for in the material is if it’s going to rock back and forth. Even blocked & screwed material with a slight cup on the underside can create a rocking problem.
I alleviate this with the use of shims, regardless of what they are. Shakes, scrap material (table saw rips) in various thicknesses, rubber blocks work fine for this. Just make sure they won’t come loose or other problems can arise. Use a carpenter’s level to level out the material as you are shimming the material.
CNC Pine Slab Milling
We’ll start first by finding the materials center or where it is you want to start from. Measure your overall length, cut off unwanted material then mark your center. Line that up with the mark that is centered on the machine and you’re good to go. If your material isn’t symmetrical then your engraving can be no higher than the narrowest width.
We’ve now visually inspected, cleaned, blocked, shimmed and leveled our slab to the spoiler board. The center of the slab is aligned to the center of the table to assure that we can achieve enough space for the engraving. The size of your table will determine the overall size of the piece you can construct and engrave.
The machine used here is a Camaster Stinger 2 SR-34 with a Y axis travel of 50.250″ and X axis travel of 36.125″. Most material I use is well under 36″ in width so my X axis isn’t really a concern for this particular example.
Create a milling box
Pine Slab milling is ready once we create the space in which to be milled. I call it the box or the area in which to be milled flat prior to engraving your design. Starting from the center of my slab I measure 24″ in each direction and mark it. I have an overall travel of 50.0″ on my Y axis, this leaves me just a little more on each end to prevent an over travel alarm.
This particular machine has a laser cross hair that I use for making marks for the construction of my box. This laser is extremely accurate and allows for me to make sure my piece is absolutely square. Move the laser to the outer most edges and make a mark with your pencil, then connect your marks with a straight edge.
Your box is now constructed, make a note of its dimensions and that’s the overall size you have to work your particular engraving. If the material isn’t symmetrical that needs to be planed down then the widest point has to be taken into consideration. You may have to mill out an area larger than your constructed box to clean the outer edges of your slab.
Now your center is done but if either side of the slab is too high you’ll want to mill that down as well. Do not remove your slab until you’ve engraved your center piece. The slab is all set and ready to accept your engraving, by moving it you may have to re-mill the top again.
Again, secure and level your material but only construct a box big enough to mill those high ends. I will use a pocketing tool path the same as I would for milling my spoiler board. Once your entire surface is planed, sand your surface to make it uniform.
I hope this article helped your CNC Pine Slab Preparation for doing large engravings. As always, thank you for taking the time to read and follow us………………….