bit change causes misalignment in cut

[4DThinker]

V-Bits will appear to be cutting deeper/wider in different areas if the board is not planar with the gantry/router travel. A centered pocket relative to a centered profile may not leave a consistent rim if there is play/flex in the system that allows the spinning bit to pull inward on conventional cuts and outward on climb cuts.

The precision collet that is available may help keep your bits centered and true. I'd grab the router and see how easy it is to move it relative to the table. The Sharks have inherent flex in them thanks to the plastic used and weight of router cantilevering away from the gantry center. On the HD 2.0 I have at work we added a 2"x2" steel angle along the back top edge to stiffen the X axis which was allowing the bit to deflect in the Y direction.

[BillK]

Personally I would use the V-bit cut generator with the V-bit rather than the profile cut. Just draw two circles that you want the V cut between. The cutting program will be much different than a profile cut. Both sides of the V will be cut separately and you will get a much better finish. I have made many coasters successfully with this approach.

If you want the angled edge to flow into the bottom, use the V-cut generator for the large circle with a depth limit. Use your preferred larger tool as the tool to clear the flat bottom depth. You'll get a much better product in the end.

Use the profile cut for the cut outs only.

[cfgenie]

I've attached the crv file with the latest cut/test I just ran.
I had ordered the precision collet last week and it came but I had not put it in until I read your post 4DThinker. Wow, what a better made collet!
I checked out the post on the vectric forum and ran that test file to determine my angle of the bit. It was very close to 90. After I did a test that was still a mess, I went out and bought a new v-bit.
Ran the same test to determine the angle and it is also very close to 90. I double checked it against an angle finder tool I have, and it showed between 89-90.
I changed the project to use ramps and leads on the v-groove, ramp on the pocket using the 23/32" flute bit, and ramps and lead in (no lead out) for the 1/4" EM to cut out. I purposely used a thicker piece of scrap this time so it left the coaster fully intact for easier inspection. I also used pine so it was nice and soft.
The result is still the same!!! I used a highlighter again to make the rim easier to see.

Later today I am going to try securing the whole machine more like suggested by 4DThinker.

BillK, I played around in the software to do as you suggested, but I couldn't get the end result to be the same as I am looking for - with the outside of the coaster having the v-groove. I want the inner wall to be straight down. Would you mind sharing your coaster project you have? Or a picture of a completed one?

Thanks everyone

[BillK]

Sure, here's a few of the many. Sometimes a V leading to the cup surface, sometimes just straight in.

[KarenW]

I agree with 4D - I'd check to make sure everything is tight first.
Then, given this problem you're having on your very first project (and how frustrating that must be!) I think I'd set aside the coasters for a short time and do a simple text cut with the v-bit just to make sure you don't have something else going on at the same time. If the text cut comes out wrong then you can think about mechanical reasons (because both files failed to cut correctly). If the text cut comes out the way it should then you can think file settings (because one cut correctly, one (the coaster) cut incorrectly).
I always find it easier to track down a problem by first eliminating those things that are working correctly.

[jimsworkshop]

I noticed that you said you were using the dust boot. Be sure that the bit extends down BELOW the hairs of the dust boot at the max depth of cut. If the boot hairs contacts the surface of the material, the router will deflect in the Y direction slightly and may be the cause of your problem. DAMHIKT. The first time when you did a successful run, the bit may have been chucked so it was "longer". On the subsequent runs, not so perhaps

-Jim-

[BillK]

Hi,

Here is your file back with a few modifications to how I probably would have done it. There is nothing wrong with the way you did it and I can't see why you wouldn't get the results you want. My experience with the Pro Plus is that a profile cut with a V bit to that depth is a heavy cut as is the pocket cut. The dust boot issue is also a reason why your getting an axis reset. Your X and Y should not change between bit changes, only the Z needs to be reset.

The mods that I made are shown in the three new toolpaths suffixed BK. The V cut you should watch in slow motion and see the difference. The pocket cut is set so it's done in two passes, the second one with a lighter removal which improves the finish.

Again, just an example of how someone else would approach this type of cut.

[drueth]

cfgenie

It looks like the pice of wood is not level or your table is not level and flat Please try this set your Z to zero Now raise the bit and and jog the router to the other 3 corrner of the block carefully lower the bit to each corner if the bit touches the board befor it reaches zero on any of the corner the problem is the board is not flat or you table is not FLAT and LEVEL. It would be my guess your table top is not level and copalner to the gantry.

I have not tried to make coaster but when I saw you could do an inlay I thought they were the neatest thing. The first few I tryed were a mess. That is when I found out that a 90 dig V bit is most likely 85 dig. and my table and shark were not FLAT and LEVEL . You can use a scrap of wood and Set the Z to zero on the scrap NOW jog the router around your table and see if the scrap will pass under the bit, is the bit tight or loose to the scrap how much do you have to raise or lower the router it get to zero. I have my table now set up were I can move to any spot on the table and only be off about 0.008+- This is not possible if you just take the shark out of the box and set it on the table.


PS I like the one that Bill did may have to try to make them.

[ohiococonut]

My Shark Pro Plus HD had a similar problem and it didn't show up until I used a Vee bit. Turns out the set screw on my "Y" axis, which is set to run the length of the table, was loose.

Physically grab ahold of the uprights on the gantry and see if you can move it back and forth. There will a little movement from the flexing of the plastic but there shouldn't be any slop. Try moving all three axis in the same manner and I'm betting you'll find the problem.

The new collet from Precision Collets will eliminate the possibility of moving the zero set point as long as you remember to tighten and loosen the nut using one hand to squeeze the wrenches.