My holes are not round

[glassocean]

Hey guy's,
Yesterdays cut did not turn out so pretty. The 1/2" holes are not perfectly round. Even the 3" outer circle is not quite right. It did the same thing in acrylic at .100 depth per pass as .250 depth per pass in MDF. Look at the top 3 holes in particular. Any ideas?

thanks
Jeff
http://aqpros.com/DSC00712.JPG

[Icutone2]

MDF is smooth, Did you use masking tape on the back side to help it track smooth?
Lee

[glassocean]

MDF is smooth, Did you use masking tape on the back side to help it track smooth?
Lee
This was cut from a 6" blank, that was inserted into, and hot glued into a 14" x 22" MDF sled.


Jeff
http://aqpros.com/DSC00713.JPG

[Digitalwoodshop]

Run a strip of masking tape on the bottom of your sled at the edge where the brass roller rides.

Grab your ROCK or QC and tug in 6 directions... I found my upper right rear Y bearing was loose, 1/8 of a turn causing my Y Truck to Rock or Move... Check for loose bearings.

Look over your Y Motor, could have a loose motor or gear box.

That is a pretty slick piece of sled. I would run 5 or 6 strips of masking tape the length of the sled to give the bottom something to grip the sand paper belts.

AL

Edit: If all that does not fix it then you may need to do calibration.

[glassocean]

Run a strip of masking tape on the bottom of your sled at the edge where the brass roller rides.

Grab your ROCK or QC and tug in 6 directions... I found my upper right rear Y bearing was loose, 1/8 of a turn causing my Y Truck to Rock or Move... Check for loose bearings.

Look over your Y Motor, could have a loose motor or gear box.

That is a pretty slick piece of sled. I would run 5 or 6 strips of masking tape the length of the sled to give the bottom something to grip the sand paper belts.

AL

Edit: If all that does not fix it then you may need to do calibration.

Al,
The only thing I found wrong was a slightly loose screw on the Z truck, I fixed it and it made no difference. I do, however, notice that when I slide the z truck left to right it will almost sputter or catch, as if something is too tight.

Jeff

[Dhaffner]

interesting post....
I've found that a rastered hole always has a "flat" edge...anyone else have that?

[Deolman]

Have you checked your head pressure lately?

[Digitalwoodshop]

That is a heavy sled.... DO a test cut of the same pattern on a 11.25 inch board with no sled.... Could be the weight of the sled....

AL

[fwharris]

Al,
The only thing I found wrong was a slightly loose screw on the Z truck, I fixed it and it made no difference. I do, however, notice that when I slide the z truck left to right it will almost sputter or catch, as if something is too tight.

Jeff

Jeff,

For the sputter/catch you might try cleaning the rails with some alcohol. You might have some build up on them from the MDF dust.

[glassocean]

Al,
I made a smaller, lighter sled out of birch plywood, and it came out pretty bad. I then cut a pattern out of a piece of MDF and it came out perfect. I'm a bit confused. It seems as if some things come out fine and others do not.
I also cleaned the rails as FWHarris stated, but I don't know if it helped.
I'm at the point of thinking the work piece is slightly moving. Has anyone ever added sand paper to the bottom of a sled, or would that be too much friction against the machines sand paper rollers?

Jeff

[deemon328]

Check your Y-belt plastic gears for built-up deposits. I use an old dental pick to keep them cleaned out.

I'd scuff the MDF in one of two ways. First, if you have a drum sander, run it through with 36 grit to create a uniform pattern. Second, if you don't have a drum sander, cut light kerfs on the table saw in a grid pattern every half inch or so. Either one of those options may help with getting the mdf to grip better.

FWIW, I never got a round hole out of the CW with the standard QC. The rock chuck makes a big difference reducing bit runout.

[Digitalwoodshop]

That is confusing.... Vacuum the sand paper belts, clean the y rails....

What direction is the error in? Y or X?

I would pull the cover off the X Gear box... You might have a single broken tooth.....

AL

[glassocean]

Check your Y-belt plastic gears for built-up deposits. I use an old dental pick to keep them cleaned out.

I'd scuff the MDF in one of two ways. First, if you have a drum sander, run it through with 36 grit to create a uniform pattern. Second, if you don't have a drum sander, cut light kerfs on the table saw in a grid pattern every half inch or so. Either one of those options may help with getting the mdf to grip better.

FWIW, I never got a round hole out of the CW with the standard QC. The rock chuck makes a big difference reducing bit runout.

Deemon, Thanks for the tips, I'll look at the possible gear jam issue first.

I really didn't seem to have these egg shaped holes and circles like I'm producing now (with the beastly sled). I have to believe something is a bit off.

Jeff

[glassocean]

That is confusing.... Vacuum the sand paper belts, clean the y rails....

What direction is the error in? Y or X?

I would pull the cover off the X Gear box... You might have a single broken tooth.....

AL

Al, not a problem with dusty sand belts or rails. I'll look at, and clean the gear teeth.

As far as the direction of miscuts, I don't know. It would help to narrow it down somewhat, wouldn't it?

Jeff

[Digitalwoodshop]

A picture of the hole with a line drawn for board length and width.

To do a circle it must move X and Y equal....

Have you changed to rubber belts?

Have you ever done calibration? Calibration converts rotation of the motor shaft and pulsed of the encoder into a scale factor number.... Converting that in the computer into real world board.....

It is possible with the scale factor number being wrong for some reason to have it think it is cutting a circle correctly by pulses of the encoder but the real world board is cut oval....

Think of it like this.... I see the 2 wheel Wheel barrels at the home center.... Picture one with 2 different size wheels..... It would only make right turns or left turns.... Never able to go in a strait line.... Scale Factor..... 20 years in the Navy dealing with Scale Factor in aiming the Guns and Missiles..... Fire Control Tech....:mrgreen:

AL

[glassocean]

A picture of the hole with a line drawn for board length and width.

To do a circle it must move X and Y equal....

Have you changed to rubber belts?

Have you ever done calibration? Calibration converts rotation of the motor shaft and pulsed of the encoder into a scale factor number.... Converting that in the computer into real world board.....

It is possible with the scale factor number being wrong for some reason to have it think it is cutting a circle correctly by pulses of the encoder but the real world board is cut oval....

Think of it like this.... I see the 2 wheel Wheel barrels at the home center.... Picture one with 2 different size wheels..... It would only make right turns or left turns.... Never able to go in a strait line.... Scale Factor..... 20 years in the Navy dealing with Scale Factor in aiming the Guns and Missiles..... Fire Control Tech....:mrgreen:

AL

Al, I'm going to give the machine a good cleaning/inspection this weekend. I'm waiting for the Rock to come in, and I want to see if this new chuck will make a difference, before I get really deep into ths issue.

As far as the rubber belts go, I wasn't aware of these, and just saw a pic of liquidguitars machine with groovy belts. Are they a big improvement, and where do you get them?

Thanks
Jeff

[Digitalwoodshop]

Order the belts from LHR. Be sure to do the calibration and drill out the holes to move the brass wheel away from the belt.

AL

[glassocean]

Well, after getting the stuck bit adapter out of the chuck, I think I figured out the problem with non-round holes. I believe the bit was loose in the adapter, since the set screw backed out. I inspected and cleaned everything I could, then did a test 3" circle cut, which came out perfect.



Jeff