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Lines in zig-zag

accuracy

#1

Hello.
After some go and back calibration process, I can say it is ok. I carved a star and a circle in de middle of the table and other in an upper corner and I can say it is almost OK.

BUT!!!.. I make a 2200 mm line in the top of the support frame and this is what it do

As you can see is a good zigzag… my question is why? the same thing happend in the middle of the panel. but I don see this problem in the star… may be are very short lines…

I am thinking in the sled mounting braces… may be they have some friction that i dont feel… or the carving bit to wide? (6mm)… the OSB is tricky to cut it have hard and soft places…

I am going to make more cuts with a thinner bit or over a plywood, but may be somebody had the same problem yet, and had resolved it. If this is the case… here I am

regards


#2

top center is a known problem area, but you say same thing happens in t he middle so I am at a loss. .What router and z axis are you using? I have never seen that particular brand before?


#3

by the moment I dont have a z axis motor, and the router is a small 500 W Makita router…i know is small…it could be the problem? https://www.makitatools.com/products/details/3709


#4

I tend to suspect the linkage kit. I’ve seen similar zig-zap pattern with ring kits, but not to that extreme (have to look close). the linkage kit might be sticking and then breaking loose. It might be happening up top because of the extreme angle?


#5

Again I think you should be able to see what is happening. A video would help to see if the linkage is jumping rather than rolling.
Also, if you cut the star and circle before, there is ‘tear-out/fruzzle’ from those cuts that the sled rides and sticks on. I have a ‘hand sandblock’ that I use to go after the cuts before the sled comes around again.


#6

what’s the total weight of the sled ?, I ask because this little Makita seem very light.
and what about your angle (gravity) ?


#7

like others have said, I would need to see a video, but my guess would be that
the sled is sticking and then jumping instead of moving smoothly

David Lang


#8

the sled weight about 5 kg… and the angle about 15…
I am going to do some adjusts in the sled and run some cuts and post you a video of how it move…but tomorrow. :wink:

thank you for your help.


#9

at 15° it is likely that there is not enough pressure on the bit.


#10

typical sled weight is closer to 10Kg (half the router, half the bricks)

you can try reducing friction by tilting the frame closer to vertical (but a
couple chunks of 2x4 under the rear legs and try it)

but check how smooth the bottom of the sled is and make sure the edges are
rounded and smooth.

OSB is a hard material to move smoothly on. There have been reports of other
people having problems with it.

David Lang


#11

OK, can not wait until tomorrow, so here i am again.
The frame angle is now 20°, I change the bit for one 2 mm diameter and I cut lines of 1 mm in depth.
Here are the graphics you ask me for:

runing a line 150 mm from frame top

https://photos.app.goo.gl/tBSp66euEMqQf66w8

the result

New photo by Mario Giacummo

then i run 2 verticals lines, one near the border:

New photo by Mario Giacummo

the border line near the bottom

New photo by Mario Giacummo

and a second one in the middle

New photo by Mario Giacummo

i can said it is near perfect all the way, from top to bottom

I think is the weight, and the OSB board, tomorrow i am going to increase the sled weight and see what hapend…

thank you for your help

regards


#12

OK, can not wait until tomorrow, so here i am again.
The frame angle is now 20°, I change the bit for one 2 mm diameter and I cut lines of 1 mm in depth.

that’s moving the wrong direction, try going to 7-12 degrees

I think is the weight, and the OSB board, tomorrow i am going to increase the sled weight and see what hapend…

additional weight may help, getting closer to vertical may help, try using spray
adhesive to put a layer of paper over the OSB to smooth out the OSB.

how smooth is the bottom of your sled? have you waxed it to make it slipperier?
are the edges of the sled sharp or rounded?

David Lang


#13

OK dlang, I am going to follow you, the sled is not rounded, I will go to near vertical, wax everything, etc, etc…

I saw an other problem…I have to move de motors up, and add 20 or therty cms to the bottom, because wuen the sled CG pass the bottom of the frame the top tilts few degrees … or put some weight where the router is.

I read above that the weight of the router is half the weight of the sled? is it?


#14

you don’t need to do them all, probably rounding the edge of the sled will be the biggest win (OSB has lots of edges for the sled to catch on, so rounding it will probably make the most difference). This doesn’t need to be a precise rounding, attacking with with sandpaper is probably ‘good enough’

adding weight won’t help, the sled is deliberately bottom heavy, and when you get too close to the bottom you run into this problem

take a long, straight board, and attach it to the bottom cross member with some sort of bracket (a board with a slot in it is good enough) and move it in and out to make it match the workpiece you are cutting.

This is what you will see referred to as a ‘skirt’ in other posts

yes, the stock router is pretty heavy, about the same weight as the two bricks.


#15

Will give less pressure on the bit. You might see increased waves. Hoping that adding weight at the bottom of the sled and balancing will do the trick.


#16

Your home made linkage looks pretty good! I’m sure you know this but make sure they aren’t rubbing/snagging where they cross. And of course make sure they aren’t snagging on the sled. It’s hard to tell from that picture how far they are from the sled.


#17

on monday i am going to buy some iron weights… by the moment i change one piece of the sled, i replace the one who run in the middle by a thinner iron piece as pillageTHENburn wrote.
New photo by Mario Giacummo

why the photos are cropped?.. here is what i did

https://photos.app.goo.gl/AFHRmNhQXtW6u7Hv9

I like this linkage, I read all the thred how it born an develop until now, a greate mind game ;0)

the only thing with it is that it have 9 points of friction, but working hard the result is greate.

Oh! and i wax the back plate… lets see next monday

good weekend


#18

Nice!
That steel piece should do the trick nicely!

The points of friction at the pivot points are actually not a very big problem because each arm acts as a long ever. This post sort of explains why: Throwing my hat in the sled modification ring That is assuming reasonable amount of friction. Those pivot points should move freely but they don’t need to be nearly frictionless.


#19

I would spend time feathering the edges of your sled and wax the bottom and edges. I use bees wax for slipperiness, I have used candle wax to fill voids. Sand, fill, wax.

Just my 2 cents

Thank you


#20

Waiting for some time to continue …