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Router falling off rings

At my wits end here,
trying to do some simple router tests on acrylic after attempting bigger cuts and them failing. I’ve upped the feed rate and lowered the router settings to the lowest, but the sled keeps falling off of the rings when it rounds certain corners. At first I thought it was getting stuck on the chips (using a 1/8 upcut bit recommended for acrylic. Feed rates as of now are vertical 100 and horizontal at 10, with the router setting at the lowest speed 10,000.
(the bit is # LMT Onsrud 63-610 Solid Carbide Upcut Spiral O Flute Cutting Tool, Inch, Uncoated (Bright) Finish, 22 Degree Helix, 1 Flute, 2.0000" Overall Length, 0.1250" Cutting Diameter, 0.2500" Shank Diameter)
Not sure what I should check - I tried recalibrating the chains and the path runs fine if I’m not running the router but playing the cut - and the router responds fine, but what can it be if it keeps coming off the chains. It does seem to cut better in middle of the material - most of the problems now seem to be in the lower right corner. We have an upright machine. I’ve attached some pictures, please let me know if I can clarify anything else for help!

Where on the sheet are you cutting? Have you tried the same cut with wood? Cutting acrylic can be pretty tough so it might be good to know if the same file works when cutting wood.

What does this mean, exacly what is happening? Is the sled falling to the floor?

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If you are cutting down and are doing too deep/fast a cut, the chains will feed
out faster than the sled will cut, the chains will go slack and the bearings
will fall off the ring.

Is this what is happening?

David Lang

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What do you mean with “upright machine”? Are you saying that you have a different angle than the usual I think 15 degrees?

It’s built in a vertical position instead of horizontal, so the cutting area is 8’ tall and 4’ wide

That seems to be what is happening, the bearings fall off of the ring, on the right bottom corner it was happening at the top of the rectangular cut, when it started going horizontally, and in the bottom left corner it is happening at the bottom of the rectangle. From what I read about cutting acrylic It was recommended to have a faster feed and lower router setting, but is there any advice for settings that would help with this? The cut is on .25" acrylic, with the initial cut being .04 or .1 and the step down being .2 but it always falls off on the first pass anyway. Seems to be ok in the middle but really not a lot of the corner is usable - it worked ok several weeks ago. I just did a recalibration with the same results. Also our bungees are pretty stretched out so I wasn’t sure if it had something to do with the slack there. Thank you!!

Just the bearings falling off the rings (only one side) so it will jerk the router off of the cutting path @Blsteinhauer88

never heard of anyone making the maslow this vertical orientation. if you used a 10’ top bar the spreadsheet says the force is ok, but I’m guessing you used a shorter bar and thus your corner accuracy is horrible.

motorSep 120.00 in Separation between chain attachment points of motors
min force 8.94
motorHt 18.00 in Height of chain attachment points above work area
max force 41.76
workWidth 48.00 in Width of work area
min angle 12.09
workHeight 96.00 in Height of work area
max angle 72.47
sledWeight 24.00 lb Weight of sled excluding chain (but inclufing router, electronics, and bricks)

I have not yet cut acrylic personally. I agree with @dlang about the depth of cut and speed. I think that 10000 is still to fast and it may be melting and become sticky. This is evident from your photo with the chips appearing to be stuck in the cut path. This might be holding the bits progress as the chains still feed. Then it falls out as gravity still pulls the sled down. I think a bit with least flutes and shallow is key with the 10000 rpm unless you can get it slower.

Thank you everyone! I’m new to everything revolving around this system and set up, and was just following parameters set up by someone else who had set it up initially. If in freecad, my tool diameter is .125 (1/4" bit) and the H is .3 (my material is .125) Does this seem like accurate Height?
Should my vertical and horizontal feed rates be the same number? The guy before me had it set up as 40in/m horizontal feed rate and 5 vertical. I’ve tried upping the vertical to 15 and found some advantage. The lowest I can set the router is 10000 so I’ve been changing between 10000 and 12000 just to see if there is any variety. The top beam is 6feet, I think we could switch to a 10 foot top beam if that would help with accuracy. I got the left corner to cut pretty well with a deeper cut but still having issues when I move to the right corner so I think it was just a lucky moment.

@Metalmaslow

We were wondering if we changed the top bar (currently 6’) to a 10’ top bar, would we need a longer chain in order to reach the bottom of the cutting area? *(as we are working with a vertical 4x8’ sheet as our cutting area.) Is the 10’ top bar in order to get 10 feet between the motors? We also only have 9" between the cutting area and the mid point of the motors, in calibration it said this was small but wasn’t sure if that just was because our set up is different. It was working before in the middle but we had never tested our corners that well. Thanks again

the problem is a vertical work surface gives poorer results. if you look at the spread sheet


and input your 72" bar height and 9" bar location you get very poor cutting performance in the bottom corners. in fact the numbers suggest only the top of your plywood gets the best results and if that is the case, you basically have a 4x4 maslow that is raised 4 feet taller for no reason.

unless you actually need the 8’ length or height in your case a 4x4 maslow gives better accuracy all thing sbeing the same because the extreme corners are avoided.

edited to add, yes a 10’ top beam would help in the lower corners a lot, but it would make the top 2 feet useless due to high chain tension in the center. so basically the 4x6 bottom portion of your vertical board would work better but your top 2’ part might damage the motors.

Thank you for your reply,
we have very limited space so that was the reasoning behind the vertical orientation. If we went with a 10’ top beam, and made the space between the motors and the top of the cutting area larger, (12" or so) would we still run into problems with the high chain tension at the top? We were also thinking of getting longer chains (are there any suggestions for the longer chains?) Thank you for all the help!

we sell longer chains on our website, but unless you use a standard horizontal layout, I doubt they would help much.

the longer the top beam the worse your top center forces.

the taller the motor top bar the better your top center forces.

unfortunately the bottom corners have the opposite effect, so you have to find the sweet spot using the spread sheet.

and the sweet spot always requires more height and more width. since you are limited on space, sounds like it is not obtainable.

#25 roller chain is readily availble on ebay

12" is very tight spacing between the beam and the top of the workpiece, 18-24"
is much better

look at the spreadsheet and play around with the values, comparing your setup
with the stock one. If you beat stock you should be in reasonable shape (the
higher you can get the min tension the better)

David Lang