Okay, things have moved on in the last week and my frame is up, it’s all sort of working. Calibration is okay, but about 30mm lower than dead centre of board, this could be due to inaccuracies in motor positioning, maybe.
Anyway, I’m here to discuss alternate sled design. Being as I’m in the yookay I’m blessed with an array of different materials and machinery options.
Routers, I have two, a Trend 2kW which is heavy, and a small Makita copy router trimmer.
I initially set out attempting to sled the Trend, figuring I’d not need to add much extra weight. I built the ring sled, figuring I’d use the Trend for big cuts, and therefore not need a z-axis. Well, I changed my mind and added a z-axis motor control.
This addition added a significant weight to one side of the router. The mount holes in the ring sledge that I’d drilled already were in a position that meant when I mounted the router to the sled and hung the whole arrangement, there was a tendancy for the router to twist the sled. As such I demounted the router and found a long length of 1/4" dowel (actually a wooden spoon handle) and inserted it in the router collet. This enabled me to hang the router on the spindle, allowing me to re position the router on the sled with it’s heaviest side down. Pretty obvious stuff really, but definitely something to consider if designing your own sled.
I’m also working on a sled and z-axis for my Makita copy trimmer. I’ve built a riser and now just need to work out how to fit it all on the sled. Consequently I’ve upped the diameter of my original sleds significantly to assist in balance.
During this ‘lack of cutting wood’ episode I’ve also come up with a Sharpie mount. It’s a metal T bracket with a 90deg bend put in it and then it’s hotglued to the sled for easyish removal, and has a couple of jubilee clips holding the sharpie in place ;¬)
Please forgive me if all of this known. It might help others.
For reducing chain sag that might be right. Kindly consider gravity (your friend) and friction (your enemy). Finding the ‘Sweet Spot’ of both is the challenge from the little I know.
The quick and dirty Inkscape can hopefully illustrate what I want to throw in.
Chain mount directly on the sled. Unusable
Chain mount raised. No force to push the cutting bit in.
Chain mount raised high without weights to have a pressure on the bit.
With a counter weight at the bottom of the sled I attempt to find that Sweet Spot. I signed up as a Beta Tester and therefore did not want to build a frame with a fixed angle and used a hinged version with a adjustable car jack instead. Hanging your sled free air you want it to match the tilt of your frame.
With all 3 options for triagular
You are right to counter balance the tilt as in one low corner you might run into problems.
Thanks Gero, that is very helpful. I think I’d got my head around it until I saw you diagram, and that has clarified things very well.
I’ve also opted to build a frame that currently just leans against the wall, so I have the option to alter the angle.
The idea of free hanging the sled away from the workpiece to match the angle is great, again, thanks.
I very much love problem solving, but also don’t like reinventing the wheel, so this community fills the gap between the two. I can problem solve until I’m stumped and then have this awesome human resource to catch me.
Thank you all so much,
Yeah, I’ve been working on a design for an easily attacheable/demountable and adjustable motor mounting. I wish for the flexibility to cut 3/4" ply as well as sheet plastics of 1-2mm thick, so desire the adjustability. Being as I have a studwall type frame, I’m able to produce a couple of sliding mounts for the top bar. I need to be able to demount my left motor to open the garage door!
Loving the graphics, many thanks.
You should be able to cut that range of thicknesses without changing the plane of the motors. I’ve been able to cut 3/4" MDF and 0.040" (~1.02mm) aluminum sheet without adjusting the motors. While this hasn’t been tested (to my knowledge), you would only need to move the motors further out if you were cutting more than an inch thick material.
That being said, having adjust ability in your motor mounts is still a good idea. At the very least, it will help you align the chains to the sled’s center of gravity. I have that issue with my machine right now. The chains are mounted a little bit below the sled’s CoG. It hasn’t really caused any issues yet (aside from throwing off my Z-depths a little), but is something I would really like to rememdy. I have some adjustment in my motor brackets, but currently they’re maxed out.
you want the second from the left (but with the bricks on there). you want the pull on the sled to be straigh, not angled.
now, this is impossible in practice because the router moves in and out, and that is a heavy thing that will through off your balance. But you want it fairly close.
In addition, you do want some down force on the router to keep the bit in the wood, you don’t want it trying to climb out.
the triangulation kits are focused on the x/y axis. But they all have some way of adjusting the height away from the sled (if by no other measure than adjusting the thickness of the mounting block)
After you get the chain mounts balanced on the sled, then you want the motors positioned to make the chains parallel to the sled.
looking at it from the front, you want the sled to be bottom heavy, otherwise it will spin because of the router torque until it hits a limit, at which point it will start flexing the chain (and generate errors)
Yeah, didn’t think I’d need much, but as I build it I’m looking to resolve issues as I go. I also wanted to find ways in which I could build in flexibility to test different angles and measurements in the hope of finding some schweet spots. I know me too well, if I just hack it together and it sort-of-works, I’m less likely to revisit issues. And, that demountable motor enabling me to open the garage door is going to have to be fixed before a delivery of sheet material ;¬)
we are trying for balanced (i.e. would hang vertically)
remember, this is an approximation as the balance in use is going to depend on how long your bit is and ho deep you are cutting (which translates into how high above the sled the heavy router motor is). The router can move over an inch, and I’m pretty sure that the movement will through of the balance angle you are working on perfecting by more than the adjustment you are trying to make.
if you do make the it want to tip the top towards the sled a bit, that may help with cutting down at the bottom edge, but you are far better off adding support for the sled there than trying to have it balance once the CG of the sled is no longer supported.