As I am using an Australian / Asia-pac router, I’ll make the comments general. The base plate (router holder) and fixings need to be durable and avoid distortion. Further I’d consider the management and maintenance (although ideally periodic and infrequent), the ability to easily access or dis-assemble components without a full breakdown! If you’ve ever worked on a car or other industry tool and required the SST (Specialised Service Tool, or welder, old tool / wrench and a plasma cutter ;-))
The underlay ideally would be ‘changeable’ although not initially over time that material will wear. To one of the previous comments, although reducing material, I think an edge maybe more subject to damage and harder to replace repair than a plate, the plate does not need to cover the entire bottom, I took the old friction plate of my router and attached it to the sled bottom, adjusted slightly for CoM. If the edge can be easily secured and replaced go for it!
What you don’t want is it wearing or ‘marking’ the material you’rer cutting, that will result in more ‘prep’ work for the finishing. Temperature stability would be key, e.g. try it with a garage door open in Alaska and Mexico winter and summer respectively!
To the wood v. metal, the consideration of Aluminium may also provide some options, I take it you’ve avoided a casting or poly-carb material from consideration, looking to cut the parts if required from the CNC?
The total mass, unless your objective is to remove the ‘brick’ will add load to your motors and drive, as well as momentum as it’s moving, remember our friend Newton.
The problem people keep running into when implementing the ‘smaller portions of
slick material’ is the added edges of the material catching on your work, or the
sled falling into areas you’ve already cut.
If you are only ever going to cut signs, or parts where you have narrow cuts,
this isn’t a problem.
But when you want to support larger pockets this matters a lot.
If the outside edge doesn’t catch the work then the inside edge wont’ either as long as it’s rounded over as the drawing illustrates. In theory the pocket would have to be over 50% of the sled area for the sled to potentially fall in, and with a 18" sled that pocket would be huge. Valid points, but probabaly never real life issues IMHO.
actually, if you are cutting an arc the same diameter of the sled, it doesn’t
need to be very big at all to fall in.
There have been a number of people who have advocated furniture sliders or
arrays of wheels, all of them who have actually tried it have reported problems
and switched back to a flat base.
correct and the chances of all 3 of these happening is about as likely as me winning the lottery. #1 arc exact same diameter #2 sizeable groove of at least 1/2 the width of the edge trim. 12mm or more most likely #3 arc about 90 degrees or more
Pretty sure you can just do the inside arc cuts first anyways and then you wouldn’t have to worry about that possibility…
wheels and pads are “point” sources, a perimeter sled is something different. I think one person did the furniture pads and no one has done the wheels that I can remember, so its mostly untested waters.
so don’t worry about it for your machine, but others need to worry about all use
cases
remember, that if it’s a wider groove, it doesn’t have to be close the the exact
diameter, and if it’s matching the lower portion of the sled it doesn’t need 90
degrees (the sled is fairly unbalanced, which is why it has trouble cutting all
the way to the bottom edge)
even with a full bottom, a rectangle 4-5 inches high is enough to get you into
trouble if it’s wide enough.
a filler piece could be added it ever needed, but I really do believe the chances of what you are describing to be very very low and extremely easy to spot ahead of time and fix with a little bit of g code alterations. Assuming that the sled with move on the exact radial center to fall into an exactly shaped radial shaped arc is a little far fetched IMHO. No sled is immune to all gigantic pocket operations a balance between practicality , useability and economics must be achieved.
Can we collectively create 3 sled designs we want to test and gather data on? I’ll have them all made and sent to you guys and we will all record our findings and aggregate the data for further analysis.
One idea I have is similar to @aluminumwelder idea but with additional rings inside of the outer ring. This could help with the issues @dlang mentioned while also reducing the surface area of the contact point.
I’m not set on any specific design as of now, but am extremely excited about the potential that this can yield.
Ok now we are getting somewhere !! I like the Idea of 2 rings.
If you need more people to test the sleds please let me know.
I’m willing to chip in $$ if needed.
16" diameter 1/8" thick round steel sled with UHMW trim
13" diameter 1/4 thick round steel sled with uHMW trim
12" diameter 1/8" thick square sled that is screwed onto a bigger 18" wood sled that has UHMW trim around edges. Smaller size makes it shippable, while still providing the benefits of have precise laser cut holes for alignment of router, ring system, or pantography systems.
Bigger circles could be cut with jig saw puzzle interlocks and bolted together if you really wanted to make them more easy to ship.
Above are my 3 suggestions. I use kethg222@gmail.com for mail order laser cut parts he is inexpensive and fast with orders and one of the few mail order laser cut places.
Happy to test – I can run comparisons with the optical calibration routine. I’ve been particularly interested in whether the noisy error I get in the corners of my work space are due to static friction.
What about 1/2 clear lexan . It would be nice to see the past and future cut , as well as being able to the dust collection cavity if incorporated into the sled.
lexan is pretty expensive, scratches easily and attracts dust, there is a scratch resistant version of it, but that is 2x the cost and most laser cutter places will not cut it due to fumes it makes and it’s tendency to self fuse. it can be done, but not sure it would be economical. some windows in a steel sled would accomplish similar visual peeking.
I agree with what you are saying David, I have tried to envison ball bearing on the bottom or small wheels which would act like the permimeter mounted material in my estimation. At the very least you are going to get a bump or deflection when the sled crossed cut lines on the edge of forward travel.
If a perimeter riding surface is the goal I think you would need a much wider portion than in @aluminumwelder has in the image above with a very wide and shallow sloped outer portion to minimize jolts and hangups.
Something like this? I sloped the inside and outside on this one.
I also had an idea of making sleds have an air fitting going into a cavity with small holes on the material side very similar to air hockey how the puck floats just an idea though.
