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A new way to think about frame size and angle

Good eyes. It is intentional. My current setup is certainly heavy. I found when I was calibrating initially, I got much better results from a heavy sled. This is probably mostly because this was before chain sag calculations were in the firmware, so eliminating as much chain sag as possible made it so the machine and the math lined up better. Also, with my shorter top beam, I got much more width out of the cut area with the heavier sled. I never really bothered changing that, given the scope of the upgrades I’m going to be doing relatively soon.

The Meticulous Z-Axis is a much lighter sled overall, and I’m going to see if it runs fine with just the weight of the assembly or if it will need additional weight as well.

Of the two, I would prefer wider over taller. But, of course, getting the full performance over a 4 x 8 would be mint! :smiley:

That sounds almost exactly like the type of deviation I was seeing when I was messing around with the max feedrate way back when.

For what it’s worth, my machine was built from a Kickstarter kit. If I remember correctly, the gears where of a higher quality then, but I could be wrong.

It’s almost like you’re reading my mind! :smiley: I did get the larger sprockets that you recommended in the thread I linked above. Combine that with the acceleration planning in the Due and I just might stand a chance using 2 flute tooling.

That is especially a problem for my current, shorter top beam. Accuracy drops off pretty quickly outside of the center 4’ part of the bed.

So what you’re saying is that, once again, I’m going back into testing mode? xD

What I am taking away from this is that it would be greatly beneficial to modify my frame to be able to handle up to 30" of Y offset. Maybe even more, depending on the math.

That’s interesting. I hadn’t really taken note of the minimum force before, but that makes a lot of sense. I’ll have to play around with the spreadsheet a little more and see what I can come up with. Do we have a threshold for how high is “too high” for the max force? When the spreadsheet makes the cell red? Are we in the land of speculation, and just not have enough data right now to know that?

we don’t have a lot of information here. I mostly try to make it less than the
stock frame. We currently have the max feed rate set a bit lower than the
machine can move due to problems reported at max speed, and going by reports
that a 30 pound sled had problems, I made it go red about the point that would
be a 30 pound sled on a stock frame.

but it’s a guesstimate, not a hard limit.

David Lang

Apologies for the delay in my response, my weekend got eaten up by a surprise Saturday shift. I haven’t had a chance to look at the forums until now.

I had a feeling that was the case. No worries, I was expecting when I wrote my earlier post that I would need to increase the height of my frame. I should have enough steel tubing on hand to make the risers I will need. I’ll feel a little bad cutting up my frame for it though! >_<

For Funsies, I plugged in the stock frame values (from the old CAD model):


So the number to beat is about 50 (lbs? not sure of the units here). Oddly enough, the minimum force is pretty low on the stock setup as well, although it beats my current setup.

I played around with the numbers for my new setup, and increasing the sled weight certainly helps with minimum force. I’m thinking that this will be my target frame dimensions:


This gives me a good margin in max force over the stock setup. Also, the minimum force is higher than my other hypothetical setups. Looks like I will probably be looking at increasing the sled weight to 30 lbs.

It’s going to take me awhile to get to the point where my machine is back up and running so I can do testing, but I’ll let you know when I get on it. Hopefully there aren’t too many more Saturday shifts in my future so I can focus on my Maslow.

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For Funsies, I plugged in the stock frame values (from the old CAD model):

So the number to beat is about 50 (lbs? not sure of the units here). Oddly enough, the minimum force is pretty low on the stock setup as well, although it beats my current setup.

Yes, the stock frame has high max force and very low minimum force. I think I
have it turn red just above 50 pounds force

I played around with the numbers for my new setup, and increasing the sled weight certainly helps with minimum force. I’m thinking that this will be my target frame dimensions:
This gives me a good margin in max force over the stock setup. Also, the minimum force is higher than my other hypothetical setups. Looks like I will probably be looking at increasing the sled weight to 30 lbs.

That looks pretty good. I hadn’t realized how much a higher top beam helps the
max force (by drastically impoving the angles)

I also think we need to experiment with settng the frame closer to vertical.
That will decrease the friction, which will leave more of the force available
to move the sled.

I’m working on getting the maslow at the makerspace running and calibrated well,
at that point I’m going to do testing with different linkage kits and frame
angles.

David Lang

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This is something I’m realizing now too. The spreadsheet you wrote up is a fantastic tool for predicting machine performance.

Makes sense. I have a fixed A-frame to support my bed at 15*, so I’m stuck with that angle for now. Depending on what test data comes back with angles, I can always make another A-frame, or even an adjustable one. One step at a time, though. I’ve been using my Maslow pretty regularly lately, so I don’t want it to be out of commission for too long! xD

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for testing, just put blocks under the back legs to tilt it forward. (that’s
what I’m planning to do)

David Lang

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Clever! Didn’t even think of that.

Alternatively, I’m putting leveling feet on it when I’m upgrading, so I could see if I get enough angle adjustment there.

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I started with 12.5 degrees. I noticed, when cutting the last pass on 3/4” ply, the bottom of the sled would pull up when the sled was moving up. I bumped the angle out closer to 15 and that helped. The sled is 24.8 lbs. It may be that the linkage needs to be lowered a bit.

check how much height you need, leveling feet may not be enough.

David Lang

linkage too high sounds like the problem.

That will also make it tip more on the sides.

David Lang

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@Kgoodman, how are things going with your 14’ wide, 30" offset top beam?

Woodcutter4, it worked great! Admittingly having a new baby stalled me from making a cut with it yet, but calibration worked and I can jog the full work area. You thinking of doing the same? I’ll let you know how accurate it is once i start cutting if so.

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Thanks for getting back to me! I have a 12’ top bar and I think that will have to be good enough for now :slight_smile:

I would love it if you could share a ton of pictures on here!

I’m going to build a new frame, once my METALMASLOW arrives here in Germany, with a profile similar to UNISTRUT and don’t mind to give the “large frame idea” a test … anything else I have to consider, to make it a real test scenario and can help the community to improve?

I don’t know how large you are talking about going, but one thing that we could
use testing on is different angles. in the past we had a little testing and know
that 20 degrees is to far from vertical (the sled sticks too much) and 5 degrees
is too close to vertical (when plunging, the sled moves away from the workpiece,
could be bit dependent)

does going closer to vertical let you go with higher feed rates, even in the
bottom corners?

David Lang

I designed the new frame to allow adjustments of the frame angle between 15 to 5 deg. …
our current tests tend to assume, that 11deg. is perfect… at least we could improve accuracy … our sled weight is about 12.5kg, motor distance 2952mm and distance to work area 505mm. The sled doesn’t tilt when its center reaches the edge of the working area by using bodybuilding weights of 2.5kg each. With bricks of same weight cog was different and sled tilting + its top never touched the working area…

Our new frame is currently planned to have a top bar of up to 3700mm and a total height of 2500mm with a adjustable skirting of 100mm around the work area…

Further we have planned to return back to bottom feed and introduce a chain tensioner using some springs, similar to barn door springs, but integrated in the hollow space of the top bar to achieve I.e. dust protection.

Budget for the above new frame is estimated with €250.

However, is there anything else you would recommend, or us to consider, so that the community can benefit?

I designed the new frame to allow adjustments of the frame angle between 15 to 5 deg. …

our current tests tend to assume, that 11deg. is perfect… at least we could improve accuracy … our sled weight is about 12.5kg, motor distance 2952mm and distance to work area 505mm. The sled doesn’t tilt when its center reaches the edge of the working area by using bodybuilding weights of 2.5kg each. With bricks of same weight cog was different and sled tilting + its top never touched the working area…

sorry, is this the result of testing? or where you plan to start testing?

Our new frame is currently planned to have a top bar of up to 3700mm and a total height of 2500mm with a adjustable skirting of 100mm around the work area…

could you experiment with the skirting? My belief is that no skirting on the top
is needed, the sides can use narrow skirting (50-100mm) and the bottom needs a
lot of skirting (150-200mm)

I would see how close you can cut to the edge without any skirting, then make
the skirting just a little wider than that.

Further we have planned to return back to bottom feed and introduce a chain
tensioner using some springs, similar to barn door springs, but integrated in
the hollow space of the top bar to achieve I.e. dust protection.

springs have the problem that they produce the most force when you need the
least, and the least when you need the most. weights provide a constant force.

If you want to make everything super slick, route the tension lines through the
tubes to weights in the legs (but it probably requires a lot of pulleys to do
that, having the lines just extend out past the workpiece and then drop down,
with pulley’s or just plumbing sweeps works well)

David Lang

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This is the data of the current frame we are using and our findings from testing by means of frame angle …

Currently we had been as close as 2cm to the bottom and top edge in the center area with good accuracy, but such is lost, once we are even 20cm off the left/right edge …

Thats why we decided to build a new frame with a top bar at least 3600mm and a frame height between 2250mm to 2500mm (skirting all around 100mm = 100mm bottom + 100mm top + 1250mm working area + >800mm distance to motors = > 2250mm …

Thank you for your advise … OK, we will experiment with some pulleys! :slight_smile:

Boris

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@buhlig How are your tests going with the larger frame? I’m very interested in your results. :slight_smile:

Vielen dank,

-Jeff

Hey @JWoody18, we ordered the UA Profiles and accessories, which are expected to be received next week … keep you posted in due course! Bis dann …