What can we improve in the hardware?

Hardware
81

Darren Hearn wrote:

I think the arm frame needs a shallow pocket around the motor/gearbox shaft (on the outside face). I opened-up all my arms this weekend (anticipating arrival of the new JST XH encoder boards/controller - also trying to understand more about non-uniform current demand across the arms) and discovered that a ring of the plastic had been worn away. The plastic debris has been trapped around the shaft and ground to a fine dust/paste consistency - no sign of harm, but it can’t be good to have that circulating around the gearbox’s output bearing.

It looks like there’s a retaining ring on the shaft that extends slightly beyond the face of the gearbox - I suspect that’s what’s causing the wear.

Interesting, @bar attempted to design the arms so that both halves are identical
(one fewer part number to keep track of, less chances for confusion when
assembling the arms.

Given that this resulted in the need for a belt guard, it’s not clear that it
ended up being a net win.

The following may be maslow 5 stuff rather than maslow 4.1. I wonder what
savings could be made if this symmetry was abandoned? (including possibly
putting the sensor between the halves of the arm, flipping the arm so that the
gear on the motor shaft is closer to the gearbox rather than on the other side,
possibly allowing for a stock size shaft on the motor rather than a custom
length one (especially when combined with my thoughts above about increasing the
diameter of the spool and eliminating the idler)

In the meantime, I would consider putting a washer under the motor bolts to
space it out a mm or so.

David Lang

82

To be clear, I don’t think the change I’m proposing would break the symmetry of the halves (which, I agree, has benefits … and drawbacks). Each arm frame (half of an arm) already has an inside/outside distinction - I’m thinking that the pocket would be applied to the outside of every arm frame (and would end-up as a non-functional but harmless “decoration” for the half of the frames that get used as bottoms of the arms). Let me know if I’m missing something here.

I may give this a shot, though I think any potential damage is already done in my case (i.e. at this point, the retaining ring already has a clear path through the plastic).

83

Darren Hearn wrote:

To be clear, I don’t think the change I’m proposing would break the symmetry
of the halves (which, I agree, has benefits … and drawbacks). Each arm frame
(half of an arm) already has an inside/outside distinction - I’m thinking that
the pocket would be applied to the outside of every arm frame (and would
end-up as a non-functional but harmless “decoration” for the half of the
frames that get used as bottoms of the arms). Let me know if I’m missing
something here.

on the other side, there is a bearing held in place by the plastic you are
wanting to notch away. It may be that there is enough space for a bearing
retainer lip with a larger hole in the center, that would need to be checked

I may give this a shot, though I think any potential damage is already done in my case (i.e. at this point, the retaining ring already has a clear path through the plastic).

good point.

David Lang

84

Got it - thanks for the clarification. I should probably quantify that, based on my sample of 4 arms, the pocket depth would be ~0.4 mm. It looks like that’s ~15% of the underlying feature’s thickness (i.e. thickness of the bearing support), so point taken that notching anything away would need to be checked first.

85

That is great feedback! I think that you are 100% right that the retaining clip there which holds the motor shaft on is rubbing on the plastic. Increasing the thickness of the encoder board would also fix that, but I think that we are going to need to re-make the mold for the arm part anyway since we’re adding bearings to the idler shaft so it’s easy to add a recess there.

Thanks for calling that out!

86

What is the gear pitch/shape for the motor/idler/spool? it looks like it’s
very close to 4.75mm/tooth (3/16")

I’m looking to eliminate the idler entirely, and if I’m right about this, a 103
tooth spool with an OD of 156mm looks like it would mesh with the motors in the
same position on the arms.

This spool would have an ID of about 124mm to hold just under 14.5 ft of belt
This would make the inner diameter of the arm at 104.75 (keeping the same
thicknesses of the hub and arm), or you could put BBs in between them for
bearings and go down to 94.3mm as the ID of the arm. This is pleanty of room to
put in a sleeve to hold any spindle up to 80mm, and even put another set of BBs
in there as bearings.

David Lang

2 Likes
87

I’ll follow up by saying that this is getting very close to the point where we
could hard mount a sleeve to the sled that the router slides in, and have 1-2
steppers with a longer lead screw connect to a top mounted clamp on the spindle
(with something to prevent the spindle from spinning, say either a brace and
bearing to stabilize the top of the lead screw, or a slot in the sleeve like the
original maslow had)

fewer parts overall, but the sleeve would be a large part, even if it’s built in
2-3 segments, but would simplify assembly

but not a 4.1 change :slight_smile:

David Lang

2 Likes
88

I’m still advocating for moving towards fixed arms for the belts and for those being at the edge of the carriage rather than using the router, or eventual tool mount sleeve, as a hinge pin. The math needed for calibration for this has been figured out, it’s just a matter of seeing if it is feasible to do something akin to that solver function I used in my code example in the actual calibration program.

This greatly reduces the needed complexity in the design of the arms because they would be able to have the motor mount in the center, which also removes the issue of the belt being near the gears that keep chewing them up when things go wrong, and allows those parts to be much smaller as well and doesn’t have them being tied to the diameter of the router/sleeve anymore, which was a problematic design restriction.

It also comes with the added benefit of the carriage orientation being maintained at all times, which should allow for off-center tooling, such as drag knives, and should also increase accuracy slightly, as the carriage rotating has some level of negative effect on that, though I couldn’t speak to exactly how much.

If coupled with a panel-saw-like gantry, this would hugely increase the versatility of the tool. My long term plan is to turn my frame into a hybrid, for both a panel saw and for the maslow, and to make it so I can mount the maslow in place of the circular saw. Still working out the best way to handle adjusting for thickness of material, but I’m no longer worried about the gantry interfering with the maslow after some testing I did of putting casters on my sled so it wouldn’t catch on paper for plotting jobs.

I still intend to design mounts for my arms that let me move them out to the “corners” of the carriage to test this with the existing hardware, I just shifted those plans to winter.

So it’s said, I do understand that this might be a bit much for a first revision, but I do feel like it’s something that would be a huge force multiplier for increasing versatility and reducing complexity.

1 Like
89

Carson Barry wrote:

I’m still advocating for moving towards fixed arms for the belts and for those
being at the edge of the carriage rather than using the router, or eventual
tool mount sleeve, as a hinge pin. The math needed for calibration for this
has been figured out, it’s just a matter of seeing if it is feasible to do
something akin to that solver function I used in my code example in the actual
calibration program.

I agree, keeping the arms at a constant height (and ideally the same height)
should have noticable advantages in stifness. The math should not be a problem.

one possible problem is that if they are too low, the sled will want to tilt.
This isn’t a problem when on the floor, but would cause grief when tilted.

This greatly reduces the needed complexity in the design of the arms because
they would be able to have the motor mount in the center, which also removes
the issue of the belt being near the gears that keep chewing them up when
things go wrong, and allows those parts to be much smaller as well and doesn’t
have them being tied to the diameter of the router/sleeve anymore, which was a
problematic design restriction.

One problem is that it takes a lot of space for the belt when you have a small
diameter spool. If you have a 15mm hub (given a 5mm motor shaft and thickness to
anchor the belt, you aren’t going to go a lot smaller than this) to fir the same
14.5 ft of belt requires that the outside diameter be about 95mm. fitting four
of these spools at the same height is a problem

It also comes with the added benefit of the carriage orientation being
maintained at all times, which should allow for off-center tooling, such as
drag knives

since drag knives swivel, this is not a problem for them.

and should also increase accuracy slightly, as the carriage
rotating has some level of negative effect on that, though I couldn’t speak
to exactly how much.

I think it depends on the precision. one nice thing about being centered on the
bit is that it’s more forgiving, if the tool isn’t centered and the sled rotates
under force (by the belts having different tension than expected) you can’t
compensate for it. Since belts act as springs, and do stretch over time (and
different belts stretch at different amounts), I would fear that it’s trading
one type of error for another, and it’s much easier to center the bits on the
armss.

If coupled with a panel-saw-like gantry, this would hugely increase the
versatility of the tool. My long term plan is to turn my frame into a hybrid,
for both a panel saw and for the maslow, and to make it so I can mount the
maslow in place of the circular saw. Still working out the best way to handle
adjusting for thickness of material, but I’m no longer worried about the
gantry interfering with the maslow after some testing I did of putting casters
on my sled so it wouldn’t catch on paper for plotting jobs.

if you have a gantry, then just build a corexy drive system, it’s much simpler
and much better supported.

I still intend to design mounts for my arms that let me move them out to the “corners” of the carriage to test this with the existing hardware, I just shifted those plans to winter.

let’s setup a new thread for this. I have ideas about what it would take.

So it’s said, I do understand that this might be a bit much for a first
revision, but I do feel like it’s something that would be a huge force
multiplier for increasing versatility and reducing complexity.

yep, not a maslor 4.1 change.

David Lang

1 Like
90

It is a MOD 1.5 gear, here are the parameters for it:

image
image422×330 7.78 KB

I believe that without the idler gear there is an issue with the arms not having space to rotate, but I could be wrong about that. Maybe it was just an issue of how much force it puts on the motor’s gearbox, but again I could be wrong about what they can handle.

91

I’ll be doing an MPCNC once I have a few other things sorted and make space for it. It’s just going to be smaller scale.

I also need a panel saw, and realized that I could save space by hybridizing the maslow frame, and that I’d have an easier time if I used that same panel saw gantry to float my maslow for most of the things I’d cut, if it worked out.

I don’t think it’s something that should be a default part, but if it gets figured out, works out, and doesn’t come with a pile of caveats, you get a hybrid machine and get to choose how to mount it each time you use it, because your maslow still works the default way. I’m at least going to give it a try with what I build for my panel saw when I finally get to it.

If the arms were fixed, it would also potentially be feasible to set up routing along a gantry for the belts to go out to the end, then make a 90 degree turn to the anchors, and create a core-xy system using the maslow platform. At least, it seems that way on it’s face. If it were a change in settings like horizontal/upright frame orientation to make it compensate for the difference in math, it would be another case of it working both ways. You’d still be able to pop it off the frame, take it to a random place and mount it up on any old flat surface, calibrate, and go, or mount it on the same frame traditionally, with the gantry slid out of the way or removed.

I understand that just doing a core-xy would be easier, and why it would be more suited. I could sum my overall thrust here with: I think the maslow might be able to do both things, and kinda wanna find out.

92

The idler doesn’t affect the amount of force needed, all it does is relocate where the motor is. If you started with the spool size and tried to have the motor against the current spool, it would have been very tight to the router and limited how close two arms could be to each other.

This keeps the motor in the same spot, but expands the spool to mesh against it directly. It results in a 103 tooth sprocket with the outer diameter being 156mm. to hold 14.5 ft of belt, the ID of the belt portion of the spool would be right about where the OD of the current spool is.

image
image1246×1090 165 KB

This image shows two belt paths (starting tangent to the encoder wheel, and ending tangent to the inner and outer limits of the spool, the dotted lines go direct from the spool to the encoder wheeland the solid lines show an idler sprocket (a standard gt2 idler with a bearing and a 3mm shaft) that moves the belts well clear of the vertical supports, but in both cases, there may be a need to modify the bearing shaft holders to clear the belt or the belt idler.

I think it would be quite hard for the belt to get into the gears with either approach, but almost impossible with the idler

1 Like
93

But when the next arm stacks on top of this one the motor will pass through the spool :cry:

94

yep, you are right, I missed that.

darn, it looked so good too. I’ll have to do some tinkering to see if I can figure anything else out

95

Bar looking at the schematics I see that gpio 39 is assigned to the Ethernet LED Controller, Is it safe to assume that on the JST version, this pin is free to assign the Motor1’s direction pin to? Thus freeing up gpio 38 for aux2?

image
image1148×136 59.3 KB

1 Like
96

A couple little ideas for the sled:

Some polar markers (too, bottom, left, right) on the sled to make setting home at 0,0 on something squares like a 4x8 a little easier. It could be subtle, just notches. I used a paint marker on mine and when I remember them they help heh.

This is a stretch perhaps but maybe a bigger ‘window’ to the material below the bit, either as a bigger opening or maybe even a plexiglass disc so we can see the murder floor without sticking our head up there with a cell phone light or trying to pry but not pry the sled up a little to see what’s up under there.

1 Like
97

Same same

98

Just wanted to mention that I am eagerly following the discussion from the sideline, and I hope that there will be some sort of overview of what the improvements are between the various interations.
Would be nice to have like a shortlist of what parts to order.

Also:
Is there a particular reason why the sled is not metal?
Would a steel sled assembly be more expensive?
Like some others I had the rod supports crack, even though I was very thorough about making sure everything was in place before tightening the screws. Not against having some plastic parts, but there might be some structural benefits to having a few more steel parts.
A steel sled would also take up less space in the box, leaving more room for other improvements, do not think there would be a significant difference in price compared to molded plastic.

99

Thunderscreech wrote:

This is a stretch perhaps but maybe a bigger ¡window¢ to the material below
the bit, either as a bigger opening or maybe even a plexiglass disc so we can
see the murder floor without sticking our head up there with a cell phone
light or trying to pry but not pry the sled up a little to see what¢s up under
there.

Bar has commented that it’s so small to improve the airspeed and improve dust
collection. IT being so small sometimes makes it hard to use other spindles.

David Lang

1 Like
100

Would the sled be cast steel? I think that ends up being pretty expensive. If it were a steel sheet that might be doable price wise, but we couldn’t have many of the features that we use