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Metal Top Pantograph kit available


#81

No, but there is some force pushing them together. From my tests with this design this is one of the biggest (and easiest to fix) sources of compounding error. If those two points move together at all then the linkage shape is no longer a parallelogram. If the linkages are not a parallelogram then the chains are not tracing a concentric circle around the bit and you lose accuracy. Keeping the sled attachment points on the sled the same distance from each other as the pivoting joints on the vertical bars is important.


#82

I’m not doing this because a 2x4 on edge isn’t strong enough, but rather to
simplify the assembly (no need to worry if the two holes are the right distance
from each other)

It also helps that I think I figured a way to get them done for vitually nothing
(by nesting them inside horizontal arms so that the same cut that cuts the
horizontal arms apart also cuts the side of the central bar)


#83

I am tempted to try a ‘click-on’ system like speaker grills.


Guess if I put enough, it should have no play and since the force is vertical little chance of comeing off by it self.
However, first I will make a 2x4 with spacers to determine the optimum hight, then run the link-kit for a while to observe the moves. After the primitive proto type is tested, I will go for an advanced version.


#84

Yeah, I saw how you nested them like that (well I didn’t “see” it, I deducted that was what you are doing based on the shape of the horizontal arms). That’s a good idea. Sharing cut lines saves a lot of time.

As far as cut-time goes, nesting them like that only costs “virtually nothing” if you were not sharing cut lines before, otherwise it’s still an extra cut. The cut distance (the length the laser travels while on (which is generally what you pay for)) is not very different between three full width bars next to each other vs three bars with a nested center. It does save some material but I doubt that’s where the bulk of the cost is.

Here’s how it shakes down with the 7" bars:


I think in large enough quantities the savings in material could be worth it.


#85

Yeah, I saw how you nested them like that (well I didn’t “see” it, I deducted
that was what you are doing based on the shape of the horizontal arms). That’s
a good idea. Sharing cut lines saves a lot of time.

that was also a clearance issue, trying to allow the horizontal arms to move up
to 80 degrees without hitting the bolts holding the horizontal arm down or the
support below it was hard, doing that offset let me make the support
significantly stronger

As far as cut-time goes, nesting them like that only costs "virtually nothing"
if you were not sharing cut lines before, otherwise it’s still an extra cut.
The cut distance (the length the laser travels while on (which is generally
what you pay for)) is not very different between three full width bars next to
each other vs three bars with a nested center. It does save some material but
I doubt that’s where the bulk of the cost is.

based on the pricing I was given, I don’t think they were sharing much, I’m
waiting for updated quotes now.

when I did the last batch of 6 (3x5" arms, 3x7" arms), it cost me $144 and I was
told about $20 of it was the SS. I asked about doing alumumum and it would have
saved me ~$24 (more from decreased cutting costs than material costs), but then
anodizing the aluminum to keep it from corroding would have cost $95)


#86

just got the word back that this shop can’t cut common lines :frowning:


#87

Bummer! I don’t understand why though… I suppose there could be a software issue but if you have a $50k+ metal cutting fiber laser I would hope and expect that you could cut shared lines. That’s crazy.


#88

I could understand their software getting confused if you make two lines
overlap, but I avoided that and made sure there was only one line.

I’ve now asked if I make tabs, can they then cut slits in the resulting solid
piece (and how much material I need to leave at the ends)

not being able to share lines results in ~+30% cutting time.


#89

I might know a guy if you want me to look into it. What is the material your using?

Thank you


#90

I would love to get other sources (and for that matter, if someone else wants to cut and distribute these, go for it)

this is the file I’m looking to get cut (ignore the trapazoid off to the left, the two large blocks of arms are what I’m trying to cut)

pantograph arms-packed.dxf (303.9 KB)


Pantograph/linkage DXF for laser cutter
#91

I know a guy that uses industrial lasers for a living on the east side of the US. I would need to tell him what to cut it out of. Can you tell me what you are currently using?

Thank you


#92

sorry, I had that in the e-mail I was composing, but missed it when I replied on the forum to make sure that the attachment works.

I’m cutting them out of 3/16 stainless steel. If the price was right, I’d seriously consider using aluminum and then anodizing them (potentially a smoother and harder surface than the unfinished stainless)


#93

I’ll reach out to my friend. I’ve known him for a few years and supported him in 3D printing. I knew what his day job was but never had a need for his services. I’ll get his input on materials and find out if they do bending as well. If so perhaps they could become a source for all the brackets used in the Maslow. It might not be until next week I have answers back.

Thank you


#94

Could you treat the two triangular holes as objects, like the circles? Then the pattern to cut would be the two outer arms, four circles and two triangles. This would greatly reduce the common lines…


#95

@blurfl that’s more or less what I did.

There are no cases of multiple lines at the same place in the drawing


#96

I guess I misunderstood ‘common lines’. Too bad, it sounds like it could have saved some cost.


#97

I guess I misunderstood ‘common lines’. Too bad, it sounds like it could have saved some cost.

I’m hoping they misunderstood as well, it looks like they took today off, so
I’ll have to follow up with them tuesday

logically it’s common lines, but I recognized that CAM software can get confused
by this, so I made it so that it only had one line at the common point


#98

For me the difference between cutting parts (for the 45˚ kit) with common (or shared) lines vs cutting each shape completely is about 2x. Due to a software problem I had to cut the first 20 or 30 kits with each part as a separate piece. It was terrible; thankfully I solved that early on and it was just the first few kits!

They tell me time is money… so in that respect common lines really can save on cost.


#99

This is what the latest iteration will look like (assuming I can find someone who can cut it)

top pantograph-center-guide.pdf (369.8 KB)


#100

David, I made an alternate version of the Fusion 360 model of the top mount system based on your onshape model:

http://a360.co/2CQXNQu

Is this the linkage kit you’re sending Gero? The horizontal arms look quite a bit larger than the one I have on my machine.

I really like that center support. I may try to machine one of those myself, it seems like it would make the assembly much stronger! :smiley:

The updated sled model (for those interested):

http://a360.co/2jXD7y0

Actually, its the same one I’ve been posting. The model updates itself :wink: