Metal Top Pantograph kit available

But can find one that can be made to fit :smile:
How many four-bolt patterns have three different lengths of bolt and at least two different kinds of nut?

The washers are there for three reasons

  1. to keep the arms from rubbing against each other as they fold against each other,reducing the friction between the parts

2.on the outside to give a good solid surface to go against the sides of the arms rather than the possibly uneven nut and bolt heads, and eat up space so that the nuts can be tightened properly (I couldn’t find any bolts with just exactly the right amount of shoulder, so I got them a bit long and the washers make up the difference)

  1. in a setup like this where the horizontal arms are interleaved on the center wood spacer, to eat up space between the arms (in the next set I do, I may make a pair of spacers to include in the kit, eliminating this need)

for reason 1 above, nylon or other slick spacers work better than any metal that may eventually corrode in contact with the stainless steel

for the spacers, anything works.

I love all the pictures.

since you made the height of the arm from the sled 3 3/16 and the horizontal arm is 3/16, cutting down a 2x4 just a bit to make it 3" (or 3" minus the thickness of two washers) would work well for the mount to the sled.

There’s no need for the pantograph mounts to go all the way through the sled (and with a stock size sled, this put one right on the far edge)

but cutting the blocks on an accurate machine makes the rest of it really easy because you are just lining up the holes.

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I’ve had two reports of the packages being damaged in shipment to the point of loosing things out of them. In one case it was just some washers, in the other case it lost one of the long arms and almost all the small stuff.

Were there any other people who had trouble with their kits?

Mine arrived sealed up, no problems at all.

Thanks!

I think my motor mounts are roughly in the same place as the original design. I made a completely overbuilt steel tube frame for my Maslow. I can’t guarantee that it will necessarily match up with a normal machine.

For reference:

Quick view of the frame as I was test fitting it.

View of the motor mounts. I wanted as much adjust-ability as possible.

Mostly finished machine. This was just when I finished getting it built, and hadn’t even made my first circular sled.

Agreed, there isn’t a need for through bolting. I wanted to make the sled fairly easy to assemble, I like when I just have to bolt things up. I got pretty good results as far as accuracy with the original sled. In the middle, it was probably ±0.5mm, mostly due to the bit deviating a little as it moved.

Further updates:

Got a picture of the washer stacks I used:

I may end up switching out the literal washer tower on the center mounting points for sleeve bearings or some sort of bronze risers. At least that way it’ll look a little more intentional.

I also took the sled back off the machine and moved the weights down a little. After running it a little bit in the previous configuration, it seems like I want the sled to be a little bottom heavy.

IMG_20171028_155101

I also ran a file over the attachment points for the chains. When I hooked everything back up, it didn’t catch like it did in the previous video. Still not sure if that was because of the twist in the chain or not enough clearance. If it comes back up, I may try to clearance it a little more and maybe even give it some silicone lubricant.

Quick video of one of my calibration tests:

So calibration. Do we have settings yet for what we should put into Ground Control? I figure that the “vertical” distance from chain to bit is 76.2mm, but I’m not sure what to use for distance between mounting points. Isn’t the point of the pantograph to make that value vary depending on where the sled is on the bed?

On the original sled, I would change the distance between mounting points to dial in the X/Y accuracy of the machine. So far, I’ve noticed that I can do the same with the pantograph, but I’m not sure if that level of accuracy will hold across the entire machine.

I wasn’t able to finish calibrating it this weekend, not enough time in the day. I hope I can get it to where I’m happy with it this week.

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Switch to triangular kinematics and you only give it one number (and it will find that through calibration) should be either 5.25 or 5.375 in

I did enable triangular kinematics., but now I think I was looking in the wrong place in the settings. I made the change in the advanced settings tab but then went back to “Maslow Settings” tab to change the values. Weird that I saw changes in calibration when I changed the other settings.

I need to change that value to 5.25" (133.35mm) or 5.375" (136.525mm)?

Yes.

Extra text tp satisfy the 20 char min

last week’s update also added support for triangular kinematics in the built in calibration process so if you want to keep it simple you have that option. If you do the built in calibration system I would love to hear your feedback because it’s new and I am sure there are ways we can improve it.

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Glad to hear it! I’ll have to update the firmware and Ground Control, but I can give it a try and let you know what I think.

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Finally got back in the shop! I was able to dial the accuracy of the machine near the center:

0.52mm off. Pretty close, but I’d like to get it closer. 136.525mm turned out to be the closest value. I may try to tighten the tolerance up a little more when I get the chance. I also would like to test the accuracy at the left top, left bottom, right top, and right bottom to see how well my calibration holds up across the bed.

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I’m looking forward to your test results. The theory is that things should be very good except near the bottom corners (where things may end up off by up to 1mm due to chain sag)

But in theory, theory and practice are the same, in practice they are not

so I am very eager to see your results.

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So unfortunately I didn’t get very good results. I think I know why and I believe I can fix much of my issues. I’ll let the video do the talking:

My takeaway from this is that I need to add weight to the sled. I have not weighed my sled yet but even by my calculations its at 21lbs, which is the same as the stock sled with only 1 brick. I made my weight system so I can easily add weight, I just need to make a few more bars. I am fairly confident that will take a lot of slop out of the chains. I may also modify my riser setup so that the linkage nuts don’t bind at the lowest corners of the bed.

Right now I have >0.5mm tolerance in the center 2’x2’ of the bed. Out to 4’ left to right its closer to >1mm. The top and out to 6’ is somewhere around 2mm, and beyond that its useless. You can actually see in the farthest out tests that the cut “drifts” towards the slack chain, making me think this is an issue with weight. So I have about a 3’x4’ area in the center of the bed where my cuts are acceptable. For my current projects, that is okay, but I will be improving this. I would like to get 4’x6’ if that’s possible. I also haven’t tried to cut too close to the fence, as it’s a 2x4 and it sits proud of a 3/4" sheet of plywood. I need to make a plywood fence to fix that.

Loosing 8" of motor spacing isn’t helping either. I really wish I had more space for the machine, I would extend the motors as far out as possible to get better results across the entire bed.

As usual, the to-do list grows. At least I enjoy doing the work :smiley:

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that does look like too little tension on the chain, so adding weight should
help (tilting to closer to vertical may help as well)

I didn’t quite get the question you were asking as you rotated the sled.

David Lang

"i would extend the motors as far out as possible to get better results across the entire bed. " Wouldn’t that increase the chain sag near the edges as the chain would have to be longer? The best option for optimal results seems to be repositioning the work piece near the center

It would mean that there is more chain on the slack side, which would increase
sag, but it also means that the chain on the other side is not as close to
vertical, which means that more of the weight of the sled is available available
to apply force to the slack side and that makes FAR more of a difference than
the added length.

David Lang

The nylock nuts on the back side of the linkage are colliding with my plywood risers. I was wondering if that’s because my machine is smaller or not, but it’s something I will be fixing by changing my riser setup to add in some clearance for the nuts.

Right now positioning all my cuts in the center of the bed until i can correct the chain sag issue. The results are good enough for my needs:

However, when I move and have more space for the machine, I will increase the distance between the motors. That will be me better results across the entire bed as @dlang mentioned above.

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ahh, I was expecting a much narrower riser (a 2x4 on edge), I didn’t think about
that.

David Lang

It fits the Maslow very well that M-shaped linkage.