Clamp Caliper - Long

Clamp Caliper - Long Version (7 inch/180mm printable caliper w/ clamp)

Features:

- Measures up to 180mm by 0.1mm (0.004 in.) increments or up to 7 inches by 0.0025 in. increments--depending, of course, on the accuracy and precision of your printer and printed material shrinkage. (See below for how to adjust the accuracy if the first print is not to scale.)

- Measures outside lengths with external jaws (bottom-left)

- Measure inside lengths with the internal jaws (top-left)

- Measure depth along an edge with the left ends of the ruler and slide

- Measure the depth of a hole with the slide's depth probe and the right end of the ruler

- Has measurement marks to the very end of the ruler, allowing for a full 0.1mm/0.0025in precision all the way to 180mm/7in.

- Has an integrated clamp to hold a measured position for reading.

- Has a printable cover, in case you don't like the pointy tips stabbing your leg while in your pocket or you just want to protect the tips of the jaws and depth probe. The cover has a small retention post that inserts into the back of the slide to keep it semi-attached and moved out of the way for taking measurements, but it can also be completely removed and reattached later.

Clamping:

A compliant mechanism clamps the slide in place while moving from an item measured to a viewing position, helping to ensure you read what you measured. Squeeze the slide to clamp it in place against the ruler. Press the lower-right corner of the slide to unclamp it. (See the video for a demo.) The first time you operate the clamp will be the hardest. It might even help to use pliers to engage it the first time. After it has been engaged once, engaging and disengaging should be much easier.

Readability:

You can print the Clamp Caliper on a one-color printer. Legibility can be improved by pausing the print and switching to a contrasting color at the base of the markings (just below the top layer), and then switching back for the top layer--like the white caliper with black markings in the photos. Or just print the top layer in a contrasting color--like the blue-on-orange, or black-on-white calipers in the photos. If you have a CMS or other material switching system, printing a contrasting layer should be simple.

Accuracy:

To adjust for shrinkage of the printed material as it cools, print out the slide, then measure it with a trusted ruler or caliper. Alternatively, in your slicer, you can adjust the scale in the x-direction to compensate for any discrepancy and reprint. For example, if your test print measures 79.2mm between the 0mm and the 80mm marks, you will want to reprint it slightly longer on the real print. To do this, set your x-scale in the slicer to 80/79.2, which is 1.01 or 101%.

Functionality:

If the slide is too tight or too loose, it can be scaled up in the y direction (default orientation) to adjust. Alternatively, the ruler could be scaled down in the y direction.

Pressure Ball:

The clamp on the slide includes a separate "pressure ball" object to allow for adjusting the grip of the clamp mechanism. If the clamp mechanism is too tight or too loose, the position of the pressure ball can be adjusted. Viewing "objects" in your slicer should allow you to see and select the pressure ball more easily. Moving it 0.1mm in the y direction will increase the clamping force, while moving it in the negative y direction will decrease the force. Some slicers see the small pressure ball and think it is at the wrong scale when importing the slide. If it asks if you want to adjust it or use different units, answer "no," or you will get a gigantic ball along with the slide.

Settings:

Nozzle 0.4mm

Layer 0.2mm

Line Width 0.4mm

Wall Generator: Classic (I generally use the Arachne wall generator, but it does not do a good job on the small tick marks on the ruler and slide.)

To adjust for filament shrinkage, I found it best to account for it in the filament settings. These are the shrinkage values I found to work:

PLA Shrinkage (XY): 99.8%

PETG Shrinkage (XY): 99.7%

Just check after your first print. Different materials, brands, and even batches may have different shrinkages.

Instructions on use of these vernier calipers:

See the instructions on the pocket-sized version of these calipers in the remix link. 

Why Print a Caliper?

There are lots of calipers. But I have some problems with most of them that spurred this creation. The first is that, as an American, I need inches and millimeters. I relate to inches. But mm are more useful, especially for 3D printing scales. While I relate to inches, most inch calipers have fractions of inches down to 1/128th of an inch. I don't relate to 1/128 of an inch. I relate to 1/16 of an inch, but any fraction smaller than that is not something I relate to. Besides, have you ever tried to figure out what 128th of an inch you are measuring on the vernier scale of one of those calipers? It's way too hard. Besides, as an engineer, I relate much better to thousandths of an inch, as in 10 thousandths (fairly loose tolerances or 5 thousandths (fairly tight tolerances). Turns out that 1/128th of an inch is about 0.008 in. or 8 thousandths of an inch. That's not a common measure. Five or ten thousandths is much more useful. This caliper fixes that problem.

The second problem is really the bigger problem for me. I have a lot of calipers. A few large, metal ones, and many plastic ones of various sizes and qualities. The metal ones have a set screw to lock in the measurement. The cheap (but handy) plastic ones don't. Stiff-sliding calipers make it hard to slide the jaws to the right position to accurately measure an object. Loosely sliding calipers make it easier to get the jaws in the right position, but then I often feel like the position may have slid before I get it into position to read the measurement. I often find myself re-measuring to see if it slid out of position or not. I sometimes adjust my grip to grab across the ruler and the slide of the caliper to limit any sliding as I move it into the reading position from the measuring position. But what if I could easily slide the jaws into the correct position and simply clamp it there, then move it into the reading position, confident that it's remaining in the measured position? That's what the compliant mechanism clamp does on this caliper. With your thumb in the right position, slide the jaws around the object, then with a simple squeeze of the thumb, the slide clamps onto the ruler, securing it while you read the measurement.

I've also found a lot of hit and miss with plastic caliper accuracy. I should just use my high quality metal ones, but I measure in different places, on a regular basis. I measure at my computer when I'm modeling something in CAD, and I need to measure parts that are going to work with it. I measure things at my 3D printer, which is upstairs in the craft room. I measure stuff in my garage, in my car, and all over the house when I'm contemplating modeling a 3d part to do a particular thing. So I've surrounded myself with cheap plastic calipers from Temu/AliExpress, which are neither consistent nor accurate. With this, I can make it as accurate as I want, and as consistent as I want.