Precreasing grids

[chris_t]

What with box-pleating, tesselations and pattern grafts, I reckon most of us must have folded a fair few grids in our time. I just wondered if anyone had any tips on how to do this accurately and/or quickly (obviously the two may not always go hand in hand). Not the most exciting of topics, I admit, but one relevant to most of us.

My tip would be to alternate horizontal and vertical sets of creases - i.e. do horizontal quarters, then vertical quarters, then hoirzontal eighths, vertical eighths, horizontal sixteenths etc. I find if you do all the horizontal ones first, the corrugation effect it has on the paper makes the vertical ones hard to line up.

Do people make each crease separately, or sometimes crease multiple layers at once - and if so, how many layers before creep becomes a problem?

Do you make an effort to ensure that creases are broadly in the right configuration (mountain vs valley) at the precreasing stage to minimise reversals later on, or is this more hassle than it is worth?

[Baltorigamist]

I take the same approach you do with precreasing--fold one set horizontal, then one vertical, then subdivide horizontally, etc. So I only crease one at a time.

Also, I try to have as many creases in the correct parity before starting as possible. It takes longer, but it's worth it long-term when you''re four hours into a collapse and one pleat doesn't want to fold right.


I also have a tip for anyone folding a really weird-numbered grid--find the number of divisions, prime-factorize that number (yes, it's the math you learned in 5th grade), and start with the largest number first.

For example, 56=7*2*2*2. So fold 7ths, then halves, then halves, then one more set of halves.


Anyone have tips on keeping the paper somewhat flat when creasing through perpendicular pleats? That almost always screws me up no matter what paper i use.

[booggerboy]

Also -

Anyone use a ruler to help folding the creases?

When pre-creasing thirds do people do this by eye, using theorem, or with ruler? (generally if I have to crease thirds in the middle of a model (e.g. ancient dragon) I will do it by eye).

I agree with the idea of creasing one set at a time in each different direction.

Last question - how do people deal with later creases when gridlines have been completed already? I tend to fold these in sections along the length rather than one long crease.

bb

[Baltorigamist]

Not if I can already find the divisions by folding, and if I can't, I use Reference Finder.

Whether I eyeball or use a theorem is really a case-by-case issue. If I'm dividing a sheet in thrids then I just pinch at 1/2 and connect to an opposite corner. But if it's a long, blunt flap/edge like in the Ancient Dragon, I'll just eyeball it. I can usually get about 97% accuracy on the first try though.

What do you mean by 'later creases?" Non-pleated sections with the grid overlaid on them, or what?

[Flame_Kurosei]

I'm guessing he means the creases on the cp that are used to make the actual model after folding the grid.
I try to see if there are any large creases that can be folded first, and then work on the smaller ones in lowering size. This is how I work grids as well.
I tend to use papers that are easily reverse-foldable, such as kraft or drawing paper, so I rarely have a problem with mountains and valleys if they aren't configured correctly on the precreasing.
However, I do alternate between mountains and valleys when precreasing though, not for correctness but mainly because it's easier/faster to pleat mountains and valleys than folding all mountains and then all valleys.

[GWB origami]

i pleat the paper. it is not the most accurate but it is probably the fastest.

[Baltorigamist]

I'm guessing he means the creases on the cp that are used to make the actual model after folding the grid.
I try to see if there are any large creases that can be folded first, and then work on the smaller ones in lowering size. This is how I work grids as well.

I just try and find the best way to arrange the flaps to flatten the base, and then I shift them as needed for shaping.

However, I do alternate between mountains and valleys when precreasing though, not for correctness but mainly because it's easier/faster to pleat mountains and valleys than folding all mountains and then all valleys.

Do you have a special tecnique for flattening the paper after one set so you can make the perpendicular pleats, or do you just try to work around the curves?

[tryingtofoldsumthing]

Hm, i have always folded all the horozontal creases first, then the vertical, but alternating makes sense and would save me alot of trouble! learn something new every time, thanks so much!

I also use reference finder, it can be very accurate and useful! As Baltorigamist said, i also use the half-mark-pinch-to-corner method for thirds. If im eyeballing it though, i pinch two creases and move them around until they match up. I then do the same in another place and connect the two creases. it works well but weakens the paper a bit.

[Baltorigamist]

When I eyeball it, I just bend one edge until the folded part looks about equal to the exposed nonfolded part. Same with eyeballing 5ths (except a 1:3 ratio) and others.
I remember I used to love folding Tamatebako cubes (3rds with 2 diagonal cuts in the center) and I didn't know the half-mark-to-corner method, so I would eyeball it all the time and I got a lot of practice.

[Sunburst]

I pretty much do like baltorigamist said. I always use reference finder for weird divisions. 'Eyeballing' is not a very good idea as it will be very noticeable the bigger your grid is.

Other than that, I noticed that folding the creases from the center of the paper and then work towards the sides helps with the accuracy. The reason for this is that every crease seems to shorten the square ever so slightly. So the more creases you have between the reference line and your current fold, the less accurate the division will be.

[GWB origami]

just discovered the wisdom of that. i was folding an 18x18 grid and was eyeballing it and it came out horribly

[booggerboy]

When I was talking about later creases I really meant smaller grid divisions, but I liked the answers.

I agree that creasing out from the middle seems more accurate, and that eyeballing can be hit and miss.

Any thoughts on precreasing at 60 degrees? The extra set introduce more inaccuracy to my attempts at gjerdes ' book...

Bb

[GWB origami]

use a protractor. that's the only thing i can think of.

[Baltorigamist]

I precreased a 60deg grid once with no problem. I just fold it normally, aligning creases with others. The only difference is that the odd angles increase the difficulty somewhat.

[Sunburst]

Another tip of mine would be to make a crease perpendicular to your grid and fold in relation to it. It's a good way to get parallel creases.