1/2 Size (48”x48”) cut area frame design needed

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Hi guys!
Apologies if this has already been discussed somewhere.

I am putting together my kit, but due to space limitations, I need to make my cat area 48” x 48” instead of the standard 4 x 8”

Is there an existing frame design for this? has this already been done a million times? Is this not recommended, not accurate?

Also, since I am going for smaller pieces and accuracy/detail. I’m going to be reinforcing @ squaring up my frame with unistrut.

Another space evening requirement of mine, is to have the assembly attached to the wall, and lay flat when not being used. I have already lined my entire wall with OSB for mounting surface.

I’m just reaching out to the community so that I can hopefully Make my mistakes on paper before hand.

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Actually only a handful of people have done this surprisingly.
Geometry of a square ratio cutting area is actually more favorable because it avoids the extreme edges of the sheet, which are harder to get accurate.

You can just use the regular frame with 10’ top cross bar and 4x4 cut area or if you really need the space you can probabaly use something as small as a 6’ top motor mount
8’ top motor mount would be a good compromise IMHO.

above post is probably most detailed plans for 4x4.

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look at the spreadsheet at

change the working area size and top beam dimensions to what you want to try and
you can get an idea of if it will work as well as the stock frame.

David Lang

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Thanks David !

I’m actually just starting to build my custom frame now. To be honest, I’m new to CNC, so these numbers I’m looking at don’t make much sense.

What are good vs bad values ?

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I’m new as well. I opened the worksheet and it mentioned something about green cells, but there weren’t any, so I colored some I thought should be green that had to do with the second machine size for comparison. Based on my basic read and understanding, you want minimum angle to be larger than 0, likely 10-15 degrees and you want the maximum angle to be less than 90, probably 75-80 and lower is better. As far as maximum force, you probably are fine at up to 40. The stock system has a min angle of 9.5, a max angle of 80.5, a min force of 3.5, and a max force of 34.25. I’m going to shrink my frame to fit in front of my car in the garage for the winter, so I’m going with a 94" motor spacing at a height of 2’ and a working size of 4’ x 6’ which will give a max force of 22 lb with angles min 16 and max 81. If I understand it correctly, this should work, but I don’t know if there is a desired force and if have the right idea for the angles. Maybe someone will correct this or provide some insight.

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focus more on the force than the angles

if the force is too high, you have trouble in the top center (and wear out the
gears faster)

if the min force is too low, you have trouble in the bottom corners

try to meet of beat the stock system :slight_smile:

David Lang

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Thanks again David.

In your opinion, what are the “Ideal Numbers” for a 48" x 48" work area ?

If I could build the perfect scenario.

also, when designing, and laying out my tool paths, is more acurate to work left to right for example?

I keep hearing that the “problem area” are top center, and bottom corners.
I also hear that the square cutting area is actually more desirable to combat these problem areas.

Thanks again for all your help!

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Thanks again David.

In your opinion, what are the “Ideal Numbers” for a 48" x 48" work area ?

there is no ‘ideal number’, it’s all a trade off for size (horizontal and
vertical)

also, when designing, and laying out my tool paths, is more acurate to work left to right for example?

no.

if you are cutting a slot through new material, left right doesn’t matter (up
down may)

if you are cutting to widen a slot, then direction matters, but it’s climb cut
vs tradtional cut, not up/down/left/right

I keep hearing that the “problem area” are top center, and bottom corners.

yes, the top center has the most tension on the chains (and most load on the
motors) so if you have any problems with power, this is where it will show up

the bottom corners have the least tension of the far chain, so if you have too
much tension on the slack side of the motor, it will show up here. This is also
where chain sag is going to be the worst. This is also where you have the least
force to move you away from the far motor, so your max cutting speed is less
(and if you are going to have the sled stick, this is where it will happen)

I also hear that the square cutting area is actually more desirable to combat these problem areas.

no, it’s just avoids the problem areas on a standard size machine, if you narrow
the machine, you will still have problems in the bottom corners of your square
machine.

the wider the machine, the more force is available in the bottom corners (and
the higher the force required in the top center)

the taller the machine, the less force is needed in the top center (and the less
force is available in the bottom corners)

David Lang

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If you make the machine taller (set the motors higher), is it assumed that the angle is steeper for the piece being cut? If I make the front leg longer, is it assumed I will make the back leg longer as well and keep the same kicker and thus move the angle more towards 90 with the floor? Is that how the weight of the sled can increase without an increase in force in the spreadsheet when the motor height is adjusted?

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when the motor hight is higher, the angles to the top center are further from
horizontal, so the motors spend less effort pulling against each other, so the
tension is less.

however, this also makes the angles to the bottom corners closer to vertical, so
more weight is on the chain to the near motor, and there is less tension on the
chain to the far motor.

similarly, if you just move the motors further apart, the angle to the top
center gets closer to horizontal and the tension goes up as the motors spend
more effort pulling against each other, but the angle for the bottom corners
moves further from vertical and so there is more tension on the far chain, and
better control of the sled.

these are not linear changes, so you can go both higher and wider and end up
better in both areas.

going to a narrower work area is the same as moving the motors further apart in
relative terms

David Lang