Machine Stitching Accurate Curves

[friquant]

How to develop the skills to accurately match curves? (You know, like a motorcyclist on a mountain highway)

Attached is an image of my practice session. A paperboard box with a smooth curve drawn on it with ink, then my "follow the blue line" exercise with the triple-feed upholstery machine.

While I ENJOY keeping the motor spinning the entire time, and taking the curves at slow, continuous speed, when practicing this way I notice that any time the outer toe is touching down, the paperboard tends to pivot about the rear (heel) part of the outer toe. Since the heel of the outer toe is NOT concentric with the needle, this leads to a couple of side effects.

Side Effect A: Any rotation of the paperboard while the outer toe is down  not only changes the direction of motion, it also moves the current position  to one side or the other.

Side Effect B: Any rotation of the paperboard while the outer toe is down increases the stitch length because in addition to the forward motion of the feed, it now has the additional lateral motion from my rotation pivoting pivots around the heel of the outer toe.

[kgg]

2 hours ago, friquant said:

How to develop the skills to accurately match curves?

Maybe adding a speed reducer would help????

kgg

[Scoutmom103]

Depending on how thick the leather (i.e. material) is, you might need an industrial chain stitch embroidery machine that uses a single needle and thread.    Meistergram Embroidery Machine, Singer 114E103 .     Check out Youtube     "Chain Stitch Embroidery" 

 

 

ChainStitchEmbroidery - YouTube

[toxo]

I don't think my brain can process this properly but I do know that the distance between two points on a curve is different compared with the same two points on a straight line if you are manipulating the leather by hand. The best machine I've seen for curves is a wheel foot machine rather than a walking foot.

 

Edited February 11 by toxo

[friquant]

11 hours ago, kgg said:

Maybe adding a speed reducer would help????

kgg

The current setup goes 110 stitches per minute at its lowest speed. That's using a servo motor and a 45mm pulley on the motor instead of the 75mm pulley it came with. In the tight corners I've been letting off the gas to rotate with the needle down.

[friquant]

3 hours ago, toxo said:

I don't think my brain can process this properly but I do know that the distance between two points on a curve is different compared with the same two points on a straight line if you are manipulating the leather by hand. The best machine I've seen for curves is a wheel foot machine rather than a walking foot.

 

Wheel foot---that's cool! With the wheel directly to the side of the needle, it appears that turning the material continuously while the motor is ticking over would be consistent in "going where you point it". I could imagine the stitch length being longer for a left hand curve and shorter for a right hand curve since the needle is offset somewhat from the wheel&dog. Not that I'm planning to get a wheel right now, this is my first heavy duty machine and I'm still learning what I can do with it and how to drive it accurately

[kgg]

22 minutes ago, friquant said:

Wheel foot---that's cool! With the wheel directly to the side of the needle, it appears that turning the material continuously while the motor is ticking over would be consistent in "going where you point it".

A wheel foot will not work with a walking foot machine. What machine are you using?

kgg

[friquant]

8 hours ago, kgg said:

A wheel foot will not work with a walking foot machine. What machine are you using?

kgg

I'm using a Pfaff 545.

[Cumberland Highpower]

That's mostly the nature of unison feed machines unfortunately.   

You're turning your work while the outer presser foot is down, and your center is anywhere other than under the needle.

Unison feed machine basically suck for leather work, but they've become the standard as they can do about everything. Leather, nylon, plastic, etc.  

You could try to train yourself to turn your work on sharp curves while the outer presser is still up, and the needle down, that might help some.  You may also want to check and see if your inner and outer foot lift is balanced. Maybe your feet don't sit square against the needleplate?  You may need to hone on the feet to fit better, more squarely.  Also try an open toe inner foot if you haven't.

Roller feed are good for tight curves and give great visibility, but really are only good on leathers that don't mar up.  They'll leave knurled tracks on top or a bit of a trough, and pretty heavy feed dog marks on the underside.  That's why they're mostly used for shoe/boot uppers.  I have a couple machines set up with large rollers that have rubber covered wheels, for visibility mostly.

Edited February 12 by Cumberland Highpower

[Cumberland Highpower]

On 2/11/2025 at 6:21 AM, Scoutmom103 said:

Depending on how thick the leather (i.e. material) is, you might need an industrial chain stitch embroidery machine that uses a single needle and thread.    Meistergram Embroidery Machine, Singer 114E103 .     Check out Youtube     "Chain Stitch Embroidery" 

 

 

ChainStitchEmbroidery - YouTube

That type of machine usually brings top dollar, might be out of his price range?  3x the cost of his PFAFF?

Edited February 12 by Cumberland Highpower

[friquant]

On 2/12/2025 at 7:33 AM, Cumberland Highpower said:

That's mostly the nature of unison feed machines unfortunately.   

You're turning your work while the outer presser foot is down, and your center is anywhere other than under the needle.

Unison feed machine basically suck for leather work, but they've become the standard as they can do about everything. Leather, nylon, plastic, etc.  

You could try to train yourself to turn your work on sharp curves while the outer presser is still up, and the needle down, that might help some.  You may also want to check and see if your inner and outer foot lift is balanced. Maybe your feet don't sit square against the needleplate?  You may need to hone on the feet to fit better, more squarely.  Also try an open toe inner foot if you haven't.

Roller feed are good for tight curves and give great visibility, but really are only good on leathers that don't mar up.  They'll leave knurled tracks on top or a bit of a trough, and pretty heavy feed dog marks on the underside.  That's why they're mostly used for shoe/boot uppers.  I have a couple machines set up with large rollers that have rubber covered wheels, for visibility mostly.

Good to know the downsides of a roller feed machine.

 

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You may also want to check and see if your inner and outer foot lift is balanced.

I set this at one point. I'll check and readjust.

 

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Maybe your feet don't sit square against the needleplate?  You may need to hone on the feet to fit better, more squarely

That sounds like a good idea. The lifting foot mostly rests toward the rear.

 

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Also try an open toe inner foot if you haven't.

What is an open toe inner foot?

[Northmount]

On 2/13/2025 at 8:22 PM, friquant said:

What is an open toe inner foot?

The foot has a slot cut in the front of the toe so you can see the needle and the leather as the needle approaches the leather.  You can cut and grind out the foot yourself.  No need to buy another foot just to get an open toe.

 

[friquant]

6 hours ago, Northmount said:

The foot has a slot cut in the front of the toe so you can see the needle and the leather as the needle approaches the leather.  You can cut and grind out the foot yourself.  No need to buy another foot just to get an open toe.

 

That makes sense...I've been focusing on the needle thread that I can see while the inner toe is in the air. Open toe would be visible more of the time