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hello
are a new member, hello to everyone. beautiful site

I wrote to you my congratulations, really good work ...
I just wanted to ask you two things
1) I can not understand how the system returns to the 0 ° position.
i don't see the picture

2) some say that the radius of the die must be smaller than the pipe to be bent. What is your experience?
 

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Discussion Starter #62
hello
are a new member, hello to everyone. beautiful site

I wrote to you my congratulations, really good work ...
I just wanted to ask you two things
1) I can not understand how the system returns to the 0 ° position.
i don't see the picture

2) some say that the radius of the die must be smaller than the pipe to be bent. What is your experience?
1)there is steel cable warped around the main shaft and spring in other end to pull it back.

2)0 fit or bit under, if you cut them bigger than tube it will oval the tube in bends more. mine are tight fit and they are cut coulple millimeters deeper than half of tube diameter.
 

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Thanks .. I think I understand.
i make the dies slightly more smallers with a "U" profile

I would like to recommend another

wanted to use a toothed rod actuated by hydraulic piston with a pinion 1/4 of teeth ...
to go in both directions ...
What do you think?
 

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Discussion Starter #65
today i had to replace caster wheels to bigger ones, small shitty plastik center ones gave up.

now it has swiveling cart wheel in every corner. makes it easy to manuver around.

i had scale in my garage and lifted it up 320kg (706lbs) with all the tooling :eek:
 

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Discussion Starter #66
started working on this mandrel stuff again. hope to get some tube next week so i can make some bends.

mounted hydraulic cylinder to pull the mandrel out and mounted mandrel holder bar to it. this cylinder will run my tube expander too, still have to make depth adjuster for it.
 

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What will the expander be used for? Did you make it yourself on a lathe? Pretty clever.
 

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Discussion Starter #70
got the tube today and i did test it but it was bit disaster:eek:

mandrell jammed inside tube and pulled my mandrell fixture in bad shape. had to cut the tube in half to get the mandrell out of the bend:laughing:

but good stuff is my crimped center cable inside mandrell didnt give up:laughing::laughing:

and after trying to figure what went wrong i did find the cause to this fuck up.

when i made the mandrell i missed a desimal in mandrel clearance it should have been 0.020"/side and i made them 0.002"/side and this must have happended when i converted mesures to metric:(:laughing:
 

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Discussion Starter #73
got the junk together and made test bend.
my clamp die was slipping during bending, i need to adjust more clamping pressure and make someting un slippery to the clamp die surfaces.

bend has kinking inside radius but its a start. need to do some mandrel adjustment and fix the clamping issue.

tube is 48,3mmx1.6mm wall(1.9"x0.063"wall) 304ss
 

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Discussion Starter #74
got the clamp to hold and been trying different mandrell depht settings and other stuff, but still small wrinkles are forming inside radius. while bending it makes hammer drill sounding friction noise:(

it might have too much friction in slider die or the mandrell sizing has some issues.

i think i will different types of greases before i make any big changes.

but here is some bend i made. used only 7 meter of tube just for testing:laughing::laughing:
 

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Nose to grindstone
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Just an observation but it looks like your using one radius along the whole profile of the die. If you were to compute this you would need a spline not just one radius. That would most likely fix all your wrinkle issues.
 

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Discussion Starter #76
Just an observation but it looks like your using one radius along the whole profile of the die. If you were to compute this you would need a spline not just one radius. That would most likely fix all your wrinkle issues.
yes the die is same radius around. kind of hard to make anything else in manual lathe using hand operated radius cutter:laughing::laughing:

been doing some digging of the how to solve wrinkling issue and seems i need to make mandrel nose clearance tighter.

tomorow i will start casting new parts.
 

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Nose to grindstone
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I think youll find the relief radius of a die is larger than the OD of the tubing by a bit. Without this relief you will crinkle tube constantly. I dont know if there are any one radius dies out there that dont crinkle tubing.
 

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I would focus on the following;

1) Make sure you can really pinch the material between your main die and the forming die (the one the material is sliding through). You may need to have the forming die cross cut to only 175 degrees rather than 180 so it give you the room to pinch it.

2) Adjust the position of the forming die up or down the Y axis (this is the rail axis).

3) Play with the mandrel up and down the same Y axis.

Mandrel dies typically are cut to a true radius because of the mandrel itself and not a spline. A spline is cut on some non mandrel machines to reduce thinning. P.S. The spline direction that is being referred to is not the CenterLine Radius of the die, but the tube diameter of the material [cross cut if you will].
 

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Discussion Starter #79
casted and machined new mandrell nose and did some testing.

bends are bit better but still there is the wrinkle pattern. mesured the differense between the high and low point of wrinkle and it was 0,10mm-0,20mm. pretty much same in bigger die and smaller die. smaller die just leaves bigger ending hump.

maybe it needs wiper die and slidin pressure die but im not gointo do anymore work to it.
i can use those bends for my headers and maybe just give inside radius some sanding love to hide wrinkle pattern.

casting - YouTube
 

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