Rod Straightening Rolling Machine

In a previous lfe we used a farmer norton roll straightening machine, Basically it had 1 convex roll, 1 concave roll and an anvil with the bar rotating between the rolls and bearing on the anvil. This bent and rotated the bars or tubes (bronze up to 8") at the same time as transporting the material through the machine. This probably not a good description ...........

You did not specify the linear spacing of your rollers, so it is not possible to tell if you need more. But, if your spacing is about 10-12 inches on center, and the zig-zag is evenly spaced, you should be fine.

I suggest that you set the last three rollers spaced for the minimum width that you want your rods to be and the first rollers 0.5 mm wider.

Then, install a preheat burner assembly upstream of the rollers. It should be direct impingement style, set for flame width about 7-7.5 mm wide and installed on top (flame down) sides and bottom. The burners should be about 2 inches long with a ribbon flame. A pressure blower, set for 12-15 inches Water Column should feed combustion air to the burners.

This should not cause any problem with heat treating because the goal is only to heat the rods to about 450-500F (well below any critical temperatures). That way, the rollers will easily straighten the rods while producing consistent final rod dimensions.

The operating cost should be relatively low. A 400 F temperature rise for wrought iron (specific heat of 0.12 and a density of 7.5) and an average length of 9 feet (rod weight of 4.1 pounds) will only require 4.1 Lbs. x 0.12 x 400F = about 200 BTUs per 9 foot bar (about 22 BTU per foot). With a feed rate of, say 20 FPM, with about 10 seconds between bars (9 feet / 20 FPM per bar plus 10 seconds per bar = 37 seconds per bar, which yields an average of about 100 bars per hour. At 22 BTU/Foot and 20 FPM feed rate, the average heat load will be 22 BTU/Ft x 20 FPM x 60 Min/Hr = 26,400 BTU per hour to maintain a 450F-500F heating. Total fuel use will be about 634,000 BTU per day, or $6.00 per day at $9.50 per MCF natural gas. A 26,400 BTUH flame will require a blower volume of 10 SCFM. The blower electricity will likely add another $0.25 per day.

Whilst this is not an answer for your rolling machine, have you considered straightening with hydraulic tensioners instead for this size of rod? If you have variations in thickness all-ready it suggests the end product dimensions are not that critical. This would take care of your original dimension variation problem with a slight variation in hydraulic pressure to compensate.

I worked at a place where they straightened rod, bar and hex bar. the hex bar used a machine similar to what You have. As I recall the operator had to make several passes to get the bar straight.

This is probably no help to You, but you are on the right track.

oilcan13