Polish Foam Converter Cuts Off-Centre Bores with a C519 Foam Boring Machine

Poznan, Poland — A cylindrical foam converter supplying mattress core producers has replaced a manual boring station with a C519 CNC automatic foam boring machine. Off-centre bore rejects fell from 4.5 percent to 0.6 percent, output rose from 45 to 68 blocks per shift, and the boring station moved from two operators to one.

The plant produces cylindrical PU rolls between 1200 and 1500 mm in diameter and up to 2300 mm in length, which are bored through the centre, fitted with a shaft and then peeled into mattress core sheets. Most orders are 50 mm bores, with 80 mm bores for a smaller group of customers running heavier shafts.

Before the change, boring was carried out on an older machine with a shorter stroke and no automatic feed. The block was clamped, bored part of the way, released, turned and bored again from the other end.

The second set-up was the source of the quality problem. The operator had to line the roll up again, and a small error at the second clamping produced a visible step in the middle of the bore. Shafts still fitted, but the roll could rock on the shaft during peeling, and the resulting sheet thickness varied around the circumference.

The measured effect was significant:

• Off-centre rejects: 4.5 percent of rolls failed the bore position check.
• Steps in the bore: present on most rolls bored in two set-ups, and reworked by hand where the step exceeded the customer limit.
• Operator time: two operators were needed, one to feed and one to align and release the roll.
• Changeover: moving from 50 mm to 80 mm bores took over an hour because the machine had to be reset, not simply re-tooled.

Three machines were compared. The deciding factor was the 2300 mm boring length, which covers a full-length roll in one continuous pass, so the second set-up disappears entirely. The other two options could not bore the full length and would have kept the two-stage process.

The 50-80 mm hole range also matched the plant's order mix. Cutter heads are changed on the spindle, so moving between 50 mm and 80 mm work is a head change and a check rather than a machine reset. The 4 kW spindle was specified to hold torque at full depth, and the 1500 kg frame keeps the spindle steady while the automatic feed advances the roll.

Installation took two days. The first day covered positioning, levelling and the electrical connection; the second covered centre height setting, a test bore on scrap foam, and operator training on the automatic feed cycle. The plant ran scrap rolls for half a shift before moving to production, which gave the operators time to get used to loading against the end stop rather than lining the roll up by eye.

• One continuous bore: the 2300 mm stroke removed the second clamping step and the step in the bore that came with it.
• Automatic feed: the roll advances at a set rate, so the operator loads and unloads instead of holding and pushing.
• Centre height setting: matching the spindle height to the roll diameter keeps the bore through the middle of the roll.
• Head change instead of reset: moving between 50 mm and 80 mm work is now a tooling change.

"The step in the middle of the bore was the problem we could not solve on the old machine," said the plant's technical manager. "We were reworking rolls by hand and telling ourselves it was normal. With one continuous bore, the step is gone, and the peeling line gets a roll that sits straight on the shaft."

The plant records bore diameter and bore length on the first roll of every batch, and inspects the cutter head at the end of each shift. Changeover between 50 mm and 80 mm is scheduled between batches rather than inside a batch, which keeps the bore size consistent through a run.

The C519 is CE certified and available with delivery at 45 working days after downpayment. Cutter heads, guide parts and remote commissioning support are supplied with each machine.