Deep Rolling and Roll Straightening Machines

HEGENSCHEIDT 7893R - Improving the fatigue strength of crankshafts

In powertrain applications, deep rolling is an attractive manufacturing technology for improving the operational stability of highly stressed crankshafts for automotive, commercial vehicle and industrial engines. The deep rolling process induces compressive residual stresses into the bearing fillets of crankshafts. HEGENSCHEIDT has had a decisive influence on this technology and has developed special machines for the economical machining of crankshafts with its deep rolling and roll straightening machines.

Application and Use

The 7893R is a universal deep rolling machine for machining crankshafts. Deep rolling and roll straightening machines from HEGENSCHEDT improve the material properties of crankshafts in terms of fatigue strength and radial runout. The combination of these two high-performance processes in one machine offers numerous advantages in terms of product quality and cost-effectiveness. Deep rolling is a process in which positive three-dimensional residual compressive stresses are induced in the bearing fillet areas of the workpiece which is subject to the highest stress by plastic deformation of the layer close to the surface. These counteract the tensile stresses that occur under load. The material is strengthened, the surface hardness increases, and the dynamic load capacity of the crankshaft is significantly increased. With optimized deep rolling processes, increased in fatigue of over 200 % can be achieved. The HEGENSCHEIDT machine impresses with its own high-performance tools for maximum tool life, an integrated laser measuring device for checking the position of the crankshaft and a measuring probe for measuring the radial run-out on the main bearings.

Added value

Flexible machine concept for deep rolling and straightening crankshafts with varying strokes, bearing spacing, and number of bearings
Angle dependent rolling for minimised run-out and reduced deformation of shoulders
Direct loading in machining position
No operating platform required due to reduced loading height of 1,100 mm
Integrated laser measuring device for checking the stroke and radial position
Automatic radial positioning
Measurement of radial run-out on all main bearings
Optional reference of the runout measurement to prisms or centers
Straightening of the crankshaft without loss of fatigue strength
High process reliability thanks to monitoring of all machining parameters
Measurement of the rolling depth
Tool breakage monitoring
New tool design for longer tool life
Self-learning roll straightening program
Automatic stroke adjustment
Fixed rollers can be quickly converted to other bearing distances
Roll straightening computer with software for all common types of crankshafts

Function

For machining, the crankshaft is automatically rotated into the correct deep rolling position via the integrated PLC-controlled spindle positioning system after loading, pre-centering, and clamped by using a compensating chuck. During the closing process, the tools enclose the main and pin bearings of the crankshaft under machine control. The grooved radii of the main and pin bearings are deep rolled with angle dependent rolling force and the total indicated radial run-out TIR is minimized during roll straightening. The system-integrated process monitoring measures the penetration depth and thus ensures process reliability. The angle dependent deep rolling process effectively counteracts axial run-out deviations caused by varying degrees of rigidity in the upper shoulders of the pin journals.

When the deep rolling rollers pass through the area of the bearing shoulders, the deep rolling force is automatically reduced and then increased again to increase the fatigue strength in the area of the crankshaft at risk of breakage. Straightening rolling reduces the existing radial runout of the crankshaft. While other straightening processes reduce the fatigue strength by up to 40%, the process developed by HEGENSCHEIDT is the only one that does not lead to a loss of fatigue strength. It even increases the fatigue strength of the crankshaft. In the combined deep rolling and straightening process, the radial runout of the crankshaft is measured after deep rolling and minimized by specifically increasing the deep rolling forces during the straightening process.

Highlights of the 7893R

Machine specification

	Type 7893-R01	Type 7893-R02	Type 7893-R03	Type 7893 R03S
Machine description	Headstock and tailstock manually adjustable Ideally suited for machining one type of crankshaft with different strokes	Headstock can be moved automatically Tailstock manually adjustable Ideally suited for machining a crankshaft family with different numbers of bearings and different strokes	Headstock and tailstock can be moved automatically Ideally suited for machining different crankshaft families	As 7893R-03, but the number of deep rolling attachments is less than the number of crankshaft bearings Machining of several crankshaft bearings in succession by moving the crankshaft (shifting) in front of the axially fixed deep rolling attachment Ideally suited for machining different crankshaft families in small quantities
Machine data
Machine dimensions (L x W x H)	5,200 mm x 2,200 mm x 2,200 mm
Machine weight	10,5 t
Machining height	1,100 mm
General specification
Power of the main drive motor	12 kW
Speed for deep rolling	120 ^min-1
Speed for straightening rolling	60 ^min-1
Measuring speed	30 ^min-1
Max. Deep rolling force	30 kN, optionally 40 kN
Workpiece data
Bearing center distance of the outer main bearings, max.	920 mm			920 mm > 920 mm on request
Roller arm length, max. (½ stroke + counterweight radius):	195 - 270 mm			195 - 270 mm > 270 mm on request
Radius counterweight for shift operation, max:	-			Determination depending on individual case
Number of machinable bearings max.	8 main bearings, 6 stroke bearings			Determination depending on individual case
Main bearing diameter, min. \| max. mm	30 \| 110 mm (> 88 mm on request)
Pivot bearing diameter, min. \| max.	30 \| 84 mm (> 84 mm on request)
Bearing width, min.	18 mm
Stroke, max.	140 mm
Bearing distance, min.	29.5 mm

Brochure

Here you will find all the contents of the 7893R as a download.

DOWNLOAD | PDF 1.71 MB

Our Services

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