Machine tool scraping is not a lost art. At Konecranes MTS, it is common practice. We can restore your machine’s alignment in your plant or ours. We have six thoroughly trained “scraper hands” on our service and modernizations team. Our scraping specialists are experienced in precision scraping the following materials:
- Cast iron
- Turcite®, Rulon® and Moglice®
Admittedly, scraping is not suited for all applications. With current trends leaning towards higher feeds and speeds, Machine Builders are utilizing linear guide ways more frequently. Linear guide ways provide a reduced co-efficient of friction along with increased acceleration and deceleration rates. Linear guides have been widely accepted by the machine builders because of their inherent ability to provide higher speeds and rapid rates. Additionally, linear guide ways are not as susceptible to the phenomena known as “slip stick”, which allows the machine to position with a higher degree of accuracy while making small incremental moves. The above advantages are not without cost as they come at the expense of dynamic stiffness.
Plain bearings (box ways) may come in the form of metal-to-metal, metal-to-turcite©/rulon© or metal-to-various polymers. Although the machines with plain bearing slides do not possess the capability of traveling at the feeds and speeds of their counterpart, the linear guide ways, they do have one significant advantage; higher dynamic stiffness. Plain bearings (box ways) require the fine art of hand scraping to obtain required geometry specifications. The “Scraper Hand” literally scrapes the metal with carbide tipped scraping tools. The repetitive exercise of rubbing the slide to replicate the way profile produces spots called contact points or “bearing”. The scraper hand meticulously “scrapes” (picks) the bearing spots until a surface contact of 60% to 70% coverage is obtained. Depending on the machine and application, as many as 25-30 spots per square inch may be required. In most applications, 10-15 spots per square inch are sufficient. Great care is taken to equally distribute the load carrying points so long term geometry and alignments can be insured. Power spotting is performed at the completion of the scraping process and produces the half moon appearance that insures adequate channels for oil distribution.
If your company is like most companies, you will have a mixture of machines with plain bearing (box ways) and linear guide ways. Konecranes’ scraping/alignment specialists possess the skills required for alignment optimization to both plain bearings (box ways) and linear guides.
Precision leveling and geometrical optimization of a complex multi-axis machine is our specialty. Often we will be asked to improve on the OEM specification and “align the machine to our customer’s requirements”. This process typically requires more time to accomplish, as we must take into account tool deflection, cutting forces and work holding. However, the end result is that the customer achieves a much closer tolerance with less scrap, and the machine maintains geometrical compliance over a longer period of time.
Precision hand scraping to obtain geometrical alignment is not a “lost art” at Konecranes Machine Tool Service, it is a valuable asset.
Contact us to see how our expertise can assist you with meeting your accuracy objectives.