First half gross profit was $7.0 million, up $4.7 million compared with the last year's first half of $2.3 million. Gross profit as a percentage of sales improved to 40.9% in the first half of 2013, a 930 basis point improvement over 31.6% in last year's first half. SG&A expense for the first six months of 2013 was $7.5 million, up $1.6 million from the prior-year period. R&D expense was $2.1 million in the first half of 2013, compared with $0.8 million in the first half of 2012, reflecting the Company's investments in growth.
Operating loss for the first half of 2013 was $2.6 million, improved from a loss of $4.4 million during the comparable prior-year period. Net loss attributable to ExOne was $3.0 million, or $0.27 per diluted share, for the first half of 2013 compared with $5.1 million for the first half of 2012.
Strategy and Outlook
Mr. S. Kent Rockwell, Chairman and CEO, noted, "We believe our results continue to demonstrate the effective execution of our growth strategies. We are increasing machine sales, expanding our PSC network and building our material and binders portfolio. We believe ExOne remains distinctively positioned as a leading industrial provider of 3D printing machines and printed products, and we expect demand to continue to increase."The Company anticipates that its 2013 revenue will be at the lower end of its previous guidance of $48 million to $52 million. The Company's expectations are based on no additional micromachine (laser drilling machine) sales in 2013 and timing of year-end shipments. Further, the weakening of the Japanese yen relative to the U.S. dollar has impacted full year revenue expectations. ExOne anticipates that its 2013 gross margin will be at the higher end of its previous guidance of 42% to 46%. Lastly, ExOne expects 2013 operating expenses to be at the upper end of its previous guidance of $18 million to $21 million.