This paper introduces the craft characteristics of casting the shell of the gearbox, including the manufacturing of the resin moulding, the application of the hard sand core and so on.

针对变速箱壳体毛坯铸造的工艺特点，介绍了其树脂模具的制造、树脂自硬砂砂芯应用等关键环节的技巧和做法。

youdao

It's hard to walk on the soft sand.

沙土地暄，不好走。

《新英汉大辞典》

By building complex, three-dimensional structures that expose the hard rock beneath the sand, Miller said, red grouper create an environment in which seaweed, coral and sponges can thrive.

Miller说通过建著复杂的空间结构使沙子底下的硬质岩石暴露出来，赤点石斑鱼创建了一个海藻，珊瑚和海绵可以繁荣生长的空间。

youdao

Most sand is made of quartz, a hard silicon crystal.

VOA: special.2010.01.04

Most people are afraid to draw the hard lines in the sand for fear of angering a friend or losing a potential client or opportunity.

FORBES: No, You Can't Pick My Brain. It Costs Too Much

Senate Minority Leader Mitch McConnell drew a hard line in the sand after the election against any new tax hikes in the fiscal cliff showdown.

FORBES: Limiting Deductions Could Be The New Tax Hike In Fiscal Cliff Avoidance

While the hard ground - because of the underlying sand drying quickly - allows the ball to travel further from the tee, the ground off the fairway is far less forgiving.

BBC: Carnoustie