Rakesh Jesadiya

We just need to pass order id in generateShipment($orderId) function from template.
below code snippet is used for generating Shipment in Magento 2, After generating Shipment automatically send the Shipment mail to a customer who has placed the order.

<?php
namespace Rbj\Shipment\Block;

class Shipment extends \Magento\Framework\View\Element\Template
{
public function __construct(
        \Magento\Framework\View\Element\Template\Context $context,
        \Magento\Sales\Api\OrderRepositoryInterface $orderRepository,
        \Magento\Sales\Model\Convert\OrderFactory $convertOrderFactory,
        \Magento\Framework\DB\TransactionFactory $transactionFactory,
        \Magento\Sales\Model\Order\Email\Sender\ShipmentSender $shipmentSender,
        \Magento\Framework\Message\ManagerInterface $messageManager,
        array $data = []
    ) {
        $this->orderRepository = $orderRepository;
        $this->orderConverter = $convertOrderFactory->create();
        $this->transactionFactory = $transactionFactory;
        $this->messageManager = $messageManager;
        $this->shipmentSender = $shipmentSender;
        parent::__construct($context, $data);
    }
/**
 * Create Shipment Based on Order Object
 * @param \Magento\Sales\Model\Order $order
 * @return $this
 */
public function generateShipment($orderId)
{
    try {
        $order = $this->orderRepository->get($orderId);
        if (!$order->getId()) {
            throw new \Magento\Framework\Exception\LocalizedException(__('The order no longer exists.'));
        }

        /* check shipment exist for order or not */
        if ($order->canShip())
        {
            // Initialize the order shipment object
            $shipment = $this->orderConverter->toShipment($order);
            foreach ($order->getAllItems() AS $orderItem) {
                // Check if order item has qty to ship or is order is virtual
                if (! $orderItem->getQtyToShip() || $orderItem->getIsVirtual()) {
                    continue;
                }
                $qtyShipped = $orderItem->getQtyToShip();
                // Create shipment item with qty
                $shipmentItem = $this->orderConverter->itemToShipmentItem($orderItem)->setQty($qtyShipped);
                // Add shipment item to shipment
                $shipment->addItem($shipmentItem);
            }
            // Register shipment
            $shipment->register();

            $shipment->getOrder()->setIsInProcess(true);

            try {
                $transaction = $this->transactionFactory->create()->addObject($shipment)
                    ->addObject($shipment->getOrder())
                    ->save();
                echo $shipmentId = $shipment->getIncrementId();
            } catch (\Exception $e) {
                $this->messageManager->addError(__('We can\'t generate shipment.'));
            }

            if ($shipment) {
                try {
                    $this->shipmentSender->send($shipment);
                } catch (\Exception $e) {
                    $this->messageManager->addError(__('We can\'t send the shipment right now.'));
                }
            }

            return $shipmentId;
        }
    } catch (\Exception $e) {
        $this->messageManager->addError($e->getMessage());
    }

    return true;
}

Call function from the template,

$orderId = 1;
$shipment = $block->generateInvoice($orderId);

Now Check from Admin panel.

Sales -> Order, Order with Id 1 has generated Shipment.